Micrel MIC4576 User Manual
MIC4576 Micrel, Inc.
C1
470µF
63V
D1
MBR360
C2
1000µF
16V
L1
33µH
GND
FB
SW
MIC4576-5.0WT
SHDN
8V to 36V
5V/3A
V
IN
3
4
25
1
Shutdown
Enable
C1
470µF
63V
MBR360
C2
1000µF
16V
L1
68µH
GND
FB
SW
MIC4576WT
SHDN
16V to 36V
12V/3A
V
IN
R2
13.0k
1%
R1
1.50k
1%
5
1
4
2
3
Shutdown
Enable
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 versions 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 conditions. 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 minimum 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
Fixed 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
Adjustable Regulator
MIC4576 Micrel, Inc.
BAT
5 SHDN
4 FB
3 GND
2 SW
1 V
IN
B
A
T
5 SHDN
4 FB
3 GND
2 SW
1 V
IN
Ordering Information
Standard
Part Number
RoHS Compliant
Part Number*
Voltage Temperature Range
Package
MIC4576-3.3BT MIC4576-3.3WT 3.3V –40ºC to +85ºC TO-220-5
MIC4576-5.0BT MIC4576-5.0WT 5.0V –40ºC to +85ºC TO-220-5
MIC4576BT MIC4576WT ADJ. –40ºC to +85ºC TO-220-5
MIC4576-3.3BU MIC4576-3.3WU 3.3V –40ºC to +85ºC TO-263-5
MIC4576-5.0BU MIC4576-5.0WU 5.0V –40ºC to +85ºC TO-263-5
MIC4576BU MIC4576WU ADJ. –40ºC to +85ºC TO-263-5
* RoHS compliant with "high-melting solder" exemption.
Pin Configuration
5-Pin TO-220 (T)
5-Pin TO-263 (U)
Pin Description
Pin Number Pin Name Pin Function
1 VIN Supply Voltage (Input): Unregulated +4V to +36V supply voltage.
2 SW Switch (Output): Emitter of NPN output switch. Connect to external storage
inductor and Shottky diode.
3, TAB GND Ground
4 FB 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.
5 SHDN Shutdown (Input): Logic low enables regulator. Logic high (> 2.4V) shuts
down regulator.
MIC4576 2 March 2006
MIC4576 Micrel, Inc.
Absolute Maximum Ratings
Supply Voltage (VIN) ....................................................+40V
Shutdown Voltage (V
Output Switch (VSW), Steady State ............................... –1V
Feedback Voltage (VFB) [Adjustable] .........................+3.8V
Storage Temperature ................................ –65°C to +150°C
) ............................–0.3V to +36V
SHDN
Operating Ratings
Supply Voltage (VIN) ....................................................+36V
Junction Temperature .............................................. +150°C
Package Thermal Resistance
TO-220, TO-263 (θJA) .........................................65°C/W
TO-220, TO-263 (θJC) ............................................ 2°C/W
Electrical Characteristics
VIN = 12V; I
Parameter Condition Min Typ Max Units
MIC4576 [Adjustable]
Feedback Voltage 1.217 1.230 1.243 V
Feedback Voltage 8V ≤ VIN ≤ 36V, 0.5A ≤ I
1.180 1.280 V
Efficiency I
Maximum Duty Cycle (On) VFB = 1.0V 90 95 %
Output Leakage Current VIN = 36V, V
output = 0V 0 2 mA
output = –1V 7.5 35 mA
Quiescent Current VFB = 1.5V 5 10 mA
Feedback Bias Current 50 100 nA
500 nA
MIC4576-3.3
Output Voltage 3.234 3.3 3.366 V
Output Voltage 6V ≤ VIN ≤ 36V, 0.5A ≤ I
3.135 3.465 V
Efficiency I
Maximum Duty Cycle (On) VFB = 2.5V 90 95 %
Output Leakage Current VIN = 36V, V
output = 0V 0 2 mA
output = –1V 7.5 35 mA
Quiescent Current VFB = 4.0V 5 10 mA
MIC4576-5.0
Output Voltage 4.900 5.0 5.100 V
Output Voltage 8V ≤ VIN ≤ 36V, 0.5A ≤ I
4.750 5.250 V
Efficiency I
Maximum Duty Cycle (On) VFB = 4.0V 90 95 %
Output Leakage Current VIN = 36V, V
output = 0V 0 2 mA
output = –1V 7.5 35 mA
Quiescent Current VFB = 6.0V 5 10 mA
= 500mA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +85°C; unless noted.
LOAD
≤ 3A 1.193 1.230 1.267 V
LOAD
= 3A, Note 1 77 %
LOAD
= 1.5V
FB
≤ 3A 3.168 3.3 3.432 V
LOAD
= 3A 72 %
LOAD
= 4.0V
FB
≤ 3A 4.800 5.0 5.200 V
LOAD
= 3A 77 %
LOAD
= 6.0V
FB
March 2006 3 MIC4576
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