October, 20, 2011.

Techcode Semiconductor Limited

www.techcodesemi.com

13

USB Power-Distribution Switches

TD9516/TD9517/TD9518/TD9519

DATASHEET

Type Application Circuit

Function Description

VIN Under-Voltage Lockout (UVLO)

The TD951X series of power switches have a built-in

under-voltage lockout circuit to keep the output shutting off

until internal circuitry is operating properly. The UVLO circuit

has hysteresis and a de-glitch feature so that it will typically

ignore undershoot transients on the input. When input

voltage exceeds the UVLO threshold, the output voltage

starts a soft-start to reduce the inrush current.

Power Switch

internal power MOSFET does not have the body diode. When IC is

off, the MOSFET prevents a current flowing from the VOUT back

to VIN and VIN to VOUT.

Current-Limit Protection

The

protection function. During current-limit, the devices limit output

current at current limit threshold. For reliable operation, the device

should not be operated in current-limit for extended period.

Short-Circuit Protection

When the output voltage drops below 1.5V, which is caused by an

over-load or a short-circuit, the devices limit the output current

down to a safe level. The short-circuit current limit is used to

reduce the power dissipation during short-circuit conditions. If the

junction temperature reaches over-temperature threshold, the

device will enter the thermal shutdown.

OCB Output

TheTD951X series of power switches provide an open-drain

output to indicate that a fault has occurred. When any of

current-limit or over-temperature protection occurs for a deglitch

open-drain output, connecting a resistor to a pull high voltage is

necessary.

Enable/Disable

Pull the ENB above 2V or EN below 0.8V will disable the device,

and pull ENB pin below 0.8V or EN above 2V will enable the

device. When the IC is disabled, the supply current is reduced to

less than 1

A. The enable input is compatible with both TTL and

CMOS logic levels. The EN/ENB pin cannot be left floating.

Over-Temperature Protection

thermal sense circuit turns off the power FET and allows the

device to cool down. When the device’s junction temperature cools

resulting in a pulsed output during continuous thermal protection.

Thermal protection is designed to protect the IC in the event of

over temperature conditions. For normal operation, the junction