MAXIM MAX8550, MAX8551 Technical data

19-3173; Rev 2; 9/04

భᄋ৙ຶৰۇ
భᄋ৙ຶৰۇ

专为台式机、笔记本和图形卡提供的

DDQ

0.7V

概述

的同步

V

TTR

的输出，

的连

1.5A

内存

DDR

的

________________________________

MAX8550/MAX8551
buck PWM

收能力的

10mA

道

MOSFET

控制器、一个用于产生

LDO

基准输出缓冲器。

，可从2V至
输出电流可高达
续电流及3A峰值电流。
均能跟踪

REFIN

非常适合于台式机、笔记本电脑及图形卡中的

集成了一个用于产生

V

V

的具有供出及吸

TT

线性稳压器以及一个用于产生

控制器驱动两个外部N沟

Buck

的输入产生最低

28V

15A。LDO

电压。这些特性使得

可吸收或供出高达

输出及

LDO

10mA
MAX8550/MAX8551

基准缓冲输出

应用。

MAX8550/MAX8551

TM

Quick-PWM

架构，具有高达

中的

PWM

控制器采用

600kHz

的可编程开关频率。

Maxim

专有的

这种控制方案易于处理宽范围的输入/输出电压比，并具
有
定的开关频率。

的负载瞬变响应，同时还能保持高效率及相对恒

100ns

MAX8550

提供完全可编程的

UVP/OVP

及
跳跃模式选项，非常适合于便携式设备应用。跳跃模式
在较轻负载下可提供高效率。

MAX8551

的目标应用为台

式机及图形卡，不具有跳脉冲功能。

VTT及VTTR

输出能够以1%的精度跟踪

V

REFIN

/2。LDO

调节器的高带宽可提供优异的瞬态响应，无需使用大容
量电容，因此可减少尺寸及成本。

Buck

视低边

控制器与

MOSFET

稳压器具有独立的电流限制。通过监

LDO

的漏－源压降，实现了

Buck

调节器的可
调节、无损耗、折返式电流限制。此外，器件还内置有
过/欠压保护机制。一旦过流故障排除，调节器即可重新
进入软启动，这有利于减少短路时的功耗。通过

SHDNA、SHDNB及STBY

输入，

MAX8550/MAX8551

允

许灵活的排序及待机功率管理。

MAX8550及MAX8551

脚薄型

QFN

封装。

均备有细小的

5mm x 5mm、28

________________________________

DDR I及DDR II

存储器电源

引

应用

台式计算机

笔记本电脑及台式笔记本电脑

图形卡

游戏控制台

RAID

网络

集成式

DDR

电源方案

____________________________________________

控制器

Buck

♦ 100ns
♦
♦ 2V至28V
♦ 1.8V/2.5V
♦
♦
♦ 1.7ms
♦过/
♦ Power-Good

LDO

♦
♦ VTT
♦ VTT与VTTR
♦
♦ 1.0V至2.8V
♦ Power-Good

____________________________

MAX8550ETI -40°C to +85°C 28 5mm × 5mm TQFN
MAX8550ETI+ -40°C to +85°C 28 5mm × 5mm TQFN
MAX8551ETI -40°C to +85°C 28 5mm × 5mm TQFN

表示无铅封装。

+

____________________________

负载阶跃响应的

高达

95%

的效率

Quick-PWM

输入电压范围

最高

固定或

600kHz

0.7V至5.5V

的可选开关频率

可调输出

折返式可编程电流限制

数字软启动及独立的关断控制

欠压保护选项

窗口比较器

单元

完全集成的

具有

±3A

VTT及VTTR

的供出/吸收能力

输出跟踪

功能

V

REFIN

/ 2

全陶瓷输出电容设计

输入电压范围

窗口比较器

PART TEMP RANGE PIN-PACKAGE

TOP VIEW

TON

OVP/UVP

(N.C. FOR

MAX8551)

REF

ILIM

POK1

POK2

STBY

1

2

3

4

5

6

7

DD

AV

SKIP

26

MAX8550
MAX8551

10

VTTR

AX8551)

(TP1 FOR

M

25

11

PGND2

GND

24

12

VTT

SHDNB

SHDNA

28

27

8

9

SS

VTTS

5mm x 5mm Thin QFN

PGND1

23

13

VTTI

DD

V

22

14

REFIN

定购信息

引脚配置

DL

21

20

BST

19

LX

18

DH

17

V

IN

16

OUT

FB

15

特性

MAX8550/MAX8551

________________________________________________________________ Maxim Integrated Products 1

本文是

正式英文资料的译文，

Maxim

不对翻译中存在的差异或由此产生的错误负责。请注意译文中可能存在文字组织或

Maxim

翻译错误，如需确认任何词语的准确性，请参考

索取免费样品和最新版的数据资料，请访问

Maxim

Maxim

典型工作电路见本数据手册末尾。

Quick-PWM是Maxim Integrated Products, Inc.

提供的英文版资料。

的主页：

www.maxim-ic.com.cn

的商标。

。

PARAMETER

CONDITIONS

MAIN PWM CONTROLLER

V

IN

228

Input Voltage Range

4.5 5.5

V

Output Adjust Range V

OUT

0.7 5.5 V

FB = OUT

0.7

FB = GND

2.5

Output Voltage Accuracy
(Note 2)

FB = V

DD

1.8

V

Soft-Start Ramp Time t

SS

Rising edge of SHDNA to full current limit 1.7 ms

TON = GND (600kHz)

219

TON = REF (450kHz)

273

389

On-Time t

ON

VIN = 15V,
V

OUT

= 1.5V

(Note 3)

571

ns

Minimum Off-Time

(Note 3)

450 ns

VIN Quiescent Supply Current I

IN

25 40 µA

VIN Shutdown Supply Current SHDNA = SHDNB = GND 1 5 µA

All on (PWM, VTT, and VTTR on) 2.5 5
SHDNA = GND (only VTT and VTTR on) 2 4

STBY = AVDD (only VTTR and PWM on) 1 2

AVDD Quiescent Supply Current I

AVDD

SHDNB = GND (only PWM on) 0.5 1

mA

AVDD + VDD Shutdown Supply
Current

SHDNA = SHDNB = GND 2 10 µA

Rising edge of V

IN

4.1

4.4 V

AVDD Undervoltage-Lockout
Threshold

Hysteresis 50 mV

VDD Quiescent Supply Current I

VDD

Set VFB = 0.8V 1 5 µA

专为台式机、笔记本和图形卡提供的
集成式

DDR

电源方案

ABSOLUTE MAXIMUM RATINGS

VINto GND .............................................................-0.3V to +30V

V

DD, AVDD

SHDNA, SHDNB, REFIN to GND..............................-0.3V to +6V

SS, POK1, POK2, SKIP, ILIM, FB to GND ................-0.3V to +6V

STBY, TON, REF, UVP/OVP to GND ........-0.3V to (AV

OUT, VTTR to GND ..................................-0.3V to (AV

DL to PGND1..............................................-0.3V to (V

DH to LX....................................................-0.3V to (V

LX to BST..................................................................-6V to +0.3V

LX to GND .................................................................-2V to +30V

VTT to GND...............................................-0.3V to (V

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

, VTTI to GND .........................................-0.3V to +6V

+ 0.3V)

DD

+ 0.3V)

DD

+ 0.3V)

DD

+ 0.3V)

BST

+ 0.3V)

VTTI

VTTS to GND............................................-0.3V to (AV

PGND1, PGND2 to GND .......................................-0.3V to +0.3V

REF Short Circuit to GND ...........................................Continuous

Continuous Power Dissipation (T

28-Pin 5mm x 5mm TQFN (derate 35.7mW/°C

above +70°C).................................................................2.86W

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +165°C

Lead Temperature (soldering, 10s) .................................+300°C

= +70°C)

A

DD

MAX8550/MAX8551

ELECTRICAL CHARACTERISTICS

(VIN= +15V, VDD= AVDD= V
= GND, PGND1 = PGND2 = LX = GND, TON = OPEN, V
are at T

= +25°C.) (Note 1)

A

SHDNA

= V

SHDNB

SYMBOL

= V

BST

= V

ILIM

VTTS

= 5V, V

= V

VTT

= V

OUT

, TA= -40°C to +85°C, unless otherwise noted. Typical values

REFIN

= V

= 2.5V, UVP/OVP = STBY = FB = SKIP

VTTI

MIN TYP MAX UNITS

+ 0.3V)

VDD, AV

2 _______________________________________________________________________________________

t

OFF_MIN

DD

0.693

2.47

1.78

TON = OPEN (300kHz) 316 352

TON = AVDD (200kHz) 461 516

170 194

213 243

200 300

4.25

0.707

2.53

1.82

专为台式机、笔记本和图形卡提供的

集成式

DDR

电源方案

ELECTRICAL CHARACTERISTICS (continued)

(VIN= +15V, VDD= AVDD= V
= GND, PGND1 = PGND2 = LX = GND, TON = OPEN, V
are at T

REFERENCE

Reference Voltage V

Reference Load Regulation I

REF Undervoltage Lockout

FAULT DETECTION

OVP Trip Threshold
(Referred to Nominal V

UVP Trip Threshold
(Referred to Nominal V

POK1 Trip Threshold
(Referred to Nominal V

POK2 Trip Threshold
(Referred to Nominal V
and V

UVP Blanking Time From rising edge of SHDNA 10 20 40 ms

OVP, UVP, POK_ Propagation
Delay

POK_ Output Low Voltage I

POK_ Leakage Current V

ILIM Adjustment Range V

ILIM Input Leakage Current 0.1 µA

Current-Limit Threshold (Fixed)
PGND1 to LX

Current-Limit Threshold
(Adjustable) PGND1 to LX

Current-Limit Threshold (Negative
Direction) PGND1 to LX

Current-Limit Threshold (Negative
Direction) PGND1 to LX

Zero-Crossing Detection
Threshold PGND1 to LX

Thermal-Shutdown Threshold +160 °C

Thermal-Shutdown Hysteresis 15 °C

= +25°C.) (Note 1)

A

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

)

OUT

)

OUT

)

OUT

VTTS

VTTR

)

SHDNA

= V

SHDNB

REF

ILIM

= V

= V

BST

AVDD = 4.5V to 5.5V; I

= 0 to 50µA 0.01 V

REF

V

rising 1.93 V

REF

Hysteresis 300 mV

UVP/OVP = AVDD (Note 4) 112 116 120 %

Lower level, falling edge, 1% hysteresis 87 90 93

Upper level, rising edge, 1% hysteresis 107 110 113

Lower level, falling edge, 1% hysteresis 87.5 90 92.5

Upper level, rising edge, 1% hysteresis 107.5 110 112.5

OVP not applicable in MAX8551 10 µs

= 4mA 0.3 V

SINK

= 5.5V, VFB = 0.8V, V

POK_

= 2V 170 200 235 mV

V

ILIM

SKIP = AV

SKIP = AV

= 5V, V

ILIM

= V

VTTS

VTT

(Note 4) -75 -60 -45 mV

DD

, V

DD

ILIM

= V

OUT

, TA= -40°C to +85°C, unless otherwise noted. Typical values

= 0 1.98 2 2.02 V

REF

= 2V (Note 4) -250 mV

= V

REFIN

= 1.3V 1 µA

VTTS

= 2.5V, UVP/OVP = STBY = FB = SKIP

VTTI

65 70 75 %

0.25 2.00 V

45 50 55 mV

3mV

MAX8550/MAX8551

%

%

_______________________________________________________________________________________ 3

专为台式机、笔记本和图形卡提供的
集成式

DDR

电源方案

ELECTRICAL CHARACTERISTICS (continued)

(VIN= +15V, VDD= AVDD= V
= GND, PGND1 = PGND2 = LX = GND, TON = OPEN, V
are at T

MOSFET DRIVERS

DH Gate-Driver On-Resistance V

DL Gate-Driver On-Resistance in
High State

DL Gate-Driver On-Resistance in
Low State

Dead Time (Additional to
Adaptive Delay)

INPUTS AND OUTPUTS

MAX8550/MAX8551

Logic Input Threshold
(SHDN_, STBY, SKIP (Note 4))

Logic Input Current
(SHDN_, STBY, SKIP (Note 4))

Dual-Mode™ Input Logic
Levels (FB)

Input Bias Current (FB) -0.1 +0.1 µA

Four-Level Input Logic Levels
(TON, OVP/UVP (Note 4))

Logic Input Current
(TON, OVP/UVP (Note 4))

OUT Discharge-Mode
On-Resistance

DL Turn-On Level During
Discharge Mode
(Measured at OUT)

Dual Mode is a trademark of Maxim Integrated Products, Inc.

= +25°C.) (Note 1)

A

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SHDNA

= V

SHDNB

= V

= V

BST

- VLX = 5V 1 4 Ω

BST

DH falling to DL rising 30

DL falling to DH rising 30

Rising edge 1.20 1.7 2.20 V

Hysteresis 225 mV

Low (2.5V output) 0.05

High (1.8V output) 2.1

High

Floating 3.15 3.85

REF 1.65 2.35

Low 0.5

FB = GND 90 175 350

FB = AV

FB adjustable mode 400 800 1600

(Note 4) 10 25 Ω

(Note 4) 0.3 V

ILIM

VTTS

DD

= 5V, V

= V

VTT

= V

OUT

, TA= -40°C to +85°C, unless otherwise noted. Typical values

REFIN

= V

= 2.5V, UVP/OVP = STBY = FB = SKIP

VTTI

14Ω

0.5 3 Ω

-1 +1 µA

AV

-

DD

0.4

-3 +3 µA

70 135 270OUT Input Resistance

ns

V

V

kΩ

4 _______________________________________________________________________________________

专为台式机、笔记本和图形卡提供的

PARAMETER

CONDITIONS

UNITS

LINEAR REGULATORS (VTTR AND VTT)

VTTI Input Voltage Range V

VTTI

1 2.8 V

VTTI Supply Current I

VTTI

I

VTT

= I

VTTR

= 0

1mA

VTTI Shutdown Current SHDNA = SHDNB = GND 10 µA

REFIN Input Impedance V

REFIN

= 2.5V 12 20 30 kΩ

REFIN Range V

REFIN

1

V

V

REFIN

rising 0.7 0.9 V

REFIN Lockout Threshold

Hysteresis 75 mV

Soft-Start Charge Current I

SS

VSS = 0 4 µA

VTT Internal MOSFET High-Side
On-Resistance

I

VTT

= -100mA, V

VTTI

= 1.5V,

AV

DD

= 4.5V

0.3 Ω

VTT Internal MOSFET Low-Side
On-Resistance

I

VTT

= 100mA, AVDD = 4.5V 0.3 Ω

VTT Output Accuracy
(Referred to V

REFIN

/ 2)

V

REFIN

= 1.5V or 2.5V, I

VTT

= 1mA -1 +1 %

V

REFIN

= 2.5V, I

VTT

= 0 to ±1.5A 1

VTT Load Regulation

V

REFIN

= 1.5V, I

VTT

= 0 to ±1A 1

%

VTT Current Limit VTT = 0 or VTTI ±3 ±5

A

VTTS Input Current I

VTTS

V

VTTS

= 1.5V, VTT open

1µA

VTTR Output Error
(Referred to V

REFIN

/ 2)

V

REFIN

= 1.5V or 2.5V, I

VTTR

= 0 -1 +1 %

VTTR Current Limit V

VTTR

= 0 or V

VTTI

mA

ELECTRICAL CHARACTERISTICS (continued)

(VIN= +15V, VDD= AVDD= V
= GND, PGND1 = PGND2 = LX = GND, TON = OPEN, V
are at T

= +25°C.) (Note 1)

A

SHDNA

= V

SHDNB

SYMBOL

= V

BST

= V

ILIM

VTTS

= 5V, V

= V

VTT

集成式

= V

OUT

, TA= -40°C to +85°C, unless otherwise noted. Typical values

REFIN

= V

VTTI

DDR

= 2.5V, UVP/OVP = STBY = FB = SKIP

MIN TYP MAX

电源方案

<0.1

2.8

MAX8550/MAX8551

0.1

Note 1: Specifications to -40°C are guaranteed by design, not production tested.
Note 2: When the inductor is in continuous conduction, the output voltage has a DC regulation level higher than the error-compara-

tor threshold by 50% of the ripple. In discontinuous conduction, the output voltage has a DC regulation level higher than the

Note 3: On-time and off-time specifications are measured from 50% point to 50% point at the DH pin with LX = GND, V

Note 4: Not applicable to the MAX8551.

trip level by approximately 1.5% due to slope compensation.

and a 250pF capacitor connected from DH to LX. Actual in-circuit times may differ due to MOSFET switching speeds.

_______________________________________________________________________________________ 5

±23 ±40 ±60

±6.5

BST

= 5V,

专为台式机、笔记本和图形卡提供的

EFFICIENCY vs. LOAD CURRENT

(TON = GND)

MAX8550/51 toc01

I

LOAD

(A)

EFFICIENCY (%)

1010.1

60

70

80

90

100

50

10

20

30

40

0

0.01 100

fSW = 600kHz

V

OUT

= 2.5V

V

OUT

= 1.8V

V

OUT

= 1.5V

SKIP = GND

SKIP = AV

DD

EFFICIENCY vs. LOAD CURRENT

(TON = OPEN)

MAX8550/51 toc02

I

LOAD

(A)

EFFICIENCY (%)

1010.1

10

20

30

40

50

60

70

80

90

100

0

0.01 100

fSW = 300kHz

V

OUT

= 2.5V

V

OUT

= 1.8V

V

OUT

= 1.5V

SKIP = GND

SKIP = AV

DD

SWITCHING FREQUENCY vs. LOAD CURRENT

(TON = GND)

MAX8550/51 toc03

I

LOAD

(A)

FREQUENCY (kHz)

11108 92 3 4 5 6 71

50

100

150

200

250

300

350

400

450

500

550

600

650

700

0

012

SKIP = GND

SKIP = AV

DD

SWITCHING FREQUENCY vs. INPUT VOLTAGE

(TON = GND)

MAX8550/51 toc04

VIN (V)

FREQUENCY (kHz)

262420 228 10 12 14 16 186

420

440

460

480

500

540

520

560

580

600

620

640

660

680

700

400

428

I

LOAD

= 12A

I

LOAD

= 0A

SWITCHING FREQUENCY vs. TEMPERATURE

(TON = GND)

MAX8550/51 toc05

TEMPERATURE (°C)

FREQUENCY (kHz)

80655035205-10-25

650

660

670

680

690

700

600

640

630

620

610

-40

I

LOAD

= 12A

OUTPUT VOLTAGE

vs. LOAD CURRENT

MAX8550/51 toc06

I

LOAD

(A)

V

OUT

(V)

12106 842

2.495

2.500

2.505

2.510

2.515

2.520

2.525

2.530

2.535

2.540

2.490
014

VIN = 15V,
TON = GND

SKIP = GND

SKIP = AV

DD

VTT VOLTAGE

vs. VTT CURRENT

MAX8550/51 toc07

I

VTT

(A)

V

VTT

(V)

21-2 -1 0

1.21

1.22

1.23

1.24

1.25

1.26

1.27

1.28

1.20

-3 3

VTTR VOLTAGE

vs. VTTR CURRENT

MAX8550/51 toc08

I

VTTR

(mA)

V

VTTR

(V)

105-10 -5 0

1.21

1.22

1.23

1.24

1.25

1.26

1.27

1.28

1.20

-15 15

LINE REGULATION

(V

OUT

vs. VIN)

MAX8550/51 toc09

VIN (V)

V

OUT

(

V

)

262420 228 10 12 14 16 186

2.46

2.47

2.48

2.49

2.50

2.51

2.52

2.53

2.54

2.55

2.45
428

I

LOAD

= 0A

I

LOAD

= 12A

集成式

DDR

电源方案

_______________________________________________________________

(V

VIN

= 12V, V

= 2.5V, TON = GND, SKIP = AVDD, circuit of Figure 8, TA= +25°C, unless otherwise noted.)

OUT

MAX8550/MAX8551

典型工作特性

6 _______________________________________________________________________________________

专为台式机、笔记本和图形卡提供的

V

DDQ

STARTUP AND SHUTDOWN INTO

LIGHT LOAD, DISCHARGE ENABLED

MAX8550/51 toc16

2ms/div

V

OUT

1V/div

VTT
1V/div

SHDNA + SHDNB
5V/div

POK1
5V/div

0V

0V

0V

0V

R

LOAD

= 10Ω,

R

VTT

= 20Ω

VTT, VTTR STARTUP AND SHUTDOWN

MAX8550/51 toc17

200µs/div

VTT
1V/div

VTTR
1V/div

SHDNB
5V/div

POK2
5V/div

0V

0V

0V

0V

I

VTT

= 1.5A, I

VTTR

= 15mA

集成式

____________________________________________________________

(V

12A

0.1A

= 12V, V

VIN

LOAD TRANSIENT (BUCK)

I

= 1.5A, I

VTT

POWER-UP WAVEFORMS

VDD = 5V, I

LOAD

0V

0V

0V

0V

= 2.5V, TON = GND, SKIP = AVDD, circuit of Figure 8, TA= +25°C, unless otherwise noted.)

OUT

VTTR

= 12A, I

= 15mA

20µs/div

VTT

200µs/div

= 1.5A, I

MAX8550/51 toc10

MAX8550/51 toc13

= 15mA

VTTR

V

OUT

100mV/div

VTT
100mV/div

VTTR
100mV/div

I

LOAD

10A/div

OUT
1V/div

VTT
2V/div

VTTR
1V/div

V

IN

10V/div

LOAD TRANSIENT VTT (-1.5A TO +1.5A)

I

= 12A, I

LOAD

0A

VTTR

= 15mA

40µs/div

POWER-DOWN WAVEFORMS

VDD = 5V, I

0V

0V

0V

0V

LOAD

= 12A, I

200µs/div

VTT

= 1.5A, I

MAX8550/51 toc11

MAX8550/51 toc14

VTTR

= 15mA

V

OUT

50mV/div

VTT
50mV/div

VTTR
50mV/div

I

VTT

2A/div

OUT
1V/div

VTT
2V/div

VTTR
1V/div

V

IN

10V/div

LOAD TRANSIENT VTT (-3A TO +3A)

I

LOAD

0A

V

DDQ

HEAVY LOAD, DISCHARGE DISABLED

I

LOAD

= 1.5A

I

VTT

0V

0V

0V

0V

= 12A, I

STARTUP AND SHUTDOWN INTO

= 12A,

DDR

电源方案

典型工作特性(续

VTTR

= 15mA

40µs/div

1ms/div

MAX8550/51 toc12

MAX8550/51 toc15

)

V

OUT

50mV/div

VTT
50mV/div

VTTR
50mV/div

I

VTT

5A/div

V

OUT

2V/div

VTT
1V/div

POK1
5V/div

SHDNA + SHDNB
5V/div

MAX8550/MAX8551

_______________________________________________________________________________________ 7

专为台式机、笔记本和图形卡提供的

SHORT CIRCUIT AND

RECOVERY OF V

DDQ

MAX8550/51 toc19

400µs/div

V

OUT

2V/div

I

LOAD

10A/div

V

IN

10V/div

I

IN

2A/div

0A

0V

0A

0V

UVP DISABLED, FOLDBACK CURRENT LIMIT

SHORT CIRCUIT AND

RECOVERY OF V

DDQ

MAX8550/51 toc20

400µs/div

V

OUT

2V/div

I

LOAD

10A/div

V

IN

10V/div

I

IN

2A/div

0A

0V

0A

0V

UVP ENABLED

SHORT CIRCUIT OF VTT

MAX8550/51 toc21

400µs/div

VTT
1V/div

I

VTT

5A/div

0A

0V

集成式

DDR

电源方案

____________________________________________________________

(V

VIN

MAX8550/MAX8551

= 12V, V

= 2.5V, TON = GND, SKIP = AVDD, circuit of Figure 8, TA= +25°C, unless otherwise noted.)

OUT

OVERVOLTAGE AND TURN-OFF

OF BUCK OUTPUT

0A

0V

0V

0V

20µs/div

MAX8550/51 toc18

I

L

25A/div

V

OUT

2V/div

DH
20V/div

DL
5V/div

典型工作特性(续

)

8 _______________________________________________________________________________________

专为台式机、笔记本和图形卡提供的

集成式

DDR

电源方案

___________________________________________________________________

引脚

1TON

2

3REF

名称

OVP/

UVP

(MAX8550)

N.C.

(MAX8551)

导通时间选择控制输入。这个四电平逻辑输入设置额定DH导通时间。连接至
接

来选择以下额定开关频率：

TON
TON = AV
TON = OPEN (300kHz)
TON = REF (450kHz)
TON = GND (600kHz)

过/欠压保护控制输入。这个四电平逻辑输入启用或禁用过压和/或欠压保护。过压极限为额定输出电压的

。欠压极限为额定输出电压的

116%

脚可启用所需功能：

OVP/UVP = AV
OVP/UVP = OPEN (启用OVP
OVP/UVP = REF (禁用OVP
OVP/UVP = GND (禁用OVP

不连接，保持开路

+2.0V

置

ILIM

(200kHz)

DD

(启用OVP

DD

*

基准电压输出。用一个

电压。当

SHDNA、SHDNB及STBY

。启用

70%

及放电模式，启用
及放电模式，禁用

及放电模式，启用

及放电模式，禁用

0.1µF (最小)

功能

OVP

UVP)
UVP)

UVP)

UVP)

电容旁路至

为低时，

的同时启用放电模式。将

GND。REF

REF

可为外部负载提供

关断。

GND、REF、AV

OVP/UVP

引脚连接至以下引

电流。可用来设

50µA

引脚说明

或不连

DD

MAX8550/MAX8551

4 ILIM

5POK1

6POK2

7STBY

8SS

9 VTTS

10 VTTR

* MAX8551

不具有

OVP

用于调整
一个电阻分压器，通常从

0.25V至2V

Buck Power-Good

低。当输出达到稳定且软启动过程结束时，

LDO Power-Good

2) 10%时，POK2
POK2

待机。连接至高电位时进入低静态模式，
效。在此模式下，

VTT与VTTR

使SS开路可禁用软启动。当

终端电源输出检测引脚。一般与
分压器连接可将

终端参考电压。

或放电模式，仅具有

调节器的谷值限流阀值。

buck

电压范围。连接

漏极开路输出。当

漏极开路输出。在正常模式下，当

为低。

为低。在待机模式下，

POK2仅从VTTR

软启动控制。从SS至地连接一个电容

调整至比

VTT

VTTR跟踪V

功能。

UVP

REF至GND

ILIM至AV

SHDNB

VTT

REFIN

/ 2

REFIN

PGND与LX

，可将限流阀值设置在

可选择

DD

输出电压高于或低于正常调整点

buck

POK2

VTT

上引入输入。

为低时SS放电至地。参见

引脚连接来精确调整至
一半的电压更高的电压。

。

两端的限流阀值为

默认限流阀值。参见

50mV

为高阻抗。关断时

POK1

VTTR或VTTS

只响应

VTTR

输出被禁用，但如果

输出根据

PWM

典型应用电路

(

上电压的

ILIM

25mV至200mV

高于或低于正常调整点(通常为

输入。关断以及当

SHDNB

SHDNA

中的C9，参见

、

POR

电压的一半。与从

REFIN

之间。这对应于

设置电流限

、或当软启动时，

10%

为低。

POK1

V

REFIN

为高，则

的状态可为开通或关断。

软启动电容选择

及软启动

UVLO

倍。连接

0.1
ILIM

部分。

低于

0.8V

缓冲器保持有

VTTR

部分。

VTT至GND

ILIM

上的

POK1

REFIN /

时，

部分)。

的电阻

至

为

_______________________________________________________________________________________ 9