MIC2171WT Microchip

MIC2171 100kHz 2.5A Switching Regulator General Description Features The MIC2171 is a complete 100kHz SMPS current-mode 2.5A, 65V internal switch rating controller with an internal 65V 2.5A power switch. 3V to 40V input voltage range Although primarily intended for voltage step-up applica- Current-mode operation, 2.5A peak tions, the floating switch architecture of the MIC2171 Internal cycle-by-cycle current limit makes it practical for step-down, inverting, and Cuk config- Thermal shutdown urations as well as isolated topologies. Twice the frequency of the LM2577 Operating from 3V to 40V, the MIC2171 draws only 7mA Low external parts count of quiescent current, making it attractive for battery Operates in most switching topologies operated supplies. 7mA quiescent current (operating) The MIC2171 is available in a 5-pin TO-220 or TO-263 for 40C to +85C operation. Fits LT1171/LM2577 TO-220 and TO-263 sockets Data sheets and support documentation can be found on Micrels web site at: www.micrel.com. Applications Laptop/palmtop computers Battery operated equipment Hand-held instruments Off-line converter up to 50W(requires external power switch) Pre-driver for higher power capability Typical Application +5V V OUT V IN (4.75V min.) 5V, 0.5A T1 4V to 6V C1* L1 D2 C1 R4* C3* 47F 15H 47F 1N5818 R1 V OUT C4 3.74k IN D1 +12V, 0.25A 470F 1% D1* SW IN R1 1N5822 SW 10.7k MIC2171 1:1.25 1% L = 12H PRI MIC2171 COMP FB R2 R3 GND C2 COMP FB 1.24k 1k 470F R2 1% R3 C3 GND 1.24k 1k 1F 1% C2 1F * Locate near MIC2171 when supply leads > 2 * Optional voltage clipper (may be reqd if T1 leakage inductance too high) Figure 1. MIC2171 5V to 12V Boost Converter Figure 2. MIC2171 5VFlyback Converter Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC2171 Ordering Information Part Number Standard RoHS Compliant* Temperature Range Package MIC2171BT MIC2171WT 40 to +85C 5-Pin TO-220 MIC2171BU MIC2171WU 40 to +85C 5-Pin TO-263 *RoHS compliant withhigh-melting solde exemption. Pin Configuration 5IN 5 IN 4SW 4SW 3GND 3GND 2FB 2FB 1COMP 1COMP Tab GND Tab GND 5-Pin TO-220 (T) 5-Pin TO-263 (U) Pin Description Pin Number Pin Name Pin Function Frequency Compensation: Output of transconductance-type error amplifier. 1 COMP Primary function is for loop stabilization. Can also be used for output voltage soft-start and current limit tailoring. 2 FB Feedback: Inverting input of error amplifier. Connect to external resistive divider to set power supply output voltage. 3 GND Ground: Connect directly to the input filter capacitor for proper operation (see applications info). 4 SW Power Switch Collector: Collector of NPN switch. Connect to external inductor or input voltage depending on circuit topology. 5 IN Supply Voltage: 3.0V to 40V M9999-051107 May 2007 2