MPQ8636-10 Datasheet, PDF (9/41 Pages) Monolithic Power Systems – High Efficiency, 10/20A, 18V Synchronous, Step-Down Converter

MPQ8636 — 10/20A, 18V, SYNCHRONOUS, STEP-DOWN CONVERTER
MPQ8636GVE-20
PIN#
1
2
3
4
5
6
7
8
15-18,
25-29
10-14,
19-23
9, 24
Name
EN
FREQ
FB
SS
AGND
PG
VCC
BST
SW
PGND
IN
Description
Enable. Digital input that turns the regulator on or off. Drive EN high to turn on the
regulator; drive it low to turn it off. Connect EN to IN through a pull-up resistor or a
resistive voltage divider for automatic startup. Do not float this pin.
Frequency Set. Require a resistor connected between FREQ and IN to set the
switching frequency. The input voltage and the resistor connected to the FREQ pin
determine the ON time. The connection to the IN pin provides line feed-forward and
stabilizes the frequency during input voltage’s variation.
Feedback. Connect to the tap of an external resistor divider from the output to GND to
set the output voltage. Place the resistor divider as close to FB pin as possible. Avoid
using vias on the FB traces.
Soft-Start. Connect an external capacitor to program the soft start time for the switch
mode regulator.
Analog Ground. The control circuit reference.
Power-Good. The output is an open drain signal. Requires a pull-up resistor to a DC
voltage to indicate HIGH if the output voltage exceeds 91% of the nominal voltage.
There is a delay from FB ≥ 91% to when PG goes high.
Internal 4.8V LDO Output. Powers the driver and control circuits. Decouple with a
≥1µF ceramic capacitor as close to the pin as possible. For best results, use X7R or
X5R dielectric ceramic capacitors for their stable temperature characteristics.
Bootstrap. Require a capacitor connected between SW and BST pins to form a floating
supply across the high-side switch driver.
Switch Output. Connect to the inductor and bootstrap capacitor. The high-side switch
drives these pins up to V_IN during the PWM duty cycle’s ON time. The inductor current
drives the SW pin negative during the OFF-time. The low-side switch’s ON-resistance
and the internal Schottky diode holds the negative voltage. Connect all SW pins using
wide PCB traces.
System Ground. Reference ground of the regulated output voltage. PCB layout
requires extra care. Connect using wide PCB traces.
Supply Voltage. Supplies power to the internal MOSFET and regulator. The
MPQ8636GVE-20 operates from a 4.5V-to-18V input rail. Requires an input
decoupling capacitor. Connect using wide PCB traces and multiple vias.
MPQ8636 Rev. 1.23
www.MonolithicPower.com
9
9/9/2013
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