Maxim Integrated MAX8632 Schematic

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General Description

The MAX8632 integrates a synchronous-buck PWM con­troller to generate V

DDQ

, a sourcing and sinking LDO lin­ear regulator to generate VTT, and a 10mA reference
output buffer to generate V

TTR

. The buck controller drives
two external n-channel MOSFETs to generate output volt­ages down to 0.7V from a 2V to 28V input with output cur­rents up to 15A. The LDO can sink or source up to 1.5A
continuous and 3A peak current. Both the LDO output
and the 10mA reference buffer output can be made to
track the REFIN voltage. These features make the
MAX8632 ideally suited for DDR memory applications in
desktops, notebooks, and graphic cards.

The PWM controller in the MAX8632 utilizes Maxim’s
proprietary Quick-PWM™ architecture with programma­ble switching frequencies of up to 600kHz. This control
scheme handles wide input/output voltage ratios with
ease and provides 100ns response to load transients
while maintaining high efficiency and a relatively con­stant switching frequency. The MAX8632 offers fully pro­grammable UVP/OVP and skip-mode options ideal in
portable applications. Skip mode allows for improved
efficiency at lighter loads.

The VTT and VTTR outputs track to within 1% of V

REFIN

/ 2.
The high bandwidth of this LDO regulator allows excel­lent transient response without the need for bulk capac­itors, thus reducing cost and size.

The buck controller and LDO regulators are provided with
independent current limits. Adjustable lossless foldback
current limit for the buck regulator is achieved by monitor­ing the drain-to-source voltage drop of the low-side
MOSFET. Additionally, overvoltage and undervoltage pro­tection mechanisms are built in. Once the overcurrent
condition is removed, the regulator is allowed to enter
soft-start again. This helps minimize power dissipation
during a short-circuit condition. The MAX8632 allows flex­ible sequencing and standby power management using
the SHDN and STBY inputs, which support all DDR
operating states.

The MAX8632 is available in a small 5mm × 5mm, 28­pin thin QFN package.

Applications

DDR I and DDR II Memory Power Supplies
Desktop Computers
Notebooks and Desknotes
Graphic Cards
Game Consoles
RAID
Networking

Features

Buck Controller

♦ Quick-PWM with 100ns Load-Step Response
♦ Up to 95% Efficiency
♦ 2V to 28V Input Voltage Range
♦ 1.8V/2.5V Fixed or 0.7V to 5.5V Adjustable Output
♦ Up to 600kHz Selectable Switching Frequency
♦ Programmable Current Limit with Foldback

Capability

♦ 1.7ms Digital Soft-Start
♦ Independent Shutdown and Standby Controls
♦ Overvoltage-/Undervoltage-Protection Option
♦ Power-Good Window Comparator

LDO Section

♦ Fully Integrated VTT and VTTR Capability
♦ VTT Has ±3A Sourcing/Sinking Capability
♦ Only 20µF Ceramic Capacitance Required for VTT
♦ VTT and VTTR Outputs Track V

REFIN

/ 2

♦ All-Ceramic Output-Capacitor Designs
♦ 1.0V to 2.8V Input Voltage Range
♦ Power-Good Window Comparator

MAX8632

Integrated DDR Power-Supply Solution

for Desktops, Notebooks, and Graphic Cards

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

Pin Configuration

19-3623; Rev 0; 3/05

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Typical Operating Circuit appears at end of data sheet.

EVALUATION KIT

AVAILABLE

Quick-PWM is a trademark of Maxim Integrated Products, Inc.

+Denotes lead-free packaging.

PART TEMP RANGE PIN-PACKAGE

MAX8632ETI+ -40°C to +85°C 28 Thin QFN 5mm × 5mm

IN

V

BST

OVP/UVP

DH

LX

MAX8632

REF

ILIM

POK1

OUT

POK2

FB

STBY

14

REFIN

VTTI

13

12

VTT

11

PGND2

10

VTTR

9

VTTS

8

SS

TOP VIEW

V

DD

PGND1

GND

SKIP

AV

DD

SHDN

TPO

DL

21 20 19 18 17 16 15

22

23

24

25

26

27

28

1234567

TON

5mm x 5mm THIN QFN

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PARAMETER

CONDITIONS

UNITS

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 SHDN 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 SHDN = GND 1 5 µA

All on (PWM, VTT, and VTTR on) 2.5 5

AVDD Quiescent Supply Current I

AVDD

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

mA

AVDD + VDD Shutdown Supply
Current

SHDN = GND 20 µA

Rising edge of V

IN

V

AVDD Undervoltage-Lockout
Threshold

Hysteresis 50 mV

VDD Quiescent Supply Current I

VDD

Set VFB = 0.8V 1 5 µA

MAX8632

Integrated DDR Power-Supply Solution for
Desktops, Notebooks, and Graphic Cards

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= +15V, VDD= AVDD= V

SHDN

= STBY = V

BST

= V

ILIM

= 5V, V

OUT

= V

REFIN

= V

VTTI

= 2.5V, UVP/OVP = TP0 = FB = SKIP

= GND, PGND1 = PGND2 = LX = GND, TON = OPEN, V

VTTS

= V

VTT

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

are at T

A

= +25°C.) (Note 1)

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.

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

V

DD, AVDD

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

SHDN, 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

DD

+ 0.3V)

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

DD

+ 0.3V)

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

DD

+ 0.3V)

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

BST

+ 0.3V)

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

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

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

VTTI

+ 0.3V)

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

DD

+ 0.3V)

PGND1, PGND2, TP0 to GND ...............................-0.3V to +0.3V

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

Continuous Power Dissipation (T

A

= +70°C)
28-Pin 5mm x 5mm Thin QFN (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 +150°C

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

SYMBOL

MIN TYP MAX

VDD, AV

t

OFF_MIN

DD

0.693

2.47

1.78

170 194

213 243

TON = open (300kHz) 316 352

TON = AVDD (200kHz) 461 516

200 300

4.05 4.25 4.40

0.707

2.53

1.82

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MAX8632

Integrated DDR Power-Supply Solution for

Desktops, Notebooks, and Graphic Cards

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= +15V, VDD= AVDD= V

SHDN

= STBY = V

BST

= V

ILIM

= 5V, V

OUT

= V

REFIN

= V

VTTI

= 2.5V, UVP/OVP = TP0 = FB = SKIP

= GND, PGND1 = PGND2 = LX = GND, TON = OPEN, V

VTTS

= V

VTT

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

are at T

A

= +25°C.) (Note 1)

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

POK2 Disable Threshold
(Measured at REFIN)

UVP Blanking Time From rising edge of SHDN 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 (Fixed,
Negative Direction) PGND1 to LX

Current-Limit Threshold
(Adjustable, Negative Direction)
PGND1 to LX

Zero-Crossing Detection
Threshold PGND1 to LX

Thermal-Shutdown Threshold +160 °C

Thermal-Shutdown Hysteresis 15 °C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

)

OUT

)

OUT

)

OUT

VTTS

VTTR

)

REF

ILIM

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 = AV

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

V

REFIN

SINK

POK_

V

= 2V 170 200 235 mV

ILIM

SKIP = AV

SKIP = AV

rising (hysteresis = 75mV typ) 0.7 0.9 V

= 4mA 0.3 V

= 5.5V, VFB = 0.8V, V

DD

DD

, V

DD

ILIM

= 0 1.98 2 2.02 V

REF

= 2V -250 mV

= 1.3V 1 µA

VTTS

112 116 120 %

65 70 75 %

10 µs

0.25 2.00 V

45 50 55 mV

-75 -60 -45 mV

3mV

%

%

1bios.ru

MAX8632

Integrated DDR Power-Supply Solution for
Desktops, Notebooks, and Graphic Cards

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VIN= +15V, VDD= AVDD= V

SHDN

= STBY = V

BST

= V

ILIM

= 5V, V

OUT

= V

REFIN

= V

VTTI

= 2.5V, UVP/OVP = TP0 = FB = SKIP

= GND, PGND1 = PGND2 = LX = GND, TON = OPEN, V

VTTS

= V

VTT

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

are at T

A

= +25°C.) (Note 1)

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

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

Logic Input Threshold
(SHDN, STBY, SKIP)

Logic Input Current
(SHDN, STBY, SKIP)

Dual-Mode™ Input Logic
Levels (FB)

Input Bias Current (FB) -0.1 +0.1 µA

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

Logic Input Current
(TON, OVP/UVP)

OUT Discharge-Mode
On-Resistance

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

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

- VLX = 5V 1 4 Ω

BST

DH falling to DL rising 30

DL falling to DH rising 50

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

DD

14Ω

0.5 3 Ω

-1 +1 µA

AV

-

DD

0.4

-3 +3 µA

70 135 270OUT Input Resistance

10 25 Ω

0.01 0.1 0.20 V

ns

V

V

kΩ

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MAX8632

Integrated DDR Power-Supply Solution for

Desktops, Notebooks, and Graphic Cards

_______________________________________________________________________________________ 5

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
trip level by approximately 1.5% due to slope compensation.

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

BST

= 5V,

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

SYMBOL

MIN

TYP

MAX

UNITS

<0.1

2.8

0.01

0.20

±6.5

0.1

±18

ELECTRICAL CHARACTERISTICS (continued)

(VIN= +15V, VDD= AVDD= V

SHDN

= STBY = V

BST

= V

ILIM

= 5V, V

OUT

= V

REFIN

= V

VTTI

= 2.5V, UVP/OVP = TP0 = FB = SKIP

= GND, PGND1 = PGND2 = LX = GND, TON = OPEN, V

VTTS

= V

VTT

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

are at T

A

= +25°C.) (Note 1)

LINEAR REGULATORS (VTTR AND VTT)

VTTI Input Voltage Range V

VTTI Supply Current I
VTTI Shutdown Current SHDN = GND 10 µA

REFIN Input Impedance V

REFIN Range V

VTT, VTTR UVLO Threshold
(Measured at OUT)

Soft-Start Charge Current I

VTT Internal MOSFET High-Side
On-Resistance

VTT Internal MOSFET Low-Side
On-Resistance

VTT Output Accuracy
(Referred to V

VTT Load Regulation

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

VTTS Input Current I

VTTR Output Error
(Referred to V

VTTR Current Limit V

VTTR Bias Current V

PARAMETER

/ 2)

REFIN

/ 2)

REFIN

VTTI

VTTI

REFIN

SS

VTTS

I

= I

VTT

REFIN

VSS = 0 4 µA

I

= -100mA, V

VTT

AV

DD

= 100mA, AVDD = 4.5V 0.3 Ω

I

VTT

V

REFIN

V

REFIN

V

REFIN

V

VTTS

V

REFIN

VTTR

REFIN

VTTR

= 2.5V 12 20 30 kΩ

= 4.5V

= 1.5V or 2.5V, I

= 2.5V, I

= 1.5V, I

= 1.5V, VTT open

= 1.5V or 2.5V, I

= 0 or V

= V

CONDITIONS

= 0

VTTI

VTT

VTT

VTTI

= 0 0.6 4 µA

VTTI

= 1.5V,

= 1mA -1 +1 %

VTT

= 0 to ±1.5A 1.3
= 0 to ±1A 1.3

= 0 -1 +1 %

VTTR

1 2.8 V

1mA

1

0.1

0.3 Ω

1µA

±32 ±50 mA

V

V

%

A

1bios.ru

MAX8632

Integrated DDR Power-Supply Solution for
Desktops, Notebooks, and Graphic Cards

6 _______________________________________________________________________________________

Typical Operating Characteristics

(V

VIN

= 12V, V

OUT

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

EFFICIENCY vs. LOAD CURRENT

(TON = GND)

MAX8632 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)

MAX8632 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)

MAX8632 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)

MAX8632 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)

MAX8632 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

MAX8632 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

MAX8632 toc07

I

VTT

(A)

V

VTT

(V)

V

VTT

(V)

21-2 -1 0

1.20

1.22

1.24

1.26

1.28

1.30

1.32

1.34

1.18

0.86

0.87

0.88

0.89

0.90

0.91

0.92

0.93

0.85

-3 3

V

VTT

= 0.9V

V

VTT

= 1.25V

VTTR VOLTAGE

vs. VTTR CURRENT

MAX8632 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)

MAX8632 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

1bios.ru

MAX8632

Integrated DDR Power-Supply Solution for

Desktops, Notebooks, and Graphic Cards

_______________________________________________________________________________________ 7

Typical Operating Characteristics (continued)

(V

VIN

= 12V, V

OUT

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

STARTUP AND SHUTDOWN INTO

LIGHT LOAD, DISCHARGE ENABLED

MAX8632 toc16a

2ms/div

V

OUT

VTT

VTTR

10V/div

500mV/div

500mV/div

500mV/div

SHDN

1.8V

0.9V

0.9V

STANDBY RESPONSE

VTT LOADED AT 10Ω TO GND

MAX8632 toc17a

2ms/div

500mV/div

500mV/div

500mV/div

5V/div

V

OUT

VTT

VTTR

STBY

1.8V

0.9V

0.9V

SHUTDOWN BY LOSS OF V

DD

MAX8632 toc16b

200µs/div

V

DD

2V/div

V

OUT

500mV/div

V

DL

5V/div
I

OUT

5A/div

0A

1.8V

4V

0V

0A

0V

0V

0V

0V

LOAD TRANSIENT (BUCK)

I

VTT

= 1.5A, I

VTTR

= 15mA

POWER-UP WAVEFORMS

VDD = 5V, I

LOAD

= 12A, I

10µs/div

VTT

200µs/div

= 1.5A, I

MAX8632 toc10

MAX8632 toc13

VTTR

= 15mA

V

OUT

100mV/div

VTT
50mV/div

VTTR
50mV/div

I

LOAD

5A/div

OUT
2V/div

VTT
1V/div

VTTR
1V/div

V

IN

10V/div

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

I

= 12A, I

LOAD

0A

VTTR

= 15mA

10µs/div

POWER-DOWN WAVEFORMS

VDD = 5V, I

0V

0V

0V

0V

LOAD

= 12A, I

200µs/div

VTT

= 1.5A, I

MAX8632 toc11

MAX8632 toc14

VTTR

= 15mA

V

OUT

50mV/div

VTT
50mV/div
VTTR
50mV/div

I

VTT

1A/div

OUT
2V/div

VTT
1V/div

VTTR
1V/div

V

IN

10V/div

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

I

LOAD

0A

HEAVY LOAD, DISCHARGE DISABLED

I

LOAD

I

VTT

0V

0V

0V

0V

MAX8632 toc12

= 12A, I

VTTR

= 15mA

10µs/div

STARTUP AND SHUTDOWN INTO

MAX8632 toc15

= 12A,

= 1.5A

1ms/div

V

OUT

50mV/div

VTT
50mV/div

VTTR
50mV/div

I

VTT

2A/div

V

OUT

1V/div

VTT
1V/div

SHDN
5V/div

POK1
5V/div

1bios.ru

MAX8632

Integrated DDR Power-Supply Solution for
Desktops, Notebooks, and Graphic Cards

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V

VIN

= 12V, V

OUT

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

OVERVOLTAGE AND TURN-OFF

OF BUCK OUTPUT

MAX8632 toc18

40µs/div

V

OUT

1V/div

V

LX

10V/div

V

DL

5V/div

0V

0V

0V

SHORT CIRCUIT AND

RECOVERY OF V

DDQ

MAX8632 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

MAX8632 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

STANDBY RESPONSE, VTT AT NO LOAD

5V/div

500mV/div

500mV/div

500mV/div

2ms/div

MAX8632 toc17b

1.8V

0.9V

0.9V

STBY

V

OUT

VTT

VTTR

SHORT CIRCUIT OF VTT

0V

MAX8632 toc21

VTT
1V/div

I

VTT

0A

400µs/div

5A/div

1bios.ru

MAX8632

Integrated DDR Power-Supply Solution for

Desktops, Notebooks, and Graphic Cards

_______________________________________________________________________________________ 9

Pin Description

PIN NAME FUNCTION

On-Time Selection-Control Input. This four-level logic input sets the nominal DH on-time. Connect to

1 TON

2

3 REF

4 ILIM

OVP/

UVP

GND, REF, AV
TON = AV
TON = open (300kHz)
TON = REF (450kHz)
TON = GND (600kHz)

Overvoltage-/Undervoltage-Protection Control Input. This four-level logic input enables or disables the
overvoltage and/or undervoltage protection. The overvoltage limit is 116% of the nominal output
voltage. The undervoltage limit is 70% of the nominal output voltage. Discharge mode is enabled when
OVP is also enabled. Connect the OVP/UVP pin to the following pins for the desired function:
OVP/UVP = AV
OVP/UVP = open (Enable OVP and discharge mode, disable UVP.)
OVP/UVP = REF (Disable OVP and discharge mode, enable UVP.)
OVP/UVP = GND (Disable OVP and discharge mode, disable UVP.)

+2.0V Reference Voltage Output. Bypass to GND with a 0.1µF (min) capacitor. REF can supply 50µA
for external loads. Can be used for setting voltage for ILIM. REF turns off when SHDN is low and
OUT < 0.1V.

Valley Current-Limit Threshold Adjustment for Buck Regulator. The current-limit threshold across PGND
and LX is 0.1 times the voltage at ILIM. Connect ILIM to a resistive divider, typically from REF to GND,
to set the current-limit threshold between 25mV and 200mV. This corresponds to a 0.25V to 2V range at
ILIM. Connect ILIM to AV
Current Limit (Buck) section.

, or leave TON unconnected to select the following nominal switching frequencies:

DD

(200kHz)

DD

(Enable OVP and discharge mode, enable UVP.)

DD

to select the 50mV default current-limit threshold. See the Setting the

DD

Buck Power-Good Open-Drain Output. POK1 is low when the buck output voltage is more than 10%

5 POK1

6 POK2

7 STBY

8SS

9 VTTS

10 VTTR Termination Reference Voltage. VTTR tracks V

above or below the normal regulation point or during soft-start. POK1 is high impedance when the
output is in regulation and the soft-start circuit has terminated. POK1 is low in shutdown.

LDO Power-Good Open-Drain Output. In normal mode, POK2 is low when either VTTR or VTTS is more
than 10% above or below the normal regulation point, which is typically REFIN / 2. In standby mode,
POK2 responds only to the VTTR input. POK2 is low in shutdown, and when V

Standby. Connect to GND for low-quiescent mode where the VTT output is open circuit. POK2 takes
input from only VTTR in this mode. PWM output can be on or off, depending on the state of SHDN.

Soft-Start Control for VTT. Connect a capacitor (C9 in the Typical Applications Circuit of Figure 8) from
SS to ground. Leave SS open to disable soft-start. SS discharges to ground when VTT is off. See the
POR, UVLO, and Soft-Start section.

Sensing Pin for Termination Supply Output. Normally connected to VTT pin to allow accurate regulation
to half the REFIN voltage. Connected to a resistive divider from VTT to GND to regulate VTT to higher
than half the REFIN voltage.

REFIN

/ 2.

is less than 0.8V.

REFIN