MIC2177
MIC2177
Micrel, Inc.
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
5.4V to 18V
C1
22µF
35V
ENABLE
20
SHUTDOWN
18
11
U1
1,2,9
VIN
OUT
EN
MIC
SYNC
2177-5.0
AUTO
COMP SGND
2.2
nF
R1
10k
C
C
6.8nF
13
14–17
10
3,8
4–7
12
100
5V Output
Efficiency
L1, 50µH
D1
MBRS130L
95
EFFICIENCY (%)
SW
PGND
FB
BIAS
19
V
OUT
5V/1A
C2
100µF
10V
90
85
80
75
V
IN
= 6V
C3
0.01µF
R1
10k
SKIP
PWM
100
1000 2500
OUTPUT CURRENT (mA)
70
10
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
MIC2177
Micrel, Inc.
Ordering Information
Part
Number
MIC2177-3.3BWM*
MIC2177-5.0BWM*
MIC2177BWM*
MIC2177-3.3YWM
MIC2177-5.0YWM
MIC2177YWM
Output
Voltage
3.3V
5.0V
adj.
3.3V
5.0V
adj.
Switching
Frequency
200kHz
200kHz
200kHz
200kHz
200kHz
200kHz
Temperature
Range
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Package
20-lead WSOP
20-lead WSOP
20-lead WSOP
20-lead WSOP
20-lead WSOP
20-lead WSOP
Lead Finish
Standard
Standard
Standard
Pb-Free
Pb-Free
Pb-Free
* Standard product will be supported as Pb-Free IAW PPCN #040004 effective 1-1-2005 pending residual depletion.,
Pin Configuration
VIN 1
VIN 2
SW 3
PGND 4
PGND 5
PGND 6
PGND 7
SW 8
VIN 9
OUT 10
20 EN
19 BIAS
18 SYNC
17 SGND
16 SGND
15 SGND
14 SGND
13 COMP
12 FB
11 AUTO
Pin Description
Pin Number
1, 2, 9
Pin Name
VIN
20-Lead Wide SOP
Pin Function
Supply Input: Controller and switch supply. Unregulated supply input to
internal regulator, output switches, and control circuitry. Requires bypass
capacitor to PGND. All three pins must be connected to V
IN
.
Switch (Output): Internal power MOSFET switch output. Both pins must be
externally connected together.
Power Ground: Output stage ground connections. Connect all pins to a
common ground plane.
Output Voltage Sense (Input): Senses output voltage to determine minimum
switch current for PWM operation. Connect directly to V
OUT
.
Automatic Mode: Connect 2.2nF timing capacitor for automatic PWM-/skip-
mode switching. Regulator operates exclusively in PWM mode when pin is
pulled low.
Feedback (Input): Error amplifier inverting input. For adjustable output
version, connect FB to external resistive divider to set output voltage. For
3.3V and 5V fixed output versions, connect FB directly to output.
Compensation: Internal error amplifier output. Connect to capacitor or series
RC network to compensate the regulator control loop.
Signal Ground: Ground connection of control section. Connect all pins to
common ground plane.
Frequency Synchronization (Input): Optional clock input. Connect to
external clock signal to synchronize oscillator. Leading edge of signal above
1.7V terminates switching cycle. Connect to SGND if not used.
Bias Supply: Internal 3.3V bias supply output. Decouple with 0.01µF
bypass capacitor and 10kΩ 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.
3,8
4,5,6,7
10
11
SW
PGND
OUT
AUTO
12
FB
13
14,15,16,17
18
COMP
SGND
SYNC
19
20
BIAS
EN
M9999-031805
2
March 2005
MIC2177
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, Output-Sense Voltage (V
EN
, V
OUT
) ................. 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
I
SS
Parameter
Input Supply Current
Condition
PWM mode, output not switching,
4.5V
≤
V
IN
≤
16.5V
skip mode, output not switching,
4.5V
≤
V
IN
≤
16.5V
V
EN
= 0V, 4.5V
≤
V
IN
≤
16.5V
V
BIAS
V
FB
V
OUT
Bias Regulator Output Voltage
Feedback Voltage
Output Voltage
V
IN
= 16.5V
MIC2177 [adj.]: V
OUT
= 3.3V, I
LOAD
= 0
MIC2177 [adj.]: V
OUT
= 3.3V,
5V
≤
V
IN
≤
16V, 10mA
≤
I
LOAD
≤
2A
MIC2177-5.0: I
LOAD
= 0
MIC2177-5.0:
6V
≤
V
IN
≤
16V, 10mA
≤
I
LOAD
≤
2A
MIC2177-3.3: I
LOAD
= 0
MIC2177-3.3:
5V
≤
V
IN
≤
16V, 10mA
≤
I
LOAD
≤
2A
V
TH
V
TL
I
FB
A
VOL
Feedback Bias Current
Undervoltage Lockout
upper threshold
lower threshold
MIC2177 [adj.]
MIC2177-5.0, MIC2177-3.3
Error Amplifier Gain
Error Amplifier Output Swing
0.6V
≤
V
COMP
≤
0.8V
upper limit
lower limit
Error Amplifier Output Current
f
O
D
MAX
t
ON min
Oscillator Frequency
Maximum Duty Cycle
Minimum On-Time
SYNC Frequency Range
SYNC Threshold
SYNC Minimum Pulse Width
I
SYNC
I
LIM
R
ON
I
SW
SYNC Leakage
Current Limit
V
SYNC
= 0V to 5.5V
PWM mode, V
IN
= 12V
skip mode
Switch On-Resistance
high-side switch, V
IN
= 12V
low-side switch, V
IN
= 12V
Output Switch Leakage
V
SW
= 16.5V
V
FB
= 1.0V
V
FB
= 1.5V
220
0.8
500
–1
3.8
0.01
4.7
600
90
110
1
250
250
10
1
5.7
1.6
source and sink
15
160
100
300
400
300
2.2
15
0.9
3.9
3.10
1.22
3.20
3.14
4.85
4.85
4.75
3.20
3.20
3.14
Min
Typ
1.0
500
1
3.30
1.245
3.3
5.0
5.0
3.3
3.3
4.25
4.15
60
20
18
1.5
0.05
25
200
0.1
35
240
150
40
20
V
V
µA
kHz
%
ns
kHz
V
ns
µA
A
mA
mΩ
mΩ
µA
Max
1.5
650
25
3.4
1.27
3.40
3.46
5.15
5.15
5.25
3.40
3.40
3.46
4.35
Units
mA
µA
µA
V
V
V
V
V
V
V
V
V
V
V
nA
µA
March 2005
3
M9999-031805
MIC2177
Symbol
Parameter
Enable Threshold
I
EN
Enable Leakage
AUTO Threshold
AUTO Source Current
Minimum Switch Current
for PWM Operation
V
FB
= 1.5V, V
AUTO
< 0.8V
V
IN
– V
OUT
= 0V
V
IN
– V
OUT
= 3V
V
EN
= 0V to 5.5V
Condition
Min
0.8
–1
0.8
7
Typ
1.6
0.01
1.6
11
220
420
Micrel, Inc.
Max
2.2
1
Units
V
µA
V
15
µA
mA
mA
General Note:
Devices are ESD sensitive. Handling precautions recommended.
M9999-031805
4
March 2005
MIC2177
Micrel, Inc.
Typical Characteristics
Oscillator Frequency
vs. Temperature
REFERENCE VOLTAGE (V)
205
200
FREQUENCY (kHz)
195
190
185
180
1.252
1.250
1.248
1.246
1.244
1.242
1.240
Reference Voltage
vs. Temperature
REFERENCE VOLTAGE (V)
3.320
3.315
3.310
3.305
3.300
3.295
3.290
3.285
Reference Voltage
vs. Temperature
MIC2177-3.3
MIC2177 [adj.]
175
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
1.238
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
3.280
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
5.030
REFERENCE VOLTAGE (V)
5.020
5.010
5.000
4.990
4.980
Reference Voltage
vs. Temperature
AMPLIFIER VOLTAGE GAIN
19.0
18.5
18.0
17.5
17.0
16.5
Error-Amplifier Gain
vs. Temperature
120
BIAS CURRENT (nA)
Feedback Input Bias Current
vs. Temperature
MIC2177-5.0
100
80
60
40
20
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
4.970
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
16.0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
5.0
4.9
Current Limit
vs. Temperature
ON-RESISTANCE (mΩ)
250
200
150
100
50
0
High-Side Switch
On-Resistance
ON-RESISTANCE (mΩ)
125°C
85°C
25°C
0°C
350
300
250
200
150
100
50
0
2
4
Low-Side Switch
On-Resistance
125°C
85°C
25°C
0°C
CURRENT LIMIT (A)
4.8
4.7
4.6
4.5
4.4
4.3
4.2
4.1
4.0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
2
4
6 8 10 12 14 16 18
INPUT VOLTAGE (V)
6 8 10 12 14 16 18
INPUT VOLTAGE (V)
12
PWM-Mode
Supply Current
OUTPUT
SWITCHING
EFFICIENCY (%)
100
95
3.3V Output
Efficiency
100
95
EFFICIENCY (%)
5V Output
Efficiency
V
IN
= 6V
SUPPLY CURRENT (mA)
10
8
6
4
2
0
2
90
85
80
75
70
65
V
IN
= 5V
8V
12V
90
8V
85
12V
80
75
70
10
SKIP
PWM
100
1000 2500
OUTPUT CURRENT (mA)
4
6 8 10 12 14 16 18
INPUT VOLTAGE (V)
60
10
SKIP
PWM
100
1000 2500
OUTPUT CURRENT (mA)
March 2005
5
M9999-031805
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