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POWER MANAGEMENT

SC1462

Pin Configuration

Applications Information

Theory of Operation

The SC1462 utilizes a switched capacitor charge pump to

generate an output voltage approximately 2×V

An internal oscillator generates two out of phase fixed fre-

quency clock signals which turn on and off internal MOS-

FET switches. During phase 1, the flying charge pump

capacitor is charged to V

During phase 2, the flying charge pump capacitor is con-

nected in series with the input voltage via S3 and S4, pro-

ducing an output voltage.

Short Circuit/Soft-Start

An internal current limit and soft-start circuit provides pro-

tection against output short circuit and limits large cur-

rent spikes generated during the initial start-up to charge

output capacitor.

If V

off and V

V

disconnected from output and the charge pump circuitry

is enabled again.

Output Current

The dropout voltage for a charge pump doubler is defined

as (2×V

specified as that which will not cause the dropout voltage

to exceed the requirements of the application. The calcu-

lation of the dropout voltage is given in the capacitor se-

lection section on Page 6. Typical dropout voltages versus

I

Thermal Shutdown

The thermal shutdown circuit provides added protection

to the SC1462. During a V

the load is excessive, the over-temperature circuitry will

shut down the charge pump if the junction temperature

exceeds approximately 140°C. The charge pump is en-

abled only if the junction temperature drops to approxi-

mately 120°C. The SC1462 will cycle in and out of ther-

mal shut down until the short circuit or the excessive load

condition on V

liability. The junction temperature can be calculated from

the following formula if the ambient temperature (T

the charge pump power dissipation (P

T

; θ

ON

S1,S2

OFF

ON

S3,S4

OFF

Charge transfer from:

Doubler

S4

12

S1

12

S3

12

Cin

S2

12