L5991 L5991A PRIMARY CONTROLLER WITH STANDBY CURRENT-MODE CONTROL PWM MULTIPOWER BCD TECHNOLOGY SWITCHING FREQUENCY UP TO 1MHz LOW START-UP CURRENT (< 120A) HIGH-CURRENT OUTPUT DRIVE SUITABLE FOR POWER MOSFET (1A) FULLY LATCHED PWM LOGIC WITH DOU- BLE PULSE SUPPRESSION PROGRAMMABLE DUTY CYCLE DIP16 SO16 100% AND 50% MAXIMUM DUTY CYCLE LIMIT STANDBY FUNCTION PROGRAMMABLE SOFT START ORDERING NUMBERS: L5991/L5991A (DIP16) L5991D/L5991AD (SO16) PRIMARY OVERCURRENT FAULT DETEC- TION WITH RE-START DELAY line or DC-DC power supply applications using a PWM UVLO WITH HYSTERESIS fixed frequency current mode control. IN/OUT SYNCHRONIZATION Based on a standard current mode PWM control- LATCHED DISABLE ler this device includes some features such as INTERNAL 100ns LEADING EDGE BLANK- programmable soft start, IN/OUT synchronization, disable (to be used for over voltage protection and ING OF CURRENT SENSE for power management), precise maximum Duty PACKAGE: DIP16 AND SO16 Cycle Control, 100ns leading edge blanking on current sense, pulse by pulse current limit, over- DESCRIPTION current protection with soft start intervention, and This primary controller I.C., developed in BCD60II Standby function for oscillator frequency reduction when the converter is lightly loaded. technology, has been designed to implement off BLOCK DIAGRAM SYNC DC-LIM V VREF CC 1 15 8 4 2 TIMING RCT 25V Vref + 3 + DC - T 15V/10V - PWM UVLO 14 9 - DIS DIS V C + 2.5V 13V 10 OUT BLANKING SQ R PWM OVER CURRENT VREF VREF OK 11 CLK 13 PGND FAULT DIS ISEN + SOFT-START 16 - STAND-BY ST-BY 1.2V SS 7 + 2.5V E/A 5 - VFB 2R 1V R 12 6 D97IN725A SGND COMP 1/23 August 2001L5991 - L5991A ABSOLUTE MAXIMUM RATINGS Symbol Parameter Value Unit VCC Supply Voltage (I < 50mA) (*) selflimit V CC I Output Peak Pulse Current 1.5 A OUT Analog Inputs & Outputs (6,7) -0.3 to 8 V Analog Inputs & Outputs (1,2,3,4,5,15,14, 13, 16) -0.3 to 6 V P Power Dissipation T = 70C (DIP16) 1 W tot amb T = 50C (SO16) 0.83 W amb T Junction Temperature, Operating Range -40 to 150 C j Tstg Storage Temperature, Operating Range -55 to 150 C (*) maximum package power dissipation limits must be observed PIN CONNECTION SYNC 1 16 ST-BY RCT 2 15 DC-LIM DC 3 14 DIS VREF 4 13 ISEN VFB 5 12 SGND COMP 6 11 PGND SS7O10UT VCC8V9C THERMAL DATA Symbol Parameter Value Unit R Thermal Resistance Junction -Ambient (DIP16) 80 C/W th j-amb Thermal Resistance Junction -Ambient (SO16) 120 C/W PIN FUNCTIONS N. Name Function 1 SYNC Synchronization. A synchronization pulse terminates the PWM cycle and discharges Ct 2 RCT Oscillator pin for external C , R , R components T A B 3 DC Duty Cycle control 4 VREF 5.0V +/-1.5% reference voltage 25C 5 VFB Error Amplifier Inverting input 6 COMP Error Amplifier Output 7 SS Soft start pin for external capacitor Css 8V Supply for internalSigna circuitry CC 9V Supply for Power section C 10 OUT High current totem pole output 11 PGND Power ground 12 SGND Signal ground 13 ISEN Current sense 14 DIS Disable. It must never be left floating. TIE to SGND if not used. 15 DC-LIM Connecting this pin to Vref, DC is limited to 50%. If it is left floating or grounded no limitation is imposed 16 ST-BY Standby. Connect a resistor to RCT. Connect to VREF or floating if not used. 2/23