US211C datasheet(4/9 Pages) UTC

4 / 9 page

US211/A/B/C

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

4 of 9

www.unisonic.com.tw

QW-R502-A67.C



APPLICATION INFORMATION

Input and Output

VIN (input) is the power source connection to the internal circuitry and the drain of the MOSFET. VOUT (output) is

the source of the MOSFET. In a typical application, current flows through the switch from VIN to VOUT toward the load.

Because the MOSFET is bidirectional when on, if VOUT is greater than VIN, current will flow from VOUT to VIN

There is no a parasitic body diode of N-MOSFET between the drain and source compared to a normal MOSFET,.

The US211 can protect damage from reverse current flow if VOUT being externally forced to a higher voltage than VIN

when the output disabled (VEN > 2V).

Enable Input

The switch will be disabled when the EN pin is in a logic low/high condition. During this condition, the internal

circuitry and MOSFET are turned off, reducing the supply current to 0.1μA typical. Floating the EN may cause

unpredictable operation. EN should not be allowed to go negative with respect to GND. The EN pin may be directly

tied to VIN (GND) to keep the part on.

Soft Start for Hot Plug-In Applications

When hot-plug events occur, the soft start is used to eliminate the upstream voltage droop due to the inrush

current. The soft-start protects power supplies from damage caused by highly capacitive loads.

Fault Flag

The fault flag is an open-drained output of an N-channel MOSFET. The flag drops low to indicate fault conditions:

current limit, thermal shutdown or VOUT < VIN − 1V. In order to reduce energy drain, a large pull-up resistor is required.

100kΩ pull-up resistor is recommended for most applications.

In the case of over current condition, the fault flag is active only if the flag response delay time (tD) has elapsed.

This ensures that FLG is asserted only upon valid over-current conditions and that erroneous error reporting is

eliminated. For example, false over-current conditions may occur during hot-plug events when extremely large

capacitive loads are connected and causes a high transient inrush current that exceeds the current limit threshold.

The FLG response delay time tD is typically 10ms.

US211C データシート(PDF) 4 Page - Unisonic Technologies