MIC2177
2.5A Synchronous Buck Regulator
General Description
The Micrel MIC2177 is a 200kHz synchronous buck (step-
down) switching regulator designed for high-efficiency,
battery-powered applications.
The MIC2177 operates from a 4.5V to 16.5V input and
features internal power MOSFETs that can supply up to 2.5A
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 MIC2177 achieves high efficiency over a wide output
current range by switching between PWM and skip mode.
Operating mode is automatically selected according to output
conditions. Switching frequency is preset to 200kHz and can
be synchronized to an external clock signal of up to 300kHz.
The MIC2177 uses current-mode control with internal current
sensing. Current-mode control provides superior line
regulation and makes the regulator control loop easy to
compensate. 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 MIC2177 is packaged in a 20-pin wide power SO
package with an operating temperature range of –40°C to
+85°C.
See the MIC2178 for externally selected PWM or skip-mode
operation.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
•
4.5V to 16.5V input voltage range
•
Dual-mode operation for high efficiency (up to 96%)
– PWM mode for > 200mA load current
– Skip mode for < 200mA load current
•
100mΩ internal power MOSFETs at 12V input
•
200kHz preset switching frequency
•
Low quiescent current
– 1.0mA in PWM mode
– 500µA in skip mode
– < 5µA in shutdown mode
•
100% duty cycle for low dropout operation
•
Current-mode control
– Simplified loop compensation
– Superior line regulation
•
Current limit
•
Thermal shutdown
•
Undervoltage lockout
Applications
•
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 18V
C1
22µF
35V
ENABLE
SHUTDOWN
20
18
11
100
U1
EN
1,2,9
5V Output
Efficiency
VIN
OUT
SW
MIC
SYNC
2177-5.0
PGND
AUTO
FB
COMP SGND BIAS
13
14–17
19
95
3,8
4–7
12
L1, 50µH
D1
MBRS130L
EFFICIENCY (%)
10
V
OUT
5V/1A
C2
100µF
10V
90
85
80
75
V
IN
= 6V
2.2
nF
R1
10k
C
C
6.8nF
C3
0.01µF
R1
10k
70
10
SKIP
PWM
100
1000 2500
OUTPUT CURRENT (mA)
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
April 2008
M9999-042108
MICREL [ MICREL SEMICONDUCTOR ]
