MIC2172_06 Datasheet, PDF (3/20 Pages) Micrel Semiconductor – 100kHz 1.25A Switching Regulators

Micrel
Pin Description
Pin Number
1
2
3
4 (MIC2172)
4 (MIC3172)
5
6
7
8
MIC2172/3172
Pin Name
S GND
COMP
FB
SYNC
EN
VIN
P GND 2
VSW
P GND 1
Pin Function
Signal Ground: Internal analog circuit ground. Connect directly to the input filter
capacitor for proper operation (see applications info). Keep separate from power
grounds.
Frequency Compensation: Output of transconductance type error amplifier.
Primary function is for loop stabilization. Can also be used for output voltage
soft-start and current limit tailoring.
Feedback: Inverting input of error amplifier. Connect to external resistive divider
to set power supply output voltage.
Synchronization/Frequency Adjust: Capacitively coupled input signal greater
than device’s free running frequency (up to 135kHz) will lock device’s oscillator
on falling edge. Oscillator frequency can be trimmed up to 135kHz by adding a
resistor to ground. If unused, pin must float (no connection).
Enable: Apply TTL high or connect to VIN to enable the regulator. Apply TTL low
or connect to ground to disable the regulator. Device draws only leakage current
(<1µA) when disabled.
Supply Voltage: 3.0V to 40V
Power Ground #2: One of two NPN power switch emitters with 0.3Ω current
sense resistor in series. Required. Connect to external inductor or input voltage
ground depending on circuit topology.
Power Switch Collector: Collector of NPN switch. Connect to external inductor or
input voltage depending on circuit topology.
Power Ground #1: One of two NPN power switch emitters with 0.3Ω current
sense resistor in series. Optional. For maximum power capability connect to P
GND 2. Floating pin reduces current limit by a factor of two.
April 2006
3
M9999-041806
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