L5971

® L5971 1.5A STEP DOWN SWITCHING REGULATOR UP TO 1.5A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 6.5V TO 28V PRECISE 1.26V (±1%) INTERNAL REFERENCE VOLTAGE OUTPUT VOLTAGE ADJUSTABLE FROM 1.26V TO 20V SWITCHING FREQUENCY ADJUSTABLE UP TO 500KHz VOLTAGE FEEDFORWARD ZERO LOAD CURRENT OPERATION INTERNAL CURRENT LIMITING (PULSE-BYPULSE AND HICCUP MODE) INHIBIT FOR ZERO CURRENT CONSUMPTION PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN SOFT START FUNCTION DESCRIPTION The L5971 is a step down monolithic power switching regulator delivering 1.5A at a voltage between 1.26V and 20V (selected by a simple external divider). Realized in BCD mixed technology, the device uses an internal power D-MOS transistor (with a typical Rdson of 0.25Ω) to obtain very high efficency and high switching speed. TYPICAL APPLICATION CIRCUIT Vi=6V to 28V R1 22K 3(4) 2(3) C2 1.2nF C5 47nF Minidip SO16W ORDERING NUMBERS: L5971 (Minidip) L5971D (SO16) A switching frequency up to 500KHz is achievable (the maximum power dissipation of the packages must be observed). Features of this new generations of DC-DC converter include pulse-by-pulse current limit, hiccup mode for short circuit protection, voltage feedforward regulation, soft-start, protection against feedback loop disconnection, inhibit for zero current consumption and thermal shutdown. The device is available in plastic dual in line, MINIDIP 8 for standard assembly, and SO16 for SMD assembly. Typical Applications: - High efficiency step-down converter - Portable computers - Battery charger - Distributed power - PDAs and Mobile Comminicators 5(11) 8(14) L5971 7(13) 4(5,6) VO=2.5V/1.5A L1 30µH R3 1(2) 6(12) C1 47µF 30V R2 9.1K C4 22nF C6 100nF D1 STPS 3L40U C8 330µF R4 D98IN832C May 2000 1/11 L5971 BLOCK DIAGRAM VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE SS_INH 2 INHIBIT SOFTSTART 1.26V COMP FB 7 8 E/A INTERNAL REFERENCE INTERNAL SUPPLY 5.1V 6 PWM BOOT R S 1.26V Q DRIVE OSCILLATOR 1 GND CBOOT CHARGE AT LIGHT LOADS 3 OSC 4 OUT D98IN833 PIN CONNECTIONS N.C. GND 1 2 3 4 5 6 7 8 D97IN596 16 15 14 13 12 11 10 9 N.C. N.C. FB COMP BOOT VCC N.C. N.C. GND SS_INH OSC OUT 1 2 3 4 D97IN595 8 7 6 5 FB COMP BOOT VCC SS_INH OSC OUT OUT N.C. N.C. Minidip SO16W PIN FUNCTIONS DIP 1 2 SO (*) 2 3 Name GND SS_INH Function Ground A logic signal (active low) disables the device (sleep mode operation). A capacitor connected between this pin and ground determines the soft start time. When this pin is grounded disables the device (driven by open collector/drain). An external resistor connected between the unregulated input voltage and this pin and a capacitor connected from this pin to ground fix the switching frequency. (Line feed forward is automatically obtained) Stepdown regulator output Not regulated DC input voltage A capacitor connected between this pin and OUT allows to drive the internal VDMOS E/A output to be used for frequency compensation Stepdown feedback input. Connecting directly this pin to the output 1.26V is obtained; a voltage divider is requested for higher output voltages 3 4 OSC 4 5 6 7 8 5, 6 11 12 13 14 OUT VCC BOOT COMP FB (*) Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die. 2/11 L5971 THERMAL DATA Symbol R th(j-amb) Parameter Thermal Resistance Junction to ambient Max. Minidip 90 (*) SO16 110 (*) Unit °C/W (*) Package mounted on board. ABSOLUTE MAXIMUM RATINGS Symbol Minidip V5, V3 V4 I4 V6-V5 V6 V7,V2 V8 Ptot Tj,Tstg S016 V11, V4 V5,V6 I5,I6 V12-V11 V12 V13,V3 V14 Bootstrap voltage Analogs input voltage (VCC = 12V) (VCC = 20V) Power dissipation a Tamb ≤ 60°C Junction and storage temperature Minidip SO16 Input voltage Output DC voltage Output peak voltage at t = 0.1µs f=200KHz Maximum output current Parameter Value 30 -1 -5 int. limit. 14 45 10 6 -0.3 1 0.8 -40 to 150 V V V V V W W °C Unit V V V ELECTRICAL CHARACTERISTICS (Tj = 25°C, Cosc = 2.7nF, Rosc = 20kΩ, VCC = 12V, unless otherwise specified.) * Specification Refered to Tj from 0 to 125 °C Symbol Parameter Test Condition Min. Typ. Max. Unit DYNAMIC CHARACTERISTIC VI Vo Operating input voltage range Output voltage * Io = 0.5A Io = 0.2 to 1.5A Vcc = 6.5 to 25V Vcc = 10V; Io = 1.5A Vcc = 6.5 to 25V Vo = 3.3V; Io = 1.5A Vi = Vcc+2VRMS; Vo = Vref; Io = 1.5A; f ripple = 100Hz Vcc = 6.5 to 25V Tj = 0 to 125°C 6.5 1.247 1.235 1.21 1.26 1.26 1.26 0.44 2.5 85 100 28 1.273 1.285 1.31 0.55 0.88 3 110 V V V V V V A % KHz dB % % * * * * Vd Il fs SVRR Dropout voltage Maximum limiting current Efficiency Switching frequency Supply voltage ripple rejection Voltage stability of switching frequency Temp. stability of switching frequency 2 90 60 3 4 6 Soft Start Soft start charge current Soft start discharge current 30 6 40 10 50 14 µA µA V µA 3/11 Inhibit VLL IsLL Low level voltage Isource Low level * * 5 0.9 15 L5971 ELECTRICAL CHARACTERISTICS (continued) Symbol Parameter Total operating quiescent current Quiescent current Total stand-by quiescent current Test Condition Pin 5 (Pin 11) Duty Cycle = 0; VFB = 1.7V Vinh