MIC2177_08 Datasheet, PDF (3/15 Pages) Micrel Semiconductor – 2.5A Synchronous Buck Regulator

Micrel, Inc.
MIC2177
Pin Description
Pin Number
1, 2, 9
3, 8
4, 5, 6, 7
10
11
12
13
14, 15, 16, 17
18
19
20
Pin Name
VIN
SW
PGND
OUT
AUTO
FB
COMP
SGND
SYNC
BIAS
EN
Pin Function
Supply Input: Controller and switch supply. Unregulated supply input to internal
regulator, output switches, and control circuitry. Requires bypass capacitor to PGND.
All three pins must be connected to VIN.
Switch (Output): Internal power MOSFET switch output. Both pins must be
externally connected together.
Power Ground: Output stage ground connections. Connect all pins to a common
ground plane.
Output Voltage Sense (Input): Senses output voltage to determine minimum switch
current for PWM operation. Connect directly to VOUT.
Automatic Mode: Connect 2.2nF timing capacitor for automatic PWM-/skip-mode
switching. Regulator operates exclusively in PWM mode when pin is pulled low.
Feedback (Input): Error amplifier inverting input. For adjustable output version,
connect FB to external resistive divider to set output voltage. For 3.3V and 5V fixed
output versions, connect FB directly to output.
Compensation: Internal error amplifier output. Connect to capacitor or series RC
network to compensate the regulator control loop.
Signal Ground: Ground connection of control section. Connect all pins to common
ground plane.
Frequency Synchronization (Input): Optional clock input. Connect to external clock
signal to synchronize oscillator. Leading edge of signal above 1.7V terminates
switching cycle. Connect to SGND if not used.
Bias Supply: Internal 3.3V bias supply output. Decouple with 0.01µF bypass
capacitor and 10kΩ to SGND. Do not apply any external load.
Enable (Input): Logic high enables operation. Logic low shuts down regulator. Do
not allow pin to float.
April 2008
3
M9999-042108