Datasheet
I
SEN
FB
GND
V
IN
CB
SW
DR
LM3477
COMP/SD
C
BYP
0.1PF
C
BOOT
0.1PF
C
SN
0.1PF
DR
FB
CB
SW
GND
V
IN
I
SEN
LM3477
*R
FB1
= R
FB2
*
(Vout - 1.26)/1.26
1
2
3
4
5
6
7
8
V
IN
4.5V - 5.5V
C
IN
120PF/20V
R
SN
0.02:
Q1
FDC653N
D
30BG100
L
3.3PH
V
OUT
2.5V, 3A
R
FB1
20.5k
R
FB2
20.0k
R
C
510
C
C1
47nF
C
OUT
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
I
SEN
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.
V
IN
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.
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