Micrel, Inc.
MIC2179
MIC2179
1.5A Synchronous Buck Regulator
General Description
The Micrel MIC2179 is a 200kHz synchronous buck (step-
down) switching regulator designed for high-efficiency, bat-
tery-powered applications.
The MIC2179 operates from a 4.5V to 16.5V input and features
internal power MOSFETs that can supply up to 1.5A 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 MIC2179 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 intel-
ligent 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 MIC2179 uses current-mode control with internal current
sensing. Current-mode control provides superior line regula-
tion and makes the regulator control loop easy to compensate.
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 MIC2179 and is packaged in a 20-lead SSOP package
with an operating temperature range of –40°C to +85°C.
Features
• 4.5V to 16.5V input voltage range
• Dual-mode operation for high efficiency (up to 96%)
PWM mode for > 150mA load current
Skip mode for <150mA load current
• 150mΩ 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
Cellular telephones
Laptop computers
Hand-held instruments
Battery Charger
Typical Application
V
IN
5.4V to 16.5V
C1
10µF
20V
Output Good
Output Low
Skip Mode
PWM Mode
U1
15
6
5
13
16,17
R1
20k
EN
PWRGD
PWM
SYNC
VIN
SW
3,4
1,2,
19,20
7
L1
22µH
D1
MBRM120
MIC
2179-3.3
PGND
FB
BIAS
14
9–12
C2
100µF
6.3V
V
OUT
3.3V/600mA
COMP SGND
8
C4
6.8nF
C3
0.01µF
R5
4.02k
Pins 4 and 18 are not connected.
Pins 3 and 4 can be connected
together for a low-impedance
connection.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
June 2009
1
M9999-063009
Micrel, Inc.
MIC2179
Part Number
Voltage
Adj.
3.3V
5.0V
Temperature Range
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
Package
20-Lead SSOP
20-Lead SSOP
20-Lead SSOP
Ordering Information
Standard*
MIC2179BSM
Pb-Free
MIC2179YSM
MIC2179-3.3BSM MIC2179-3.3YSM
MIC2179-5.0BSM MIC2179-5.0YSM
* Standard product will be supported as Pb-Free IAW PCCN #040004 effective 1-1-2005 pending residual depletion.
Pin Configuration
PGND 1
PGND 2
SW 3
NC 4
PWM 5
PWRGD 6
FB 7
COMP 8
SGND 9
SGND 10
20 PGND
19 PGND
18 NC
17 VIN
16 VIN
15 EN
14 BIAS
13 SYNC
12 SGND
11 SGND
20-Lead Wide SSOP
Pin Description
Pin Number
1, 2, 19, 20
3
5
Pin Name
PGND
SW
PWM
Pin Function
Power Ground: Connect all pins to central ground point.
Switch (Output): Internal power MOSFET output switches.
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 (V
REF
).
6
7
8
9–12
13
PWRGD
FB
COMP
SGND
SYNC
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.
Supply Voltage (Input): Requires bypass capacitor to PGND. Both pins
must be connected to V
IN
.
14
15
16, 17
4, 18
BIAS
EN
VIN
NC
not internally connected.
June 2009
2
M9999-063009
Micrel, Inc.
MIC2179
Absolute Maximum Ratings
(1)
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
(2)
Supply Voltage (V
IN
) .......................................4.5V to 16.5V
Junction Temperature Range (T
J
) ............ –40°C to +125°C
Electrical Characteristics
(3)
Symbol
I
SS
V
IN
= 7.0V; T
A
= 25°C,
bold
indicates –40°C ≤ T
A
≤ 85°C; unless noted.
Parameter
Condition
Input Supply Current
PWM mode, output not switching,
4.5V ≤ V
IN
≤ 16.5V
Min
Typ
1.0
600
1
3.10
1.22
3.20
3.14
4.85
4.85
4.75
3.20
3.20
3.14
3.90
3.30
1.245
3.3
5.0
5.0
3.3
3.3
4.25
4.15
60
20
15
0.9
15
160
V
FB
= 1.0V
V
FB
= 1.5V
100
300
220
0.8
500
PWM mode, V
IN
= 12V
V
SYNC
= 0V to 5.5V
–1
3.4
0.01
4.3
600
160
140
1
350
350
10
1
5.5
1.6
400
300
2.2
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
750
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
skip mode, output not switching,
4.5V ≤ V
IN
≤ 16.5V
V
BIAS
V
FB
V
OUT
Bias Regulator Output Voltage
Feedback Voltage
Output Voltage
V
EN
= 0V, 4.5V ≤ V
IN
≤ 16.5V
V
IN
= 16.5V
MIC2179-5.0: I
LOAD
= 0
MIC2179 [adj.]: V
OUT
= 3.3V,
5V ≤ V
IN
≤ 16V, 10mA ≤ I
LOAD
≤ 1A
MIC2179 [adj.]: V
OUT
= 3.3V, I
LOAD
= 0
MIC2179-3.3: I
LOAD
= 0
MIC2179-5.0:
6V ≤ V
IN
≤ 16V, 10mA ≤ I
LOAD
≤ 1A
MIC2179-3.3:
5V ≤ V
IN
≤ 16V, 10mA ≤ I
LOAD
≤ 1A
upper threshold
lower threshold
V
TH
I
FB
V
TL
Undervoltage Lockout
Feedback Bias Current
Error Amplifier Gain
Error Amplifier Output Swing
Error Amplifier Output Current
MIC2179 [adj.]
MIC2179-5.0, MIC2179-3.3
0.6V ≤ V
COMP
≤ 0.8V
upper limit
lower limit
source and sink
A
VOL
D
MAX
f
O
Oscillator Frequency
Maximum Duty Cycle
Minimum On-Time
SYNC Frequency Range
SYNC Threshold
SYNC Minimum Pulse Width
t
ON min
I
LIM
I
SYNC
SYNC Leakage
Current Limit
Switch On-Resistance
Output Switch Leakage
skip mode
R
ON
I
SW
V
SW
= 16.5V
low-side switch, V
IN
= 12V
high-side switch, V
IN
= 12V
June 2009
3
M9999-063009
Micrel, Inc.
Symbol
I
EN
I
PWM
Parameter
Enable Threshold
Enable Leakage
PWM Threshold
PWM Leakage
PWRGD Threshold
V
EN
= 0V to 5.5V
V
PWM
= 0V to 5.5V
Condition
Min
0.8
–1
0.6
–1
1.09
4.33
2.87
Typ
1.6
0.01
1.1
0.01
1.13
4.54
3.00
0.25
0.01
Max
2.2
1
1.4
1
1.17
4.75
3.13
0.4
1
MIC2179
Units
V
µA
V
µA
V
V
V
V
µA
MIC2179 [adj.]: measured at FB pin
MIC2179-5.0: measured at FB pin
MIC2179-3.3: measured at FB pin
PWRGD Output Low
PWRGD Off Leakage
Notes:
V
PWRGD
= 5.5V
I
SINK
= 1.0mA
1.
Exceeding the absolute maximum rating may damage the device.
2.
The device is not guaranteed to function outside its operating rating.
3.
Specification for packaged product only.
General.
Devices are ESD sensitive. Handling precautions recommended.
June 2009
4
M9999-063009
Micrel, Inc.
MIC2179
Typical Characteristics
Oscillator Frequency
vs. Temperature
REFERENCE VOLTAGE (V)
205
FREQUENCY (kHz)
200
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)
MIC2179 [adj.]
3.320
3.315
3.310
3.305
3.300
3.295
3.290
3.285
Reference Voltage
vs. Temperature
MIC2179-3.3
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
MIC2179-5.0
19.0
18.5
18.0
17.5
17.0
16.5
Error-Amplifier Gain
vs. Temperature
BIAS CURRENT (nA)
120
100
Feedback Input Bias Current
vs. Temperature
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)
ON-RESISTANCE (mΩ)
ON-RESISTANCE (mΩ)
CURRENT LIMIT (A)
5.5
5.3
5.1
4.9
4.7
4.5
4.3
4.1
Current Limit
vs. Temperature
350
300
250
200
150
100
50
0
2
4
High-Side Switch
On-Resistance
125°C
85°C
25°C
0°C
400
350
300
250
200
150
100
50
0
2
4
Low-Side Switch
On-Resistance
125°C
85°C
25°C
0°C
3.9
3.7
3.5
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
6 8 10 12 14 16 18
INPUT VOLTAGE (V)
6 8 10 12 14 16 18
INPUT VOLTAGE (V)
12
SUPPLY CURRENT (mA)
10
8
6
4
2
0
2
4
PWM-Mode
Supply-Current
OUTPUT
SWITCHING
EFFICIENCY (%)
95
90
85
80
75
70
65
Skip- and PWM-Mode
Efficiency
5.4V
PWM
8.4V
Skip
8.4V
PWM
5.4V
Skip
100
600
OUTPUT CURRENT (mA)
6 8 10 12 14 16 18
INPUT VOLTAGE (V)
60
10
June 2009
5
M9999-063009
嵌入式系统
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