L4964HT STMicroelectronics

L4964 HIGH CURRENT SWITCHING REGULATOR . 4 A OUTPUT CURRENT . 5.1 V TO 28 V OUTPUT VOLTAGE RANGE . 0 TO 100 % DUTY CYCLE RANGE . PRECISE ( 3 %) ON-CHIP REFERENCE . SWITCHING FREQUENCY UP TO 120 KHz . VERY HIGH EFFICIENCY (UP TO 90 %) . VERY FEW EXTERNAL COMPONENTS . SOFT START . RESET OUTPUT MULTIWATT15 Vertical (Plastic Package) . CURRENT LIMITING .INPUT FOR REMOTE INHIBIT AND SYN- ORDERING NUMBER : L4964 CHRONUS PWM . THERMAL SHUTDOWN DESCRIPTION The L4964 is a stepdown power switching regulator delivering 4A at a voltage variable from 5.1V to 28V. Features of the device include overload protection, soft start, remote inhibit, thermal protection, a reset output for microprocessors and a PWM comparator input for synchronization in multichip configurations. The L4964 is mounted in a 15-lead Multiwatt plas- tic power package and requires very few external MULTIWATT15 Horizontal components. (Plastic Package) Efficient operation at switching frequencies up to ORDERING NUMBER : L4964HT 120kHz allows a reduction in the size and cost of ex- ternal filter components. PIN CONNECTION (top view) Pins 1, 4, 15 must not be connected. Leave open circuit. 1/13 July 2003L4964 PIN FUNCTIONS N Name Function 1 N.C. Must not be connected. Leave open circuit. 2 Output Regulator Output. 3 Supply Voltage Unregulated Voltage Input. An internal regulator powers the L4964s internal logic. 4 N.C. Must not be connected. Leave open circuit. 5 Soft Start Soft Start Time Constant. A capacitor is connected between this terminal and ground to define the soft start time constant. This capacitor also determines the average short circuit output current. 6 Inhibit Input TTL - Level Remote Inhibit. A logic high level on this input disables the L4964. 7 Sync Input Multiple L4964s are synchronized by connecting the pin 7 inputs together and omitting the oscillator RC network on all but one device. 8 Ground Common Ground Terminal. 9 Frequency A series RC network connected between this terminal and ground determines the Compensation regulation loop gain characteristics. 10 Feedback The Feedback Terminal of the Regulation Loop. The output is connected directly to Input this terminal for 5.1 V operation it is connected via a divider for higher voltages. 11 Oscillator A parallel RC network connected to this terminal determines the switching frequency. The pin must be connected to pin 7 input when the internal oscillator is used. 12 Reset Input Input of the Reset Circuit. The threshold is roughly 5 V. It may be connected to the beedback point or via a divider to the input. 13 Reset Delay A capacitor connected between this terminal and ground determines the reset signal delay time. 14 Reset Output Open Collector Reset Signal Output. This output is high when the supply is safe. 15 N.C. Must not be connected. Leave open circuit. BLOCK DIAGRAM 2/13