FB

PGOOD

COMP

NC

PVIN

PVIN

SW

SS/TRK

AVIN

VCC

EN

PGND

PGND

SW

AGND

SYNCOUT

EP

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

LM20154

SNVS531G – OCTOBER 2007 – REVISED MARCH 2013

www.ti.com

Connection Diagram

Figure 1. Top View

HTSSOP Package

PIN DESCRIPTIONS

Pin #

Name

Description

1

SS/TRK

Soft-Start or Tracking control input. An internal 5 µA current source charges an external capacitor to set the

Soft-Start ramp rate. If driven by a external source less than 800 mV, this pin overrides the internal reference

that sets the output voltage. If left open, an internal 1ms Soft-Start ramp is activated.

2

FB

Feedback input to the error amplifier from the regulated output. This pin is connected to the inverting input of

the internal transconductance error amplifier. An 800 mV reference connected to the non-inverting input of the

error amplifier sets the closed loop regulation voltage at the FB pin.

3

PGOOD

Power good output signal. Open drain output indicating the output voltage is regulating within tolerance. A

pull-up resistor of 10 to 100 k

Ω is recommend for most applications.

4

COMP

External compensation pin. Connect a resistor and capacitor to this pin to compensate the device.

5

NC

These pins must be connected to GND to ensure proper operation.

6,7

PVIN

Input voltage to the power switches inside the device. These pins should be connected together at the device.

A low ESR capacitor should be placed near these pins to stabilize the input voltage.

8,9

SW

Switch pin. The PWM output of the internal power switches.

10,11

PGND

Power ground pin for the internal power switches.

12

EN

Precision enable input for the device. An external voltage divider can be used to set the device turn-on

threshold. If not used the EN pin should be connected to PVIN.

13

VCC

Internal 2.7V sub-regulator. This pin should be bypassed with a 1 µF ceramic capacitor.

14

AVIN

Analog input supply that generates the internal bias. Must be connected to VIN through a low pass RC filter.

15

AGND

Quiet analog ground for the internal bias circuitry.

16

SYNCOUT

Frequency synchronization output. This NMOS open drain output provides a signal that has the same

frequency as the internal oscillator, but is shifted by 180 degrees.

EP

Exposed Pad

Exposed metal pad on the underside of the package with a weak electrical connection to ground. It is

recommended to connect this pad to the PC board ground plane in order to improve heat dissipation.

2

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