TO 3.5A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 55V 3.3V AND 5.1V (±1%) FIXED OUTPUT, AND ADJUSTABLE OUTPUTS FROM: 50V (3.3V type) 50V (5.1 type) FREQUENCY ADJUSTABLE TO 300KHz VOLTAGE FEED FORWARD ZERO LOAD CURRENT OPERATION (min 1mA) INTERNAL CURRENT LIMITING (PULSE BY PULSE AND HICCUP MODE) PRECISE 5.1V (1.5%) REFERENCE VOLTAGE EXTERNALLY AVAILABLE INPUT/OUTPUT SYNCHRONIZATION FUNCTION INHIBIT FOR ZERO CURRENT CONSUMPTION (100µA Typ. at VCC = 24V) PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN OUTPUT OVERVOLTAGE PROTECTION SOFT START FUNCTION TYPICAL APPLICATION CIRCUIT (POWERDIP)
DESCRIPTION The is a step down monolithic power switching regulator delivering 3.5A at fixed voltages or 5.1V and using a simple external divider output adjustable voltage to 50V. Realized in BCD mixed technology, the device
uses an internal power D-MOS transistor (with a typical Rdson 0.15ohm) to obtain very high efficiency and very fast switching times. Switching frequency to 300KHz are achievable (the maximum power dissipation of the packages must be observed). A wide input voltage range between to 55V and output voltages regulated from to 40V cover the majority of the today applications. Features of this new generation of DC-DC conPIN CONNECTIONS (Top view) verter includes pulse by pulse current limit, hiccup mode for output short circuit protection, voltage feed forward regulation, soft start, input/output synchronization, protection against feedback loop disconnection, inhibit for zero current consumption and thermal shutdown. Packages available are in plastic dual in line, DIP18 (12+3+3) for standard assembly, and SO20 (12+4+4) for SMD assembly.
INH 16(18) 7(8) VCC 8(9) CBOOT CHARGE ZERO CURRENT INHIBIT VREF GOOD INTERNAL REFERENCE INTERNAL SUPPLY 5.1V VCC
Symbol Rth(j-pin) Rth(j-amb) Parameter Thermal Resistance Junction to pin Thermal Resistance to Ambient Max. Powerdip 15 80 Unit °C/W
Symbol V18 V10 Ptot V20 V11 Parameter Input voltage Output DC voltage Output peak voltage 0.1µs f=200KHz Maximum output current Bootstrap voltage Analogs input voltage (VCC = 24V) Analogs input voltage (VCC = 24V) (VCC = 20V) (VCC = 20V) Inhibit Power dissipation a Tpins 90°C (Tamb 70°C no copper area) (Tamb 70°C 4cm copper area on PCB) Power dissipation a Tpins = 90°C Junction and storage temperature DIP 12+3+3 SO20 Value -1 -5 int. limit. Vcc 150 °C Unit V
Powerdip SO20 NAME COMP INH BOOT SYNC Vcc OUT VFB DESCRIPTION E/A output to be used for frequency compensation A logic signal (active high) disables the device (sleep mode operation). If not used it must be connected to GND; if floating the device is disabled. A capacitor connected between this pin and the output allows to drive the internal D-MOS. Input/Output synchronization. Unregulated DC input voltage Stepdown regulator output. Stepdown feedback input. Connecting the output directly to this pin results in an output voltage of 3.3V for the L4973V3.3 and 5.1V. An external resistive divider is required for higher output voltages. For output voltage less than 3.3V, see note and Figure 32. Reference voltage externally available. Signal ground An external resistor connected between the unregulated input voltage and Pin 1 and a capacitor connected from Pin 1 to ground fixes the switching frequency. (Line feed forward is automatically obtained)