6

Description

Theory of Operation

Designed for speed, the ISL6608 dual MOSFET driver controls

both high-side and low-side N-Channel FETs from one

externally provided PWM signal.

A rising edge on PWM initiates the turn-off of the lower

MOSFET (see Figure 1, Timing Diagram). After a short

Specifications section. Adaptive shoot-through circuitry

monitors the LGATE voltage. When LGATE has fallen below

1V, UGATE is allowed to turn ON. This prevents both the

lower and upper MOSFETs from conducting simultaneously,

or shoot-through.

A falling transition on PWM indicates the turn-off of the upper

MOSFET and the turn-on of the lower MOSFET. A short

voltage is monitored, and the lower gate is allowed to rise

after the upper MOSFET gate-to-source voltage drops below

MOSFET.

This driver is optimized for converters with large step down

compared to the upper MOSFET because the lower

MOSFET conducts for a much longer time in a switching

period. The lower gate driver is therefore sized much larger

to meet this application requirement.

The 0.5

Ω on-resistance and 4A sink current capability

enable the lower gate driver to absorb the current injected to

the lower gate through the drain-to-gate capacitor of the

lower MOSFET and prevent a shoot through caused by the

high dv/dt of the phase node.

PWM

UGATE

LGATE

1V

2.5V

1V

FIGURE 1. TIMING DIAGRAM

ISL6608