LC1126

Preliminary

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

5 of 6

www.unisonic.com.tw

QW-R102-050.a

FUNCTION DESCRIPTIONS

Power-On-Reset

A Power-On-Reset (POR) circuit monitors the VCC pin voltage (VCC) for power-on-reset function to prevent

wrong operation. The built-in POR circuit keeps the output shutting off until internal circuit is operating properly..

Internal Soft-Start

An internal soft-start provides an internal soft-start circuitry to control rise rate of the output voltage and limit the

current surge during start-up. The typical soft-start interval is about 1ms.

Output Voltage Regulation

An error amplifier working with a temperature compensated 0.5V reference and an output NMOS regulates output

to the preset voltage. The error amplifier designed with high bandwidth and DC gain provides very fast transient

response and less load regulation.

Under-Voltage Protection (UVP)

UTC LC1126 monitors the voltage on FB pin after soft-start process is finished. Therefore the UVP is disabling

during soft-start. When the voltage on FB pin falls below the under-voltage threshold, the UVP circuit shuts off the

output immediately. After a while (~70% Duty), UTC LC1126 starts a new soft-start to regulate output.

Thermal Shutdown

A thermal shutdown circuit limits the junction temperature of UTC LC1126. When the junction temperature

exceeds +150°C, a thermal sensor turns off the output NMOS, allowing the device to cool down. The regulator

regulates the output again through initiation of new soft-start cycle after the junction temperature cools by 50°C,

resulting in a pulsed output during continuous thermal overload conditions.

TYPICAL APPLICATION CIRCUIT

C3

0.1µF

U1

1

2

GND

3 POK

UTC LC1126

DRV

FB

EN

6

5

4

10K

56pF

Q1

MOSFET N

R1

43K

R2

39K

C2

10µF

4.7µF

C1

R2 )

C4