Si9140

Vishay Siliconix

Document Number: 70026

S-40699—Rev. H, 19-Apr-04

www.vishay.com

7

PIN DESCRIPTION

The positive power supply for all functional blocks except

output driver. A bypass capacitor of 0.1 mF (minimum) is

recommended.

Pin 2: MON

Non-inverting input of a comparator. Inverting input is tied

internally to reference voltage. This comparator is typically

used to monitor the output voltage and to flag the processor

when the output voltage falls out of regulation.

This is an open drain output. It will be held at ground when the

voltage at MON (Pin 2) is less than the internal reference. An

external pull-up resistor will pull this pin high if the MON pin (Pin

Pin 4: COMP

This pin is the output of the error amplifier. A compensation

network is connected from this pin to the FB pin to stabilize the

system. This pin drives one input of the internal pulse width

modulation comparator.

Pin 5: FB

The inverting input of the error amplifier. An external resistor

divider is connected to this pin to set the regulated output

voltage. The compensation network is also connected to this

pin.

Pin 6: NI

The non-inverting input of the error amplifier. In normal

reference.

This pin supplies a 1.5-V reference.

Pin 8: GND (Ground)

Pin 9: ENABLE

A logic high on this pin allows normal operation. A logic low

places the chip in the standby mode. In standby mode normal

operation is disabled, supply current is reduced, the oscillator

A resistor connected from this pin to ground sets the

See the oscillator section of the description of operation.

An external capacitor is connected to this pin to set the

oscillator frequency.

0.75

exceeds 1.2 V, the chip operates normally. There is a built-in

hysteresis of 165 mV.

This CMOS push-pull output pin drives the external p-channel

MOSFET. This pin will be high in the standby mode. A

This CMOS push-pull output pin drives the external n-channel

MOSFET. This pin will be low in the standby mode. A

The positive terminal of the power supply which powers the

CMOS output drivers. A bypass capacitor is required.