LT1776 Wide Input Range, High Efficiency, Step-Down Switching Regulator UFEATURESDESCRIPTION ■ Wide Input Range: 7.4V to 40V The LT®1776 is a wide input range, high efficiency Buck ■ Tolerates Input Transients to 60V (step-down) switching regulator. The monolithic die in- ■ 700mA Peak Switch Rating cludes all oscillator, control and protection circuitry. The ■ Adaptive Switch Drive Maintains Efficiency at High part can accept input voltages as high as 60V and contains Load Without Pulse Skipping at Light Load an output switch rated at 700mA peak current. Current ■ True Current Mode Control mode control delivers excellent dynamic input supply ■ 200kHz Fixed Operating Frequency rejection and short-circuit protection. ■ Synchronizable to 400kHz The LT1776 contains several features to enhance effi- ■ Low Supply Current in Shutdown: 30µA ciency. The internal control circuitry is normally powered ■ Available in 8-Pin SO and PDIP Packages via the VCC pin, thereby minimizing power drawn directly U from the VIN supply (see Applications Information). The APPLICATIONS action of the LT1776 switch circuitry is also load depen- ■ dent. At medium to high loads, the output switch circuitry Automotive DC/DC Converters ■ maintains fast rise time for good efficiency. At light loads, Cellular Phone Battery Charger Accessories ■ rise time is deliberately reduced to avoid pulse skipping IEEE 1394 Step-Down Converters behavior. The available SO-8 package and 200kHz switching fre- quency allow for minimal PC board area requirements. , LTC and LT are registered trademarks of Linear Technology Corporation. UTYPICAL APPLICATION VIN Efficiency vs VIN and ILOAD 8V TO 40V 5 90 VIN 1 2 SHDN VCC 80 100µH* 3 5V VSW 70 + + 400mA 39µF 100µF LT1776 MBR160 36.5k 63V 10V 1% 60 7 FB 6 8 50 SYNC VC EFFICIENCY (%) 2200pF 40 12.1k VIN = 10V 1% VIN = 20V GND 22k 100pF 30 VIN = 30V 4 VIN = 40V 20 *43T #30 ON MAGNETICS 1776 F01 1 10 100 1000 MPP #55030 LOAD CURRENT (mA) 1776 TA01 Figure 1 1
