LT1074/LT1076 Step-Down Switching Regulator ponents, are included on the chip. The topology is a classic FEATURES positive buck configuration but several design innova- 5A Onboard Switch (LT1074) tions allow this device to be used as a positive-to-negative Operates Up to 60V Input converter, a negative boost converter, and as a flyback 100kHz Switching Frequency converter. The switch output is specified to swing 40V Greatly Improved Dynamic Behavior below ground, allowing the LT1074 to drive a tapped- Available in Low Cost 5 and 7-Lead Packages inductor in the buck mode with output currents up to 10A. Only 8.5mA Quiescent Current The LT1074 uses a true analog multiplier in the feedback Programmable Current Limit loop. This makes the device respond nearly instanta- Micropower Shutdown Mode neously to input voltage fluctuations and makes loop gain independent of input voltage. As a result, dynamic behav- U APPLICATIO S ior of the regulator is significantly improved over previous designs. Buck Converter with Output Voltage Range of 2.5V On-chip pulse by pulse current limiting makes the LT1074 to 50V nearly bust-proof for output overloads or shorts. The input Tapped-Inductor Buck Converter with 10A Output voltage range as a buck converter is 8V to 60V, but a self- at 5V boot feature allows input voltages as low as 5V in the Positive-to-Negative Converter inverting and boost configurations. Negative Boost Converter Multiple Output Buck Converter The LT1074 is available in low cost TO-220 or DD packages with frequency pre-set at 100kHz and current limit at 6.5A (LT1076 = 2.6A). A 7-pin TO-220 package is also available DESCRIPTIO which allows current limit to be adjusted down to zero. In The LT 1074 is a 5A (LT1076 is rated at 2A) monolithic addition, full micropower shutdown can be programmed. bipolar switching regulator which requires only a few See Application Note 44 for design details. external parts for normal operation. The power switch, all A fixed 5V output, 2A version is also available. See LT1076-5. oscillator and control circuitry, and all current limit com- , LTC and LT are registered trademarks of Linear Technology Corporation. Buck Converter Efficiency TYPICAL APPLICATIO LT1074 Basic Positive Buck Converter 100 L1** 50H (LT1074) V = 12V, V = 20V OUT IN 100H (LT1076) 90 5V V V IN SW 5A * USE MBR340 FOR LT1076 10V TO 40V ** COILTRONICS 50-2-52 (LT1074) 80 LT1074 R1 MBR745* 100-1-52 (LT1076) V = 5V, V = 15V 2.8k OUT IN PULSE ENGINEERING, INC. 1% 70 FB PE-92114 (LT1074) GND V C PE-92102 (LT1076) R2 R3 L = 50H TYPE 52 CORE 60 HURRICANE HL-AK147QQ (LT1074) 2.21k 2.7k DIODE = MBR735 HL-AG210LL (LT1076) 1% + + C3 C2 C1 RIPPLE CURRENT RATING I /2 OUT 50 200F 0.01F 500F 0 12 3 4 5 6 25V OUTPUT LOAD CURRENT (A) LT1074TA01 LT1074TPC27 sn1074 1074fds 1 EFFICIENCY (%) U ULT1074/LT1076 ABSOLUTE AXI U RATI GS (Note 1) Input Voltage I Pin Voltage (Forced) ............................................ 5.5V LIM LT1074/ LT1076 .................................................. 45V Maximum Operating Ambient Temperature Range LT1074HV/LT1076HV ......................................... 64V Commercial .................................................0C to 70C Switch Voltage with Respect to Input Voltage Industrial ................................................ 40C to 85C LT1074/ LT1076 .................................................. 64V Military (OBSOLETE) .....................55C to 125C LT1074HV/LT1076HV ......................................... 75V Maximum Operating Junction Temperature Range Switch Voltage with Respect to Ground Pin (V Negative) Commercial ............................................... 0C to 125C SW LT1074/LT1076 (Note 7) ..................................... 35V Industrial .............................................. 40C to 125C LT1074HV/LT1076HV (Note 7) ........................... 45V Military (OBSOLETE) .................... 55C to 150C Feedback Pin Voltage..................................... 2V, +10V Maximum Storage Temperature ............... 65C to 150C Shutdown Pin Voltage (Not to Exceed V ) .............. 40V Lead Temperature (Soldering, 10 sec)...................... 300C IN UUW PACKAGE/ORDER I FOR ATIO ORDER PART FRONT VIEW ORDER PART BOTTOM VIEW V V 5 V NUMBER NUMBER IN C IN 4 V TAB IS SW 1 3 GND GND LT1076CQ 2 LT1074CK CASE 2 V IS GND C LT1076IQ 3 LT1074HVCK 4 1 FB/SENSE LT1074MK Q PACKAGE FB V SW LT1074HVMK 5-LEAD PLASTIC DD K PACKAGE LT1076CK 4-LEAD TO-3 METAL CAN LT1076: = 4C, = 30C/W JC JA LT1076HVCK LT1074: = 2.5C, = 35C/W JC JA LT1076: = 4C, = 35C/W JC JA LT1076MK LT1076CR FRONT VIEW LT1076HVMK OBSOLETE PACKAGE 7 SHDN LT1076IR Consider the T5 Package for Alternate Source 6 V C LT1076HVCR TAB IS 5 FB/SENSE 4 GND GND LT1076HVIR 3 I FRONT VIEW LT1074CT LIM 2 V SW 5 V LT1074HVCT 1 V IN IN 4 V SW LT1074IT R PACKAGE TAB IS 7-LEAD PLASTIC DD 3 GND LT1074HVIT GND 2 V C LT1076: = 4C, = 30C/W LT1076CT JC JA 1 FB LT1076HVCT T PACKAGE 5-LEAD PLASTIC TO-220 LT1074CT7 LT1076IT FRONT VIEW LEADS ARE FORMED STANDARD FOR LT1074HVCT7 LT1076HVIT STRAIGHT LEADS, ORDER FLOW 06 SHDN 7 6 V C LT1074IT7 FB 5 TAB IS LT1074: = 2.5C, = 50C/W JC JA GND 4 LT1074HVIT7 LT1076: = 4C, = 50C/W JC JA GND I 3 LIM V LT1076CT7 2 SW 1 V IN LT1076HVCT7 T7 PACKAGE 7-LEAD PLASTIC TO-220 LT1074: = 2.5C, = 50C/W JC JA LT1076: = 4C, = 50C/W JC JA 2 *Assumes package is soldered to 0.5 IN of 1 oz. copper over internal ground plane or over back side plane. Consult LTC Marketing for parts specified with wider operating temperature ranges. sn1074 1074fds 2 U WWW