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产品型号EL7551CU的概述

芯片EL7551CU的概述芯片EL7551CU是一款专为显示器和影像处理设计的高性能驱动器。该芯片通过其高度集成的设计，兼具多种功能，广泛应用于各类显示器驱动、图像处理及视频应用。EL7551CU的设计旨在满足现代显示技术对高分辨率、高清晰度和高动态范围的需求。芯片的核心功能包括电流控制、亮度调节及色彩管理等，它可以通过各种信号接口与其他设备进行连接，以实现最佳的工作性能。EL7551CU的高效率和低功耗特性使其在诸如LED显示屏、LCD显示器、液晶电视及其他视觉传达设备中备受青睐。芯片EL7551CU的详细参数 EL7551CU具有诸多重要的电气参数，其关键特性包括： 1. 工作电压范围：2.7V至5.5V，适用于多种供电情况。 2. 工作温度范围：-40°C至85°C，使其在极端环境下也能稳定工作。 3. 输出电流：最大可达100mA，支持高亮度显示需求。 4. 像素时钟频率...

产品型号EL7551CU的Datasheet PDF文件预览

EL7551C - Preliminary

Monolithic 1 Amp DC:DC Step-down Regulator

Features

General Description

• Integrated synchronous MOSFETs

and current mode controller

• 1A continuous output current

• Up to 95% efficiency

• 4.5V to 5.5V input voltage

• Adjustable output from 1V to 3.8V

• Cycle-by-cycle current limit

• Precision reference

• ±0.5% load and line regulation

• Adjustable switching frequency to

1MHz

• Oscillator synchronization

possible

• Internal soft start

The EL7551C is an integrated, synchronous step-down regulator with

output voltage adjustable from 1.0V to 3.8V. It is capable of delivering

1A continuous current at up to 95% efficiency. The EL7551C operates

at a constant frequency pulse width modulation (PWM) mode, making

external synchronization possible. Patented on-chip resistorless cur-

rent sensing enables current mode control, which provides cycle-by-

cycle current limiting, over-current protection, and excellent step load

response. The EL7551C is available in a fused-lead 16-pin QSOP

package. With proper external components, the whole converter fits

into a less than 0.4 in²area. The minimal external components and

small size make this EL7551C ideal for desktop and portable

applications.

The EL7551C is specified for operation over the -40°C to +85°C tem-

perature range.

• Over temperature protection

• Under voltage lockout

• 16-pin QSOP package

Applications

Typical Application Diagram

• DSP, CPU Core and IO Supplies

• Logic/Bus Supplies

• Portable Equipment

• DC:DC Converter Modules

• GTL + Bus Power Supply

SGND

COSC

VDD

PGND

VIN

PGND 16

VREF 15

FB 14

0.1µF 270pF

Ordering Information

0.1µF

Part No

Package

Tape & Reel

Outline #

39W

2.37k

EL7551CU

16-Pin QSOP

MDP0040

1kW

VDRV 13

LX 12

10µH

(3.3V,

1A)

10µF

ceramic

47µF

LX 11

0.1µF

VIN

VHI 10

(4.5V-

5.5V)

PGND 9

EL7551C

Manufactured under U.S. Patent No. 57,323,974

Note: All information contained in this data sheet has been carefully checked and is believed to be accurate as of the date of publication; however, this data sheet cannot be a “controlled document”. Current revisions, if any, to these

specifications are maintained at the factory and are available upon your request. We recommend checking the revision level before finalization of your design documentation.

EL7551C - Preliminary

Monolithic 1 Amp DC:DC Step-down Regulator

Absolute Maximum Ratings (T = 25°C)

Supply Voltage between V_INor V_DDand GND

+6.5V

Storage Temperature

-65°C to +150°C

-40°C to +85°C

+135°C

V_LXVoltage

Input Voltage

V_HIVoltage

V_IN+0.3V

Operating Ambient Temperature

Operating Junction Temperature

GND -0.3V, V_DD+0.3V

GND -0.3V, V_LX+6V

Important Note:

All parameters having Min/Max specifications are guaranteed. Typ values are for information purposes only. Unless otherwise noted, all tests are at the

specified temperature and are pulsed tests, therefore: T_J= T_C= T_A.

DC Characteristics

V_DD= V_IN= 5V, T_A= T_J= 25°C, C_OSC= 1.2nF, unless otherwise specified.

Parameter

V_REF

Description

Reference Accuracy

Conditions

Min

Typ

1.26

Max

Unit

1.24

1.28

V_REFTC

Reference Temperature Coefficient

Reference Load Regulation

Oscillator Ramp Amplitude

Oscillator Charge Current

ppm/°C

V_REFLOAD

V_RAMP

I_{OSC_CHG}

I_{OSC_DIS}

0 < I_REF< 50µA

-1

1.15

200

0.1V < V_OSC< 1.25V

V_EN= 4V, F_OSC= 120kHz

EN = 0

µA

Oscillator Discharge Current

I_VDD+V_DRVV_DD+V_DRVSupply Current

3.5

1.5

I_{VDD_OFF}

V_{DD_OFF}

V_{DD_ON}

T_OT

V_DDStandby Current

V_DDfor Shutdown

3.5

V_DDfor Startup

3.95

4.45

Over Temperature Threshold

Over Temperature Hysteresis

Internal FET Leakage Current

Peak Current Limit

135

°C

T_HYS

°C

I_LEAK

EN = 0, L_X= 5V (low FET), L_X= 0V (high FET)

Wafer level test only

µA

I_LMAX

R_DSON

R_DSONTC

V_FB

FET On Resistance

0.2

mW/°C

R_DSONTempco

Output Initial Accuracy

Output Line Regulation

Output Load Regulation

Output Temperature Stability

Feedback Input Pull Up Current

EN Input High Level

I_LOAD= 0A

0.960

0.975

0.5

0.99

V_{FB_LINE}

V_{FB_LOAD}

V_{FB_TC}

I_FB

V_IN= 5V, DV_IN= 10%, I_LOAD= 0A

0.1A < I_LOAD< 1A

0.5

-40°C < T_A< 85°C, I_LOAD= 0.5A

V_FB= 0V

±1

100

3.2

200

V_{EN_HI}

V_{EN_LO}

I_EN

EN Input Low Level

Enable Pull Up Current

V_EN= 0

-4

-2.5

µA

Closed Loop AC Electrical Characteristics

V_S= V_IN= 5V, T_A= T_J= 25°C, C_OSC= 1.2nF, unless otherwise specified.

Parameter Description

F_OSCOscillator Initial Accuracy

t_SYNC

M_SS

t_BRM

t_LEB

Conditions

Min

Typ

117

Max

Unit

kHz

105

130

Minimum Oscillator Sync Width

Soft Start Slope

0.5

V/ms

FET Break Before Make Delay

High Side FET Minimum On Time

Maximum Duty Cycle

150

D_MAX

EL7551C - Preliminary

Monolithic 1 Amp DC:DC Step-down Regulator

Pin Descriptions

Pin Number

Pin Name

SGND

COSC

VDD

PGND

VIN

Pin Function

Control circuit negative supply.

Oscillator timing capacitor. FOSC can be approximated by: FOSC (kHz) = 0.1843/COSC, COSC in µF.

Control circuit positive supply.

Ground return of the regulator. Connected to the source of the low-side synchronous NMOS power FET.

Power supply input of the regulator. Connected to the drain of the high-side NMOS power FET.

Chip Enable, active high. A 2µA internal pull-up current enables the device if the pin is left open.

Ground return of the regulator.

VIN

PGND

VHI

Positive supply of the high-side driver.

Inductor drive pin. High current digital output whose average voltage equals the regulator output voltage.

Positive supply of the low-side driver and input voltage for the high-side boot strap.

VDRV

Voltage feedback input. Connected to an external resistor divider between VOUT and GND. A 125nA pull-up current

forces VOUT to VS in the event that FB is floating.

VREF

PGND

Bandgap reference bypass capacitor. Typically 0.1µF to GND.

Ground return of the regulator.

EL7551C - Preliminary

Monolithic 1 Amp DC:DC Step-down Regulator

Typical Performance Curves

Efficiency vs I

Power Loss vs I

=5V

V =5V

100

0.25

0.2

0.15

0.1

0.05

V =2.5V

V =1.8V

V =1.5V

V =1.2V

V =1V

V =3.3V

F =500kHz

V =1V

L=Coilcraft DO3316P-472

0.1

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

Load Current I (A)

Output Current I (A)

Efficiency vs I

V =3.3V

Load Regulation

V =3.3V

100

0.6

0.4

0.2

=4.5V

=5.5V

=5V

=5.5V

V =4.5V

-0.2

-0.4

-0.6

F =500kHz

L=Coilcraft DO3316P-472

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

Load Current I (A)

Line Regulation

V =3.3V

REF

vs Temperature

0.6

0.5

0.4

0.3

0.2

0.1

1.258

1.256

1.254

1.252

1.25

I =0.1A

I =1A

1.248

1.246

1.244

1.242

-0.1

-0.2

-0.3

-0.4

4.5

4.7

4.9

5.1

5.3

5.5

-40

110

160

(V)

Temperature (°C)

EL7551C - Preliminary

Monolithic 1 Amp DC:DC Step-down Regulator

Typical Performance Curves

Oscillator Frequency vs Temperature

Input Current vs Temperature

(Enable connected to GND)

0.96

390

=5.5V

0.94

0.92

0.9

385

380

375

370

365

360

=5V

V =4.5V

0.88

0.86

0.84

0.82

0.8

-40

120

-40

Temperature (°C)

110

160

Temperature (°C)

Switching Waveforms

=5V, V =3.8V, I =1A

Switching Frequency vs C

OSC

1400

1200

1000

800

600

400

200

400

600

(pF)

800

1000

OSC

Transient Response

=5V, V =3.8V, I =0A-1A

Power-Up

V =5V, V =3.8V, I =1A

EL7551C - Preliminary

Monolithic 1 Amp DC:DC Step-down Regulator

Typical Performance Curves

Power-Down

Releasing EN

V =5V, V =3.8V, I =1A

=5V, V =3.8V, I =1A

Shut-Down

=5V, V =3.8V, I =1A

Short-Circuit Protection

V =5V

EL7551C - Preliminary

Monolithic 1 Amp DC:DC Step-down Regulator

Block Diagram

0.1µF

270pF

VREF

COSC

Voltage

Reference

Thermal

Shut-down

VDRV

Oscillator

Controller

Supply

VHI

VIN

39W

VDD

Power

FET

0.1µF

10µH

0.1µF

PWM

Controller

Drivers

OUT

Power

FET

2370W

1kW

47µF

PGND

Current

Sense

SGND

EL7551C - Preliminary

Monolithic 1 Amp DC:DC Step-down Regulator

Applications Information

Circuit Description

General

ited by the output LC filter and can react more quickly to

changes in line and load conditions. This feed-forward

characteristic also simplifies AC loop compensation

since it adds a zero to the overall loop response. Through

proper selection of the current-feedback to voltage-feed-

back ratio the overall loop response will approach a one-

pole system. The resulting system offers several advan-

tages over traditional voltage control systems, including

simpler loop compensation, pulse by pulse current limit-

ing, rapid response to line variation and good load step

response.

The EL7551C is a fixed frequency, current mode con-

trolled DC:DC converter with integrated N-channel

power MOSFETs and a high precision reference. The

device incorporates all the active circuitry required to

implement a cost effective, user-programmable 1A syn-

chronous step-down regulator suitable for use in DSP

core power supplies.

Theory of Operation

The heart of the controller is an input direct summing

comparator which sum voltage feedback, current feed-

back, slope compensation ramp and power tracking

signals together. Slope compensation is required to pre-

vent system instability that occurs in current-mode

topologies operating at duty-cycles greater than 50%

and is also used to define the open-loop gain of the over-

all system. The slope compensation is fixed internally

and optimized for 500mA inductor ripple current. The

power tracking will not contribute any input to the com-

parator steady-state operation. Current feedback is

measured by the patented sensing scheme that senses the

inductor current flowing through the high-side switch

whenever it is conducting. At the beginning of each

oscillator period the high-side NMOS switch is turned

on. The comparator inputs are gated off for a minimum

period of time of about 150ns (LEB) after the high-side

switch is turned on to allow the system to settle. The

Leading Edge Blanking (LEB) period prevents the

detection of erroneous voltages at the comparator inputs

due to switching noise. If the inductor current exceeds

the maximum current limit (ILMAX) a secondary over-

current comparator will terminate the high-side switch

on time. If ILMAX has not been reached, the feedback

voltage FB derived from the regulator output voltage

VOUT is then compared to the internal feedback refer-

ence voltage. The resultant error voltage is summed with

the current feedback and slope compensation ramp. The

high-side switch remains on until all four comparator

inputs have summed to zero, at which time the high-side

switch is turned off and the low-side switch is turned on.

However, the maximum on-duty ratio of the high-side

switch is limited to 95%. In order to eliminate cross-con-

The EL7551C is composed of 5 major blocks:

1. PWM Controller

2. NMOS Power FETs and Drive Circuitry

3. Bandgap Reference

4. Oscillator

5. Thermal Shut-down

PWM Controller

The EL7551C regulates output voltage through the use

of current-mode controlled pulse width modulation. The

three main elements in a PWM controller are the feed-

back loop and reference, a pulse width modulator whose

duty cycle is controlled by the feedback error signal, and

a filter which averages the logic level modulator output.

In a step-down (buck) converter, the feedback loop

forces the time-averaged output of the modulator to

equal the desired output voltage. Unlike pure voltage-

mode control systems, current-mode control utilizes

dual feedback loops to provide both output voltage and

inductor current information to the controller. The volt-

age loop minimizes DC and transient errors in the output

voltage by adjusting the PWM duty-cycle in response to

changes in line or load conditions. Since the output volt-

age is equal to the time-averaged of the modulator

output, the relatively large LC time constant found in

power supply applications generally results in low band-

width and poor transient response. By directly

monitoring changes in inductor current via a series sense

resistor the controller's response time is not entirely lim-

EL7551C - Preliminary

Monolithic 1 Amp DC:DC Step-down Regulator

duction of the high-side and low-side switches a 15ns

break-before-make delay is incorporated in the switch

drive circuitry. The output enable (EN) input allows the

regulator output to be disabled by an external logic con-

trol signal.

Oscillator

The system clock is generated by an internal relaxation

oscillator with a maximum duty-cycle of approximately

95%. Operating frequency can be adjusted through the

COSC pin or can be driven by an external source. If the

oscillator is driven by an external source care must be

taken in selecting the ramp amplitude. Since CSLOPE

value is derived from the COSC ramp, changes to COSC

ramp will change the CSLOPE compensation ramp

which determine the open-loop gain of the system.

Output Voltage Setting

In general:

------

= 0.975V ´ 1 +

OUT

When external synchronization is required, always

choose C_OSCsuch that the free-running frequency is at

least 20% lower than that of sync source to accommo-

date component and temperature variations. Figure 1

shows a typical connection.

However, due to the relatively low open loop gain of the

system, gain errors will occur as the output voltage and

loop-gain is changed. This is shown in the performance

curves. A 100nA pull-up current from FB to VDD forces

VOUT to GND in the event that FB is floating.

NMOS Power FETs and Drive Circuitry

The EL7551C integrates low on-resistance (60mW)

NMOS FETs to achieve high efficiency at 1A. In order

to use an NMOS switch for the high-side drive it is nec-

essary to drive the gate voltage above the source voltage

(LX). This is accomplished by bootstrapping the VHI

pin above the LX voltage with an external capacitor

CVHI and internal switch and diode. When the low-side

switch is turned on and the LX voltage is close to GND

potential, capacitor CVHI is charged through internal

switch to VDRV, typically 5V. At the beginning of the

next cycle the high-side switch turns on and the LX pins

begin to rise from GND to VIN potential. As the LX pin

rises the positive plate of capacitor CVHI follows and

eventually reaches a value of VDRV+VIN, typically

10V, for VDRV=VIN=5V. This voltage is then level

shifted and used to drive the gate of the high-side FET,

via the VHI pin. A value of 0.1µF for CVHI is

recommended.

100pF

BAT54S

External

Oscillator

EL7551C

Figure 1. Oscillator Synchronization

Thermal Shut-down

An internal temperature sensor continuously monitors

die temperature. In the event that die temperature

exceeds the thermal trip-point, the system is in fault state

and will be shut down. The upper and low trip-points are

set to 135°C and 115°C respectively.

Reference

A 1.5% temperature compensated bandgap reference is

integrated in the EL7551C. The external VREF capaci-

tor acts as the dominant pole of the amplifier and can be

increased in size to maximize transient noise rejection.

A value of 0.1µF is recommended.

EL7551C - Preliminary

Monolithic 1 Amp DC:DC Step-down Regulator

Start-up Delay

A capacitor can be added to the EN pin to delay the con-

verter start-up (Figure 2) by utilizing the pull-up current.

The delay time is approximately:

t (ms) = 1200 ´ C(mF)

OUT

TIME

EL7551C

Figure 2. Start-up Delay

In addition, the bypass capacitor connected to the VDD

pin needs to be as close to the pin as possible.

Layout Considerations

The layout is very important for the converter to func-

tion properly. Power Ground ( ) and Signal Ground (---)

should be separated to ensure that the high pulse current

in the Power Ground never interferes with the sensitive

signals connected to Signal Ground. They should only

be connected at one point (normally at the negative side

of either the input or output capacitor.)

The heat of the chip is mainly dissipated through the

PGND pins. Maximizing the copper area around these

pins is preferable. In addition, a solid ground plane is

always helpful for the EMI performance.

The demo board is a good example of layout based on

these principles. Please refer to the EL7551C Applica-

tion Brief for the layout.

The trace connected to pin 14 (FB) is the most sensitive

trace. It needs to be as short as possible and in a “quiet”

place, preferably between PGND or SGND traces.

EL7551C - Preliminary

Monolithic 1 Amp DC:DC Step-down Regulator

General Disclaimer

Specifications contained in this data sheet are in effect as of the publication date shown. Elantec, Inc. reserves the right to make changes in the cir-

cuitry or specifications contained herein at any time without notice. Elantec, Inc. assumes no responsibility for the use of any circuits described

herein and makes no representations that they are free from patent infringement.

WARNING - Life Support Policy

Elantec, Inc. products are not authorized for and should not be used

within Life Support Systems without the specific written consent of

Elantec, Inc. Life Support systems are equipment intended to sup-

port or sustain life and whose failure to perform when properly used

in accordance with instructions provided can be reasonably

Elantec Semiconductor, Inc.

675 Trade Zone Blvd.

Milpitas, CA 95035

Telephone: (408) 945-1323

(888) ELANTEC

expected to result in significant personal injury or death. Users con-

templating application of Elantec, Inc. Products in Life Support

Systems are requested to contact Elantec, Inc. factory headquarters

to establish suitable terms & conditions for these applications. Elan-

tec, Inc.’s warranty is limited to replacement of defective

components and does not cover injury to persons or property or

other consequential damages.

Fax:

(408) 945-9305

European Office: +44-118-977-6020

Japan Technical Center: +81-45-682-5820

Printed in U.S.A.

EL7551CU相关文章

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EL7551CU产品参数

型号:	EL7551CU
是否Rohs认证：	不符合
生命周期：	Obsolete
零件包装代码：	SOIC
包装说明：	QSOP-16
针数：	16
Reach Compliance Code：	not_compliant
ECCN代码：	EAR99
HTS代码：	8542.39.00.01
风险等级：	5.61
Is Samacsys：	N
模拟集成电路 - 其他类型：	SWITCHING REGULATOR
控制模式：	CURRENT-MODE
控制技术：	PULSE WIDTH MODULATION
最大输入电压：	5.5 V
最小输入电压：	4.5 V
标称输入电压：	5 V
JESD-30 代码：	R-PDSO-G16
功能数量：	1
端子数量：	16
最高工作温度：	85 °C
最低工作温度：	-40 °C
最大输出电流：	2 A
封装主体材料：	PLASTIC/EPOXY
封装形状：	RECTANGULAR
封装形式：	SMALL OUTLINE
认证状态：	Not Qualified
表面贴装：	YES
切换器配置：	BUCK
最大切换频率：	1200 kHz
温度等级：	INDUSTRIAL
端子形式：	GULL WING
端子位置：	DUAL
Base Number Matches：	1

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产品型号EL7551CU的概述

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