33099 datasheet(8/18 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33099

FUNCTIONAL DESCRIPTION

INTRODUCTION

FUNCTIONAL DESCRIPTION

INTRODUCTION

The 33099 is specifically designed for regulation of an

automotive system voltage using diode-rectified alternator

charging systems commonly found in automotive

applications. The 33099 provides either an analog or digital

duty cycle control of an ON/OFF ratio of an alternator field

current at a fixed frequency. This provides for a Load

Response Control (LRC) of the alternator field current at low

engine RPM to eliminate engine speed hunting and vibration

owing to abrupt torque loading of the engine when a sudden

electrical load is applied to the system. Four LRC rates are

selectable using a combination of pins 7 and 8 being

connected to ground.

The 33099 provides a regulated voltage feedback system

to activate the alternator field current in response to system

load current. The output voltage is monitored by an internal

voltage divider scheme and compared to an internal voltage

ramp referenced to a bandgap voltage. The 33099 regulates

the system voltage to 14.8 V for the DW suffix and to 14.6 V

for the CDW suffix by generating a pulse width modulation

(PWM) voltage waveform at the GATE of an external

MOSFET to provide an average alternator field coil current as

a function of the internal voltage comparison.

33099 Datasheet(PDF) 8 Page - Freescale Semiconductor, Inc