UC2845AN各脚功能电路原理芯片引脚定义引脚图及功能IC贸易商-中国IC网-芯三七

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产品型号UC2845AN的概述

UC2845AN 芯片概述 UC2845AN是一款专用于电源管理的集成电路，广泛应用于开关电源以及各种电源转换器中。作为一种高性能的PWM（脉冲宽度调制）控制器，UC2845AN特别设计用于离线与高频DC-DC转换。该芯片能够实现对输出电压和电流的精准控制，使其在众多领域中成为一种理想的选择。 UC2845AN的技术规格使得其在高能效、紧凑尺寸和低成本方面展现出卓越的性能，极具市场竞争力。在许多高要求应用中，UC2845AN以其高频响应能力和精确的控制能力获得了广泛的认可。芯片 UC2845AN 详细参数 UC2845AN的主要参数包括： 1. 输入电压范围：4.5V~40V 2. 工作温度范围：-40℃至 +85℃ 3. 最大输出电流：1A 4. 频率范围：100kHz至500kHz 5. 输出极性：推挽输出 6. 价格：通常在$1.50到$5.00不等，取决于销售渠道和数量。 ...

产品型号UC2845AN的Datasheet PDF文件预览

UC284XA

UC384XA

HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER

NOT FOR NEW DESIGN

FEATURES

Figure 1. Package

■ TRIMMED OSCILLATOR DISCHARGE

CURRENT

■ CURRENT MODE OPERATION TO 500kHz

AUTOMATIC FEED FORWARD

COMPENSATION

DIP-8

SO-8

■ LATCHING PWM FOR CYCLE-BY-CYCLE

CURRENT LIMITING

■ INTERNALLY TRIMMED REFERENCE WITH

UNDERVOLTAGE LOCKOUT

■ HIGH CURRENT TOTEM POLE OUTPUT

UNDERVOLTAGE LOCKOUT WITH

HYSTERESIS

■ LOW START-UP CURRENT (< 0.5mA)

DOUBLE PULSE SUPPRESSION

Table 1. Order Codes

Part Number

Package

UC2842AD1; UC3842AD1;

UC2843AD1; UC3843AD1;

UC2844AD1; UC3844AD1;

UC2845AD1; UC3845AD1

SO-8

DIP-8

UC2842AN; UC3842AN;

UC2843AN; UC3843AN;

UC2844AN; UC3844AN;

UC2845AN; UC3845AN

DESCRIPTION

The UC384xA family of control ICs provides the

necessary features to implement off-line or DC to

DC fixed frequency current mode control schemes

with a minimal external parts count. Internally im-

plemented circuits include a trimmed oscillator for

precise DUTY CYCLE CONTROL under voltage

lockout featuring start-up current less than 0.5mA,

a precision reference trimmed for accuracy at the

error amp input, logic to insure latched operation,

a PWM comparator which also provides current

limit control, and a totem pole output stage de-

signed to source or sink high peak current. The

output stage, suitable for driving N-Channel MOS-

FETs, is low in the off-state.

Differences between members of this family are

the under-voltage lockout thresholds and maxi-

mum duty cycle ranges. The UC3842A and

UC3844A have UVLO thresholds of 16V (on) and

10V (off), ideally suited off-line applications The

corresponding thresholds for the UC3843A and

UC3845A are 8.5 V and 7.9V. The UC3842A and

UC3843A can operate to duty cycles approaching

100%. A range of the zero to < 50 % is obtained by

the UC3844A and UC3845A by the addition of an

internal toggle flip flop which blanks the output off

every other clock cycle.

Figure 2. Block Diagram (toggle flip flop used only in UC3844A and UC3845A)

UVLO

34V

REF

VREF

5V 50mA

S/R

GROUND

INTERNAL

BIAS

2.50V

VREF GOOD

LOGIC

OUTPUT

RT/CT

OSC

ERROR AMP.

VFB

PWM

LATCH

COMP

CURRENT

SENSE

CURRENT

SENSE

COMPARATOR

D95IN331

REV. 5

1/16

May 2004

UC384XA - UC284XA

Table 2. Absolute Maximum Ratings

Symbol

Parameter

Value

Unit

V_i

Supply Voltage (low impedance source)

Supply Voltage (Ii < 30mA)

Self Limiting

±1

I_O

Output Current

µJ

E_O

Output Energy (capacitive load)

Analog Inputs (pins 2, 3)

– 0.3 to 5.5

Error Amplifier Output Sink Current

Power Dissipation at T_amb≤ 25 °C (DIP-8)

Power Dissipation at T_amb≤ 25 °C (SO-8)

Storage Temperature Range

P_tot

T_stg

T_J

1.25

800

°C

– 65 to 150

– 40 to 150

300

Junction Operating Temperature

Lead Temperature (soldering 10s)

T_L

* All voltages are with respect to pin 5, all currents are positive into the specified terminal.

Figure 3. DIP-8/SO-8 Pin Connection (Top view)

COMP

V_FB

V_REF

I_SENSE

R_T/C_T

OUTPUT

GROUND

D95IN332

Table 3. Pin Description

N°

COMP

V_FB

Function

This pin is the Error Amplifier output and is made available for loop compensation.

This is the inverting input of the Error Amplifier. It is normally connected to the switching power

supply output through a resistor divider.

I_SENSE

A voltage proportional to inductor current is connected to this input. The PWM uses this

information to terminate the output switch conduction.

R_T/C_T

The oscillator frequency and maximum Output duty cycle are programmed by connecting

resistor R_Tto V_refand cpacitor C_Tto ground. Operation to 500kHz is possible.

GROUND This pin is the combined control circuitry and power ground.

OUTPUT This output directly drives the gate of a power MOSFET. Peak currents up to 1A are sourced

and sunk by this pin.

V_CC

V_ref

This pin is the positive supply of the control IC.

This is the reference output. It provides charging current for capacitor C_Tthrough resistor R_T.

2/16

UC384XA - UC284XA

Table 4. Thermal Data

Symbol

Parameter

DIP-8

SO-8

Unit

R_{th j-amb}

Thermal Resistance Junction-ambient

Max.

100

150

°C/W

Table 5. Electrical Characteristcs

( [note 1] Unless otherwise stated, these specifications apply for -25 < T_amb< 85°C for UC284XA;

0 < T_amb< 70°C for UC384XA; V_i= 15V (note 5); R_T= 10K; C_T= 3.3nF)

UC284XA

UC384XA

Symbol

Parameter

Test Condition

Unit

Min. Typ. Max. Min. Typ. Max.

REFERENCE SECTION

V_REF

∆V_REF

Output Voltage

T_j= 25°C I_o= 1mA

12V ≤ V_i≤ 25V

1 ≤ I_o≤ 20mA

4.95 5.00 5.05 4.90 5.00 5.10

mV/°C

Line Regulation

Load Regulation

∆V_REF/∆

Temperature Stability

Total Output Variation

Output Noise Voltage

(Note 2)

0.2

Line, Load, Temperature

4.9

5.1 4.82

5.18

e_N

10Hz ≤ f ≤ 10KHz

T_j= 25°C (note 2)

µV

Long Term Stability

amb = 125°C, 1000Hrs

(note 2)

Output Short Circuit

-30 -100 -180 -30 -100 -180 mA

ISC

OSCILLATOR SECTION

f_OSCFrequency

f_OSC

V_REF

V_OSC

I_dischg

T_j= 25°C

–

0.2

–

0.2

KHz

∆

Frequency Change with Volt. V_CC= 12V to 25V

Frequency Change with Temp. T_A= T_lowto T_high

∆

–

Oscillator Voltage Swing

Discharge Current (V_OSC=2V)

(peak to peak)

T_J= 25°C

–

1.6

8.3

–

1.6

8.3

–

7.8

8.8

7.8

8.8

ERROR AMP SECTION

V₂

I_b

Input Voltage

V_PIN1= 2.5V

V_FB= 5V

2.45 2.50 2.55 2.42 2.50 2.58

µA

Input Bias Current

A_VOL

-0.1

-1

-0.1

-2

2V ≤ V_o≤ 4V

T_J= 25°C

0.7

Unity Gain Bandwidth

MHz

PSRR Power Supply Rejec. Ratio 12V ≤ V_i≤ 25V

I_o

Output Sink Current

V_PIN2= 2.7V

_PIN1= 1.1V

I_o

Output Source Current

V_OUTHigh

V_PIN2= 2.3V V_PIN1= 5V

-0.5

-1

-0.5

-1

V_PIN2= 2.3V;R_L= 15KΩ to

6.2

Ground

V_OUTLow

V_PIN2= 2.7V;R_L= 15KΩ to

0.8

1.1

0.8

1.1

Pin 8

CURRENT SENSE SECTION

G_V

V₃

Gain

(note 3 & 4)

2.85

0.9

3.15 2.85

3.15 V/V

Maximum Input Signal

Supply Voltage Rejection

Input Bias Current

Delay to Output

V_PIN1= 5V (note 3)

12 ≤ V_i≤ 25V (note 3)

1.1

0.9

1.1

SVR

I_b

-2

µA

-10

150 300

3/16

UC384XA - UC284XA

Table 5. Electrical Characteristcs (continued)

( [note 1] Unless otherwise stated, these specifications apply for -25 < T_amb< 85°C for UC284XA;

0 < T_amb< 70°C for UC384XA; V_i= 15V (note 5); R_T= 10K; C_T= 3.3nF)

UC284XA

UC384XA

Symbol

Parameter

Test Condition

Unit

Min. Typ. Max. Min. Typ. Max.

OUTPUT SECTION

V_OLOutput Low Level

I_SINK= 20mA

0.1

1.6

0.4

2.2

0.1

1.6

0.4

2.2

I_SINK= 200mA

V_OH

Output High Level

I_SOURCE= 20mA

13.5

0.7

13.5

0.7

I_SOURCE= 200mA

V_OLS

t_r

UVLO Saturation

Rise Time

V_CC= 6V; I

_SINK= 1mA

1.2

T_j= 25°C

C_L= 1nF ⁽²⁾

150

t_f

Fall Time

T_j= 25°C

150

C_L= 1nF ⁽²⁾

UNDER-VOLTAGE LOCKOUT SECTION

Start Threshold

X842A/4A

7.8

8.4

9.0

14.5

7.8

8.4

17.5

9.0

X843A/5A

X842A/4A

Min Operating Voltage

After Turn-on

8.5

11.5

PWM SECTION

Maximum Duty Cycle

X842A/3A

X844A/5A

100

Minimum Duty Cycle

TOTAL STANDBY CURRENT

I_st

Start-up Current

V_i= 6.5V for UCX843A/

45A

0.3

0.5

0.3

0.5

V_i= 14V for UCX842A/44A

V_PIN2= V_PIN3= 0V

I_i= 25mA

0.3

0.5

0.3

0.5

I_i

Operating Supply Current

Zener Voltage

V_iz

Notes: 1. Max package power dissipation limits must be respected; low duty cycle pulse techniques are used during test maintain T_jas close

to T_ambas possible.

2. These parameters, although guaranteed, are not 100% tested in production.

3. Parameter measured at trip point of latch with V_PIN2= 0.

4. Gain defined as : A = ∆V_PIN1/∆V_PIN3; 0 ≤ V_PIN3≤ 0.8V

5. Adjust V_iabove the start threshold before setting at 15 V.

4/16

UC384XA - UC284XA

Figure 4. Open Loop Test Circuit.

V_REF

4.7KΩ

R_T

2N2222

V_i

V_REF

0.1µF

100KΩ

COMP

V_FB

V_i

ERROR AMP.

ADJUST

1KΩ

0.1µF

I_SENSE

R_T/C_T

I_SENSE

4.7KΩ

OUTPUT

GROUND

ADJUST

5KΩ

OUTPUT

GROUND

C_T

D95IN343

High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and

bypass capacitors should be connected close to pin 5 in a single point ground. The transistor and 5 KΩ

potentiometer are used to sample the oscillator waveform and apply an adjustable ramp to pin 3.

Figure 5. Oscillator Frequency vs Timing

Resistance

Figure 7. Oscillator Discharge Current vs.

Temperature.

D95IN335

dischg

D96IN362

(Hz)

(mA)

V =15V

=2V

OSC

8.5

8.0

7.5

7.0

100K

10K

-55 -25

75 100 T (˚C)

300

10K

30K

R (Ω)

Figure 6. Maximum Duty Cycle vs Timing

Resistor

Figure 8. Error Amp Open-Loop Gain and

Phase vs. Frequency.

D95IN337

D96IN363

(dB)

(Hz)

V =15V

V =2V to 4V

R =100K

Gain

T =25˚C

Phase

120

150

180

-20

100

10K 100K 1M f(Hz)

300

10K

30K

R (Ω)

5/16

UC384XA - UC284XA

Figure 9. Current Sense Input Threshold vs.

Error Amp Output Voltage.

Figure 12. Output Saturation Voltage vs. Load

Current.

(V)

D95IN338

(V)

sat

D95IN341

Source Saturation

(Load to Ground)

V =15V

-1

-2

1.0

T =25˚C

T =-40˚C

T =25˚C

V =15V

0.8

0.6

0.4

0.2

0.0

80µs Pulsed Load 120Hz Rate

T =125˚C

T =-40˚C

T =25˚C

T =-40˚C

Sink Saturation

(Load to V )

GND

V (V)

200

400

600

I (mA)

Figure 10. Reference Voltage Change vs.

Source Current..

Figure 13. Supply Current vs. Supply Voltage.

D95IN339

D95IN342

(mA)

V =15V

T =-40˚C

T =125˚C

R =10K

C =3.3nF

V =0V

=0V

Sense

T =25˚C

100 I (mA)

ref

V (V)

Figure 11. Reference Short Circuit Current vs.

Temperature..

D95IN340

(mA)

V =15V

R ≤0.1Ω

100

-55 -25

75 100 T (˚C)

6/16

UC384XA - UC284XA

Figure 14. Output Waveform.

Figure 15. Output Cross Conduction

Figure 16. Oscillator and Output Waveforms.

V_i

5V REG

OUTPUT

PWM

R_T

OUTPUT

LARGE R_T/SMALL C_T

CLOCK

OSCILLATOR

I_D

C_T

OUTPUT

SMALL R_T/LARGE C_T

GND

D95IN344

Figure 17. Error Amp Configuration.

2.5V

1mA

V_FB

Z_i

COMP

Z_f

D95IN345

7/16

UC384XA - UC284XA

Figure 18. Under Voltage Lockout.

ON/OFF COMMAND

TO REST OF IC

V_i

I_CC

<17mA

<0.5mA

UC3842A UC3843A

UC3844A UC3845A

V_ON

16V

10V

8.4V

7.6V

V_CC

V_OFFV_ON

V_OFF

D95IN346mod

Figure 19. Current Sense Circuit.

ERROR

AMPL.

I_S

COMP

CURRENT

SENSE

COMPARATOR

CURRENT

SENSE

R_S

GND

D95IN347

Peak current (i_s) is determined by the formula

1.0V

------------

≈

Smax

A small RC filter may be required to suppress switch transients.

Figure 20. Slope Compensation Techniques.

V_REG

R_T

R_T/C_T

I_S

R_SLOPE

R₁

C_T

I_SENSE

C_T

I_SENSE

R_SLOPE

R₁

R_S

GND

D95IN348

8/16

UC384XA - UC284XA

Figure 21. Isolated MOSFET Drive and Current Transformer Sensing.

V_CC

V_in

ISOLATION

BOUNDARY

5.0V

ref

V_GSWaveforms

50% DC

25% DC

N_S

V_{(pin 1)}-1.4

I_pk

( )

3R_S

N_P

COMP/LATCH

R_S

N_S

N_P

D95IN349

Figure 22. Latched Shutdown.

OSC

BIAS

1mA

3905

3903

D95IN350

SCR must be selected for a holding current of less than 0.5mA at T_A(min)

The simple two transistor circuit can be used in place of the SCR as shown. All resistors are 10K.

9/16

UC384XA - UC284XA

Figure 23. Error Amplifier Compensation

From V_O

R_i

2.5V

1mA

R_dC_f

R_f

Error Amp compensation circuit for stabilizing any current-mode topology except

for boost and flyback converters operating with continuous inductor current.

From V_O

R_P

2.5V

1mA

R_i

C_P

R_d

C_f

R_f

D95IN351

Error Amp compensation circuit for stabilizing current-mode boost and flyback

topologies operating with continuous inductor current.

Figure 24. External Clock Synchronization.

V_REF

BIAS

OSC

R_T

C_T

EXTERNAL

SYNC INPUT

0.01µF

47Ω

D95IN352

The diode clamp is required if the Sync amplitude is large enough to cause

the bottom side of C_Tto go more than 300mV below ground

10/16

UC384XA - UC284XA

Figure 25. External Duty Cycle Clamp and Multi Unit Synchronization.

V_REF

R_A

R_B

BIAS

OSC

NE555

TO ADDITIONAL

UCX84XAs

1.44

(R_A+ 2R_B)C

R_B

R_A+ 2R_B

f =

D_max

D95IN353

Figure 26. Soft-Start Circuit

5V_ref

BIAS

OSC

1mA

1MΩ

D95IN354

11/16

UC384XA - UC284XA

Figure 27. Soft-Start and Error Amplifier Output Duty Cycle Clamp.

V_CCV_in

5V_ref

BIAS

OSC

1mA

V_Clamp

Comp/Latch

R_S

BC109

R₁

V_CLAMP

R_S

V_CLAMP= ·

where 0 <V_CLAMP<1V

I_pk(max)

D95IN355

R₁+ R₂

12/16

UC384XA - UC284XA

Figure 28. SO-8 Mechanical Data & Package Dimensions

inch

DIM.

OUTLINE AND

MECHANICAL DATA

MIN. TYP. MAX. MIN.

TYP. MAX.

0.069

1.35

0.10

1.10

0.33

0.19

4.80

1.75 0.053

0.25 0.004

1.65 0.043

0.51 0.013

0.25 0.007

5.00 0.189

0.010

0.065

0.020

0.010

(1)

0.197

3.80

4.00

0.15

0.157

0.050

1.27

5.80

0.25

0.40

6.20 0.228

0.50 0.010

1.27 0.016

0˚ (min.), 8˚ (max.)

0.10

0.244

0.020

0.050

ddd

0.004

Note: (1) Dimensions D does not include mold flash, protru-

sions or gate burrs.

SO-8

Mold flash, potrusions or gate burrs shall not exceed

0.15mm (.006inch) in total (both side).

0016023 C

13/16

UC384XA - UC284XA

Figure 29. DIP-8 Mechanical Data & Package Dimensions

inch

DIM.

OUTLINE AND

MECHANICAL DATA

MIN.

TYP. MAX. MIN.

3.32

TYP. MAX.

0.131

0.51

1.15

0.020

1.65 0.045

0.55 0.014

0.304 0.008

10.92

0.065

0.022

0.356

0.204

0.012

0.430

7.95

9.75 0.313

2.54

0.384

0.100

7.62

0.300

7.62

0.300

6.6

0.260

5.08

0.200

3.18

3.81 0.125

1.52

0.150

DIP-8

0.060

14/16

UC384XA - UC284XA

Table 6. Revision History

Date

Revision

Description of Changes

March 1999

May 2004

First Issue in EDOCS

NOT FOR NEW DESIGN

15/16

UC384XA - UC284XA

Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences

of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted

by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject

to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not

authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.

The ST logo is a registered trademark of STMicroelectronics.

All other names are the property of their respective owners

STMicroelectronics GROUP OF COMPANIES

Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan -

Malaysia - Malta - Morocco - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States

www.st.com

16/16

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UC2845AN产品参数

型号:	UC2845AN
是否无铅：	不含铅
生命周期：	Active
IHS 制造商：	ROCHESTER ELECTRONICS INC
零件包装代码：	DIP
包装说明：	DIP,
针数：	8
Reach Compliance Code：	unknown
风险等级：	5.08
Is Samacsys：	N
模拟集成电路 - 其他类型：	SWITCHING CONTROLLER
控制模式：	CURRENT-MODE
控制技术：	PULSE WIDTH MODULATION
最大输入电压：	25 V
最小输入电压：	8.2 V
标称输入电压：	15 V
JESD-30 代码：	R-PDIP-T8
JESD-609代码：	e4
长度：	9.81 mm
湿度敏感等级：	1
功能数量：	1
端子数量：	8
最高工作温度：	85 °C
最低工作温度：	-40 °C
最大输出电流：	1 A
封装主体材料：	PLASTIC/EPOXY
封装代码：	DIP
封装形状：	RECTANGULAR
封装形式：	IN-LINE
峰值回流温度（摄氏度）：	260
座面最大高度：	5.08 mm
表面贴装：	NO
切换器配置：	SINGLE
最大切换频率：	500 kHz
温度等级：	INDUSTRIAL
端子面层：	NICKEL PALLADIUM GOLD
端子形式：	THROUGH-HOLE
端子节距：	2.54 mm
端子位置：	DUAL
处于峰值回流温度下的最长时间：	NOT SPECIFIED
宽度：	7.62 mm
Base Number Matches：	1

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