MIC4576
Micrel, Inc.
MIC4576
200kHz Simple 3A Buck Regulator
General Description
The MIC4576 is a series of easy to use fixed and adjustable
BiCMOS step-down (buck) switch-mode voltage regulators.
The 200kHz MIC4576 duplicates the pinout and function of
the 52kHz LM2576. The higher switching frequency may
allow up to a 2:1 reduction in output filter inductor size.
The MIC4576 is available in 3.3V, and 5V fixed output ver-
sions or a 1.23V to 33V adjustable output version. Both
versions are capable of driving a 3A load with excellent line
and load regulation.
The feedback voltage is guaranteed to ±2% tolerance for
adjustable versions, and the output voltage is guaranteed to
±3% for fixed versions, within specified voltages and load con-
ditions. The oscillator frequency is guaranteed to ±10%.
In shutdown mode, the regulator draws less than 200µA
standby current. The regulator performs cycle-by-cycle
current limiting and thermal shutdown for protection under
fault conditions.
This series of simple switch-mode regulators requires a mini-
mum number of external components and can operate using
a standard series of inductors. Frequency compensation is
provided internally.
The MIC4576 is available in TO-220 (T) and TO-263 (U)
packages for the industrial temperature range.
Features
• Fixed 200kHz operation
• 3.3V, 5V, and adjustable output versions
• Voltage over specified line and load conditions:
Fixed version: ±3% max. output voltage
Adjustable version: ±2% max. feedback voltage
• Guaranteed 3A switch current
• Wide 4V to 36V input voltage range
• Wide 1.23V to 33V output voltage range
• Requires minimum external components
• < 200µA typical shutdown mode
• 75% efficiency (adjustable version > 75% typical)
• Standard inductors are 25% of typical LM2576 values
• Thermal shutdown
• Overcurrent protection
• 100% electrical thermal limit burn-in
Applications
•
•
•
•
•
•
•
Simple high-efficiency step-down (buck) regulator
Efficient preregulator for linear regulators
On-card switching regulators
Positive-to-negative converter (inverting buck-boost)
Battery Charger
Negative boost converter
Step-down to 3.3V for Intel Pentium™
and similar microprocessors
Typical Applications
Shutdown
Enable
5
SHDN
SW
2
L1
33µH
5V/3A
C2
1000µF
16V
8V to 36V
C1
470µF
63V
1
MIC4576-5.0WT
V
IN
FB
GND
3
4
D1
MBR360
Fixed Regulator
Shutdown
Enable
5
SHDN
SW
2
L1
68µH
R2
13.0k
1%
R1
1.50k
1%
12V/3A
16V to 36V
1
C1
470µF
63V
MIC4576WT
FB
V
IN
GND
3
4
MBR360
C2
1000µF
16V
Adjustable Regulator
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 2006
1
MIC4576
MIC4576
Micrel, Inc.
Ordering Information
Standard
Part Number
MIC4576-3.3BT
MIC4576-5.0BT
MIC4576BT
MIC4576-3.3BU
MIC4576-5.0BU
MIC4576BU
RoHS Compliant
Part Number*
MIC4576-3.3WT
MIC4576-5.0WT
MIC4576WT
MIC4576-3.3WU
MIC4576-5.0WU
MIC4576WU
Voltage
3.3V
5.0V
ADJ.
3.3V
5.0V
ADJ.
Temperature Range
–40ºC to +85ºC
–40ºC to +85ºC
–40ºC to +85ºC
–40ºC to +85ºC
–40ºC to +85ºC
–40ºC to +85ºC
Package
TO-220-5
TO-220-5
TO-220-5
TO-263-5
TO-263-5
TO-263-5
* RoHS compliant with "high-melting solder" exemption.
Pin Configuration
5
4
3
2
1
SHDN
FB
GND
SW
V
IN
TAB
5-Pin TO-220 (T)
5
4
3
2
1
SHDN
FB
GND
SW
V
IN
TAB
5-Pin TO-263 (U)
Pin Description
Pin Number
1
2
3,
TAB
4
Pin Name
SW
GND
FB
V
IN
Pin Function
Supply Voltage (Input): Unregulated +4V to +36V supply voltage.
Switch (Output): Emitter of NPN output switch. Connect to external storage
inductor and Shottky diode.
Ground
Feedback (Input): Output voltage feedback to regulator. Connect to output
of supply for fixed versions. Connect to 1.23V tap of resistive divider for
adjustable versions.
Shutdown (Input): Logic low enables regulator. Logic high (> 2.4V) shuts
down regulator.
5
SHDN
MIC4576
2
March 2006
MIC4576
Micrel, Inc.
Absolute Maximum Ratings
Supply Voltage (V
IN
) .................................................... +40V
Shutdown Voltage (V
SHDN
)............................–0.3V to +36V
Output Switch (V
SW
), Steady State ............................... –1V
Feedback Voltage (V
FB
) [Adjustable] ......................... +3.8V
Storage Temperature ................................ –65°C to +150°C
Operating Ratings
Supply Voltage (V
IN
) .................................................... +36V
Junction Temperature .............................................. +150°C
Package Thermal Resistance
TO-220, TO-263 (θ
JA
) ......................................... 65°C/W
TO-220, TO-263 (θ
JC
) ............................................ 2°C/W
Electrical Characteristics
V
IN
= 12V; I
LOAD
= 500mA; T
J
= 25°C,
bold
values indicate –40°C ≤ T
J
≤ +85°C; unless noted.
Parameter
Condition
MIC4576 [Adjustable]
Feedback Voltage
Feedback Voltage
Efficiency
Maximum Duty Cycle (On)
Output Leakage Current
8V ≤ V
IN
≤ 36V, 0.5A ≤ I
LOAD
≤ 3A
I
LOAD
= 3A,
Note 1
V
IN
= 36V, V
FB
= 1.5V
output = 0V
output = –1V
V
FB
= 1.5V
V
FB
= 1.0V
1.217
1.193
1.180
90
1.230
1.230
77
95
0
7.5
5
50
2
35
10
100
500
3.366
3.432
3.465
1.243
1.267
1.280
V
V
V
%
%
mA
mA
mA
nA
nA
V
V
V
%
%
2
35
10
5.100
5.200
5.250
mA
mA
mA
V
V
V
%
%
2
35
10
mA
mA
mA
Min
Typ
Max
Units
Quiescent Current
Feedback Bias Current
MIC4576-3.3
Output Voltage
Output Voltage
Efficiency
Maximum Duty Cycle (On)
Output Leakage Current
3.234
6V ≤ V
IN
≤ 36V, 0.5A ≤ I
LOAD
≤ 3A
I
LOAD
= 3A
3.168
3.135
90
3.3
3.3
72
95
0
7.5
5
V
IN
= 36V, V
FB
= 4.0V
output = 0V
output = –1V
V
FB
= 4.0V
4.900
8V ≤ V
IN
≤ 36V, 0.5A ≤ I
LOAD
≤ 3A
I
LOAD
= 3A
4.800
4.750
90
V
FB
= 2.5V
Quiescent Current
MIC4576-5.0
Output Voltage
Output Voltage
Efficiency
Maximum Duty Cycle (On)
Output Leakage Current
5.0
5.0
77
95
0
7.5
5
V
IN
= 36V, V
FB
= 6.0V
output = 0V
output = –1V
V
FB
= 6.0V
V
FB
= 4.0V
Quiescent Current
March 2006
3
MIC4576
MIC4576
Parameter
MIC4576 / -3.3 / -5.0
Oscillator Frequency
Saturation Voltage
Current Limit
Standby Quiescent Current
SHDN Input Logic Level
I
OUT
= 3A
peak current, t
ON
≤ 3µs; V
FB
= 0V
V
SHDN
= 5V (regulator off), V
FB
= 0V
4.2
3.5
2.2
2.4
180
200
1.7
5.2
50
1.4
1.2
4
0.01
Condition
Min
Typ
Micrel, Inc.
Max
220
2.3
2.5
7.9
8.5
200
Units
kHz
V
V
A
A
µA
V
V
1.0
0.8
30
10
V
V
µA
µA
V
OUT
= 0V (regulator off)
V
OUT
= 3.3V or 5V (regulator on)
SHDN Input Current
V
SHDN
= 5V (regulator off)
V
SHDN
= 0V (regulator on)
–10
General Note:
Devices are ESD protected, however, handling precautions are recommended.
Note 1:
V
OUT
= 5V
MIC4576
4
March 2006
MIC4576
Micrel, Inc.
Block Diagrams
+36V max.
V
IN
Shutdown
Enable
C
IN
SHDN
Internal
Regulator
200kHz
Oscillator
Thermal
Shutdown
Current
Limit
Com-
parator
Driver
3A
Switch
1.23V
Bandgap
R1
R2
GND
SW
D1
L1
V
OUT
C
OUT
Error
Amp.
MIC4576-x.x
FB
Block Diagram with External Components
Fixed Step-Down Regulator
+36V max.
V
IN
Shutdown
Enable
C
IN
SHDN
Internal
Regulator
200kHz
Oscillator
Thermal
Shutdown
Current
Limit
Com-
parator
Driver
3A
Switch
1.23V
Bandgap
SW
D1
L1
V
OUT
C
OUT
R1
Error
Amp.
MIC4576
[Adjustable]
FB
GND
R2
Block Diagram with External Components
Adjustable Step-Down Regulator
March 2006
5
MIC4576
微控制器 MCU
