MIC2179
Micrel
MIC2179
1.5A Synchronous Buck Regulator
General Description
The Micrel MIC2179 is a 200kHz synchronous buck (step-
down) switching regulator designed for high-efficiency, bat-
tery-powered applications.
The MIC2179 operates from a 4.5V to 16.5V input and
features internal power MOSFETs that can supply up to 1.5A
output current. It can operate with a maximum duty cycle of
100% for use in low-dropout conditions. It also features a
shutdown mode that reduces quiescent current to less than
5µA.
The MIC2179 achieves high efficiency over a wide output
current range by operating in either PWM or skip mode. The
operating mode is externally selected, typically by an intelli-
gent system, which chooses the appropriate mode according
to operating conditions, efficiency, and noise requirements.
The switching frequency is preset to 200kHz and can be
synchronized to an external clock signal of up to 300kHz.
The MIC2179 uses current-mode control with internal current
sensing. Current-mode control provides superior line regula-
tion and makes the regulator control loop easy to compen-
sate. The output is protected with pulse-by-pulse current
limiting and thermal shutdown. Undervoltage lockout turns
the output off when the input voltage is less than 4.5V.
The MIC2179 and is packaged in a 20-lead SSOP package
with an operating temperature range of –40°C to +85°C.
Features
• 4.5V to 16.5V input voltage range
• Dual-mode operation for high efficiency (up to 96%)
PWM mode for > 150mA load current
Skip mode for <150mA load current
• 150mΩ internal power MOSFETs at 12V input
• 200kHz preset switching frequency
• Low quiescent current
1.0mA in PWM mode
600µA in skip mode
< 5µA in shutdown mode
• Current-mode control
Simplified loop compensation
Superior line regulation
• 100% duty cycle for low dropout operation
• Current limit
• Thermal shutdown
• Undervoltage lockout
Applications
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High-efficiency, battery-powered supplies
Buck (step-down) dc-to-dc converters
Cellular telephones
Laptop computers
Hand-held instruments
Battery Charger
Typical Application
V
IN
5.4V to 16.5V
C1
10µF
20V
R1
20k
U1
15
6
5
13
16,17
VIN
EN
PWRGD
PWM
SYNC
COMP SGND
8
9–12
Output Good
Output Low
Skip Mode
PWM Mode
SW
MIC
2179-3.3
PGND
FB
BIAS
14
3,4
1,2,
19,20
L1
22µH
D1
MBRM120
C2
100µF
6.3V
V
OUT
3.3V/600mA
7
R2
10k
C4
6.8nF
C3
0.01µF
Pins 4 and 18 are not connected.
Pins 3 and 4 can be connected
together for a low-impedance
connection.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
June 1998
1
MIC2179
MICREL [ MICREL SEMICONDUCTOR ]
