L296 STMicroelectronics

L296 L296P HIGH CURRENT SWITCHING REGULATORS . 4 A OUTPUT CURRENT . 5.1 V TO 40 V OUTPUT VOLTAGE RANGE 0 TO 100 % DUTY CYCLE RANGE . PRECISE (2 %) ON-CHIP REFERENCE SWITCHING FREQUENCY UP TO 200 KHz . VERY HIGH EFFICIENCY (UP TO 90 %) . VERY FEW EXTERNAL COMPONENTS SOFT START . RESET OUTPUT . Multiwatt EXTERNAL PROGRAMMABLE LIMITING (15 lead) . CURRENT (L296P) . CONTROL CIRCUIT FOR CROWBAR SCR ORDERING NUMBERS : INPUT FOR REMOTE INHIBIT AND . L296 (Vertical) L296HT (Horizontal) SYNCHRONUS PWM L296P (Vertical) L296PHT (Horizontal) . THERMAL SHUTDOWN DESCRIPTION The L296 and L296P are stepdown power switching The L296 and L296P are mounted in a 15-lead Mul- regulators delivering 4 A at a voltage variable from tiwatt plastic power package and requires very few 5.1 V to 40 V. external components. Features of the devices include soft start, remote in- Efficient operation at switching frequencies up to hibit, thermal protection, a reset output for micro- 200 KHz allows a reduction in the size and cost of processors and a PWM comparator input for syn- external filter components. A voltage sense input chronization in multichip configurations. and SCR drive output are provided for optional The L296P incudes external programmable limiting crowbar overvoltage protection with an external current. SCR. PIN CONNECTION (top view) 1/22 June 2000L296 - L296P PIN FUNCTIONS N Name Function 1 CROWBAR INPUT Voltage Sense Input for Crowbar Overvoltage Protection. Normally connected to the feedback input thus triggering the SCR when V exceeds nominal by 20 %. May out also monitor the input and a voltage divider can be added to increase the threshold. Connected to ground when SCR not used. 2 OUTPUT Regulator Output 3 SUPPLY VOLTAGE Unrergulated Voltage Input. An internal Regulator Powers the L296s Internal Logic. 4 CURRENT LIMIT A resistor connected between this terminal and ground sets the current limiter threshold. If this terminal is left unconnected the threshold is internally set (see electrical characteristics). 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 device. 7 SYNC INPUT Multiple L296s 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 INPUT The Feedback Terminal on the Regulation Loop. The output is connected directly to this terminal for 5.1V operation it is connected via a divider for higher voltages. 11 OSCILLATOR A parallel RC networki connected to this terminal determines the switching frequency. This 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 feedback 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 CROWBAR OUTPUT SCR gate drive output of the crowbar circuit. BLOCK DIAGRAM 2/22