Micrel, Inc.

MIC2101/02

August 2012

3

M9999-080712-A

Pin Configuration (Continued)

Pin Number

Pin Name

Pin Function

7

DH

High-Side Drive Output. High-current driver output for external high-side MOSFET of a buck

resistor between DH pin and the gate of the high-side N-channel MOSFET can slow down the turn-

on and turn-off speed of the MOSFET.

8

SW

Switch Node and Current-Sense input. High current output driver return. The SW pin connects

directly to the switch node. Due to the high-speed switching on this pin, the SW pin should be

routed away from sensitive nodes. The SW pin also senses the current by monitoring the voltage

across the low-side MOSFET during OFF time. In order to sense the current accurately, connect the

low-side MOSFET drain to the SW pin using a Kelvin connection.

9, 11

NC

No Connection.

10

BST

Voltage supply input for the high-side N-channel MOSFET driver, which can be powered by a

bootstrapped circuit connected between VDD and SW, using a Schottky diode and a 0.1μF ceramic

capacitor. Adding a small resistor at BST pin can slow down the turn-on speed of the high-side

MOSFET.

12

AGND

Signal ground for VDD and the control circuitry, which is connected to thermal pad electronically.

The signal ground return path should be separate from the power ground (PGND) return path.

13

FB

Feedback Input. Input to the transconductance amplifier of the control loop. The FB pin is regulated

to 0.8V. A resistor divider connecting the feedback to the output is used to set the desired output

voltage.

14

PG

Power Good Output. Open drain output, an external pull-up resistor to VDD or external power rails

is required.

15

EN

Enable Input. A logic signal to enable or disable the buck converter operation. The EN pin is CMOS

compatible. Logic high enables the device, logic low shutdowns the regulator. In the disable mode,

the VDD supply current for the device is minimized to 0.7mA typically.

16

VIN

Supply Voltage. The VIN operating voltage range is from 4.5V to 38V. A 1μF ceramic capacitor from

VIN to AGND is required for decoupling.

EP

ePad

Exposed Pad. Connect the EPAD to PGND plain on the PCB to improve the thermal performance.