mic3172 Micrel Semiconductor, mic3172 Datasheet - Page 2

• Manufacturer Part Number: mic3172
• Description: 100khz 1.25a Switching Regulators
• Manufacturer: Micrel Semiconductor

MIC2172/3172
Pin Configuration
Pin Description
M9999-042205
Pin Number
4 (MIC2172)
4 (MIC3172)
*SYNC/
1
2
3
5
6
7
8
S GND
COMP
†
EN
FB
1
2
3
4
MIC2172*/3172
8-pin DIP (N)
Pin Name
Ordering Information
P GND 2
P GND 1
S GND
COMP
SYNC
MIC2172BM
MIC3172BM
MIC2172BN
MIC3172BN
V
EN
V
Standard
FB
†
SW
IN
8
7
6
5
P GND 1
V
P GND 2
V
SW
I N
Part Number
MIC2172YN
MIC2172YM
MIC3172YN
MIC3172YM
Pb-Free
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 V
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.
2
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Temperature
Range
*SYNC/
S GND
COMP
†
EN
FB
8-pin plastic DIP
8-pin plastic DIP
8-lead SOIC
8-lead SOIC
1
2
3
4
8-lead SOIC (M)
Package
MIC2172*/3172
IN
to enable the regulator. Apply
†
8
7
6
5
P GND 1
V
P GND 2
V
SW
I N
Micrel, Inc.
April 2005