L4971D

L4971 1.5A STEP DOWN SWITCHING REGULATOR 1 ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 2 FEATURES Figure 1. Package UP TO 1.5A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 8V TO 55V PRECISE 3.3V (±1%) INTERNAL REFERENCE VOLTAGE OUTPUT VOLTAGE ADJUSTABLE FROM 3.3V TO 50V SWITCHING FREQUENCY ADJUSTABLE UP TO 300KHz VOLTAGE FEEDFORWARD ZERO LOAD CURRENT OPERATION INTERNAL CURRENT LIMITING (PULSEBYPULSE AND HICCUP MODE) INHIBIT FOR ZERO CURRENT CONSUMPTION PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN SOFT START FUNCTION DIP8 SO16W Table 1. Order Codes Part Number Package L4971 DIP8 L4971D SO16W L4971D013TR SO16 in Tape & Reel A switching frequency up to 300KHz is achievable (the maximum power dissipation of the packages must be observed). A wide input voltage range between 8V to 55V and output voltages regulated from 3.3V to 50V cover the majority of today’s applications. 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, DIP8 for standard assembly, and SO16W for SMD assembly. DESCRIPTION The L4971 is a step down monolithic power switching regulator delivering 1.5A at a voltage between 3.3V and 50V (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. Figure 1. Block Diagram Vi=8V to 55V 5 8 R1 20K L4971 3 C1 220µF 63V C7 220nF C2 2.7nF C5 100nF 2 4 1 7 R2 9.1K C4 22nF L1 126µH (77120) 6 C6 100nF D1 STPS 3L60U VO=3.3V/1.5A C8 330µF D97IN748A May 2005 Rev. 11 1/13 L4971 Figure 2. Block Diagram VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE 2 SS_INH INHIBIT SOFTSTART 3.3V INTERNAL REFERENCE INTERNAL SUPPLY 5.1V 7 COMP 6 8 FB E/A PWM R 3.3V Q S CBOOT CHARGE AT LIGHT LOADS DRIVE OSCILLATOR 1 3 OSC BOOT 4 GND D97IN594 OUT Figure 3. Pin Connections N.C. 1 16 N.C. GND 2 15 N.C. GND 1 8 FB SS_INH 3 14 FB SS_INH 2 7 COMP OSC 4 13 COMP OSC 3 6 BOOT OUT 5 12 BOOT OUT 4 5 VCC OUT 6 11 VCC N.C. 7 10 N.C. N.C. 8 9 N.C. D97IN595 D97IN596 DIP8 SO16 Table 2. Pin Description DIP SO (*) Name Function 1 2 GND 2 3 SS_INH 3 4 OSC 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) 4 5, 6 OUT Stepdown regulator output 5 11 VCC Unregulated DC input voltage 6 12 BOOT A capacitor connected between this pin and OUT allows to drive the internal DMOS Transistor 7 13 COMP E/A output to be used for frequency compensation 8 14 FB 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 disabled the device (driven by open collector/drain). Stepdown feedback input. Connecting directly to this pin results in an output voltage of 3.3V. An external resistive divider is required for higher output voltages. (*) Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die. 2/13 L4971 Table 3. Absolute Maximum Ratings Symbol Minidip S016 V5 V11 V4 V5,V6 I4 I5,I6 V6-V5 V12-V11 Parameter Input voltage Value Unit 58 V Output DC voltage -1 V Output peak voltage at t = 0.1µs f=200KHz -5 V Maximum output current int. limit. 14 V V6 V12 Bootstrap voltage 70 V V7 V13 Analogs input voltage (VCC = 24V 12 V V2 V3 Analogs input voltage (VCC = 24V) 13 V V8 V14 (VCC = 20V) 6 -0.3 V V DIP8 1 W SO16 0.8 W -40 to 150 °C Ptot Tj,Tstg Power dissipation a Tamb ≤60°C Junction and storage temperature Table 4. Thermal Data Symbol Rth(j-amb) Parameter Thermal Resistance Junction to ambient Max. DIP8 SO16 Unit 90 (*) 110 (*) °C/W (*) Package mounted on board. 3 ELECTRICAL CHARACTERISTCS Table 5. (Tj = 25°C, Cosc = 2.7nF, Rosc = 20kΩ, VCC = 24V, unless otherwise specified.) * Specification Refered to Tj from 0 to 125°C Symbol Parameter Test Condition Min. Typ. Max. Unit 55 V DYNAMIC CHARACTERISTIC VI Operating input voltage range Vo = 3.3 to 50V; Io = 1.5A Vo Output voltage Io = 0.5A 3.33 3.36 3.39 V Io = 0.2 to 1.5A 3.292 3.36 3.427 V 3.22 3.36 3.5 V 0.44 0.55 V 0.88 V 3 A Vcc = 8 to 55V Vd Dropout voltage * * 8 Vcc = 10V; Io = 1.5A * Il fs SVRR Maximum limiting current Efficiency Vcc = 8 to 55V * 2 Vo = 3.3V; Io = 1.5A Switching frequency 2.5 85 * 90 100 % 110 60 KHz dB Supply voltage ripple rejection Vi = Vcc+2VRMS; Vo = Vref; Io = 1.5A; f ripple = 100Hz Voltage stability of switching frequency Vcc = 8 to 55V 3 Temp. stability of switching frequency Tj = 0 to 125°C 4 6 % % 3/13 L4971 Table 5. (Tj = 25°C, Cosc = 2.7nF, Rosc = 20kΩ, VCC = 24V, unless otherwise specified.) * Specification Refered to Tj from 0 to 125°C Soft Start Soft start charge current 30 40 50 µA Soft start discharge current 6 10 14 µA 0.9 V 5 15 µA 4 6 mA Inhibit VLL Low level voltage * IsLL Isource Low level * DC Characteristics Iqop Iq Iqst-by Total operating quiescent current Quiescent current Duty Cycle = 0; VFB = 3.8V 2.5 3.5 mA Total stand-by quiescent current Vinh