ST890 datasheet(9/20 Pages) STMICROELECTRONICS

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ST890

Maximum rating

9/20

2.1

Functional description

2.1.1

Output current limit

ILIM is the output current that ST890 limits under the condition VO (output voltage) > 1.6 V.

When ILIM is reached, the Fault pin is asserted.

2.1.2

Output short circuit protection

The ST890 provides short circuit protection by limiting the output current during a short

circuit event.

Isc is the output short circuit current limit level (typ 1.2 x ILIM). When the output is short circuit

such as VO < 1.6 V, the ST890 limits the output current to no more than the Isc level.

When the output is short circuit, the Fault pin is asserted.

2.1.3

Programming ILIM

The ST890's ILIM can be programmed through the external resistor, RSET connected at the

SET pin (pin 5).

ILIM is determined by the following relationships:

Equation 1

Equation 2

therefore:

Equation 3

2.1.4

Fault pin

The Fault pin (pin 8) is an open drain active low output. This pin should be connected to an

external pull-up resistor.

The Fault pin is asserted low when:

–IOUT reaches the programmed ILIM value

–

A short circuit event occurs

–

The device goes into thermal protection

2.1.5

Thermal protection

The ST890's thermal protection is triggered to turn off the switch when the junction

temperature exceeds 130°C (typ).

SET

1110

SET

LIM

SET

1110

1.24

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