LM5008

SNVS280G – APRIL 2004 – REVISED MARCH 2013

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During each off-time, the SW pin is at approximately 0V, and the bootstrap capacitor charges from Vcc through

the internal diode. The minimum OFF timer, set to 300ns, 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 turn-on losses and current over-shoot.

Thermal Protection

The LM5008 should be operated so the junction temperature does not exceed 125°C during normal operation.

An internal Thermal Shutdown circuit is provided to protect the LM5008 in the event of a higher than normal

junction temperature. When activated, typically at 165°C, the controller is forced into a low power reset state,

device overheating. When the junction temperature reduces below 140°C (typical hysteresis = 25°C), the Vcc

regulator is enabled, and normal operation is resumed.

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