UCC28880DR原理图各脚功能电路原理芯片引脚定义引脚图及功能-中国IC网-芯三七

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UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

UCC28881 700V、225mA 低静态电流离线转换器

1 特性

3 说明

1

•

集成 14Ω、700V 功率金属氧化物半导体场效应晶

UCC28881 在单片器件中集成了控制器和 14Ω、700V

体管 (MOSFET)

功率 MOSFET。该器件还集成了高电压电流源，能够

在经整流的市电电压下直接启动和运行。UCC28881

与 UCC28880 属于同一器件系列，具备高电流处理能

力。

•

集成高电压电流源，用于内置器件偏置电源

集成电流感测

内部软启动

自偏置开关（直接在经整流的市电电压下启动和运

行）

该器件的静态电流较低，能够提供出色的效率。凭借

UCC28881，使用最少的外部组件即可构建降压、降压

/升压以及反激拓扑等最常用的转换器拓扑。

•

支持降压、降压/升压和反激拓扑结构

器件静态电流 <100μA

在负载电路短路期间提供稳定的电流保护

保护

UCC28881 集成了控制功率级启动的软启动功能，能

够最大程度地减小功率级组件所受的压力。

–

电流限制保护

过载和输出短路保护

过热保护

器件信息⁽¹⁾

部件号

UCC28881

封装

SOIC (7)

封装尺寸（标称值）

5.00mm x 6.20mm

(1) 要了解所有可用封装，请见数据表末尾的可订购产品附录。

2 应用

•

AC-DC 电源

（非隔离式降压转换器，其在连续导通模式 (CCM)

和断续导通模式 (DCM) 下的

输出电流分别高达 225mA 和 150mA）

•

电表、家庭自动化开关模式电源 (SMPS)

支持微控制器 (MCU)、射频 (RF) 和物联网 (IoT)

的设备的偏置电源

•

家用电器、大型家用电器和发光二极管 (LED) 驱动

器

40

35

30

25

20

15

10

5

简化电路原理图

UCC28881

1

2

3

4

GND DRAIN

8

GND

FB

NC

6

5

V_IN

VDD

HVIN

+

V_OUT

-

2.7-W Low-Side Buck Standby Power

0

UCC28881 Power Consumption

-5

50

100

150

200

250

300

AC Input Voltage (V_RMS

)

D001

1

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.

English Data Sheet: SLUSC36

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

8.3 Feature Description................................................. 10

8.4 Device Functional Modes........................................ 12

Application and Implementation ........................ 16

9.1 Application Information............................................ 16

9.2 Typical Application .................................................. 16

1

2

3

4

5

6

7

特性.......................................................................... 1

应用.......................................................................... 1

说明.......................................................................... 1

修订历史记录 ........................................................... 2

Device Comparison ............................................... 3

Pin Configuration and Functions......................... 3

Specifications......................................................... 4

7.1 Absolute Maximum Ratings ...................................... 4

7.2 ESD Ratings.............................................................. 4

7.3 Recommended Operating Conditions....................... 5

7.4 Thermal Information.................................................. 5

7.5 Electrical Characteristics........................................... 6

7.6 Switching Characteristics.......................................... 6

7.7 Typical Characteristics ............................................. 7

Detailed Description .............................................. 9

8.1 Overview ................................................................... 9

8.2 Functional Block Diagram ......................................... 9

9

10 Power Supply Recommendations ..................... 26

11 Layout................................................................... 26

11.1 Layout Guidelines ................................................ 26

11.2 Layout Example .................................................... 26

12 器件和文档支持 ..................................................... 27

12.1 器件支持 ............................................................... 27

12.2 社区资源................................................................ 27

12.3 商标....................................................................... 27

12.4 静电放电警告......................................................... 27

12.5 Glossary................................................................ 27

13 机械、封装和可订购信息....................................... 27

8

4 修订历史记录

Changes from Revision A (December 2015) to Revision B

Page

•

已更改文档标题“UCC28881 700V、225mA 低静态电流离线开关”至“UCC28881 700V、225mA 低静态电流离线转换

器”。 ....................................................................................................................................................................................... 1

Changes from Original (November 2015) to Revision A

Page

•

已更改销售状态“产品预览”至“量产数据”。............................................................................................................................. 1

2

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

5 Device Comparison

Power Handling Capability with Different Topologies

MAXIMUM OUTPUT CURRENT

MAXIMUM OUTPUT POWER

for 85 ~ 265 VAC OPEN FRAME DESIGN

PRODUCT

NON-ISOLATED BUCK

100 mA

FLYBACK

3 W

UCC28880

UCC28881

225 mA

4.5 W

6 Pin Configuration and Functions

D package

8-Pin SOIC

Top View

GND

FB

1

8

DRAIN

2

3

4

6

5

NC

VDD

HVIN

Pin Functions

I/O

DESCRIPTION

NAME

DRAIN

FB

NO.

8

P

I

Drain pin

3

Feedback terminal

Ground

GND

HVIN

NC

1

G

2

G

Ground

5

P

Supply pin

6

N/C

O

Not internally connected

VDD

4

Supply pin, supply is provided by internal LDO

3

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

7 Specifications

7.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)

(1) (2) (3)

MIN

MAX

700

UNIT

(4)

(5)

HVIN

–0.3

V

DRAIN

Internally

clamped

700

770

V

I_DRAIN

FB

Positive drain current single pulse, pulse max duration 25 μs

mA

V

Negative drain current

–700

–0.3

6

VDD

I_VDD

T_J

VDD is supplied from low impedance source

VDD is supplied from high impedance source

Junction temperature

V

400

150

260

150

µA

°C

Lead temperature 1.6 mm (1/16 inch) from case 10 seconds

Storage temperature range

T_stg

–65

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings

only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended

Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) All voltages are with respect to GND. Currents are positive into, negative out of the specified terminal. These ratings apply over the

operating ambient temperature ranges unless otherwise noted.

(3) The device is not rated to withstand operating conditions when multiple parameters are at or near, absolute maximum ratings.

(4) T_A= 25°C

(5) The MOSFET drain to source voltage is less than 400V

7.2 ESD Ratings

UNIT

Human Body Model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins

except HVIN pin

±2000

±1500

±500

V

(1)

V_(ESD)

Electrostatic discharge

Human Body Model (HBM) per ANSI/ESDA/JEDEC JS-001, HVIN pin

Charged device model (CDM), per JEDEC specification JESD22-C101,

(2)

all pins

(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.

(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

4

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

7.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)

MIN

NOM

MAX

UNIT

V

V_VDD

V_FB

T_J

Voltage On VDD pin

5

Voltage on FB pin

–0.2

–40

5

V

Operating junction temperature

+125

°C

7.4 Thermal Information

UCC28881

D (SOIC)

7 PINS

134.4

42.6

(1)

THERMAL METRIC

UNIT

R_θJA

R_θJC(top)

R_θJB

ψ_JT

Junction-to-ambient thermal resistance

Junction-to-case (top) thermal resistance

Junction-to-board thermal resistance

Junction-to-top characterization parameter

°C/W

85

6.4

ψ_JB

Junction-to-board characterization parameter

76

(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application

report, SPRA953.

5

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

7.5 Electrical Characteristics

V_HVIN= 30 V, T_A= T_J= –40°C to +125°C (unless otherwise noted)

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

V_HVIN(min)

I_NL

Minimum Voltage to start-up

30

100

V

Internal supply current, no load FB = 1.25 V (> V_{FB_TH}

)

58

86

µA

Internal supply current, full

FB = 0.75 V (> V_{FB_TH}

load

I_FL

)

120

µA

I_CH0

I_CH1

Charging VDD Cap current

V_VDD= 0 V,

–3.8

–1.6

–0.4

mA

V_VDD= 4.4V, V_FB= 1.25 V

–3.40

–1.30

–0.25

Internally regulated low

Voltage supply (supplied from

HVIN pin)

V_VDD

4.5

5.0

5.5

V

V_{FB_TH}

FB pin reference threshold

VDD turn-on threshold

VDD turn-off threshold

VDD UVLO Hysteresis

Maximum Duty Cycle

0.96

3.55

3.28

0.27

45%

1.03

3.92

1.105

4.28

3.89

0.39

55%

630

V

V_VDD(on)

V_VDD(off)

ΔV_VDD(uvlo)

D_MAX

VDD low-to-high

VDD high-to-low

FB = 0.75 V

3.62

0.345

Static, T_A= –40°C

Static, T_A= 25°C

Static, T_A= 125°C

mA

I_LIMIT

Current Limit

330

315

440

570

Thermal Shutdown

Temperature

T_J(stop)

T_J(hyst)

BV

Internal junction temperature

138.5

37.

150

45

°C

V

Thermal Shutdown Hysteresis Internal junction temperature

Power MOSFET Breakdown

T_J= 25°C

700

Voltage

Power MOSFET On-

Resistance (includes internal

sense-resistor)

I_D= 60 mA, T_J= 25°C

I_D= 60 mA, T_J= 125°C

14

24

18

30

Ω

R_DS(on)

V_DRAIN= 700V, T_J= 25°C

V_DRAIN= 400 V, T_J= 125°C

5

µA

Power MOSFET off state

leakage current

DRAIN_I_LEAKAGE

20

V_HVIN= 700 V, T_J= 25°C, V_VDD

5.8 V

=

4.0

6.0

7.5

6.7

36.0

µA

HVIN_I_OFF

HVIN off state current

VDD clamp voltage

V_HVIN= 400 V, T_J= 125°C, V_VDD

5.8 V

=

20

µA

V

V_VDD(clamp)

I_VDD= 250 µA

7.5

7.6 Switching Characteristics

over operating free-air temperature range (unless otherwise noted)

MIN

52

TYP

62

MAX

75

UNIT

kHz

µs

f_SW(max)

t_{ON_MAX}

t_{OFF_MIN}

t_MIN

Maximum switching frequency

Maximum switch on time (current limiter not triggered), FB = 0.75 V

Minimum switch off time follows every t_ONtime, FB = 0.75 V

Minimum on time

6.5

8.3

9.7

6.5

8.3

9.7

µs

0.17

130

0.27

200

450

0.30

270

µs

t_OFF(ovl)

t_{ON_TO}

Max off time (OL condition), t_OFF(ovl)= t_SW– t_ON(max)

Inductor current run away protection time threshold

µs

ns

6

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

7.7 Typical Characteristics

1.6

1.5

1.4

1.3

1.2

1.1

1

1.2

1.15

1.1

1.05

1

0.9

0.8

0.7

0.6

0.5

0.4

0.95

0.9

0.85

0.8

50

150

250

350

450

550

650

750

-40

-20

0

20

40

60

80

100 120 140

Temperature (^oC)

Drain Current Slope (mA/ms)

D002

D301

Figure 2. I_LIMITvs Drain Current Slope

Figure 1. I_LIMITvs Temperature

1.5

1.4

1.3

1.2

1.1

1

1.2

I_CH0

I_CH1

1.15

1.1

1.05

1

0.9

0.8

0.7

0.6

0.5

0.95

0.9

I_FL

I_NL

0.85

-40

-20

0

20

40

60

80

100 120 140

-40

-20

0

20

40

60

80

100 120 140

Temperature (^oC)

Temperature (°C)

D001

D303

Figure 4. I_CH0and I_CH1vs Temperature

Figure 3. I_NLand I_FLvs Temperature

900

800

700

600

500

400

300

200

100

0

1.01

1.005

1

V_VDD(on)

V_VDDHysteresis

0.995

0.99

0.985

0.98

I_DRAIN25^oC

I_DRAIN125^oC

0

5

10 15 20 25 30 35 40 45 50 55 60

Drain to Source Voltage (V)

-40

-20

0

20

40

60

80

100 120 140

Temperature (^oC)

D316

D305

Figure 6. I_DSvs V_DSat 25°C and 125°C

Figure 5. V_VDD(on)and V_VDDHysteresis vs Temperature

7

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

Typical Characteristics (continued)

1.02

1.01

1

1.01

1

0.99

0.98

0.97

0.96

0.99

0.98

0.97

0.96

-50

0

50

100

150

-40

-20

0

20

40

60

80

100 120 140

Temperature (^oC)

Temperature (°C)

D012

D308

Figure 7. Maximum Switching Frequency vs Temperature

Figure 8. V_{FB_TH}vs Temperature

1.05

1.045

1.04

1.12

1.1

1.08

1.06

1.04

1.02

1

1.035

1.03

1.025

1.02

1.015

1.01

0.98

0.96

0.94

0.92

0.9

1.005

1

T_OFF(min)

T_ON(max)

0.995

0.99

-40

-20

0

20

40

60

80

100 120 140

-40

-20

0

20

40

60

80

100 120 140

Temperature (°C)

D001

Temperature (^oC)

D310

Figure 9. t_ON(max)and t_OFF(min)vs Temperature

Figure 10. DRAIN breakdown voltage vs Temperature

140

136

132

128

124

120

116

112

108

104

100

0

200

400

600

800

1000

1200

1400

Copper Area (mm²)

D0201

Figure 11. R_THJ_Avs Copper Area

8

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

8 Detailed Description

8.1 Overview

The UCC28881 integrates a controller and a 700-V power MOSFET into one monolithic device. The device also

integrates a high-voltage current source, enabling start up and operation directly from the rectified mains voltage.

UCC28881 is the same family device as UCC28880 and it provides higher power handling capability.

The low-quiescent current of the device enables excellent efficiency. The device is suitable for non-isolated AC-

to-DC low-side buck and buck-boost configurations with level-shifted direct feedback, but also more traditional

high-side buck, buck boost and low-power flyback converters with low standby power can be built using a

minimum number of external components.

The device generates its own internal low-voltage supply (5 V referenced to the device’s ground, GND) from the

integrated high-voltage current source. The PWM signal generation is based on a maximum constant on-time,

minimum off-time concept, with the triggering of the on-pulse depending on the feedback voltage level. Each on-

pulse is followed by a minimum off-time to ensure that the power MOSFET is not continuously driven in an on-

state. The PWM signal is AND-gated with the signal from a current limit circuit. No internal clock is required, as

the switching of the power MOSFET is load dependent. A special protection mechanism is included to avoid

runaway of the inductor current when the converter operates with the output shorted or in other abnormal

conditions that can lead to an uncontrolled increase of the inductor current. This special protection feature keeps

the MOSFET current at a safe operating level. The device is also protected from other fault conditions with

thermal shutdown, under-voltage lockout and soft-start features.

8.2 Functional Block Diagram

HVIN

5

High Voltage

Current Source

8

DRAIN

Thermal

Shutdown

Gate

VDD

4

LDO

S

R

Q

UVLO

Current

Limit

Control and

Reference

Leading Edge

Blanking Time

V_{REF_TH}= 1 V

PWM Controller

and Output Short

Circuit Protection

+

LEB

FB

3

1, 2

GND

9

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

8.3 Feature Description

The UCC28881 integrates a 700-V rated power MOSFET switch, a PWM controller, a high-voltage current

source to supply a low-voltage power supply regulator. A bias and reference block, thermal shutdown and the

following protection features, current limiter, under voltage lockout (UVLO) and overload protection for situations

like short circuit at the output are also integrated inside UCC28881. UCC28881 is the same family device as

UCC28880 and it provides higher power handling capability.

The positive high-voltage input of the converter node (VIN+) functions as a system reference ground for the

output voltage in low-side topologies. In the low-side buck topology the output voltage is negative with respect to

the positive high-voltage input (VIN+), and in low-side buck-boost topology the output voltage is positive with

respect to the positive high-voltage input (VIN+).

In low-side buck and buck-boost topologies, the external level-shifted direct feedback circuit can be implemented

by two resistors and a high-voltage PNP transistor.

In high-side buck configuration, as well as in non-isolated flyback configuration, the output voltage is positive with

respect to the negative high-voltage input (VIN–), which is the system reference ground.

UCC28881 can operate under continuous conduction mode (CCM) or discontinuous conduction mode (DCM)

mode. CCM operation allows the converter to deliver more output power because of less current ripple. However,

it requires a higher inductor value and generally results in lower efficiency due to the added losses associated

with diode reverse recovery current. DCM mode operation uses a smaller inductor and achieves better efficiency,

but the output current handling capability is reduced because of increased current ripple. The table below shows

the current handling capability in DCM and CCM operation for the UCC28880, UCC28881 family.

Table 1. Current Handling Capability for UCC28880 and UCC28881

DEVICE

CURRENT HANDLING MODE

Discontinuous Conduction Mode (DCM)

Continuous Conduction Mode (CCM)

Discontinuous Conduction Mode (DCM)

Continuous Conduction Mode (CCM)

230 V_AC±15%

150 mA

85 V ~ 265 V_AC

150 mA

UCC28881

UCC28880

225 mA

70 mA

100 mA

When the bus voltage is higher than 400 V, it is recommended to limit operation to DCM mode only to avoid the

diode reverse recovery current and the associated internal MOSFET stress. Due to the higher switching loss and

device stresses at higher bus voltage, it is recommended to keep the converter input voltage less than 560 V for

the buck applications.

UCC28881 power handling capability is reduced at higher ambient temperature, as a function of the power

dissipation of the device, the device's recommended maximum operating junction temperature and the thermal

dissipation capability of the total system. De-rating of the output current according to maximum ambient

temperature can be estimated from Figure 12. The de-rating estimation assumes CCM operation, 10 µJ of

switching loss and 135°C/W R_θJAand 30-kHz, full-load switching frequency. This is a conservative estimation.

The thermal handling capability can be more accurately determined through experimental measurement. For

more information on thermal evaluation methods see the IC Package and Thermal Metrics application report:

SPRA953.

10

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

1.2

1.1

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

-40

-20

0

20

40

60

80

100 120 140

Ambient Temperature (^oC)

D012

Figure 12. Output Current (De-Rating Factor) vs. Temperature

It is required to use fast recovery diode for the buck freewheeling diode. When designed in CCM, the diode

reverse recovery time should be less than 35 ns to keep low reverse recovery current and the switching loss. For

example, STTH1R06A provides 25-ns reverse recovery time. When designed in DCM, a slower diode can be

used, but the reverse-recovery time should be kept less than 75 ns. MURS160 can fit the requirement.

The device has a low-standby power consumption (no-load condition), only 18 mW (typical) when connected to a

230-V_ACmains and 9 mW when connected to an 115-V_ACmains.

The standby power does not include the power dissipated in the external feedback path, the power dissipated in

the external pre-load, the inductor in the freewheeling diode and the converter input stage (rectifiers and filter).

11

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

8.4 Device Functional Modes

8.4.1 Start-Up Operation

The device includes a high-voltage current source connected between the HVIN pin and the internal supply for

the regulator. When the voltage on the HVIN pin rises, the current source is activated and starts to supply current

to the internal 5-V regulator. The 5-V regulator charges the external capacitor connected between VDD pin and

GND pin. When the VDD voltage exceeds the VDD turn-on threshold, V_VDD(on), device starts operations. The

minimum voltage across HVIN and GND pins, to ensure enough current to charge the capacitance on VDD pin,

is V_HVIN(min). At the First switching cycle the minimum MOSFET off time is set to be >100 μs and cycle-by-cycle is

progressively reduced up to t_OFF(min)providing soft start.

8.4.2 Feedback and Voltage Control Loop

The feedback circuit consists of a voltage comparator with the positive input connected to an internal reference

voltage (referenced to GND) and the negative input connected to FB pin. When the feedback voltage at the FB

pin is below the reference voltage V_{FB_TH}logic high is generated at the comparator output. This logic high

triggers the PWM controller, which generates the PWM signal turning on the MOSFET. When the feedback

voltage at the FB pin is above the reference voltage, it indicates that the output voltage of the converter is above

the targeted output voltage set by the external feedback circuitry and PWM is stopped.

12

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

Device Functional Modes (continued)

8.4.3 PWM Controller

UCC28881 operates under on/off control. When the FB pin voltage is below internal reference 1 V, the converter

is switching and sending power to the load. When the FB pin voltage is above internal reference 1 V, the

converter shuts off and stops delivering power to the load.

The PWM controller does not need a clock signal. The PWM signal’s frequency is set to f_SW(max)= (1/(t_ON(max)

t_OFF(min))) which occurs when the voltage on the FB pin is continuously below V_{FB_TH}

+

.

PWM duty cycle is determined by both the peak current and maximum on time. At each switching cycle, after

turn on, the MOSFET is turned off if its current reaches the fixed peak-current threshold or its on time reaches

the maximum value of on-time pulse t_ON(max)

.

Normally the converter would operate under frequency control, which means the converter is only enabled one

switching cycle and then disabled. Next switching cycle starts when output voltage decays and the feedback

enable the converter again. This way, the converter appears to operate under variable switching frequency

control.

The user might observe the converter operates in burst mode that converter is enabled for multiple switching

cycles and then stopped for multiple switching cycles. This causes larger output voltage ripple. However, due to

the infrequent switching it actually helps on the standby power at no load.

V_FB

V_{FB_TH}

t

FB_COMP_OUT

t

PWM

t

CURRENT LIMIT

t

RSTN

t

GATE

t

t_ON(max)

t_OFF(min)

t_ON(max)

t_OFF(min)

t_ON(max)

t_OFF(min)

t_ON(max)

t_OFF(min)

Figure 13. UCC28881 Timing Diagram

13

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

Device Functional Modes (continued)

8.4.4 Current Limit

The current limit circuit senses the current through the power MOSFET. The sensing circuit is located between

the source of the power MOSFET and the GND pin. When the current in the power MOSFET exceeds the

threshold I_LIMIT, the internal current limit signal goes high, which sets the internal RSTN signal low. This disables

the power MOSFET by driving its gate low. The current limit signal is set back low after the falling edge of the

PWM signal. After the rising edge of the GATE signal, there is a blanking time. During this blanking time, the

current limit signal cannot go high. This blanking time and the internal propagation delay result in minimum on

time, t_MIN

.

8.4.5 Inductor Current Runaway Protection

To protect the device from overload conditions, including a short circuit at the output, the PWM controller

incorporates a protection feature which prevents the inductor current from runaway. When the output is shorted

the inductor demagnetization is very slow, with low di/dt, and when the next switching cycle starts energy stored

in the inductance is still high. After the MOSFET switches on, the current starts to rise from pre-existing DC value

and reaches the current-limit value in a short duration of time. Because of the intrinsic minimum on-time of the

device the MOSFET on-time cannot be lower than t_MIN, in an overload or output short circuit the energy

inductance is not discharged sufficiently during MOSFET off-time, it is possible to lose control of the current

leading to a runaway of the inductor current. To avoid this, if the on-time is less than t_{ON_TO}(t_{ON_TO}is a device

internal time out), the controller increases the MOSFET off-time (t_OFF). If the MOSFET on-time is longer than

t_{ON_TO}then t_OFFis decreased. The controller increases t_OFF, cycle-by-cycle, through discrete steps until the on-

time continues to stay below t_{ON_TO}. The t_OFFis increased up to t_OFF(ovl)after that, if the on-time is still below

t_{ON_TO}the off-time is kept equal to t_OFF(ovl). The controller decreases t_OFFcycle-by-cycle until the on-time

continues to stay above t_{ON_TO}up to t_OFF(min). This mechanism prevents control loss of the inductor current and

prevents over stress of the MOSFET (see typical waveforms in Figure 14 and Figure 15). At start up, the t_OFFis

set to t_OFF(ovl)and reduced cycle-by-cycle (if the on-time is longer than t_{ON_TO}) up to t_OFF(min)providing a soft start

for the power stage.

L_[LaLÇ

Lnducꢁor /urrenꢁ

5rꢀin /urrenꢁ

t

ꢁ_{hb_a!ó}

ꢁ_hCC

tía

/urrenꢁ [imiꢁ

[9.

t

~200 ns

ꢁ_{hb_Çh}

~200 ns

ꢁ_{hb_Çh}

t

Lncreꢀse ꢁ

( 5ecreꢀse f_{í

5ecreꢀse ꢁ_hCC

(Lncreꢀse f_{í

hCC

)

/bÇ_Lb

Dꢀꢁe

t

t_ON

Figure 14. Current Runaway Protection Logic Timing Diagram

14

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

Device Functional Modes (continued)

hutput {ꢀorted Iere

V_FB

V_{FB_TH}

I_LIMIT

Lb5Ü/Çhw

/Üww9bÇ

5w!Lb

/Üww9bÇ

t

t_{ON_TO}

D!Ç9

t_{ON_TO}

t

t_ON< t_{ON_TO}

t_ON> t_{ON_TO}

t_ON< t_{ON_TO}

Figure 15. Current Runaway Protection, Inductor and MOSFET Current

A minimal value needs to be imposed on the inductance value to avoid nuisance tripping of the protection feature

that prevents the loss of control of the inductor current. Inadvertent operation of the protection feature limits the

output-power capability of the converter. This condition depends on the converter's maximum input operating

voltage and temperature. Use Equation 1 to calculate your minimum inductance value.

V

IN max

(

)

L >

ì t_{ON_ TO}

I_LIMIT

(1)

In this equation, V_IN(max)is the maximum voltage on the DC input. If the input is a rectifed AC voltage, it should

be the peak value of the maximum AC line. For a DC input case, it should be the maximum DC input voltage.

If the inductance value is too low, such that the MOSFET on-time is always less than t_{ON_TO}timeout and the

device progressively increases the MOSFET off-time up to t_OFF(ovl), the output power is reduced and the

converter fails to supply the load.

8.4.6 Over Temperature Protection

If the junction temperature rises above T_J(stop), the over temperature protection is triggered. This disables the

power MOSFET switching. To re-enable the switching of the MOSFET the junction temperature has to fall by

T_J(hyst)below the T_J(stop)where the device moves out of over temperature protection.

15

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

9.1 Application Information

The UCC28881 can be used in various application topologies with direct or isolated feedback. The device can be

used in low-side buck, where the output voltage is negative, or as a low-side buck-boost configuration, where the

output voltage is positive. In both configurations the common reference node is the positive input node (VIN+).

The device can also be configured as a LED driver in either of the above mentioned configurations. If the

application requires the AC-to-DC power supply output to be referenced to the negative input node (VIN–), the

UCC28881 can also be configured as a traditional high-side buck as shown in Figure 16. In this configuration,

the voltage feedback is sampling the output voltage VOUT, making the DC regulation less accurate and load

dependent than in low-side buck configuration, where the feedback is always tracking the VOUT. However, high-

conversion efficiency can still be obtained.

9.2 Typical Application

9.2.1 13-V, 225-mA High-Side Buck Converter

Figure 16 shows a typical application example of a non-isolated power supply, where the UCC28881 is

connected in a high-side buck configuration having an output voltage that is positive with respect to the negative

high-voltage input (VIN–). The output voltage is set to 13 V in this example, but can easily be changed by

changing the value of R_FB1. This application can be used for a wide variety of household appliances and

automation, or any other applications where mains isolation is not required.

L2

R_F

D2

HVIN

VDD

FB

DRAIN

UCC28881

GND

C_VDD

C₁

+

VIN

-

R_FB1

C2

C_FB

R_FB2

D4

L1

+

D1

C_L

R_L

VOUT

-

D3

Figure 16. Universal Input, 12-V, 225-mA Output High-Side Buck

16

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

Typical Application (continued)

9.2.1.1 Design Requirements

Table 2. Design Specification

DESCRIPTION

DESIGN INPUT

MIN

TYP

MAX

UNIT

V_IN

AC input voltage

Line frequency

Output current

85

47

0

265

63

V_RMS

Hz

f_LINE

I_OUT

225

mA

DESIGN REQUIREMENTS

P_NL

No-load input power

500

17.5

350

mW

V

V_OUT

ΔV_OUT

η

Output voltage

12.5

70%

13

Output voltage ripple

Converter full-load efficiency

mV

9.2.1.2 Detailed Design Procedure

9.2.1.2.1 Input Stage (R_F, D2, D3, C1, C2, L2)

•

Resistor R_Fis a flame-proof fusible resistor. R_Flimits the inrush current, and also provide protection in case

any component failure causes a short circuit. Value for its resistance is generally selected between 4.7 Ω to

15 Ω.

•

A half-wave rectifier is chosen and implemented by diode D2 (1N4937). It is a general purpose 1-A, 600-V

rated diode. It has a fast reverse recovery time (200 ns) for improved differential-mode-conducted EMI noise

performance. Diode D3 (1N4007) is a general purpose 1-A, 1-kV rated diode with standard reverse recovery

time (>500 ns), and is added for improved common-mode-conducted EMI noise performance. D3 can be

removed and replaced by a short if not needed.

•

EMI filtering is implemented by using a single differential-stage filter (C1-L2-C2).

Capacitors C1 and C2 in the EMI filter also acts as storage capacitors for the high-voltage input DC voltage

(VIN). The required input capacitor size can be calculated according Equation 2.

»

…

ÿ

Ÿ

≈

∆

«

’

÷

◊

V_{BULK min}

2ìP

1

(

)

IN

ì

-

ì arccos

f_{LINE min}

RCT 2ì p

2 ì V

(

)

IN min

(

)

Ÿ

⁄

C_{BULK min}

=

(

)

2ì V²

- V_B²_{ULK min}

IN min

(

)

(

)

where

•

C_BULK(min)is minimum value for the total input capacitor value (C1 + C2 in the schematic of Figure 16).

RCT = 1 in case of half wave rectifier and RCT = 2 in case of full-wave rectifier .

P_INis the converter input power.

V_IN(min)is the minimum RMS value of the AC input voltage.

V_BULK(min)is the minimum allowed voltage value across bulk capacitor during converter operation.

f_LINE(min)is the minimum line frequency when the line voltage is V_IN(min)

.

The converter input power can be easily calculated as follow:

•

The converter maximum output power is: P_OUT= I_OUTx V_OUT= 0.225 A x 13 V = 2.925 W

Assuming the efficiency η = 68% the input power is P_IN= P_OUT/η = 4.178 W

Using the following values for the other parameters

•

V_BULK(min)= 80 V

V_IN(min)= 85 V_RMS(from design specification table)

f_LINE(min)= 57 Hz

(2)

17

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

C_BULK(min)= 15.6 μF. Considering that electrolytic capacitors, generally used as bulk capacitor, have 20% of

tolerance in value, the minimum nominal value required for C_BULKis:

C_BULK(min)

C_BULKn(min)

>

= 19.5mF

1- TOL

(

)

CBULK

(3)

Select C1 and C2 to be 10 μF each (C_BULK= 10 μF + 10 μF = 20 μF > C_BULKn(min)).

By using a full-wave rectifier allows a smaller capacitor for C1 and C2, almost 50% smaller.

9.2.1.2.2 Regulator Capacitor (C_VDD

)

Capacitor C_VDDacts as the decoupling capacitor and storage capacitor for the internal regulator. A 100-nF, 10-V

rated ceramic capacitor is enough for proper operation of the device's internal LDO.

9.2.1.2.3 Freewheeling Diode (D1)

The freewheeling diode has to be rated for high-voltage with as short as possible reverse-recovery time (t_rr).

The maximum reverse voltage that the diode should experience in the application, during normal operation, is

given by Equation 4.

V_D1(max)= 2ìV_IN(max)= 2ì265V =375V

(4)

A margin of 20% is generally considered.

The use of a fast recovery diode is required for the buck-freewheeling rectifier. When designed in CCM, the

diode reverse recovery time should be less than 35 ns to keep low reverse recovery current and the switching

loss. For example, STTH1R06A provides 25-ns reverse recovery time. When designed in DCM, slower diode can

be used, but the reverse recovery time should be kept less than 75 ns. MURS160 can fit the requirement.

9.2.1.2.4 Output Capacitor (C_L)

The value of the output capacitor impacts the output ripple. Depending on the combination of capacitor value and

equivalent series resistor (R_ESR). A larger capacitor value also has an impact on the start-up time. For a typical

application, the capacitor value can start from 47 μF, to hundreds of μF. A guide for sizing the capacitor value

can be calculated by the following equations:

I_LIMIT-I_OUT

440mA - 225mA

62kHz ì350mV

C_L> 20 ì

= 20 ì

= 200mF

f_{SW max}ì DV_OUT

(

)

(5)

(6)

DV_OUT

I_LIMIT

R_ESR

<

= 0.8W

Take into account that both C_Land R_ESRcontribute to output voltage ripple. A first pass capacitance value can be

selected and the contribution of C_Land R_ESRto the output voltage ripple can be evaluated. If the total ripple is

too high the capacitance value has to increase or R_ESRvalue must be reduced. In the application example C_L

was selected (330 µF) and it has an R_ESRof 0.03 Ω. So the R_ESRcontributes for 4% of the total ripple. The

formula that calculates C_Lis based on the assumption that the converter operates in burst of twenty switching

cycles. The number of bursts per cycle could be different, the formula for C_Lis a first approximation.

9.2.1.2.5 Pre-Load Resistor (R_L)

The pre-load resistor connected at the output is required for the high-side buck topology. Unlike low side buck

topology, the output voltage is directly sensed, in high-side buck topology the output is sampled and estimated.

At no-load condition, because the feedback loop runs with its own time constant, the buck converter operates

with a fixed minimum switching frequency. Select the pre-load resistor or using a zener diode to prevent output

voltage goes too high at no-load condition.

A simple zener diode would be a good choice without going through the calculation. Besides the simplifying the

calculation, zener diode doesn't consumes power at heavy load condition, which helps to improve the converter

heavy-load efficiency.

18

UCC28881

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ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

A simple resistor can also be used to limit the output voltage at no load condition. However, this resistor

connects to the output all the time and it reduces the full-load efficiency. The pre-load resistor can be calculated

based on below equation or based on experiments. In this equation, the V_MAXis allowed maximum output

voltage, and V_REGis the regulated output voltage.

4ì V_MAX²ì V

- V_REGC_FBì R_FB1+R_FB2

(

)

(

)

MAX

R_L=

ì

2

V_MAX+ V_REG

L₁ìI_LIMIT

(7)

9.2.1.2.6 Inductor (L1)

Initial calculations:

Half of the peak-to-peak ripple current at full load:

DI = 2ì I -I_OUT

(

)

L

LIMIT

(8)

When operating in DCM, the peak-to-peak current ripple is the peak current of the device.

Average MOSFET conduction minimum duty cycle at continuous conduction mode is:

V_OUT+ V_d

D_MIN

=

V_IN(max)- V_d

(9)

(10)

(11)

If the converter operates in discontinuous conduction mode:

I_OUTV_OUT+ V_d

D_MIN= 2ì

I_LIMIT

V_IN(max)- V_d

Maximum allowed switching frequency at V_IN(max)and full load:

D_MIN

F_{SW _ VIN(max)}

=

t_{ON_ TO}

Switching frequency has a maximum value limit of f_SW(max)

The worst case I_LIMIT= 315 mA, but assuming ΔI_L= 180 mA.

.

The converter works in continuous conduction mode (ΔI_L< I_LIMIT) so based on V_OUT= 13 V, V_d= 0.5 V and

V_IN(max)= 375 V

V_OUT+ V_d

D_MIN

=

= 3.61%

V_IN(max)- V_d

(12)

The maximum allowed switching frequency is 62 kHz because the calculated value exceeds it.

D_MIN

F_{SW _ VIN(max)}

=

= 80kHz >f_SW(max)= 62kHz

t_{ON_ TO}

(13)

The duty cycle does not force the MOSFET on time to go below t_{ON_TO}. If D_MIN/T_{ON_TO}< f_SW(max), the switching

frequency is reduced by current runaway protection and the maximum average switching frequency is lower than

f_SW(max), the converter can't support full load.

The minimum inductance value satisfies both the following conditions:

V_OUT+ V_d

L >

= 1mH

DI_LìF_{SW _ VIN max}

(

)

(14)

(15)

V

IN max

375V

(

)

L >

ì t_{ON_ TO}

=

ì 450ns @ 536mH

I_LIMIT

315mA

In the application example, 1 mH is selected as the minimum standard value that satisfy Equation 14 and

Equation 15.

19

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

9.2.1.2.7 Feedback Path (C_FB, R_FB1and R_FB2) and Load Resistor (R_L)

In low-side buck converter the output voltage is always sensed by the FB pin and UCC28881 internal controller

can turn on the MOSFET on VOUT. In high-side buck converter applications the information on the output

voltage value is stored on C_FBcapacitor. This information is not updated in real time. The information on C_FB

capacitor is updated just after MOSFET turn-off event. When the MOSFET is turned off, the inductor current

forces the freewheeling diode (D1 in Figure 16) to turn on and the GND pin of UCC28881 goes negative at -V_d1

(where V_d1is the forward drop voltage of diode D1) with respect to the negative terminal of bulk capacitor (C1 in

Figure 16). When D1 is on, through diode D4, the C_FBcapacitor is charged at V_OUT– V_d4+ V_d1. Set the output

voltage regulation level using Equation 16.

V_OUT(T)- V_d4+ V_d1- V_{FB _ TH}V_OUT(T)- V_{FB _ TH}

R_FB1

R_FB2

=

@

V_{FB _ TH}

where

•

V_{FB_TH}is the FB pin reference voltage.

V_{OUT_T}is the target output voltage.

R_FB1, R_FB2is the resistance of the resistor divider connected with FB pin (see Figure 16)

The capacitor C_FBafter D1 is discharged with a time constant that is τ_FB= C_FBx (R_FB1+ R_FB2).

Select the time constant τ_FB, given in Equation 17

(16)

(17)

t_FB= C_FBì R_FB1+R_FB2= 0.1ìC ìR

(

)

L

LOAD

In this equation, R_LOADis the full load resistor value.

The time constant selection leads to a slight output-voltage increase in no-load or light-load conditions. In order

to reduce the output-voltage increase, increase τ_FB. The drawback of increasing τ_FBis t in high-load conditions

V_OUTcould drop.

Because of the nature of sample and hold of output voltage feedback, the feedback loop components need some

adjustment after the initial design. The larger time constant of the feedback components leads to lower no-load

switching frequency. As the results, the no-load standby power and light-load voltage regulation are improved.

Because of larger time constant, at heavier load, the load regulation start to get worse. On the contrast,

decreasing the time constant makes the heavy load regulation better but increases the no-load standby power

and makes the light-load voltage regulation worse. Some tradeoff is required to make the regulation and standby

power. Below table summarizes the relationship between the feedback loop time constant and the load

regulation. This can be used for an easy guideline for fine tuning the circuit performance.

Table 3. Feedback Loop Time Constant Adjustment

FEEDBACK LOOP TIME

HEAVY-LOAD OUTPUT

VOLTAGE RIPPLE

NO-LOAD REGULATION

STANDBY POWER

CONSTANT (τ_FB

)

Increase

Better

Worse

Better

Worse

Decrease

20

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

9.2.1.3 Application Curves

Figure 17 shows the output voltage vs output current. Different curves correspond to different converter AC input

voltages. Figure 18 shows efficiency changes vs output power. Different curves correspond to different converter

AC input voltages.

18

16

14

12

10

8

100

90

80

70

60

50

40

30

20

10

0

115V AC

230V AC

6

4

115V AC

230V AC

2

0

0.05

0.1

0.15

0.2

0.25

0

0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7

Output Power (W)

3

Output Current (A)

D001

Figure 17. Output IV Characteristic

Figure 18. Efficiency vs P_OUT

Table 4. Converter Efficiency

V_{IN_AC}(V_RMS

)

LOAD (mA)

EFFICIENCY (%)

AVERAGE EFFICIENCY (%)

115

50

82

81

80

81

100

150

225

50

230

80.8

100

150

225

Table 5. Key Component List for 13-V 225-mA High-Side Buck Converter

DES

DESCRIPTION

Bulk capacitor, 10 μF, 450 V

PART NUMBER

EEUED2W100

MANUFACTURER⁽¹⁾

C1, C2

C_FB

Panasonic

Feedback capacitor, ceramic, 0.015 μF, 50 V

Output capacitor, 330 μF, 35 V

C0805C153K5RACTU

EEU-FM1V331L

STTH1R06A

Kemet

C_L

Panasonic

D1

Buck freewheeling diode, ultrafast, 600 V, 1 A

ST Microelectronics

Fairchild semiconductor

D2, D3

Rectifier diodes, standard recovery rectifier, 1000

V, 1 A

1N4007

D4

Feedback diode, standard recovery rectifier, 600 V, 1N4006-T

1 A

Diodes Inc.

L1

L2

Buck inductor, 1 mH, 0.4 A,

7447471102

Wurth Elektronik

Bourns

Filter inductor, 1 mH, 0.2 A

5800-102-RC

R_FB1

R_FB2

Upper feedback resistor 121 kΩ, 1%

Lower feedback resistor, 10.0 kΩ, 1%

ERJ-6ENF1213V

ERJ-6ENF1002V

Panasonic

(1) See Third-Party Products Discalimer

21

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

9.2.2 Additional UCC28881 Application Topologies

9.2.2.1 Low-Side Buck and LED Driver – Direct Feedback (Level Shifted)

Features include:

•

Output Referenced to Input

Negative Output (V_OUT) with Respect to VIN+

Step Down: V_OUT< V_IN

Direct Level-Shifted Feedback

R_FB1

D1

+

C_L

VOUT

-

Q1

L1

HVIN

+

VIN

-

VDD

FB

DRAIN

UCC28881

GND

R_FB2

Figure 19. Low-Side Buck, Direct Feedback (Level Shifted)

RSENSE

C1

R2

Q2

D1

RFB1

C_L

R1

+

Current Feedback

L1

VIN

-

HVIN

VOUT

VDD

FB

DRAIN

Q1

UCC28881

GND

RFB1

Figure 20. Low-Side Buck LED Driver, Direct Feedback (Level Shifted)

22

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

9.2.2.2 High-Side Buck Converter

Features include:

•

Output Referenced to Input

Positive Output (V_OUT) with Respect to VIN–

Step Down (V_OUT< V_IN)

HVIN

VDD

FB

DRAIN

+

VIN

-

UCC28881

GND

10 ꢀ

D2

C_FB

R_FB2

L1

+

D1

C_L

VOUT

-

Figure 21. High-Side Buck Converter Schematic

9.2.2.3 Non-Isolated, Low-Side Buck-Boost Converter

Features Include:

•

Output Referenced to Input

Positive Output (V_OUT) with Respect to VIN+

Step Up, Step Down: V_OUT> V_INor V_OUT< V_IN

Direct Level-Shifted Feedback

C_L

+

VOUT

-

D1

L1

HVIN

VDD

DRAIN

+

VIN

-

UCC28881

FB

GND

R_FB2

Figure 22. Low-Side Buck-Boost Converter

23

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

9.2.2.4 Non-Isolated, High-Side Buck-Boost Converter

Features include:

•

Output Referenced to Input

Positive Output (V_OUT) with Respect to VIN–

Step Up, Step Down: V_OUT> V_INor V_OUT< V_IN

HVIN

VDD

FB

DRAIN

UCC28881

GND

+

VIN

-

R_FB1

D2

C_FB

R_FB2

+

D1

C_L

VOUT

L1

-

Figure 23. High-Side Buck-Boost Converter

9.2.2.5 Non-Isolated Flyback Converter

Features include:

•

Output Referenced to Input

Positive Output (V_OUT) with Respect VIN–

Direct Feedback

Higher Output Current Capability, 4.5 W for 85 V_AC~ 265 V_ACInput and 6 W for 176 V_AC~ 265 V_ACInput

R_FB1

C_L

HVIN

+

VDD

FB

DRAIN

VOUT

-

VIN

-

UCC28881

GND

C_VDD

R_FB2

Figure 24. Non-Isolated Flyback Configuration

24

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

9.2.2.6 Isolated Flyback Converter

Features include:

•

Output Isolated from Input

Direct Feedback

Higher Output Current Capability, 4.5 W for 85 V_AC~ 265 V_ACInput and 6 W for 176 V_AC~ 265V_ACInput

+

C_L

VOUT

-

HVIN

+

VIN

-

VDD

FB

DRAIN

UCC28881

GND

C_VDD

R_FB

Figure 25. Isolated Flyback Converter

25

UCC28881

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

www.ti.com.cn

10 Power Supply Recommendations

The VDD capacitor recommended value is 100 nF to ensure high-phase margin of the internal 5-V regulator and

it should be placed close to VDD pin and GND pins to minimize the series resistance and inductance.

The VDD pin provides a regulated 5-V output but it is not intended as a supply for external load. Do not supply

VDD pin with external voltage source (for example the auxiliary winding of flyback converter).

Always keep GND pin 1 and GND pin 2 connected together with the shortest possible connection.

11 Layout

11.1 Layout Guidelines

•

In both buck and buck-boost low-side configurations, the copper area of the switching node DRAIN should be

minimized to reduce EMI.

Similarly, the copper area of the FB pin should be minimized to reduce coupling to feedback path. Loop C_L,

Q1, R_FB1should be minimized to reduce coupling to feedback path.

In high-side buck and buck boost the GND, VDD and FB pins are all part of the switching node so the copper

area connected with these pins should be optimized. Large copper area allows better thermal management,

but it causes more common mode EMI noise. Use the minimum copper area that is required to handle the

thermal dissipation.

•

Minimum distance between 700-V coated traces is 1.41 mm (60 mils).

11.2 Layout Example

Figure 26 shows and example PCB layout for UCC28881 in low-side buck configuration.

L2

D2

Rf

C1

C2

AC

INPUT

D3

GND_IC

FB

DRAIN

L1

D1

NC

VDD

HVIN

Rfb1

Rfb2

Q1

= top layer

= bottom layer

= connect top and bot

CL

RL

DC

OUTPUT

Figure 26. UCC28881 Layout Example

26

UCC28881

www.ti.com.cn

ZHCSEL3B –NOVEMBER 2015–REVISED JANUARY 2016

12 器件和文档支持

12.1 器件支持

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Use.

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E2E is a trademark of Texas Instruments.

All other trademarks are the property of their respective owners.

12.4 静电放电警告

这些装置包含有限的内置 ESD 保护。存储或装卸时，应将导线一起截短或将装置放置于导电泡棉中，以防止 MOS 门极遭受静电损

伤。

12.5 Glossary

SLYZ022 — TI Glossary.

This glossary lists and explains terms, acronyms, and definitions.

13 机械、封装和可订购信息

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27

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PACKAGE OUTLINE

D0007A

SOIC - 1.75 mm max height

SCALE 2.800

SMALL OUTLINE INTEGRATED CIRCUIT

C

SEATING PLANE

.228-.244 TYP

[5.80-6.19]

.004 [0.1] C

A

PIN 1 ID AREA

8

1

.100

[2.54]

2X

.189-.197

[4.81-5.00]

NOTE 3

.150

[3.81]

4X .050

[1.27]

4

5

7X .012-.020

[0.31-0.51]

B

.150-.157

[3.81-3.98]

NOTE 4

.069 MAX

[1.75]

.010 [0.25]

C A B

.005-.010 TYP

[0.13-0.25]

SEE DETAIL A

.010

[0.25]

.004-.010

[0.11-0.25]

0 - 8

.016-.050

[0.41-1.27]

DETAIL A

TYPICAL

(.041)

[1.04]

4220728/A 01/2018

NOTES:

1. Linear dimensions are in inches [millimeters]. Dimensions in parenthesis are for reference only. Controlling dimensions are in inches.

Dimensioning and tolerancing per ASME Y14.5M.

2. This drawing is subject to change without notice.

3. This dimension does not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, or gate burrs shall not

exceed .006 [0.15] per side.

4. This dimension does not include interlead flash.

5. Reference JEDEC registration MS-012, variation AA.

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EXAMPLE BOARD LAYOUT

D0007A

SOIC - 1.75 mm max height

SMALL OUTLINE INTEGRATED CIRCUIT

7X (.061 )

[1.55]

SYMM

SEE

DETAILS

1

8

7X (.024)

[0.6]

(.100 )

[2.54]

SYMM

5

4

4X (.050 )

[1.27]

(.213)

[5.4]

LAND PATTERN EXAMPLE

EXPOSED METAL SHOWN

SCALE:8X

SOLDER MASK

OPENING

SOLDER MASK

OPENING

METAL UNDER

SOLDER MASK

METAL

EXPOSED

METAL

EXPOSED

METAL

.0028 MAX

[0.07]

ALL AROUND

.0028 MIN

[0.07]

ALL AROUND

SOLDER MASK

DEFINED

NON SOLDER MASK

DEFINED

SOLDER MASK DETAILS

4220728/A 01/2018

NOTES: (continued)

6. Publication IPC-7351 may have alternate designs.

7. Solder mask tolerances between and around signal pads can vary based on board fabrication site.

www.ti.com

EXAMPLE STENCIL DESIGN

D0007A

SOIC - 1.75 mm max height

SMALL OUTLINE INTEGRATED CIRCUIT

7X (.061 )

[1.55]

SYMM

1

8

7X (.024)

[0.6]

(.100 )

[2.54]

SYMM

5

4

4X (.050 )

[1.27]

(.213)

[5.4]

SOLDER PASTE EXAMPLE

BASED ON .005 INCH [0.125 MM] THICK STENCIL

SCALE:8X

4220728/A 01/2018

NOTES: (continued)

8. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate

design recommendations.

9. Board assembly site may have different recommendations for stencil design.

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产品导航

产品型号UCC28880DR的概述

产品型号UCC28881的Datasheet PDF文件预览

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