• Product introduction

LT1247CS8

1MHz off-line current mode PWM and DC/DC converter

peculiarity

• Current-mode operation up to 1MHz
• A 30ns current sense delay
• Current sensing leading-edge blanking
• Pin compatible with UC1842
• Hysteresis undervoltage lockout
• No cross-conducted current
• Trim the bandgap datum
• 1A totem pole output

description

® LT 1246/LT1247 8-pin, fixed frequency, current mode, pulse width modulator. These devices are designed to be plug-in compatible with the industry-standard UC1842 PWM circuit version improvements. The LT1246/LT1247 are optimized for off-line and DC/DC converter applications. They contain a temperature-compensated reference, a high-gain error amplifier, a current-sense comparator, and a high-current totem pole output stage, ideal for driving power MOSFETs. Start-up, which has now been reduced to less than 250μA. Cross-conduction current spikes in the totem pole output stage have been eliminated, enabling 1MHz practical operation. Some new features have been included. Cutting-edge blanking has been added to current sense comparators. This minimizes or eliminates the filters normally required. Eliminating this filter allows the operation of the current sensing loop with minimal delay. The car has two frequencies of oscillation circuit and sinking current, these parameters are tightly specified. The output stage is clamped to a maximum of 18V and is on. Output and reference outputs are actively pulled low during undervoltage lockout.