LM2574-3.3YN Microchip

LM2574 Micrel, Inc. LM2574 52kHz Simple 0.5A Buck Regulator General Description Features The LM2574 family is a series of easy to use xed and ad- 3.3V, 5V, 12V, and adjustable output versions justable switching voltage regulators. The LM2574 contains Adjustable version output 1.23V to 37V 4% max. over all of the active circuitry necessary to construct a stepdown line and load conditions. (buck) switching regulator and requires a minimum of external Guaranteed 0.5A output current components. Wide input voltage, up to 40V Thermal shutdown and current limit protection The LM2574 is available in 3.3V and 5V xed output ver- Requires only 4 external components. sions, or an adjustable version with an output voltage range Shutdown capability (standby mode) of 1.23V to 37V. Output voltage is guaranteed to 4% for Low power standby mode < 200A Typical specied input and load conditions. High-efciency The LM2574 can supply 0.5A while maintaining excellent 52kHz xed frequency internal oscillator line and load regulation. The output switch includes cycle- Uses standard inductors by-cycle current limiting, as well as thermal shutdown for full protection under fault conditions. Applications An external shutdown connection selects operating or standby Simple high-efciency step-down (buck) regulator modes. Standby current is less than 200A. Efcient pre-regulator for linear regulators On-card switching regulators Heat sinks are generally unnecessary due the regulators Positive to negative converter (buck-boost) high efciency. Adequate heat transfer is usually provided by soldering all package pins to a printed circuit board. The LM2574 includes internal frequency compensation and an internal 52kHz xed frequency oscillator guaranteed to 10% of the frequency. Circuits constructed around the LM2574 use a standard series of inductors which are available from several different manufacturers. All support documentation can be found on Micrels web site at www.micrel.com. Typical Application 40V MAX UNREGULATED DC IN FB V IN REGULATED OUTPUT C 330H IN LM2574 0.5A 22F OUT PWR SIG ON/ GND GND OFF C OUT 11DQ05 220F Figure 1. Fixed Output Regulator Circuit Micrel, Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 474-1000 LM2574 Micrel, Inc. Ordering Information Part Number Junction Temp. Range Package Standard Pb-Free LM2574BN LM2574YN 40C to +85C 8-pin Plastic DIP LM2574-3.3BN LM2574-3.3YN 40C to +85C 8-pin Plastic DIP LM2574-5.0BN LM2574-5.0YN 40C to +85C 8-pin Plastic DIP Pin Conguration 8 NC FB 1 7 OUTPUT SIG GND 2 6 NC ON/OFF 3 PWR GND 4 5 VIN 8-Pin DIP (N) M9999-072805 2 July 2005