MPQ8632-8 datasheet(11/46 Pages) MPS

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MPQ8632 HIGH EFFICIENCY 18V SYNCHRONOUS STEP-DOWN CONVERTER FAMILY FOR 4A TO 20A

MPQ8632 Rev.1.24

www.MonolithicPower.com

8/28/2013

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

MPQ8632GVE-15, MPQ8632GVE-20

PIN #

Name

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.

FREQ

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.

AGND

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.

VCC

Internal 4.8V LDO Output. Powers the driver and control circuits. 5V external bias

can disable the internal LDO. 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.

BST

Bootstrap. Require a capacitor connected between SW and BST pins to form a

floating supply across the high-side switch driver.

15-18,

25-29

Switch Output. Connect to the inductor and bootstrap capacitor. The high-side switch

drives these pins up to VIN 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.

10-14, 19-23

PGND

System Ground. Reference ground of the regulated output voltage. PCB layout

requires extra care. Connect using wide PCB traces.

9, 24

Supply Voltage. Supplies power to the internal MOSFET and regulator. The

MPQ8632GVE operate from a 4.5V-to-18V input rail. If 5V external bias is tied to

VCC pin, the input voltage can be low as 2.5V. Requires an input decoupling

capacitor. Connect using wide PCB traces and multiple vias.

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