LT1676 Wide Input Range, High Efficiency, Step-Down Switching Regulator FEATURES DESCRIPTIO n Wide Input Range: 7.4V to 60V The LT 1676 is a wide input range, high efficiency Buck n 700mA Peak Switch Current Rating (step-down) switching regulator. The monolithic die in- n Adaptive Switch Drive Maintains Efficiency at High cludes all oscillator, control and protection circuitry. The Load Without Pulse Skipping at Light Load part can accept input voltages as high as 60V and contains n True Current Mode Control an output switch rated at 700mA peak current. Current n 100kHz Fixed Operating Frequency mode control offers excellent dynamic input supply rejec- n Synchronizable to 250kHz tion and short-circuit protection. n Low Supply Current in Shutdown: 30m A The LT1676 contains several features to enhance effi- n Available in 8-Pin SO and PDIP Packages ciency. The internal control circuitry is normally powered via the V pin, thereby minimizing power drawn directly CC U from the V supply (see Applications Information). The IN APPLICATIO S action of the LT1676 switch circuitry is also load depen- n Automotive DC/DC Converters dent. At medium to high loads, the output switch circuitry n Telecom 48V Step-Down Converters maintains high rise time for good efficiency. At light loads, n Cellular Phone Battery Charger Accessories rise time is deliberately reduced to avoid pulse skipping n IEEE 1394 Step-Down Converters behavior. The available SO-8 package and 100kHz switching fre- quency allow for minimal PC board area requirements. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIO V IN Efficiency vs V and I IN LOAD 8V TO 50V 5 90 V IN 1 2 80 SHDN V CC 220m H* 3 5V V 70 SW 400mA + + 39m F 100m F 36.5k MBR160 LT1676 63V 10V 60 1% 7 FB 50 6 8 SYNC V C 2200pF V = 12V 40 IN 12.1k V = 24V IN 1% 30 22k 100pF GND V = 36V IN V = 48V IN 4 20 *65T 30 ON MAGNETICS 1676 F01 1 10 100 1000 MPP 55030 I (mA) LOAD 1676 TA01 Figure 1 1 EFFICIENCY (%) U ULT1676 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) Supply Voltage ........................................................ 60V ORDER PART TOP VIEW Switch Voltage ......................................................... 60V NUMBER SHDN 1 8 V SHDN, SYNC Pin Voltage........................................... 7V C LT1676CN8 V 2 7 FB V Pin Voltage ....................................................... 30V CC CC LT1676CS8 V 3 6 SYNC FB Pin Voltage ........................................................... 3V SW LT1676IN8 GND 4 5 V Operating Junction Temperature Range IN LT1676IS8 LT1676C ................................................ 0 C to 125 C N8 PACKAGE S8 PACKAGE 8-LEAD PDIP 8-LEAD PLASTIC SO S8 PART MARKING LT1676I ............................................ 40 C to 125 C T = 125 C, q = 130 C/ W (N8) JMAX JA Storage Temperature Range ................. 65 C to 150 C T = 125 C, q = 110 C/ W (S8) JMAX JA 1676 Lead Temperature (Soldering, 10 sec).................. 300 C 1676I Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25 C. A V = 48V, V open, V = 5V, V = 1.4V unless otherwise noted. IN SW CC C SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Power Supplies V Minimum Input Voltage 6.7 7.0 V IN(MIN) l 7.4 V I V Supply Current V = 0V 620 800 m A VIN IN C l 900 m A I V Supply Current V = 0V 3.2 4.0 mA VCC CC C l 5.0 mA V V Dropout Voltage (Note 2) l 2.8 3.1 V VCC CC Shutdown Mode I V = 0V 30 50 m A VIN SHDN l 75 m A Feedback Amplifier V Reference Voltage 1.225 1.240 1.255 V REF l 1.215 1.265 V I FB Pin Input Bias Current 600 1500 nA IN g Feedback Amplifier Transconductance D lc = 10m A 400 650 1000 m mho m l 200 1500 m mho I , I Feedback Amplifier Source or Sink Current 60 100 170 m A SRC SNK l 45 220 m A V Feedback Amplifier Clamp Voltage 2.0 V CL Reference Voltage Line Regulation 12V V 60V l 0.01 %/V IN Voltage Gain 200 600 V/V Output Switch V Output Switch On Voltage I = 0.5A 1.0 1.5 V ON SW I Switch Current Limit (Note 3) l 0.55 0.70 1.0 A LIM Current Amplifier Control Pin Threshold Duty Cycle = 0% 0.9 1.1 1.25 V Control Voltage to Switch Transconductance 2 A/V 2 U W U W U WW