MP8040 – HIGH CURRENT POWER HALF BRIGDE
MP8040 Rev. 1.61 www.MonolithicPower.com 5
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TM
SW Output
The SW output drives the load. It is controlled
by the logic input signal at PWM. When the
signal at PWM is high (above 2V), the high-side
switch is turned on. When the signal at PWM is
low (less than 0.4V), the low-side switch is
turned on.
The MP8040 uses internal N-Channel
MOSFETs for both the high-side and low-side
switches. The high-side MOSFET gate drive is
powered from the voltage between SW and BS,
allowing BS to rise above the SP input voltage
to power the high-side MOSFET. To do this a
bootstrap capacitor is connected between SW
and BS. When the low-side switch is on, the
capacitor is internally charged from the voltage
at DRV, which is also internally generated.
There is a dead time region (typically 40ns)
where both the upper and lower switches are
off (see Figure 2).
Both the high-side and low-side switches have
internal current limits to prevent failure due to
excessive load current. Once the current limit is
reached, both output switches are turned off
and the fault output is asserted (driven low).
Shutdown
The MP8040 includes a 2.5µA shutdown mode.
When SHDN is high, both output switches are
turned off and the input current drops to 2.5µA.
When the MP8040 is shutdown, the internally
generated voltage at DRV drops to 0V, and the
fault output (FLT) is asserted (driven low). If the
shutdown mode is not used, connect SHDN
directly to GND.
Fault Output
The MP8040 includes a fault indicator output
(FLT). This is an active-low open drain output.
The MP8040 detects faults due to over-current
(>9A), over-temperature (>160°C), under-
voltage at SP (<6.5V), or if the part is disabled.
Connect FLT to DRV or to an external voltage
up to 6V through a 27kΩ or greater resistor.
When any of the 3 fault conditions are detected,
both output switches are turned off and the SW
output is high-impedance.
Thermal Shutdown
The MP8040 includes a thermal overload
protection circuit. If the die temperature rises
above 160°C, the output switches are turned off
and the fault output is asserted. Once the
thermal overload circuit is tripped, the die
temperature must drop below 140°C before
automatically restarting.
V
SP
3/4 V
SP
1/2 V
SP
1/4 V
SP
TIME
SW
DT (RISE) DT (FALL)
DEAD TIME RISING = 20ns
DEAD TIME FALLING = 40ns
MP8040_F01
MP8040
SP
GND
2
4
3
SW
V
SP
Figure 2—Dead Time
