Buck Regulator. MIC2178 Datasheet

MIC2178 Regulator. Datasheet pdf. Equivalent

Part MIC2178
Description 2.5A Synchronous Buck Regulator
Feature MIC2178 Micrel, Inc. MIC2178 2.5A Synchronous Buck Regulator General Description The Micrel MIC217.
Manufacture Micrel Semiconductor
Total Page 15 Pages
Datasheet
Download MIC2178 Datasheet



MIC2178
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
• 100minternal 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
VIN
5.4V to 18V
C1
22µF
35V
Ouput Good
Output Low
C2
22µF
35V
R1
20k
ON
OFF
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
10k
C3
6.8nF
13
14–17
19
C4
0.01µF
L1, 33µH
D1
MBRS140
R2
10k
C5
220µF
10V
VOUT
5V/2.5A
C6
220µF
10V
5V Output
Efficiency
100
95
90 VIN = 6V
85
80
75
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
March 2005 1 M9999-031805



MIC2178
MIC2178
Ordering Information
Part Number
Standard*
Pb-Free
Voltage Junction Temp.
MIC2178BWM
MIC2178YWM
ADJ –40°C to +85°C
MIC2178-3.3BWM
MIC2178-3.3YWM
3.3V
–40°C to +85°C
MIC2178-5.0BWM
MIC2178-5.0YWM
5.0V
–40°C to +85°C
* Standard product will be supported as Pb-Free IAW PPCN #040004 effective 1-1-2005.
Micrel, Inc.
Package
20-lead WSOIC
20-lead WSOIC
20-lead WSOIC
Pin Configuration
VIN 1
VIN 2
SW 3
PGND 4
PGND 5
PGND 6
PGND 7
SW 8
VIN 9
PWM 10
20 EN
19 BIAS
18 SYNC
17 SGND
16 SGND
15 SGND
14 SGND
13 COMP
12 FB
11 PWRGD
20-Lead Wide Power SOIC
Pin Description
Pin Number
1, 2, 9
3, 8
4, 5, 6, 7
10
11
12
13
14, 15, 16, 17
18
19
20
Pin Name
VIN
SW
PGND
PWM
PWRGD
FB
COMP
SGND
SYNC
BIAS
EN
Pin Function
Supply Voltage (Input): Requires bypass capacitor to PGND. All three pins
must be connected to VIN.
Switch (Output): Internal power MOSFET output switches. Both pins must
be externally connected together.
Power Ground: Connect all pins to central ground point.
PWM/Skip-Mode Control (Input): Logic-level input. Controls regulator
operating mode. Logic low enables PWM mode. Logic high enables skip
mode. Do not allow pin to float.
Error Flag (Output): Open-drain output. Active low when FB input is 10%
below the reference voltage (VREF).
Feedback (Input): Connect to output voltage divider resistors.
Compensation: Output of internal error amplifier. Connect capacitor or
series RC network to compensate the regulator control loop.
Signal Ground: Connect all pins to ground, PGND*.
Frequency Synchronization (Input): Optional. Connect an external clock
signal to synchronize the oscillator. Leading edge of signal above 1.7V
terminates switching cycle. Connect to SGND if not used.
Internal 3.3V Bias Supply: Decouple with 0.01µF bypass capacitor to
SGND. Do not apply any external load.
Enable (Input): Logic high enables operation. Logic low shuts down
regulator. Do not allow pin to float.
M9999-031805 2 March 2005





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