JAJSGD0I April 2004 – October 2018 LM5008
PRODUCTION DATA.
The LM5008 integrates an N-Channel Buck switch and associated floating high voltage gate driver. The gate driver circuit works in conjunction with an external bootstrap capacitor and an internal high voltage diode. A 0.01-µF ceramic capacitor (C4) connected between the BST pin and SW pin provides the voltage to the driver during the on-time.
During each off-time, the SW pin is at approximately 0 V, and the bootstrap capacitor charges from VCC through the internal diode. The minimum off-timer, set to 300 ns, ensures a minimum time each cycle to recharge the bootstrap capacitor.
An external re-circulating diode (D1) carries the inductor current after the internal Buck switch turns off. This diode must be of the ultra-fast or Schottky type to minimize turnon losses and current overshoot.