L1136

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

9 of 9

www.unisonic.com.tw

QW-R502-464.b

FUNCTIONAL DESCRIPTION (Cont.)

4. Over-current protection circuit

An over-current protection circuit is contained in the UTC L1136. It aims at preventing the output transistor from

internally-fixed to about typically 200mA when short-circuit condition is applied in output pin, and the initial value is

restored for the output voltage, if releasing a short circuit once.

Caution

: This over-current protection circuit does not work as for thermal protection. If this IC maintains short

circuiting for a long time inside, take care to the conditions of input voltage and the load current, therefore,

under the usage conditions including short circuit, the IC’s consumption will not exceed power dissipation

of the package.

5. Thermal shutdown circuit

A thermal shutdown circuit is included to prevent this device from being damaged for overheat. The thermal

shutdown circuit operates to stop regulating when the junction temperature becomes higher than 150°C (TYP.), and

it turns back to normal operation when the junction temperature is lower than 120°C (TYP.).

Due to self-heating of the UTC L1136, if the thermal shutdown circuit starts operating, it stops regulating so that

the output voltage drops. When the regulating operation stops, the IC’s temperature goes down due to the UTC

L1136

does not generate heat itself. When the temperature drops, the thermal shutdown circuit is released to restart

regulating, thus this IC generates heat again. Repeating this procedure makes waveform of the output voltage

pulse-like form. Stop/Restart of regulation continues unless decreasing either/both of the input voltage and the

output voltage for reducing the internal current consumption, or decreasing the ambient temperature.

Thermal Shutdown Circuit (Note)

Operation: 150°C (Typ.)

Release: 120°C (Typ.)

Set value

Note: Junction Temperature

6. Rush current control circuit

The rush current control circuit is designed to protect against the rush current occurs during power-on or when

the ON/OFF pin is ON. The rush current is specified to typically 400mA immediately after power-on or from the

ON/OFF pin is ON until the specified time (100μs min.) which is set internally.

Caution

: Due to the thermal shutdown protection circuit, the junction temperature drops to 120°C (TYP.), after

stopping regulation, the circuit is released to restart regulation; in this case, pay attention to the period

which is to limit rush current to be shorter (10μs min.).

UTC assumes no responsibility for equipment failures that result from using products at values that

exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or

other parameters) listed in products specifications of any and all UTC products described or contained

herein. UTC products are not designed for use in life support appliances, devices or systems where

malfunction of these products can be reasonably expected to result in personal injury. Reproduction in

whole or in part is prohibited without the prior written consent of the copyright owner. The information

presented in this document does not form part of any quotation or contract, is believed to be accurate

and reliable and may be changed without notice.