Features and Benefits
- Current Mode Operation to 1MHz
- 30ns Current Sense Delay
- <250µA Low Start-Up Current
- Current Sense Leading Edge Blanking
- Pin Compatible with UC1842
- Undervoltage Lockout with Hysteresis
- No Cross-Conduction Current
- Trimmed Bandgap Reference
- 1A Totem Pole Output
The LT1246/LT1247 are 8-pin, fixed frequency, current mode, pulse width modulators. These devices are designed to be improved plug compatible versions of the industry standard UC1842 PWM circuit. The LT1246/LT1247 are optimized for off-line and DC/DC converter applications. They contain a temperature compensated reference, high gain error amplifier, current sensing comparator, and a high current totem pole output stage ideally suited to driving power MOSFETs. Start-up current has been reduced to less than 250µA. Cross-conduction current spikes in the totem pole output stage have been eliminated, making 1MHz operation practical. Several new features have been incorporated. Leading edge blanking has been added to the current sense comparator. This minimizes or eliminates the filter that is normally required. Eliminating this filter allows the current sense loop to operate with minimum delays. Trims have been added to the oscillator circuit for both frequency and sink current, and both of these parameters are tightly specified. The output stage is clamped to a maximum VOUT of 18V in the on state. The output and the reference output are actively pulled low during under-voltage lockout.
- Off-Line Converters
- DC/DC Converters
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (3)
DC227A-C: Demo Board for the LT1247 1MHz Off-Line Current Mode PWM and DC/DC Converter.
DC227A-A: Demo Board for the LT1247 1MHz Off-Line Current Mode PWM and DC/DC Converter.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
Models for the following parts are available in LTspice:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.