QFN RHA40

(power pad connected to ground)

VIN3

LX3

LX3

VIN

LX2

LX1

LX1

1

2

3

4

5

6

11

12

13

14

15

16

17

18

19

20

7

8

9

10

LX2

VIN2

29

28

27

26

25

24

23

22

21

30

40

39

38

37

36

35

34

33

32

31

GND

VIN

VIN

BST3

EN3

VIN1

BST1

EN2

BST2

EN1

GND

TPS65251-1, TPS65251-2, TPS65251-3

www.ti.com

SLVSC70A – JANUARY 2015 – REVISED JANUARY 2015

5 Pin Configuration and Functions

Pin Functions

PIN

I/O

DESCRIPTION

NAME

NO.

Current limit setting for Buck 3. Fit a resistor from this pin to ground to set the peak current limit on the output

RLIM3

1

I

inductor.

SS3

2

I

Soft-start pin for Buck 3. Fit a small ceramic capacitor to this pin to set the converter soft-start time.

Compensation for Buck 3. Fit a series RC circuit to this pin to complete the compensation circuit of this

COMP3

3

O

converter.

FB3

4

I

Feedback input for Buck 3. Connect a divider set to 0.8 V from the output of the converter to ground.

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 the internal autonomous clock. If external synchronization is

ROSC

6

I

used, the 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 output

RLIM1

10

I

inductor.

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

EN1

11

I

allows 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

LX1

O

Switching node for Buck 1

15

16

LX2

O

Switching node for Buck 2

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.

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Product Folder Links: TPS65251-1 TPS65251-2 TPS65251-3