Maxim MAX8632ETI Schematic [ru]

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 VTTR. 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

PART

PIN-PACKAGE

MAX8632ETI+

28 Thin QFN-EP* 5mm × 5mm

Ordering Information

9

8

11

12

13

14

10

23

22

25

26

27

28

24

21 20 19 18 17 16 15

1234567

MAX8632

5mm x 5mm THIN QFN

TOP VIEW

GND

PGND1

DL

LX

V

IN

OUT

FB

REFIN

VTTI

VTT

PGND2

VTTR

VTTS

SS

POK2

POK1

ILIM

REF

OVP/UVP

TON

BST

DH

AV

DD

V

DD

SHDN

SKIP

TPO

STBY

Pin Configuration

19-3623; Rev 1; 10/05

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.
* EP = Exposed pad.

TEMP RANGE

-40°C to +85°C

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

MAX8632

Integrated DDR Power-Supply Solution for

Desktops, Notebooks, and Graphic Cards

_______________________________________________________________________________________ 3

PARAMETER

CONDITIONS

UNITS

REFERENCE

Reference Voltage V

REF

AVDD = 4.5V to 5.5V; I

REF

= 0

2

V

Reference Load Regulation I

REF

= 0 to 50µA

V

V

REF

rising

V

REF Undervoltage Lockout

Hysteresis

mV

FAULT DETECTION

OVP Trip Threshold

(Referred to Nominal V

OUT

)

UVP/OVP = AV

DD

120 %

UVP Trip Threshold
(Referred to Nominal V

OUT

)

65 70 75 %

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

POK1 Trip Threshold
(Referred to Nominal V

OUT

)

Upper level, rising edge, 1% hysteresis

113

%

Lower level, falling edge, 1% hysteresis

90

POK2 Trip Threshold
(Referred to Nominal V

VTTS

and V

VTTR

)

Upper level, rising edge, 1% hysteresis

%

POK2 Disable Threshold
(Measured at REFIN)

V

REFIN

rising (hysteresis = 75mV typ) 0.7 0.9 V

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

OVP, UVP, POK_ Propagation
Delay

10 µs

POK_ Output Low Voltage I

SINK

= 4mA 0.3 V

POK_ Leakage Current V

POK_

= 5.5V, VFB = 0.8V, V

VTTS

= 1.3V 1 µA

ILIM Adjustment Range V

ILIM

V

ILIM Input Leakage Current 0.1 µA

Current-Limit Threshold (Fixed)
PGND1 to LX

45 50 55 mV

Current-Limit Threshold
(Adjustable) PGND1 to LX

V

ILIM

= 2V

235 mV

Current-Limit Threshold (Fixed,

Negative Direction) PGND1 to LX

SKIP = AV

DD

-75 -60 -45 mV

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

SKIP = AV

DD

, V

ILIM

= 2V

mV

Zero-Crossing Detection
Threshold PGND1 to LX

3mV

Thermal-Shutdown Threshold

°C

Thermal-Shutdown Hysteresis 15 °C

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)

SYMBOL

MIN TYP MAX

1.98

1.93

300

112 116

107 110

87.5

107.5 110 112.5

0.25 2.00

170 200

-250

+160

2.02

0.01

92.5

MAX8632

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

4 _______________________________________________________________________________________

PARAMETER

CONDITIONS

UNITS

MOSFET DRIVERS

DH Gate-Driver On-Resistance V

BST

- VLX = 5V 1 4 Ω

DL Gate-Driver On-Resistance in
High State

14Ω

DL Gate-Driver On-Resistance in
Low State

0.5 3 Ω

DH falling to DL rising 30

Dead Time (Additional to
Adaptive Delay)

DL falling to DH rising 50

ns

INPUTS AND OUTPUTS

Rising edge

1.7

V

Logic Input Threshold
(SHDN, STBY, SKIP)

Hysteresis

mV

Logic Input Current
(SHDN, STBY, SKIP)

-1 +1 µA

Low (2.5V output)

Dual-Mode™ Input Logic
Levels (FB)

High (1.8V output) 2.1

V

Input Bias Current (FB)

µA

High

AV

DD

-

0.4

Floating

REF

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

Low 0.5

V

Logic Input Current
(TON, OVP/UVP)

-3 +3 µA

FB = GND 90

350

FB = AV

DD

70

270OUT Input Resistance

FB adjustable mode

kΩ

OUT Discharge-Mode
On-Resistance

10 25 Ω

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

0.1

V

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.

SYMBOL

MIN TYP MAX

1.20

-0.1 +0.1

3.15 3.85

1.65 2.35

400 800 1600

0.01

225

175

135

2.20

0.05

0.20

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.

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

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 SHDN = GND 10 µA

REFIN Input Impedance V

REFIN

= 2.5V 12 20 30 kΩ

REFIN Range V

REFIN

1

V

VTT, VTTR UVLO Threshold
(Measured at OUT)

0.1

V

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 1.3

VTT Load Regulation

V

REFIN

= 1.5V, I

VTT

= 0 to ±1A 1.3

%

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

VTTR Bias Current V

REFIN

= V

VTTI

= 0 0.6 4 µA

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)

<0.1

2.8

0.01

0.20

±6.5

0.1

±18 ±32 ±50

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

MAX8632

Integrated DDR Power-Supply Solution for

Desktops, Notebooks, and Graphic Cards

_______________________________________________________________________________________ 7

LOAD TRANSIENT (BUCK)

MAX8632 toc10

10µs/div

V

OUT

100mV/div

VTT
50mV/div

VTTR
50mV/div

I

LOAD

5A/div

0A

I

VTT

= 1.5A, I

VTTR

= 15mA

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

MAX8632 toc11

10µs/div

V

OUT

50mV/div

VTT

50mV/div
VTTR
50mV/div

I

VTT

1A/div

0A

I

LOAD

= 12A, I

VTTR

= 15mA

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

MAX8632 toc12

10µs/div

V

OUT

50mV/div

VTT
50mV/div

VTTR
50mV/div

I

VTT

2A/div

0A

I

LOAD

= 12A, I

VTTR

= 15mA

POWER-UP WAVEFORMS

MAX8632 toc13

200µs/div

OUT
2V/div

VTT
1V/div

VTTR
1V/div

V

IN

10V/div

0V

0V

0V

0V

VDD = 5V, I

LOAD

= 12A, I

VTT

= 1.5A, I

VTTR

= 15mA

POWER-DOWN WAVEFORMS

MAX8632 toc14

200µs/div

OUT
2V/div

VTT
1V/div

VTTR
1V/div

V

IN

10V/div

0V

0V

0V

0V

VDD = 5V, I

LOAD

= 12A, I

VTT

= 1.5A, I

VTTR

= 15mA

STARTUP AND SHUTDOWN INTO

HEAVY LOAD, DISCHARGE DISABLED

MAX8632 toc15

400s/div

V

OUT

1V/div

VTT
500mV/div

V

DL

10V/div

0V

0V

0V

0V

I

LOAD

= 10A,

I

VTT

= 1.5A

SHDN
5V/div

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

400s/div

V

OUT

1V/div

VTT
500mV/div

V

DL

10V/div

0V

0V

0V

0V

SHDN
5V/div

I

LOAD

= 1A,

I

VTT

= NO LOAD

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

MAX8632

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

8 _______________________________________________________________________________________

STANDBY RESPONSE, VTT AT NO LOAD

MAX8632 toc17b

2ms/div

500mV/div

500mV/div

500mV/div

5V/div

V

OUT

VTT

VTTR

STBY

1.8V

0.9V

0.9V

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

SHORT CIRCUIT OF VTT

MAX8632 toc21

400µs/div

VTT
1V/div

I

VTT

5A/div

0A

0V

MAX8632

Integrated DDR Power-Supply Solution for

Desktops, Notebooks, and Graphic Cards

_______________________________________________________________________________________ 9

Pin Description

PIN NAME FUNCTION

1TON

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

DD

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

TON = AV

DD

(200kHz)
TON = open (300kHz)
TON = REF (450kHz)
TON = GND (600kHz)

2

OVP/

UVP

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

DD

(Enable OVP and discharge mode, enable UVP.)
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.)

3 REF

+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.

4 ILIM

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

DD

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

Current Limit (Buck) section.

5 POK1

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

6 POK2

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

REFIN

is less than 0.8V.

7 STBY

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.

8SS

Soft-Start Control for VTT. Connect a capacitor (C9 in 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.

9 VTTS

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.

10 VTTR Termination Reference Voltage. VTTR tracks V

REFIN

/ 2.