LC1111G-AG6-R datasheet(6/7 Pages) UTC

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LC1111

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LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

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www.unisonic.com.tw

QW-R102-072.a

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FUNCTION DESCRIPTION

Power-On-Reset (POR)

The UTC LC1111 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. Typical POR threshold

is 4.0V with 0.4V hysteresis.

Soft-Start

The UTC LC1111 provides an adjustable soft-start circuitry to control rise rate of the output voltage and limit the

current surge during start-up. The soft-start time is set with a capacitor from the SS pin to the ground. The capacitor

is charged to VP with a constant 4.5mA (typ.) current source.

Under-Voltage Protection (UVP)

The UTC LC1111 monitors the voltage on FB. When the voltage on FB falls below the under-voltage threshold,

the UVP circuit shuts off the output voltage immediately by pulling down DRV to 0V and latches UTC LC1111off,

requiring either a VCC POR or EN re-enable again to restart. The UTC LC1111 UVP is activated after VOUT voltage

has reached 90% POK threshold while the UTC LC1111 UVP is activated after VCC has been applied to VCC pin.

Enable Control

The UTC LC1111 has a dedicated enable pin (EN). A logic low signal applied to this pin shuts down the output.

Following a shutdown, a logic high signal re-enables the output through initiation of a new soft-start cycle. It’s not

necessary to use an external transistor to save cost.

Power-OK and Delay

The UTC LC1111 indicates the status of the output voltage by monitoring the feedback voltage (VFB) on FB pin.

As the VFB rises and reaches the rising Power-OK voltage threshold (VPOKTH), an internal delay function starts to

work. At the end of the delay time, the IC turns off the internal NMOS of the POK to indicate that the output is ok. As

the VFB falls and reaches the falling Power-OK voltage threshold, the IC turns on the NMOS of the POK (after a

debounce time of 5ms typical).

Output Voltage Regulation

The UTC LC1111 is a linear regulator controller. An external N-channel MOSFET should be connected to DRV

as the pass element. The output voltage set by the resistor divider is determined by:

)

•

VOUT

（

Where R1 is connected from VOUT to FB and R2 is connected from FB to GND.

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