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L296P Dataheets PDF



Part Number L296P
Manufacturers STMicroelectronics
Logo STMicroelectronics
Description HIGH CURRENT SWITCHING REGULATORS
Datasheet L296P DatasheetL296P Datasheet (PDF)

® 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 EXTERNAL PROGRAMMABLE LIMITING CURRENT (L296P) CONTROL CIRCUIT FOR CROWBAR SCR INPUT FOR REMOTE INHIBIT AND SYNCHRONUS PWM THERMAL SHUTDOWN Multiwatt (15 lead) ® ORDERING NUMBERS : L296.

  L296P   L296P



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® 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 EXTERNAL PROGRAMMABLE LIMITING CURRENT (L296P) CONTROL CIRCUIT FOR CROWBAR SCR INPUT FOR REMOTE INHIBIT AND SYNCHRONUS PWM THERMAL SHUTDOWN Multiwatt (15 lead) ® ORDERING NUMBERS : L296 (Vertical) L296HT (Horizontal) L296P (Vertical) L296PHT (Horizontal) DESCRIPTION The L296 andL296P are stepdownpowerswitching regulators delivering 4 A at a voltage variable from 5.1 V to 40 V. Featuresof the devices includesoft start, remoteinhibit, thermal protection, a reset output for microprocessors and a PWM comparator input for synchronization in multichip configurations. The L296P incudes external programmable limiting current. PIN CONNECTION (top view) The L296 and L296P are mounted in a 15-lead Multiwatt® plasticpowerpackageand requiresvery few external components. Efficient operation at switching frequencies up to 200 KHz allows a reduction in the size and cost of external filter components. A voltage sense input and SCR drive output are provided for optional crowbar overvoltage protection with an external SCR. June 2000 1/22 L296 - L296P PIN FUNCTIONS N° 1 Name CROWBAR INPUT Function Voltage Sense Input for Crowbar Overvoltage Protection. Normally connected to the feedback input thus triggering the SCR when V out exceeds nominal by 20 %. May also monitor the input and a voltage divider can be added to increase the threshold. Connected to ground when SCR not used. Regulator Output Unrergulated Voltage Input. An internal Regulator Powers the L296s Internal Logic. 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). 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. TTL – Level Remote Inhibit. A logic high level on this input disables the device. Multiple L296s are synchronized by connecting the pin 7 inputs together and omitting the oscillator RC network on all but one device. Common Ground Terminal A series RC network connected between this terminal and ground determines the regulation loop gain characteristics. 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. 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. 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. A capacitor connected between this terminal and ground determines the reset signal delay time. Open collector reset signal output. This output is high when the supply is safe. SCR gate drive output of the crowbar circuit. 2 3 4 OUTPUT SUPPLY VOLTAGE CURRENT LIMIT 5 SOFT START 6 7 8 9 10 11 12 13 14 15 INHIBIT INPUT SYNC INPUT GROUND FREQUENCY COMPENSATION FEEDBACK INPUT OSCILLATOR RESET INPUT RESET DELAY RESET OUTPUT CROWBAR OUTPUT BLOCK DIAGRAM 2/22 L296 - L296P CIRCUIT OPERATION (refer to the block diagram) The L296 and L296P are monolithic stepdown switching regulators providing output voltages from 5.1V to 40V and delivering 4A. The regulationloop consists of a sawtoothoscillator, error amplifier, comparatorand the outputstage. An error signal is produced by comparing the output voltage with a precise 5.1V on-chipreference(zener zap trimmed to ± 2 %). This error signalis then compared with the sawtooth signal to generate the fixed frequencypulse width modulatedpulseswhich drive the output stage.The gain and frequencystability of the loop can be adjustedby an externalRC network connectedto pin9. Closing the loop directlygives an outputvoltageof 5.1V.Higher voltagesare obtained by inserting a voltage divider. Output overcurrents at switch on are prevented by the soft start function. The error amplifier output is initially clamped by the external capacitor Css and allowed to rise, linearly, as this capacitor is charged by a constant current source. Outputoverloadprotection is provided in the form of a current limiter. The load current is sensed by an internal metal resistor connected to a comparator. When the load current exceeds a preset threshold this comparator sets a flip flop which disables the outputstage and discharges the soft start capacitor. A second comparator resets the flip flop when the voltage across the soft start capacitor has fallen to Figure 1 : Reset Output Waveforms 0.4V. The output stage is thus re-enabled and the output vol.


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