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POWER MANAGEMENT

SC4501

Block Diagram

SHDN

COMP

ROSC

7

REG_GOOD

EA

-

FB

2

SS

8

REFERENCE

VOLTAGE

3

IN

6

1

CMP

-

+

SUPPLY

INTERNAL

SHUTDOWN

THERMAL

REG

1.1V

1.242V

+

4.6

µA

ENABLE

ENABLE

+

R

Q

S

PWM

CLK

-

+

+

CLK

+

-

ISEN

ILIM

+

-

I-LIMIT

Σ

GND

4

SW

5

R

OSCILLATOR

SLOP E COMP

1.5

µA

REG

SENSE

Figure 2. SC4501 (MSOP-8) Block Diagram.

Block Diagram

Pin Descriptions (MSOP-8)

Pin

Pin Name

Pin Function

1

COMP

The output of the internal transconductance error amplifier. This pin is used for loop compensation.

2

FB

The inverting input of the error amplifier. Tie to an external resistive divider to set the output voltage.

3

SHDN

Shutdown Pin. The accurate 1.1V shutdown threshold and the 4.6uA shutdown pin current

hysteresis allow the user to set the undervoltage lockout threshold and hysteresis for the switching

regulator. Pulling this pin below 0.1V causes the converter to shut down to low quiescent current.

Tie this pin to IN if the UVLO and the shutdown features are not used. This pin should not be left

floating.

4

GND

Ground. Tie to the ground plane.

5

SW

Collector of the internal power transistor. Connect to the boost inductor and the rectifying diode.

6

IN

Power Supply Pin. Bypassed with capacitors close to the pin.

7

ROSC

A resistor from this pin to the ground sets the switching frequency.

8

SS

Soft-Start Pin. A capacitor from this pin to the ground lengthens the start-up time and reduces start-

up current.

Exposed Pad

The exposed pad must be soldered to the ground plane on the PCB for good thermal conduction.