LM3100

1

2

3

4

5

6

7

8

9

10

20

19

18

17

16

15

14

13

11

12

SW

SW

N/C

VIN

VIN

BST

GND

SS

N/C

N/C

N/C

N/C

PGND

PGND

VCC

RON

EN

FB

N/C

TST

EP

LM3100

SNVS421F – JANUARY 2006 – REVISED DECEMBER 2009

www.ti.com

Connection Diagram

Figure 1. 20-lead Plastic

eTSSOP

Pin Functions

Pin Descriptions

Pin

Name

Description

Application Information

1,9,10,12,19,20

N/C

No Connection

These pins must be left unconnected.

2, 3

SW

Switching Node

Internally connected to the buck switch source. Connect to

output inductor.

4, 5

VIN

Input supply voltage

Supply pin to the device. Nominal input range is 4.5V to

36V.

6

BST

Connection for bootstrap capacitor

Connect a 0.033µF capacitor from SW pin to this pin. An

internal diode charges the capacitor during the high-side

switch off-time.

7

GND

Analog Ground

Ground for all internal circuitry other than the synchronous

switches.

8

SS

Soft-start

An internal 8µA current source charges an external

capacitor to provide the soft- start function.

11

TST

Test mode enable pin

Force the device into test mode. Must be connected to

ground for normal operation.

13

FB

Feedback

Internally connected to the regulation and over-voltage

comparators. The regulation setting is 0.8V at this pin.

Connect to feedback divider.

14

EN

Enable pin

Connect a voltage higher than 1.26V to enable the

regulator.

15

RON

On-time Control

An external resistor from VIN to this pin sets the high-side

switch on-time.

16

VCC

Start-up regulator Output

Nominally regulated to 6V. Connect a capacitor of not less

than 680nF between VCC and GND for stable operation.

17, 18

PGND

Power Ground

Synchronous rectifier MOSFET source connection. Tie to

power ground plane.

DAP

EP

Exposed Pad

Thermal connection pad, connect to GND.

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

2

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