Datasheet MIC4576 Datasheet (Micrel)

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 [phone] • fax + 1 [phone] • 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

MIC4576 Micrel, Inc.

Parameter Condition Min Typ Max Units

MIC4576 / -3.3 / -5.0

Oscillator Frequency 180 200 220 kHz

Saturation Voltage I

2.5 V

Current Limit peak current, tON ≤ 3µs; VFB = 0V 4.2 5.2 7.9 A

3.5 8.5 A

Standby Quiescent Current V

SHDN Input Logic Level V

2.4 V

V

0.8 V

SHDN Input Current V
V

General Note: Devices are ESD protected, however, handling precautions are recommended.

Note 1: V

OUT

= 5V

= 3A 1.7 2.3 V

OUT

= 5V (regulator off), VFB = 0V 50 200 µA

SHDN

= 0V (regulator off) 2.2 1.4 V

OUT

= 3.3V or 5V (regulator on) 1.2 1.0 V

OUT

= 5V (regulator off) 4 30 µA

SHDN

= 0V (regulator on) –10 0.01 10 µA

SHDN

MIC4576 4 March 2006

200kHz

Oscillator

1.23V

Bandgap

3A
Switch

Thermal

Shutdown

Current

Limit

Driver

Internal

Regulator

FB

SW

GND

V

IN

+36V max.

C

IN

C

OUT

L1

D1

Shutdown
Enable

SHDN

V

OUT

MIC4576

[Adjustable]

R1

R2

Com-

parator

Error
Amp.

200kHz

Oscillator

1.23V

Bandgap

3A
Switch

Thermal

Shutdown

Current

Limit

Driver

Internal

Regulator

FB

SW

GND

V

IN

+36V max.

C

IN

C

OUT

L1

D1

Shutdown
Enable

SHDN

V

OUT

MIC4576-x.x

R1

R2

Com-

parator

Error
Amp.

Block Diagram with External Components

Adjustable Step-Down Regulator

Block Diagram with External Components

Fixed Step-Down Regulator

MIC4576 Micrel, Inc.

Block Diagrams

March 2006 5 MIC4576

MIC4576 Micrel, Inc.

C1

470

µF

35V

D1
1N5822

C2
1000µF
16V

L1

33

µH

GND

FB

SW

MIC4576-3.3BT

SHDN

6V to 24V

3.3V/3A

V

IN

C1 Nichicon UPL1V471MPH, ESR = 0.046Ω
C2 Nichicon UPL1C221MPH, ESR = 0.047Ω
D1 Motorola 1N5822
L1 Coiltronics PL52C-33-1000, DCR = 0.036Ω
L1 Bi HM77-30004, DCR = 0.045Ω, Note 2

Functional Description

The MIC4576 is a variable duty cycle switch-mode regulator
with an internal power switch. Refer to the block diagrams.

Supply Voltage

The MIC4576 operates from a +4V to +36V unregulated
input. Highest efficiency operation is from a supply voltage
around +15V.

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.

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
the 1.23V tap to FB.

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.

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.

Output Switching

When the internal switch is on, an increasing current flows
from the supply V
output capacitor C

through external storage inductor L1, to

IN,

and the load. Energy is stored in the

OUT

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 C

OUT

.

Output Capacitor

External output capacitor C

provides stabilization and

OUT

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.

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.

For a mathematical approach to component selection and
circuit design, refer to Application Note 14.

Note 2: Surface-mount component.

MIC4576 6 March 2006

MIC4576 Micrel, Inc.

C1

470

µF

35V

D1
1N5822

C2
1000

µF

16V

L1

33

µH

GND

FB

SW

MIC4576-5.0BT

SHDN

8V to 24V

5V/3A

V

IN

C1 Nichicon UPL1J471MPH, ESR = 0.046Ω
C2 Nichicon UPL1C102MPH, ESR = 0.047Ω
D1 Motorola MBR5822
L1 Coiltronics PL52C-33-1000, DCR = 0.036
L1 Bi HM77-30004, DCR = 0.045Ω, Note 2

3

4

25

1

Figure 3. 8V–24V to 5V/3A Buck Converter

Through Hole

C1

470

µF

63V

D1
MBR360

C2
1000µF
16V

L1

33

µH

GND

FB

SW

MIC4576-5.0BT

SHDN

8V to 36V

5V/3A

V

IN

C1 Nichicon UPL1J471MRH, ESR = 0.039Ω
C2 Nichicon UPL1C102MPH, ESR = 0.047Ω
D1 Motorola MBR360
L1 Coiltronics PLS2C-33-1000, DCR = 0.036
L1 Bi HM77-30004, DCR = 0.045Ω, Note 2

3

4

25

1

Figure 4. 8V–36V to 5V/3A Buck Converter

Through Hole

C1

470

µF

63V

MBR360

C2
1000

µF

16V

L1

68

µH

GND

FB

SW

MIC4576BT

SHDN

16V to 36V

12V/3A

V

IN

R2

13.0k
1%

R1

1.50k
1%

C1 Nichicon UPL1J471MPH, ESR = 0.039Ω
C2 Nichicon UPL1C102MPH, ESR = 0.047Ω
D1 Motorola MBR360
L1 Bi HM77-29006, DCR = 0.08Ω

5

1

4

2

3

Figure 5. 16V–36V to 12V/3A Buck Converter

Through Hole

D1
MBR360

C2
1000µF
16V

L1

33µH

GND

FB

SW

MIC4576-5.0BT

SHDN

V

IN

8V to 36V

V

OUT

5V/4A

V

IN

3

4

25

1

C3

470µF

63V

D2
MBR360

L2

33µH

GND

SW

FB

MIC4576-5.0BT

SHDN

V

IN

3

2

4

5

1

4

1

2

3

8

U3
LM358

C5

0.01µF

R3

10K

R1

0.1Ω

C1
470µF
63V

C4
1000µF
16V

R2

0.1Ω

C1, C3 Nichicon UPL1J471MRH, ESR = 0.039Ω
C2, C4 Nichicon UPL1C102MPH, ESR = 0.047Ω
D1, D2 Motorola MBR360
L1, L2 Coiltronics PL52C-33-1000, DCR = 0.036
R1, R2 KRL SP-1-A1-0R100J
U3 National LM358

U1

U2

V

IN

Figure 6. Parallel Switching Regulators

Note 2: Surface-mount component.

March 2006 7 MIC4576

MIC4576 Micrel, Inc.

0.018 ±0.008
(0.46 ±0.20)

0.268 REF

(6.81 REF)

0.032 ±0.005
(0.81 ±0.13)

0.550 ±0.010
(13.97 ±0.25)

7°

Typ.

SEATING
PLANE

0.578 ±0.018
(14.68 ±0.46)

0.108 ±0.005
(2.74 ±0.13)

0.050 ±0.005
(1.27 ±0.13)

0.150 D ±0.005
(3.81 D ±0.13)

0.400 ±0.015
(10.16 ±0.38)

0.177 ±0.008
(4.50 ±0.20)

0.103 ±0.013
(2.62±0.33)

0.241 ±0.017
(6.12 ±0.43)

0.067 ±0.005
(1.70 ±0.127)

inch

(mm)

Dimensions:

0.067 ±0.005 0.032 ±0.003

0.360 ±0.005

0.600 ±0.025

0.405 ±0.005

0.060 ±0.005

0.176 ±0.005

8° MAX

0.100 ± 0.01

0.050 ±0.005

0.015 ±0.002

0.004

+0.004
–0.008

SEATING PLANE

0.065 ±0.010
20°± 2°

DIM. = INCH

Package Information

MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA

5-Pin TO-220 (T)

TEL + 1 [phone] FAX + 1 [phone] WEB http://www.micrel.com

5-Pin TO-263 (U)

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�

MIC4576 8 March 2006

Micrel for any damages resulting from such use or sale.

© 2005 Micrel, Inc.