HR1000A – RESONANT HALF-BRIDGE CONTROLLER
The internal 12µA current source turns on when
the BO voltage drops below 1.25V, and turns
off when the BO voltage exceeds 1.25V. When
the BO voltage drops below 1.25V, the IC shuts
down the gate drive, and consumes very little
power as per the residual current in the EC
table. Calculate the input-voltage resistor
divider with the desired ON (VinON) and OFF
(VinOFF) input voltage as below:
VinON -VinOFF
RH =
12⋅10−6
1.25
RL = RH ⋅
VinOFF −1.25
Figure 15: High-Side Gate Driver
Low-Side Gate Drive
For additional protection, when the BO voltage
exceeds the internal 5.5V clamp voltage, the IC
will shutdown. When the BO voltage is between
1.25V and 5.5V, the IC will restart.
The LG pin provides the gate driver signal for
the low-side MOSFET. The maximum absolute
rating table shows that the maximum LG pin
voltage is 16V. Under some conditions, a large
voltage spike occurs on the LG pin due to
oscillations from the long gate-driver wire, the
MOSFET parasitic capacitance, and the small
gate-driver resistor. This voltage spike is
dangerous to the LG pin, so add a 15V Zener
diode close to the LG and GND pins.
High-Side Gate Driver
The external BST capacitor provides energy to
the high-side gate driver. An integrated
bootstrap diode charges this capacitor through
VCC. This diode simplifies the external driving
circuit for the high-side switch, allowing the BST
capacitor to charge when the low side MOSFET
is on.
To provide enough gate driver energy and
considering the BST capacitor charge time, use
a 100nF-to-1μF capacitor for the BST capacitor.
Figure 16: Low-Side Gate Driver
HR1000A Rev. 1.01
8/30/2012
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