ISL6613B Intersil Corporation, ISL6613B Datasheet - Page 7

• Manufacturer Part Number: ISL6613B
• Description: (ISL6612B / ISL6613B) Advanced Synchronous Rectified Buck MOSFET Drivers
• Manufacturer: Intersil Corporation

Description
Operation
Designed for versatility and speed, the ISL6612B and
ISL6613B MOSFET drivers control both high-side and low-side
N-Channel FETs of a half-bridge power train from one
externally provided PWM signal.
Prior to VCC exceeding its POR level, the Pre-POR over-
voltage protection function is activated during initial start-up; the
upper gate (UGATE) is held low and the lower gate (LGATE),
controlled by the Pre-POR overvoltage protection circuits, is
connected to the PHASE. Once the VCC voltage surpasses the
VCC Rising Threshold (See Electrical Specifications), the PWM
signal takes control of gate transitions. A rising edge on PWM
initiates the turn-off of the lower MOSFET (see Timing
Diagram). After a short propagation delay [t
gate begins to fall. Typical fall times [t
Electrical Specifications section. Adaptive shoot-through
circuitry monitors the PHASE voltage and determines the upper
gate delay time [t
upper MOSFETs from conducting simultaneously. Once this
delay period is complete, the upper gate drive begins to rise
[t
A falling transition on PWM results in 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
circuitry determines the lower gate delay time, t
PHASE voltage and the UGATE voltage are monitored, and
the lower gate is allowed to rise after PHASE drops below a
level or the voltage of UGATE to PHASE reaches a level
depending upon the current direction (See next section for
details). The lower gate then rises [t
MOSFET.
thresholds outlined in the ELECTRICAL SPECIFICATIONS
RU
] and the upper MOSFET turns on.
PWM
UGATE
LGATE
t
PDLL
PDHU
FU
PDLU
]. Again, the adaptive shoot-through
]. This prevents both the lower and
] is encountered before the upper
t
FL
7
t
PDHU
RL
FL
t
RU
], turning on the lower
] are provided in the
t
PDHL
PDLL
], the lower
PDHL
FIGURE 1. TIMING DIAGRAM
t
ISL6612B, ISL6613B
RL
t
. The
PDLU
t
FU
1.5V<PWM<3.2V
Advanced Adaptive Zero Shoot-Through Deadtime
Control (Patent Pending)
These drivers incorporate a unique adaptive deadtime control
technique to minimize deadtime, resulting in high efficiency
from the reduced freewheeling time of the lower MOSFETs’
body-diode conduction, and to prevent the upper and lower
MOSFETs from conducting simultaneously. This is
accomplished by ensuring either rising gate turns on its
MOSFET with minimum and sufficient delay after the other has
turned off.
During turn-off of the lower MOSFET, the PHASE voltage is
monitored until it reaches a -0.2V/+0.8V trip point for a
forward/reverse current, at which time the UGATE is released
to rise. An auto-zero comparator is used to correct the r
drop in the phase voltage preventing from false detection of the
-0.2V phase level during r
of zero current, the UGATE is released after 35ns delay of the
LGATE dropping below 0.5V. During the phase detection, the
disturbance of LGATE’s falling transition on the PHASE node is
blanked out to prevent falsely tripping. Once the PHASE is
high, the advanced adaptive shoot-through circuitry monitors
the PHASE and UGATE voltages during a PWM falling edge
and the subsequent UGATE turn-off. If either the UGATE falls
to less than 1.75V above the PHASE or the PHASE falls to less
than +0.8V, the LGATE is released to turn on.
Three-State PWM Input
A unique feature of these drivers 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 driver outputs 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
determine when the lower and upper gates are enabled.
t
TSSHD
t
PDTS
DS(ON
conduction period. In the case
t
1.0V<PWM<2.6V
TSSHD
July 27, 2006
t
PDTS
DS(ON)
FN9205.3