TPS65251

SLVSAA4F – JUNE 2010 – REVISED JULY 2015

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Pin Functions (continued)

PIN

I/O

DESCRIPTION

NAME

NO.

Synchronous clock input. If there is a sync clock in the system, connect to the pin. When not used connect to

SYNC

5

I

GND.

Oscillator set. This resistor sets the frequency of internal autonomous clock. If external synchronization is used

ROSC

6

I

resistor should be fitted and set to about 70% of external clock frequency.

FB1

7

I

Feedback pin for Buck 1. Connect a divider set to 0.8 V from the output of the converter to ground.

Compensation pin for Buck 1. Fit a series RC circuit to this pin to complete the compensation circuit of this

COMP1

8

O

converter.

SS1

9

I

Soft-start pin for Buck 1. Fit a small ceramic capacitor to this pin to set the converter soft-start time.

Current limit setting pin for Buck 1. Fit a resistor from this pin to ground to set the peak current limit on the

RLIM1

10

I

output inductor.

Enable pin for Buck 1. A low level signal on this pin disables it. If pin is left open a weak internal pullup to V3V

EN1

11

I

will allow for automatic enable. For a delayed start-up add a small ceramic capacitor from this pin to ground.

BST1

12

I

Bootstrap capacitor for Buck 1. Fit a 47-nF ceramic capacitor from this pin to the switching node.

VIN1

13

I

Input supply for Buck 1. Fit a 10-µF ceramic capacitor close to this pin.

14

Switching node for Buck 1

LX1

O

15

16

Switching node for Buck 2

LX2

O

17

VIN2

18

I

Input supply for Buck 2. Fit a 10-µF ceramic capacitor close to this pin.

BST2

19

I

Bootstrap capacitor for Buck 2. Fit a 47-nF ceramic capacitor from this pin to the switching node.

Enable pin for Buck 2. A low level signal on this pin disables it. If pin is left open a weak internal pullup to V3V

EN2

20

I

will allow for automatic enable. For a delayed start-up add a small ceramic capacitor from this pin to ground.

Current limit setting for Buck 2. Fit a resistor from this pin to ground to set the peak current limit on the output

RLIM2

21

I

inductor.

SS2

22

I

Soft-start pin for Buck 2. Fit a small ceramic capacitor to this pin to set the converter soft-start time.

Compensation pin for Buck 2. Fit a series RC circuit to this pin to complete the compensation circuit of this

COMP2

23

O

converter

FB2

24

I

Feedback input for Buck 2. Connect a divider set to 0.8 V from the output of the converter to ground.

LOW_P

25

I

Low-power operation mode (active high) input for TPS65251

GND

26

Ground pin

Powergood. Open-drain output asserted after all converters are sequenced and within regulation. Polarity is

PGOOD

27

O

factory selectable (active high default).

V7V

28

O

Internal supply. Connect a 10-

μF ceramic capacitor from this pin to ground.

V3V

29

O

Internal supply. Connect a 3.3-

μF to 10-μF ceramic capacitor from this pin to ground.

AGND

30

Analog ground. Connect all GND pins and the power pad together.

GND

31

Ground pin

VIN

32

I

Input supply

VIN

33

I

Input supply

VIN

34

I

Input supply

GND

35

Ground pin

36

Switching node for Buck 3

LX3

O

37

VIN3

38

Input supply for Buck 3. Fit a 10-µF ceramic capacitor close to this pin.

BST3

39

I

Bootstrap capacitor for Buck 3. Fit a 47-nF ceramic capacitor from this pin to the switching node.

Enable pin for Buck 3. A low level signal on this pin disables it. If pin is left open a weak internal pullup to V3V

EN3

40

I

will allow for automatic enable. For a delayed start-up add a small ceramic capacitor from this pin to ground.

PAD

—

—

Power pad. Connect to ground.

4

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