MICREL MIC4575

MIC4575
200kHz Simple 1A Buck Regulator
General Description
Features
The MIC4575 is a series of easy to use fixed and
adjustable BiCMOS step-down (buck) switch-mode voltage
regulators. The 200kHz MIC4575 duplicates the pinout
and function of the 52kHz LM2575. The higher switching
frequency may allow up to a 2:1 reduction in output filter
inductor size.
The MIC4575 is available in 3.3V, and 5V fixed output
versions or a 1.23V to 20V adjustable output version. Both
versions are capable of driving a 1A 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 MIC4575 is available in TO-220 (T) and TO-263 (U)
packages for the industrial temperature range.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
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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 1A switch current
Wide 4V to 24V input voltage range
Wide 1.23V to 20V output voltage range
Requires minimum external components
< 200µA typical shutdown mode
75% efficiency (adjustable version > 75% typical)
Standard inductors and capacitors are25% of typical
LM2575 values
• Thermal shutdown
• Overcurrent protection
• 100% electrical thermal limit burn-in
Applications
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Simple high-efficiency step-down (buck) regulator
Efficient pre-regulator for linear regulators
On-card switching regulators
Positive-to-negative converter (inverting buck-boost)
Battery charger
Negative boost converter
Step-down 6V to 3.3V for Intel Pentium® and similar
microprocessors
___________________________________________________________________________________________________________
Typical Application
Shutdown
Enable
8V to 24V
C1
150µF
35V
5
1
SHDN
SW
MIC4575-5.0_T
VIN
FB
GND
2
L1
5.0V/1A
68µH
4
3
D1
1N5819
C2
330µF
16V
Fixed Regulator
Adjustable Regulator
Pentium is a registered trademark of Intel Corporation
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
July 2009
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Micrel, Inc.
MIC4575
Ordering Information
Part Number
Standard
RoHS Compliant*
Voltage
Temperature Range
Package
MIC4575-3.3BT
MIC4575-3.3WT
3.3V
–40° to +85°C
5-Pin TO-220
MIC4575-5.0BT
MIC4575-5.0WT
5.0V
–40° to +85°C
5-Pin TO-220
MIC4575BT
MIC4575WT
Adj.
–40° to +85°C
5-Pin TO-220
MIC4575-3.3BU
MIC4575-3.3WU
3.3V
–40° to +85°C
5-Pin TO-263
MIC4575-5.0BU
MIC4575-5.0WU
5.0V
–40° to +85°C
5-Pin TO-263
MIC4575BU
MIC4575WU
Adj.
–40° to +85°C
5-Pin TO-263
* RoHS compliant with ‘high-melting solder’ exemption.
TAB
Pin Configuration
5-Pin TO-220 (T)
5
4
3
2
1
SHDN
FB
GND
SW
VIN
5-Pin TO-263 (U)
Pin Description
Pin Number
Pin Name
1
IN
2
SW
3, TAB
GND
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.
July 2009
Pin Function
Supply Voltage (Input): Unregulated +4V to +40V supply voltage.
Switch (Output): Emitter of NPN output switch. Connect to external storage
inductor and Shottky diode.
Ground.
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MIC4575
Absolute Maximum Ratings
(1)
Supply Voltage (VIN) ..................................................+40V
Shutdown Voltage (VSHDN)............................. –0.3V to +36V
Output Switch (VSW) .......................................................–1V
Storage Temperature (Ts) ........................... –65°C to 150°C
ESD(2)
Operating Ratings
Supply Voltage (VIN).....................................................+24V
Junction Temperature (TJ) ....................................... +150°C
Package Thermal Resistance
TO-220, TO-263 (θJA) ........................................65°C/W
TO-220, TO-263 (θJC) ..........................................2°C/W
Electrical Characteristics(4)
VIN = 12V; ILOAD = 200mA; TJ = 25°C, bold values indicate –40°C< TJ < +85°C, unless noted.
Parameter
Condition
Min
Typ
Max
Units
1.217
1.230
1.230
1.243
V
1.267
1.280
V
V
%
100
500
nA
nA
3.366
V
3.432
3.465
V
V
%
5.100
V
5.200
5.250
V
V
%
220
kHz
1.3
1.5
V
V
%
3.0
3.2
A
A
0
7.5
5
50
1.4
2
35
10
200
mA
mA
mA
µA
1.2
1.0
0.8
30
10
V
V
V
V
µA
µA
MIC4575 [Adjustable]
Feedback Voltage
Feedback Voltage
Efficiency
Feedback Bias Current
8V ≤ VIN ≤ 24V, 0.2A ≤ ILOAD ≤ 1A
1.193
1.180
ILOAD = 1A, VOUT = 5V
77
50
MIC4575-3.3
Output Voltage
Output Voltage
Efficiency
MIC4575-5.0
Output Voltage
Output Voltage
Efficiency
MIC4575 / -3.3 / -5.0
3.234
6V ≤ VIN ≤ 24V, 0.2A ≤ ILOAD ≤ 1A
3.168
3.135
ILOAD = 1A
72
4.900
8V ≤ VIN ≤ 24V, 0.2A ≤ ILOAD ≤ 1A
4.800
4.750
ILOAD = 1A
Oscillator Frequency
Saturation Voltage
IOUT = 1A
Maximum Duty Cycle (On)
Current Limit
FB connected to 0V
Peak Current, tON ≤ 3µs
Output Leakage Current
VIN = 24V, FB connected to 0V
Output = 0V
Output = –1V
SHDN = 5V (regulator off)
VOUT = 0V (regulator off)
SHDN Input Current
VOUT = 3.3 or 5V (regulator on)
5.0
5.0
77
180
Quiescent Current
Standby Quiescent Current
SHDN Input Logic Level
3.3
3.3
90
1.7
1.3
2.2
2.4
SHDN = 5V (regulator off)
SHDN = 0V (regulator on)
–10
200
1
95
2.2
4
0.01
Notes:
1. The MIC4575 is not guaranteed to survive a short circuit to ground for input voltage above 24V.
2. Devices are ESD sensitive. Handling precautions recommended.
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MIC4575
Functional Diagram
Block Diagram with External Components
Fixed Step-Down Regulator
⎛
⎜
⎝
⎛
⎜
⎝
⎛
⎜
⎝
⎛
⎜
⎝
Block Diagram with External Components
Adjustable Step-Down Regulator
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MIC4575
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.
Functional Description
The MIC4575 is a variable duty cycle switch-mode
regulator with an internal power switch. Refer to the
block diagrams.
Supply Voltage
The MIC4575 operates from a +4V to +24V 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.
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.
Enable/Shutdown
The shutdown (SHDN) input is TTL compatible. Ground
the input if unused. A logic-low enables the regulator. A
logic-high shuts down the internal regulator which
reduces the current to typically 50µA.
Feedback
Fixed versions of the regulator have an internal resistive
divider from the feedback (FB) pin. Connect FB directly
to the output line.
Adjustable versions require an external resistive voltage
divider from the output voltage to ground, connected
from the1.23V tap to FB.
Output Capacitor
External output capacitor COUT provides stabilization and
reduces ripple.
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.
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MIC4575
Application 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.
For a mathematical approach to component selection
and circuit design, refer to Application Note 14.
Figure 4. 6V–24V to 3.3V/1A Buck Converter
Low-Profile Surface Mount
Figure 1. 6V–24V to 3.3V/1A Buck Converter
Through Hole
Figure 5. 8V–24V to 5V/1A Buck Converter
Low-Profile Surface Mount
Figure 2. 8V–24V to 5V/1A Buck Converter
Through Hole
5
16V to 24V
1
C1
68µF
63V
SHDN
SW
MIC4575BT
FB
VIN
2
4
GND
3
C1
C2
D1
L1
Nichicon
Nichicon
Motorola
Sumida
L1
150µH
MBR160
Figure 6. 16V–24V to 12V/1A Buck Converter
Low-Profile Surface Mount
12V/1A
R2
13.0k
1%
R1
1.50k
1%
C2
330µF
16V
MBR160
Figure 3. 16V–24V to 12V/1A Buck Converter
Through Hole
Figure 7. 6V–24V to 3.3V/1A Buck Converter
Lower-Cost Surface Mount
Note 2: Surface-mount component.
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MIC4575
Figure 8. 8V–24V to 5V/1A Buck Converter
Lower-Cost Surface Mount
Figure 10. 8V–18V to –5V/0.2A Buck-Boost Converter
Through Hole
Figure 9. 16V–24V to 12V/1A Buck Converter
Lower-Cost Surface Mount
Figure 11. 5V to –5V/0.3A Buck-Boost Converter
Through Hole
5
VIN
8V to 18V
1
C1
22µF
35V
SHDN
SW
2
4
FB
4
1
MIC4575BU
VIN
GND
3
C1
C2
C4
D1
T1
L1
T1
68µH
3
1µH
R2
3.01k
1%
C4
220µF
10V
R1
1.00K
1%
2
D1
MBRS130LT3
VOUT
5V/1A
L1
C3
3300pF
5mVP-P
C2
220µF
10V
AVX
AVX
AVX
Motorola MBRS130LT3
Coiltronics
Coilcraft DO1608C-102
Figure 12. Low Output-Noise Regulator (5mV Output Ripple )
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MIC4575
5
VIN
8V to 18V
1
C1
22µF
35V
SHDN
SW
2
FB
4
MIC4575BU
VIN
T1
68µH
2
+VOUT/+IOUT
5V/0.5A
1
R2
3.01k
1%
R1
1.00K
1%
GND
3
D1
MBRS130LT3
C3
3300pF
C2
220µF
10V
4
C5
220µF
10V
L1
3
+I
C1
C2
C4
C5
D1
D2
T1
AVX
AVX
AVX
AVX
Motorola MBRS130LT3
Motorola MBRS130LT3
Coiltronics
C4
220µF
10V
D2
MBRS130LT3
+ –I
-VOUT/-IOUT
-5V/0.5A
at VIN 15V
Load Regulation 5%
A
+V
+ 0.5V
DC
V – 0.5V
40% then – I
40% then – I
× (1 – DC)
Figure 13. Split ±5V Supply
Figure 14. Adjustable (0V–12V) Output-Voltage Regulator
U1
5
VIN
4V to 15V
C1
150µF
35V
1
SHDN
SW
MIC4575BT
FB
VIN
GND
2
L1
68µH
VOUT
1V/1A
3
4
1
2
U2
LM358
3
D1
1N5819
R1
R2
249
1%
1.00k
1%
C2
330µF
16V
R3
1k
C1
C2
D1 Motorola 1N5819
L1
U2 National LM358
Figure 15. Low Output-Voltage Regulator (1V)
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MIC4575
Figure 16. 1A Battery Charger (6–8 cells)
D3
1N4148
5
VIN
8V to 24V
1
SHDN
MIC4575-BT
FB
VIN
GND
V
Micrel
National
Micrel
Nichicon
Nichicon
Motorola
Motorola
Motorola
Coiltronics
KRL
Siliconix
1N5819
1N5819
1N4148
C2
330µF
16V
R2
100
1%
C4
1000pF
VIN
3
R7
1k
MIC4575BT
LM358
LM4041CIZ-1.2
D2
1N5819
R1
0.1
D1
1N5819
R6
3k
4
3
C1
150µF
35V
U1
U2
U3
C1
C2
D1
D2
D3
L1
R1
Q1
SW
L1
68µH
2
1
2
U2A
1/2LM358
R3
10k
VIN
8
C3
0.01µF
U2B
1/2 LM358
5
7
DZ1
1N5244
14V
Q1
VN2222LL
SP-1-A1-0R100J
VN2222LL
IOUT
0.1A to 1A
2-8 Cells
VBATT
R5
10k
VR1
10k
U3
LM4041CIZ-1.2
6
4
R4
1.21k
1%
/ 0.9 + 2.5V
Figure 17. 0.1A–1A Variable-Current Battery Charger
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Micrel, Inc.
MIC4575
Figure 18. 1A Battery Charger (2–8 Cells)
Figure 19. Remote-Sensing Regulator
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MIC4575
Figure 20. 6V–18V to Split ±12V/100mA Supply
Figure 21. 1A Battery Charger
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MIC4575
⎛
⎝⎜
⎛
⎜⎝
Figure 22. Improved Adjustable Output-Voltage Regulator (0V–12V)
Figure 23. Switchable Battery-Pack Charger
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MIC4575
⎛
⎝⎜
⎛
⎜⎝
Figure 24. Lithium-Ion Battery Charger with End-of-Charge Flag
⎛
⎝⎜
⎛
⎜⎝
Figure 25. Low Output-Noise Regulator (<1mV)
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MIC4575
Package Information
5-Pin TO-220 (T)
5-Pin TO-263 (U)
July 2009
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Micrel, Inc.
MIC4575
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
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can 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 Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 1997 Micrel, Incorporated.
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