L1136L-XX-AF5-R datasheet(8/9 Pages) UTC

8 / 9 page

L1136

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

8 of 9

www.unisonic.com.tw

QW-R502-464.e

FUNCTIONAL DESCRIPTION

1. Basic Operation

The UTC L1136‘s block diagram is shown in the following. (Fig.1)

The UTC L1136 has an error amplifier, and it compares the reference voltage (VREF) with VFB, which is the

output voltage resistance-divided by feedback resistors RS and RF. It supplies the gate voltage necessary to

maintain the constant output voltage which is not influenced by the input voltage and temperature change, to the

output transistor.

VIN

VREF

Current

Supply

Error Amplifier

Reference

Voltage Circuit

VSS

Fig.1

VFB

VOUT

Parasitic

Diode

2. Output Transistor

For L1136, the output transistor is a P-channel MOSFET with low on-resistance.

In order to protect against inverse current, make sure that VOUT does not exceed VIN+0.3V, because of a

parasitic diode between the VIN and VOUT pin, when the potential of VOUT became higher than VIN.

3. Shutdown Pin (ON/OFF pin)

The shutdown pin is used to turn on and turn off this regulator.

When the ON/OFF pin is set to the shutdown level, the entire internal circuit stops operating. For reducing the

current dissipation, the internal P-channel MOSFET is shut down. The VOUT pin is set to the VSS level by the internal

dividing resistor of several hundred kΩ between the VOUT and VSS pin.

Note: When the ON/OFF pin voltage is in the range of 0.3V~1.0V, the current dissipation increases. The

architecture of the ON/OFF pin can be seen in Fig. 2 Since the ON/OFF pin is neither pulled down nor pulled up

internally, do not use it in the floating state.

ON/OFF Pin

Internal Circuits

VOUT Pin Voltage

Current Consumption

“

L”: Power off

Stop

VSS level

ISS2

“

H”: Power on

Operate

Set value

ISS1

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