© 2014 Exar Corporation

XR79115

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exar.com/XR79115

Rev 1B

Pin Assignments

Type: A = Analog, I = Input, O = Output, I/O = Input/Output, PWR = Power, OD = Open-Drain

Pin No.

Pin Name

Type

Description

1

SS

A

Soft-start pin. Connect an external capacitor between SS and AGND to program the soft-start

rate based on the 10uA internal source current.

2

PGOOD

OD, O

3

FB

A

Feedback input to feedback comparator. Connect with a set of resistors to VOUT and AGND in

order to program VOUT.

4, 67, AGND

Pad

AGND

A

Analog ground. Control circuitry of the IC is referenced to this pin.

5

VIN

PWR

IC supply input. Provides power to internal LDO.

6

VCC

PWR

VCC should be tied to VIN.

7, GL pad

GL

O

Driver output for Low-side N-channel synchronous MOSFET. It is internally connected to the

gate of the FET. Leave this pin floating.

8

PGND

PWR

Controller low-side driver ground. Connect with a short trace to closest PGND pins or PGND

pad.

13-23, 54,

55, PGND

pads

PGND

PWR

Ground of the power stage. Should be connected to the system’s power ground plane.

9-12, 24-29,

SW Pad

SW

PWR

Switching node. It is internally connected. Use thermal vias and/or sufficient PCB land area in

order to heatsink the low-side FET and the inductor.

30-53,

VOUT pads

VOUT

PWR

Output of the power stage. Place the output filter capacitors as close as possible to these pins.

56-62, PVIN

Pad

PVIN

PWR

Power stage input voltage. Place the input filter capacitors as close as possible to these pins.

63, 64, BST

Pad

BST

A

Controller high-side driver supply pin. It is internally connected to SW via a 0.1uF bootstrap

capacitor. Leave these pins floating.

65

ILIM

A

Over-current protection programming. Connect with a short trace to SW pins.

66

EN/MODE

I

Precision enable pin. Pulling this pin above 1.9V will turn the IC on and it will operate in Forced

CCM. If the voltage is raised above 3.0V, then the IC will operate in DCM or CCM depending

on load.

68

TON

A

Constant on-time programming pin. Connect with a resistor to AGND.