MIC2204
Micrel
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
10kΩ 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
“
Applications Information”
section for more detail.
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 1µF 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 6.5µA). 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.
MIC2204
Master
VIN
10kΩ
SYNC_IN
SYNC_OUT
FB
MIC2204
Slave
VIN
SW
BIAS
SYNC_IN
SYNC_OUT
FB
SW
BIAS
Figure 1. SYNC_OUT
January 2004
7
M0214-012904
MICREL [ MICREL SEMICONDUCTOR ]
