ISEN

FB

GND

VIN

CB

SW

DR

LM3477

COMP/SD

CBYP

0.1PF

CBOOT

0.1PF

CSN

0.1PF

DR

FB

CB

SW

GND

VIN

ISEN

LM3477

*RFB1 = RFB2

* (Vout - 1.26)/1.26

1

2

3

4

5

6

7

8

VIN

4.5V - 5.5V

CIN

120PF/20V

RSN

0.02:

Q1

FDC653N

D

30BG100

L

3.3PH

VOUT

2.5V, 3A

RFB1

20.5k

RFB2

20.0k

RC

510

CC1

47nF

COUT

47PF

ceramic

COMP/SD

LM3477

SNVS141K – OCTOBER 2000 – REVISED MARCH 2013

www.ti.com

Typical Application Circuit

Figure 1. Typical High Efficiency Step-Down (Buck) Converter

Connection Diagram

Figure 2. 8 Lead (VSSOP-8 Package)

PIN DESCRIPTION

Pin Name

Pin Number

Description

ISEN

1

Current sense input pin. Voltage generated across an external sense resistor is fed into this

pin.

COMP/SD

2

Compensation pin. A resistor-capacitor combination connected to this pin provides

compensation for the control loop. Pull this pin below 0.65V to shutdown.

FB

3

Feedback pin. The output voltage should be adjusted using a resistor divider to provide

1.270V at this pin.

GND

4

Ground pin.

SW

5

Switch Node. Source of the external MOSFET is connected to this node.

DR

6

Drive pin. The gate of the external MOSFET should be connected to this pin.

CB

7

Boot-strap pin. A capacitor must be connected between this pin and SW pin (pin 5) for proper

operation. The voltage developed across this capacitor provides the gate drive for the external

MOSFET.

VIN

8

Power Supply Input pin.

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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