MIC2178_05 Datasheet, PDF (1/15 Pages) Micrel Semiconductor – 2.5A Synchronous Buck Regulator

MIC2178
Micrel, Inc.
MIC2178
2.5A Synchronous Buck Regulator
General Description
The Micrel MIC2178 is a 200kHz synchronous buck (step-
down) switching regulator designed for high-efficiency, bat-
tery-powered applications.
The MIC2178 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 MIC2178 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 MIC2178 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 MIC2178 and is packaged in a 20-lead wide power SOIC
package with an operating temperature range of –40°C to
+85°C.
See the MIC2177 for automatic selection of 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
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
• High-efficiency, battery-powered supplies
• Buck (step-down) dc-to-dc converters
• Palmtop computers
• Laptop computers
• Cellular telephones
• Hand-held instruments
• Battery Chargers
Typical Application
V_IN
5.4V to 18V
C1
22µF
35V
Ouput Good
Output Low
C2
22µF _ON
35V
OFF
R1
20k
ENABLE
U1
1,2,9
VIN
20 _{EN MIC2178-5.0 OUT} 10
11 _PWRGD
SW ^3,8
Skip Mode
PWM Mode
10
PWM
PGND ^4–7
18 _SYNC
FB ¹²
COMP SGND BIAS
R1 ¹³
10k
C3
6.8nF
14–17
19
C4
0.01µF
L1, 33µH
D1
MBRS140
R2
10k
C5
220µF
10V
V_OUT
5V/2.5A
C6
220µF
10V
5V Output
Efficiency
100
95
90
V_IN = 6V
85
80
75
SKIP
PWM
70
10
100
1000 2500
OUTPUT CURRENT (mA)
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 [phone] • fax + 1 [phone] • http://www.micrel.com
March 2005
1
M9999-031805