MIC2179
Micrel
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 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 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 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 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
R1
20k
U1
15
6
5
13
16,17
VIN
EN
PWRGD
PWM
SYNC
COMP SGND
8
9–12
Output Good
Output Low
Skip Mode
PWM Mode
SW
MIC
2179-3.3
PGND
FB
BIAS
14
3,4
1,2,
19,20
L1
22µH
D1
MBRM120
C2
100µF
6.3V
V
OUT
3.3V/600mA
7
R2
10k
C4
6.8nF
C3
0.01µF
Pins 4 and 18 are not connected.
Pins 3 and 4 can be connected
together for a low-impedance
connection.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
June 1998
1
MIC2179
MIC2179
Micrel
Ordering Information
Part Number
MIC2179BSM
MIC2179-3.3BSM
MIC2179-5.0BSM
Voltage
Adjustable
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
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
).
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
.
not internally connected.
6
7
8
9–12
13
PWRGD
FB
COMP
SGND
SYNC
14
15
16, 17
4, 18
BIAS
EN
VIN
NC
MIC2179
2
June 1998
MIC2179
Micrel
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
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
MIC2179 [adj.]: V
OUT
= 3.3V, I
LOAD
= 0
MIC2179 [adj.]: V
OUT
= 3.3V,
5V
≤
V
IN
≤
16V, 10mA
≤
I
LOAD
≤
1A
MIC2179-5.0: I
LOAD
= 0
MIC2179-5.0:
6V
≤
V
IN
≤
16V, 10mA
≤
I
LOAD
≤
1A
MIC2179-3.3: I
LOAD
= 0
MIC2179-3.3:
5V
≤
V
IN
≤
16V, 10mA
≤
I
LOAD
≤
1A
V
TH
V
TL
I
FB
A
VOL
Feedback Bias Current
Undervoltage Lockout
upper threshold
lower threshold
MIC2179 [adj.]
MIC2179-5.0, MIC2179-3.3
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
3.4
0.01
4.3
600
160
140
1
350
350
10
1
5.5
1.6
source and sink
15
160
100
300
400
300
2.2
15
0.9
3.90
3.10
1.22
3.20
3.14
4.85
4.85
4.75
3.20
3.20
3.14
Min
Typ
1.0
600
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
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
June 1998
3
MIC2179
MIC2179
Symbol
Parameter
Enable Threshold
I
EN
I
PWM
Enable Leakage
PWM Threshold
PWM Leakage
PWRGD Threshold
V
PWM
= 0V to 5.5V
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
I
SINK
= 1.0mA
V
PWRGD
= 5.5V
V
EN
= 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
Micrel
Units
V
µA
V
µA
V
V
V
V
µA
General Note:
Devices are ESD sensitive. Handling precautions recommended.
MIC2179
4
June 1998
MIC2179
Micrel
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)
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
120
BIAS CURRENT (nA)
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)
5.5
CURRENT LIMIT (A)
5.3
5.1
4.9
4.7
4.5
4.3
4.1
3.9
Current Limit
vs. Temperature
ON-RESISTANCE (mΩ)
350
300
250
200
150
100
50
0
2
4
High-Side Switch
On-Resistance
ON-RESISTANCE (mΩ)
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
3.7
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 (%)
Skip- and PWM-Mode
Efficiency
95
90
85
80
75
70
65
5.4V
Skip
100
600
OUTPUT CURRENT (mA)
8.4V
PWM
8.4V
Skip
5.4V
PWM
6 8 10 12 14 16 18
INPUT VOLTAGE (V)
60
10
June 1998
5
MIC2179
聊聊、笑笑、闹闹
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
