SP6122ACUSLASHTR datasheet(4/19 Pages) SIPEX

4 / 19 page

Date: 10/02/04

SP6122 Low Voltage, Micro 8, PFET, Buck Controller

PIN DESCRIPTION

PIN #

PIN NAME

DESCRIPTION

VCC

Main Supply Pin: A RC filter as shown in the application circuit is

recommended. The decoupling capacitor needs to be close to the pin.

FFLAG

Fault Flag Pull-down Pin: Sinks current during a fault condition. Can

be hooked up to ENABLE to initiate Hiccup Timing.

VOUT

Regulated Output Voltage: This voltage is divided internally and

compared to a 1.5%, 1.25V reference at the PFM comparator.

ENABLE

Enable Input: Floating this pin or pulling above 1.45V enables the

part. Pulling this pin to less than 0.9V will disable the part. A minimum

100pF capacitor is required between this pin and Ground to ensure

proper startup. If FFLAG is hooked to ENABLE, the capacitor on

ENABLE will control hiccup timing.

ISENSE

Negative Input to the Over Current Amplifier/Comparator: This input

is subtracted from the ISET input and gained by a factor of 3.3. The

output of this amplifier is compared with a 0.5V threshold, yielding a

150mV threshold. This threshold has a 3800 ppm/°C temperature

coefficient. If the subtraction exceeds 150mV, charge is pumped into

a capacitor until the capacitor hits VCC/2. At this time, the over current

fault is activated. If ISET = 0V and ISENSE = VCC, the part enters an

unprotected, 150µA quiescent current mode.

ISET

Positive Input to the Over Current Amplifier: 20µA flows into the ISET

pin if it is pulled through a resistor to VIN. This current has a

4300ppm/°C temperature coefficient and can be used via external

resistor to raise the overcurrent trip point from 150mV to some higher

value. If ISET = 0V and ISENSE = 0V, the part enters an unprotected,

250µA quiescent current mode.

GND

Power and Analog Ground: Hook directly to output ground.

PDRV

Drive for PFET High Side Switch: 1nF/20ns Output Driver.

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