Features: 5A Onboard Switch (LT1074)
100kHz Switching Frequency
Greatly Improved Dynamic Behavior
Available in Low Cost 5 and 7-Lead Packages
Only 8.5mA Quiescent Current
Programmable Current Limit
Operates Up to 60V Input
Micropower Shutdown ModeApplicationBuck Converter with Output Voltage Range of 2.5V to 50V
Tapped-Inductor Buck Converter with 10A Output at 5V
Positive-to-Negative Converter
Negative Boost Converter
Multiple Output Buck ConverterSpecificationsInput Voltage
LT1074/ LT1076............................................................. 45V
LT1074HV/LT1076HV ..................................................... 64V
Switch Voltage with Respect to Input Voltage
LT1074/ LT1076.............................................................. 64V
LT1074HV/LT1076HV ..................................................... 75V
Switch Voltage with Respect to Ground Pin (V SW Negative)
LT1074/LT1076 (Note 7)................................................. 35V
LT1074HV/LT1076HV (Note 7) ....................................... 45V
Feedback Pin Voltage..........................................2V, +10V
Shutdown Pin Voltage (Not to Exceed V IN ).................. 40V
I LIM Pin Voltage (Forced)............................................. 5.5V
Maximum Operating Ambient Temperature Range
Commercial..........................................................0 to 70
Industrial..................................................... 40 to 85
Military................................................. ........55 to 125
Maximum Operating Junction Temperature Range
Commercial.......................................................0 to 125
Industrial.....................................................40 to 125
Military..........................................................55 to 150
Maximum Storage Temperature ................ 65 to 150
Lead Temperature (Soldering, 10 sec)........................300
DescriptionThe LT(R) 1074 is a 5A (LT1076 is rated at 2A) monolithic bipolar switching regulator which requires only a few external parts for normal operation. The power switch, all oscillator and control circuitry, and all current limit components, are included on the chip. The topology is a classic positive "buck" configuration but several design innov ations allow this device to be used as a positive-to-negative converter, a negative boost converter, and as a flyb ack converter. The switch output is specified to swing 40V below ground, allowing the LT1074 to drive a tapped-inductor in the buck mode with output currents up to 10A.
The LT1074 uses a true analog multiplier in the feedback loop. This makes the device respond nearly instanta neously to input voltage fluctuations and makes loop gain independent of input voltage. As a result, dynamic behavior of the regulator is significantly improved over previous designs.
On-chip pulse by pulse current limiting makes the LT1074 nearly bust-proof for output overloads or shorts. The input voltage range as a buck converter is 8V to 60V, but a self-boot feature allows input voltages as low as 5V in the inverting and boost configurations.
The LT1074 is available in low cost TO-220 or TO-3 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 which allows current limit to be adjusted down to zero. In addition, full micropower shutdown can be programmed. See Application Note 44 for design details.
A fixed 5V output, 2A version is also available. See LT1076-5.
LT1074 Data Sheet
