January 2004

7

M0214-012904

MIC2204

Micrel

Functional Description

VIN

VIN provides power to the output and to the internal bias

supply. The supply voltage range is from 2.3V to 5.5V. A

minimum 1

µF ceramic is recommended for bypassing the

input supply.

Enable

The enable pin provides a logic level control of the output. In

the off state, supply current of the device is greatly reduced

(typically 6.5

µA). Also, in the off state, the output drive is

placed in a “tri-stated” condition, where both the high-side

P-Channel MOSFET and the low-side N-Channel are in an off

or non-conducting state. Do not drive the enable pin above

the supply voltage.

SYNC_IN

SYNC_IN enables the ability to change the fundamental

switching frequency. The SYNC_IN frequency has a mini-

mum frequency of 1.8MHz and a maximum sync frequency

of 2.5MHz.

Careful attention should be paid to not driving the SYNC_IN

pin greater than the supply voltage. While this will not damage

the device, it will cause improper operation.

SYNC_OUT

Since SYNC_OUT is an open collector output that provides

a signal equal to the internal oscillator frequency, multiple

MIC2204s to be connected together in a master-slave con-

figuration for frequency matching of the converters. A typical

10k

Ω is recommended for a pull-up resistor.

BIAS

The bias supply is an internal 2.3V linear regulator that

supplies the internal biasing voltage to the MIC2204. A 10nF

ceramic capacitor is required on this pin for bypassing. Do not

use the BIAS pin as a supply. The BIAS pin was designed to

supply internal power and not external circuitry.

Feedback

The feedback pin provides the control path to control the

output. A resistor divider connecting the feedback to the

output is used to adjust the desired output voltage. Refer to

the “Feedback” material in the

section for more detail.

10k

Ω

SYNC_IN

VIN

MIC2204

Master

SYNC_OUT

SW

BIAS

FB

SYNC_IN

VIN

MIC2204

Slave

SYNC_OUT

SW

BIAS

FB

Figure 1. SYNC_OUT