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MP8712 Datasheet(PDF) 17 Page - Monolithic Power Systems
MPS [Monolithic Power Systems]
MP8712 Datasheet(HTML) 17 Page - Monolithic Power Systems
/ 26 page
MP8712 – 18V, 12A, SYNCHRONOUS STEP-DOWN CONVERTER
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2017 MPS. All Rights Reserved.
Power Good (PG)
Power good (PG) indicates whether the output
voltage is in the normal range compared to the
internal reference voltage. PG is an open-drain
structure. An external pull-up supply is needed.
During power-up, the PG output is pulled low.
This indicates to the system to remain off and
keep the load on the output to a minimum. This
helps reduce inrush current at start-up.
When the output voltage is between 90% and
115% of the nominal voltage and the soft start
is finished, the PG signal is pulled high. When
the output voltage is lower than 85% after the
soft start finishes, the PG signal remains low.
When the output voltage is higher than 115% of
the nominal voltage, PG is switched low. The
PG signal rises high again after the output
voltage drops below 105% of the nominal
PG uses a deglitch time whenever VOUT
crosses the UV/OV rising and falling threshold.
The PG output is pulled low immediately when
either EN UVLO, input UVLO, OCP, or OTP is
Input Over-Voltage Protection (VIN OVP)
The MP8712 monitors VIN to detect an input
over-voltage (OV) event. This function is only
active when the output is in OV. When the
output is in an over-voltage protection (OVP)
state, output discharge is enabled, charging the
input voltage high. When the input voltage
exceeds the input OVP threshold, both the HS-
FET and LS-FET stop switching.
Output Over-Voltage Protection (OVP)
The MP8712 monitors FB to detect an over-
voltage event. When the FB voltage becomes
higher than 125% of the internal reference
regulation mode, and the input voltage may be
charged up during this time. When input OVP is
triggered, the IC stops switching. Once the
input voltage drops below the VIN OVP
recovery threshold, the IC begins switching.
OVP auto-retry mode occurs only if the soft
Dynamic regulation mode is defined as turning
on the low side until the low-side negative
current limit is triggered, and then the body
diode of the HS-FET freewheels the current.
The output power charges to the input, which
may trigger a VIN OVP function. In VIN OVP,
neither the HS-FET or LS-FET turn on and stop
charging VIN to a higher voltage. If the output is
still over-voltage and the input voltage has
dropped below the VIN OVP threshold, repeat
dynamic regulation mode. If the output voltage
is lower than 110% of the internal reference
voltage, then output OVP is exited.
Output Absolute Over-Voltage Protection
The MP8712 monitors VOUT to detect absolute
over-voltage protection. When VOUT is larger
than 6.5V, the controller enters dynamic
regulation mode. Absolute OVP can work once
both the input voltage and EN are higher than
their rising thresholds. Therefore, this function
can work even in a soft-start period.
Thermal shutdown prevents the chip from
operating at exceedingly high temperatures.
When the silicon die temperature exceeds
160°C, the entire chip shuts down. When the
temperature is less than its lower threshold
(typically 140°C), the chip is enabled again.
Floating Driver and Bootstrap Charging
An external bootstrap capacitor powers the
floating power MOSFET driver. This floating
driver has its own UVLO protection. This
UVLO’s rising threshold is 2.4V with a
hysteresis of 150mV. The bootstrap capacitor
voltage is regulated internally by VIN through
D1, M1, C4, L1, and C2 (see Figure 4). If V
exceeds 3.3V, U1 regulates M1 to maintain
a 3.3V BST voltage across C4.
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