MIC2177 Datasheet, PDF (1/16 Pages) Micrel Semiconductor – 2.5A Synchronous Buck Regulator

MIC2177
Micrel
MIC2177
2.5A Synchronous Buck Regulator
General Description
The Micrel MIC2177 is a 200kHz synchronous buck (step-
down) switching regulator designed for high-efficiency, bat-
tery-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 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 MIC2177 is packaged in a 20-lead 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.
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
6V to 16.5V
C1
22µF
35V
C2
22µF
35V
ON
OFF
AUTO
MODE
Mode
PWM
MODE
C6
2.2nF
U1
ENABLE _{20 EN}
1,2,9
VIN
OUT ¹⁰
MIC2177-5.0 SW ^3,8
11 _AUTO
PGND ^4–7
L1, 33µH
D1
MBRS140
18 _SYNC
FB ¹²
COMP SGND BIAS
R7 ¹³
15k
C5
10nF
14–17
19
C4
0.01µF
C7
220µF
10V
V_OUT
5V/2.5A
C3
220µF
10V
5V Output
Efficiency
100
95
90
V_IN = 6V
85
80
75
70
10
SKIP
PWM
100
1000 2500
OUTPUT CURRENT (mA)
April 1999
1
MIC2177