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MIC2178-3.3BWM

P1-P3P4-P6P7-P9P10-P12P13-P15
March 2005 1 M9999-031805
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.
Typical Application
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
BIASSGND
EN
COMP
PGND
FB
OUT
VIN
C5
220µF
10V
V
OUT
5V/2.5A
L1, 33µH
C3
6.8nF
C4
0.01µF
R2
10k
MIC2178-5.0
PWM
SYNC
R1
10k
V
IN
5.4V to 18V
C2
22µF
35V
U1
20
18
10
13
14–17 19
12
4–7
3,8
1,2,9
D1
MBRS140
SW
10
ENABLE
ON
OFF
PWRGD
11
R1
20k
Skip Mode
PWM Mode
Ouput Good
Output Low
C6
220µF
10V
C1
22µF
35V
70
75
80
85
90
95
100
10 100 1000 2500
EFFICIENCY (%)
OUTPUT CURRENT (mA)
5V Output
Efficiency
V
IN
= 6V
SKIP
PWM
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
MIC2178 Micrel, Inc.
M9999-031805 2 March 2005
Pin Description
Pin Number Pin Name Pin Function
1, 2, 9 VIN Supply Voltage (Input): Requires bypass capacitor to PGND. All three pins
must be connected to V
IN
.
3, 8 SW Switch (Output): Internal power MOSFET output switches. Both pins must
be externally connected together.
4, 5, 6, 7 PGND Power Ground: Connect all pins to central ground point.
10 PWM 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.
11 PWRGD Error Flag (Output): Open-drain output. Active low when FB input is 10%
below the reference voltage (V
REF
).
12 FB Feedback (Input): Connect to output voltage divider resistors.
13 COMP Compensation: Output of internal error amplifier. Connect capacitor or
series RC network to compensate the regulator control loop.
14, 15, 16, 17 SGND Signal Ground: Connect all pins to ground, PGND*.
18 SYNC 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.
19 BIAS Internal 3.3V Bias Supply: Decouple with 0.01µF bypass capacitor to
SGND. Do not apply any external load.
20 EN Enable (Input): Logic high enables operation. Logic low shuts down
regulator. Do not allow pin to float.
Pin Configuration
2VIN
3SW
4PGND
5PGND
6PGND
7PGND
1VIN
8SW
9
VIN
EN20
BIAS19
SYNC18
SGND17
SGND16
SGND15
10
PWM
14
13
12
11
PWRGD
FB
COMP
SGND
20-Lead Wide Power SOIC
Ordering Information
Part Number
Standard* Pb-Free Voltage Junction Temp. Package
MIC2178BWM MIC2178YWM ADJ –40°C to +85°C 20-lead WSOIC
MIC2178-3.3BWM MIC2178-3.3YWM 3.3V –40°C to +85°C 20-lead WSOIC
MIC2178-5.0BWM MIC2178-5.0YWM 5.0V –40°C to +85°C 20-lead WSOIC
* Standard product will be supported as Pb-Free IAW PPCN #040004 effective 1-1-2005.
March 2005 3 M9999-031805
MIC2178 Micrel, Inc.
Absolute Maximum Ratings
Supply Voltage [100ms transient] (V
IN
) ......................... 18V
Output Switch Voltage (V
SW
) ........................................ 18V
Output Switch Current (I
SW
) ......................................... 6.0A
Enable, PWM Control Voltage (V
EN
, V
PWM
) ................. 18V
Sync Voltage (V
SYNC
) ..................................................... 6V
Operating Ratings
Supply Voltage (V
IN
) ..................................... 4.5V to 16.5V
Junction Temperature Range (T
J
) ........... –40°C to +125°C
Electrical Characteristics
V
IN
= 7.0V; T
A
= 25°C, bold indicates –40°C ≤ T
A
≤ 85°C; unless noted.
Symbol Parameter Condition Min Typ Max Units
I
SS
Input Supply Current PWM mode, output not switching, 1.0 1.5 mA
4.5V ≤ V
IN
≤ 16.5V
skip mode, output not switching, 600 750 µA
4.5V ≤ V
IN
≤ 16.5V
V
EN
= 0V, 4.5V ≤ V
IN
≤ 16.5V 1 25 µA
V
BIAS
Bias Regulator Output Voltage V
IN
= 16.5V 3.10 3.30 3.4 V
V
FB
Feedback Voltage MIC2178 [adj.]: V
OUT
= 3.3V, I
LOAD
= 0 1.22 1.245 1.27 V
V
OUT
Output Voltage MIC2178 [adj.]: V
OUT
= 3.3V, 3.20 3.3 3.40 V
5V ≤ V
IN
≤ 16V, 10mA ≤ I
LOAD
≤ 2A 3.14 3.46 V
MIC2178-5.0: I
LOAD
= 0 4.85 5.0 5.15 V
MIC2178-5.0: 4.85 5.0 5.15
6V ≤ V
IN
≤ 16V, 10mA ≤ I
LOAD
≤ 2A 4.75 5.25 V
MIC2178-3.3: I
LOAD
= 0 3.20 3.3 3.40 V
MIC2178-3.3: 3.20 3.3 3.40 V
5V ≤ V
IN
≤ 16V, 10mA ≤ I
LOAD
≤ 2A 3.14 3.46 V
V
TH
Undervoltage Lockout upper threshold 4.25 4.35 V
V
TL
lower threshold 3.90 4.15 V
I
FB
Feedback Bias Current MIC2178 [adj.] 60 150 nA
MIC2178-5.0, MIC2178-3.3 20 40 µA
A
VOL
Error Amplifier Gain 0.6V ≤ V
COMP
≤ 0.8V 15 18 20
Error Amplifier Output Swing upper limit 0.9 1.5 V
lower limit 0.05 0.1 V
Error Amplifier Output Current source and sink 15 25 35 µA
f
O
Oscillator Frequency 160 200 240 kHz
D
MAX
Maximum Duty Cycle V
FB
= 1.0V 100 %
t
ON min
Minimum On-Time V
FB
= 1.5V 300 400 ns
SYNC Frequency Range 220 300 kHz
SYNC Threshold 0.8 1.6 2.2 V
SYNC Minimum Pulse Width 500 ns
I
SYNC
SYNC Leakage V
SYNC
= 0V to 5.5V –1 0.01 1 µA
I
LIM
Current Limit PWM mode, V
IN
= 12V 3.8 4.7 5.7 A
skip mode 600 mA
R
ON
Switch On-Resistance high-side switch, V
IN
= 12V 90 250 mΩ
low-side switch, V
IN
= 12V 110 250 mΩ
I
SW
Output Switch Leakage V
SW
= 16.5V 1 10 µA
P1-P3P4-P6P7-P9P10-P12P13-P15

MIC2178-3.3BWM

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Description:
Voltage Regulators - Switching Regulators 2.5A 200kHz Synchronous Switche
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