Micrel, Inc.

MIC2124

June 2010

2

M9999-060810-D

Ordering Information

Part Number

Voltage

Switching Frequency

Junction Temp. Range

Package

Lead Finish

MIC2124YMM

Adj.

300kHz

–40° to +125°C

10-Pin MSOP

Pb-Free

Pin Configuration

10-Pin MSOP (MM)

Pin Description

Pin Number

Pin Name

Pin Function

1

HSD

High-Side N-MOSFET Drain Connection (Input): Input voltage for the internal sensing of external

power stage supply. The HSD operating voltage range is from 3V to 18V. Input capacitors between

HSD and the power ground (PGND) are required.

2

EN/COMP

Enable (Input): Floating = enable, logic low = shutdown. In the off state, supply current of the device is

greatly reduced (typically 1mA).

COMP (Output): Output of the gm error amplifier and connects to the components for the external

compensation.

3

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 adjust the desired output

voltage.

4

GND

loop for the signal ground should be separate from the power ground (PGND) loop.

5

IN

Input Voltage (Input): Power to the internal reference and control sections of the MIC2124. The IN

operating voltage range is from 3V to 5.5V. A 2.2µF ceramic capacitors from IN to GND are

6

DL

Low-Side Drive (Output): High-current driver output for external low-side MOSFET. The DL driving

voltage swings from ground-to-IN.

7

PGND

Power Ground. PGND is the ground path for the MIC2124 buck converter power stage. The PGND

pin connects to the sources of low-side N-Channel MOSFETs, the negative terminals of input

capacitors, and the negative terminals of output capacitors. The loop for the power ground should be

as small as possible and separate from the Signal ground (GND) loop.

8

DH

High-Side Drive (Output): High-current driver output for external high-side MOSFET. The DH driving

9

LX

Switch Node (Input): High-current output driver return. The LX pin connects directly to the switch

node. Due to the high speed switching on this pin, the LX pin should be routed away from sensitive

nodes.

Current Sense input (Input): LX pin also senses the current for the current mode control and short

circuit protection 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 LX using a Kelvin connection.

10

BST

Boost (Output): Bootstrapped voltage to the high-side N-channel MOSFET driver. A Schottky diode is

connected between the IN pin and the BST pin. A boost capacitor of 0.1μF is connected between the

BST pin and the LX pin. Adding a small resistor at BST pin can slow down the turn-on time of high-

side N-Channel MOSFETs.