Micrel MIC4576-3.3BT 200khz simple 3a buck regulator Datasheet

MIC4576
Micrel, Inc.
MIC4576
200kHz Simple 3A Buck Regulator
General Description
Features
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.
• 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
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.
Applications
•
•
•
•
•
•
•
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.
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
5
Shutdown
Enable
8V to 36V
C1
470µF
63V
1
SHDN
SW
MIC4576-5.0WT
VIN
FB
GND
L1
2
5V/3A
33µH
4
D1
MBR360
3
C2
1000µF
16V
Fixed Regulator
Shutdown
Enable
16V to 36V
C1
470µF
63V
5
1
SHDN
SW
MIC4576WT
FB
VIN
GND
2
L1
68µH
4
MBR360
3
12V/3A
R2
13.0k
1%
R1
1.50k
1%
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
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
TAB
5
4
3
2
1
SHDN
FB
GND
SW
VIN
5-Pin TO-220 (T)
TAB
5
4
3
2
1
SHDN
FB
GND
SW
VIN
5-Pin TO-263 (U)
Pin Description
Pin Number
Pin Name
1
VIN
MIC4576
2
SW
3, TAB
GND
4
FB
5
SHDN
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.
2
March 2006
MIC4576
Micrel, Inc.
Absolute Maximum Ratings
Operating Ratings
Supply Voltage (VIN) .................................................... +40V
Shutdown Voltage (VSHDN)............................–0.3V to +36V
Output Switch (VSW), Steady State ............................... –1V
Feedback Voltage (VFB) [Adjustable] ......................... +3.8V
Storage Temperature ................................ –65°C to +150°C
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; ILOAD = 500mA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +85°C; unless noted.
Parameter
Condition
Min
Typ
Max
Units
1.217
1.230
1.243
V
1.193
1.180
1.230
1.267
1.280
V
V
77
%
90
95
%
MIC4576 [Adjustable]
Feedback Voltage
Feedback Voltage
8V ≤ VIN ≤ 36V, 0.5A ≤ ILOAD ≤ 3A
Efficiency
ILOAD = 3A, Note 1
Maximum Duty Cycle (On)
VFB = 1.0V
Output Leakage Current
VIN = 36V, VFB = 1.5V
output = 0V
output = –1V
Quiescent Current
VFB = 1.5V
Feedback Bias Current
0
7.5
2
35
mA
mA
5
10
mA
50
100
500
nA
nA
3.234
3.3
3.366
V
3.168
3.135
3.3
3.432
3.465
V
V
72
%
90
95
%
MIC4576-3.3
Output Voltage
Output Voltage
6V ≤ VIN ≤ 36V, 0.5A ≤ ILOAD ≤ 3A
Efficiency
ILOAD = 3A
Maximum Duty Cycle (On)
VFB = 2.5V
Output Leakage Current
VIN = 36V, VFB = 4.0V
output = 0V
output = –1V
Quiescent Current
VFB = 4.0V
MIC4576-5.0
Output Voltage
Output Voltage
8V ≤ VIN ≤ 36V, 0.5A ≤ ILOAD ≤ 3A
Efficiency
ILOAD = 3A
Maximum Duty Cycle (On)
VFB = 4.0V
Output Leakage Current
VIN = 36V, VFB = 6.0V
output = 0V
output = –1V
Quiescent Current
VFB = 6.0V
March 2006
0
7.5
2
35
mA
mA
5
10
mA
4.900
5.0
5.100
V
4.800
4.750
5.0
5.200
5.250
V
V
90
3
77
%
95
%
0
7.5
2
35
mA
mA
5
10
mA
MIC4576
MIC4576
Parameter
Micrel, Inc.
Condition
Min
Typ
Max
Units
180
200
220
kHz
1.7
2.3
2.5
V
V
5.2
7.9
8.5
A
A
50
200
µA
MIC4576 / -3.3 / -5.0
Oscillator Frequency
Saturation Voltage
IOUT = 3A
Current Limit
peak current, tON ≤ 3µs; VFB = 0V
Standby Quiescent Current
VSHDN = 5V (regulator off), VFB = 0V
SHDN Input Logic Level
VOUT = 0V (regulator off)
4.2
3.5
2.2
2.4
VOUT = 3.3V or 5V (regulator on)
SHDN Input Current
VSHDN = 5V (regulator off)
VSHDN = 0V (regulator on)
–10
1.4
V
V
1.2
1.0
0.8
V
V
4
0.01
30
10
µA
µA
General Note: Devices are ESD protected, however, handling precautions are recommended.
Note 1:
VOUT = 5V
MIC4576
4
March 2006
MIC4576
Micrel, Inc.
Block Diagrams
+36V max.
VIN
Shutdown
Enable
SHDN
CIN
Internal
Regulator
Thermal
Shutdown
200kHz
Oscillator
Driver
Comparator
Error
Amp.
Current
Limit
3A
Switch
L1
SW
VOUT
D1
COUT
1.23V
Bandgap
R1
FB
R2
MIC4576-x.x
GND
Block Diagram with External Components
Fixed Step-Down Regulator
+36V max.
VIN
Shutdown
Enable
SHDN
CIN
Internal
Regulator
Thermal
Shutdown
200kHz
Oscillator
Comparator
Error
Amp.
Current
Limit
Driver
3A
Switch
L1
SW
VOUT
D1
1.23V
Bandgap
COUT
R1
FB
MIC4576 [Adjustable]
R2
GND
Block Diagram with External Components
Adjustable Step-Down Regulator
March 2006
5
MIC4576
MIC4576
Micrel, Inc.
Functional Description
The MIC4576 is a variable duty cycle switch-mode regulator
with an internal power switch. Refer to the block diagrams.
A higher feedback voltage increases the error amplifier output
voltage. A higher error amplifier voltage (comparator inverting
input) causes the comparator to detect only the peaks of the
sawtooth, reducing the duty cycle of the comparator output.
A lower feedback voltage increases the duty cycle.
Supply Voltage
The MIC4576 operates from a +4V to +36V unregulated
input. Highest efficiency operation is from a supply voltage
around +15V.
Output Switching
When the internal switch is on, an increasing current flows
from the supply VIN, through external storage inductor L1, to
output capacitor COUT and the load. Energy is stored in the
inductor as the current increases with time.
Enable/Shutdown
The shutdown (SHDN) input is TTL compatible. Ground the
input if unused. A logic-low enables the regulator. A logichigh shuts down the internal regulator which reduces the
current to typically 50µA.
When the internal switch is turned off, the collapse of the
magnetic field in L1 forces current to flow through fast recovery
diode D1, charging COUT.
Feedback
Fixed versions of the regulator have an internal resistive
divider from the feedback (FB) pin. Connect FB directly to
the output line.
Output Capacitor
External output capacitor COUT provides stabilization and
reduces ripple.
Adjustable versions require an external resistive voltage
divider from the output voltage to ground, connected from
the 1.23V tap to FB.
Return Paths
During the on portion of the cycle, the output capacitor and
load currents return to the supply ground. During the off
portion of the cycle, current is being supplied to the output
capacitor and load by storage inductor L1, which means that
D1 is part of the high-current return path.
Duty Cycle Control
A fixed-gain error amplifier compares the feedback signal
with a 1.23V bandgap voltage reference. The resulting error
amplifier output voltage is compared to a 200kHz sawtooth
waveform to produce a voltage controlled variable duty cycle
output.
Applications Information
The applications circuits that follow have been constructed
and tested. Refer to Application Note 15 for additional information, including efficiency graphs and manufacturer’s
addresses and telephone numbers for most circuits.
5
6V to 24V
C1
470µF
35V
C1
C2
D1
L1
L1
1
SHDN
SW
MIC4576-3.3BT
FB
VIN
GND
3
Nichicon
Nichicon
Motorola
Coiltronics
Bi
2
L1
For a mathematical approach to component selection and
circuit design, refer to Application Note 14.
3.3V/3A
5
33µH
4
D1
1N5822
6V to 36V
C2
1000µF
16V
C1
470µF
63V
UPL1V471MPH, ESR = 0.046Ω
UPL1C221MPH, ESR = 0.047Ω
1N5822
PL52C-33-1000, DCR = 0.036Ω
HM77-30004, DCR = 0.045Ω, Note 2
C1
C2
D1
L1
L1
Figure 1. 6V–24V to 3.3V/3A Buck Converter
Through Hole
Note 2:
1
SHDN
SW
MIC4576-3.3BT
VIN
FB
GND
3
Nichicon
Nichicon
Motorola
Coiltronics
Bi
2
L1
3.3V/3A
33µH
4
D1
MBR360
C2
1000µF
16V
UPL1J471MRH, ESR = 0.039Ω
UPL1C102MPH, ESR = 0.047Ω
MBR360
PL52C-33-1000 DCR = 0.036
HM77-30004, DCR = 0.045Ω, Note 2
Figure 2. 6V–36V to 3.3V/3A Buck Converter
Through Hole
Surface-mount component.
MIC4576
6
March 2006
MIC4576
Micrel, Inc.
5
8V to 24V
C1
470µF
35V
1
SHDN
SW
MIC4576-5.0BT
FB
VIN
GND
C1 Nichicon
C2 Nichicon
D1 Motorola
L1 Coiltronics
L1 Bi
3
L1
2
5V/3A
5
33µH
8V to 36V
C2
1000µF
16V
4
D1
1N5822
C1
470µF
63V
C1
C2
D1
L1
L1
UPL1J471MPH, ESR = 0.046Ω
UPL1C102MPH, ESR = 0.047Ω
MBR5822
PL52C-33-1000, DCR = 0.036
HM77-30004, DCR = 0.045Ω, Note 2
16V to 36V
1
C1
470µF
63V
SHDN
VIN
SW
MIC4576BT
GND
Nichicon
Nichicon
Motorola
Bi
MIC4576-5.0BT
VIN
FB
GND
3
Nichicon
Nichicon
Motorola
Coiltronics
Bi
FB
L1
2
2
L1
5V/3A
33µH
4
D1
MBR360
C2
1000µF
16V
UPL1J471MRH, ESR = 0.039Ω
UPL1C102MPH, ESR = 0.047Ω
MBR360
PLS2C-33-1000, DCR = 0.036
HM77-30004, DCR = 0.045Ω, Note 2
12V/3A
68µH
4
MBR360
3
C1
C2
D1
L1
SW
Figure 4. 8V–36V to 5V/3A Buck Converter
Through Hole
Figure 3. 8V–24V to 5V/3A Buck Converter
Through Hole
5
1
SHDN
R2
13.0k
1%
R1
1.50k
1%
C2
1000µF
16V
UPL1J471MPH, ESR = 0.039Ω
UPL1C102MPH, ESR = 0.047Ω
MBR360
HM77-29006, DCR = 0.08Ω
Figure 5. 16V–36V to 12V/3A Buck Converter
Through Hole
U1
5
VIN
8V to 36V
1
SHDN
SW
MIC4576-5.0BT
FB
VIN
GND
R1
0.1Ω
L1
2
33µH
D1
MBR360
C1
470µF
63V
R3
10K
C5
0.01µF
VIN
8
2
1
3
C3
470µF
63V
SHDN
FB
MIC4576-5.0BT
SW
VIN
GND
3
C1, C3
C2, C4
D1, D2
L1, L2
R1, R2
U3
Nichicon
Nichicon
Motorola
Coiltronics
KRL
National
U3
LM358
4
U2
1
C2
1000µF
16V
4
3
5
VOUT
5V/4A
4
L2
2
33µH
D2
MBR360
R2
0.1Ω
C4
1000µF
16V
UPL1J471MRH, ESR = 0.039Ω
UPL1C102MPH, ESR = 0.047Ω
MBR360
PL52C-33-1000, DCR = 0.036
SP-1-A1-0R100J
LM358
Figure 6. Parallel Switching Regulators
Note 2:
Surface-mount component.
March 2006
7
MIC4576
MIC4576
Micrel, Inc.
Package Information
0.150 D ±0.005
(3.81 D ±0.13)
0.177 ±0.008
(4.50 ±0.20)
0.400 ±0.015
(10.16 ±0.38)
0.050 ±0.005
(1.27 ±0.13)
0.108 ±0.005
(2.74 ±0.13)
0.241 ±0.017
(6.12 ±0.43)
0.578 ±0.018
(14.68 ±0.46)
SEATING
PLANE
7°
Typ.
0.550 ±0.010
(13.97 ±0.25)
0.067 ±0.005
(1.70 ±0.127)
0.268 REF
(6.81 REF)
0.032 ±0.005
(0.81 ±0.13) 0.018 ±0.008
(0.46 ±0.20)
0.103 ±0.013
(2.62±0.33)
Dimensions: inch
(mm)
5-Pin TO-220 (T)
0.405 ±0.005
0.065 ±0.010
20°±2°
0.176 ±0.005
0.050 ±0.005
0.060 ±0.005
0.360 ±0.005
0.600 ±0.025
SEATING PLANE
0.004 +0.004
–0.008
0.067 ±0.005
8° MAX
0.032 ±0.003
0.100 ±0.01
0.015 ±0.002
DIM. = INCH
5-Pin TO-263 (U)
MICREL INC.
2180 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by�
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not�
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's
use or sale of Micrel Pr�
Micrel for any damages resulting from such use or sale.
© 2005 Micrel, Inc.
MIC4576
8
March 2006
Similar pages