ISL6210 Intersil Corporation, ISL6210 Datasheet - Page 6

• Manufacturer Part Number: ISL6210
• Description: Dual Synchronous Rectified MOSFET Drivers
• Manufacturer: Intersil Corporation

Timing Diagram
Description
Theory of Operation
Designed for speed, the ISL6210 dual MOSFET driver
controls both high-side and low-side N-Channel FETs for two
separate channels of a Multiphase PWM system from two
independent PWM signals.
A rising edge on PWM initiates the turn-off of the lower
MOSFET (see Timing Diagram). After a short propagation
delay [t
[t
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
propagation delay [t
gate begins to fall [t
voltage is monitored, and the lower gate is allowed to rise
after the upper MOSFET gate-to-source voltage drops below
1V. The lower gate then rises [t
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 0.5Ω on-resistance and 4A sink current capability
enable the lower gate driver to absorb the current injected to
PWM
UGATE
LGATE
FL
t
PDLL
] are provided in the Electrical Specifications section.
PDLL
], the lower gate begins to fall. Typical fall times
t
PDHU
FU
PDLU
1V
]. The upper MOSFET gate-to-source
t
] is encountered before the upper
RU
6
RL
t
PDLU
], turning on the lower
t
PDHL
1V
FIGURE 1. TIMING DIAGRAM
2.5V
t
RL
ISL6210
t
FL
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.
Diode Emulation
Diode emulation allows for higher converter efficiency under
light-load situations. With diode emulation active, the
ISL6210 will detect the zero current crossing of the output
inductor and turn off LGATE. This ensures that
discontinuous conduction mode (DCM) is achieved. Diode
emulation is asynchronous to the PWM signal. Therefore,
the ISL6210 will respond to the FCCM input immediately
after it changes state.
NOTE: Intersil does not recommend Diode Emulation use with
r
MOSFET can cause gross current measurement inaccuracies.
Three-State PWM Input
A unique feature of the ISL6210 and other Intersil drivers is
the addition of a shutdown window to the PWM input. If the
PWM signal enters and remains within the shutdown window
for a set holdoff time, the output drivers are disabled and
both MOSFET gates are pulled and held low. The shutdown
state is removed when the PWM signal moves outside the
shutdown window. Otherwise, the PWM rising and falling
thresholds outlined in the ELECTRICAL SPECIFICATIONS
determine when the lower and upper gates are enabled.
Adaptive Shoot-Through Protection
Both drivers incorporate adaptive shoot-through protection
to prevent upper and lower MOSFETs from conducting
simultaneously and shorting the input supply. This is
accomplished by ensuring the falling gate has turned off one
MOSFET before the other is allowed to turn on.
DS(ON)
t
TSSHD
t
current sensing topologies. The turn-OFF of the low side
PTS
t
RU
t
TSSHD
t
FU
t
PTS
November 28, 2006
FN6392.0