MICREL MIC4575 Datasheet

MIC4575 Micrel

MIC4575

200kHz Simple 1A Buck Voltage Regulator

General Description

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.

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 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 are

25% of typical LM2575 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 6V to 3.3V for Intel Pentium™
and similar microprocessors

Typical Applications

Shutdown
Enable

6V to 24V

22µF

C1

35V

Shutdown
Enable

8V to 24V

C1

150µF

35V

5

1

V

IN

SHDN

MIC4575-5.0BT

1

V

IN

MIC4575BU

GND

3

25

SW

4

FB

GND

3

D1
1N5819

Fixed Regulator

L1

68µH

D1

MBRS130LT3

SWSHDN

FB

2

4

Adjustable Regulator

L1

68µH

R2

2.37k
1%

R1

1.24k
1%

5.0V/1A

C2
330µF
16V

C3
3300pF

3.6V/1A

C2
330µF

6.3V

4-106 April 1998•

MIC4575 Micrel

Ordering Information

Part Number Voltage Temperature Range Package

MIC4575-3.3BT 3.3V –40°C to +85°C 5-lead TO-220
MIC4575-5.0BT 5.0V –40°C to +85°C 5-lead TO-220
MIC4575BT Adjustable –40°C to +85°C 5-lead TO-220
MIC4575-3.3BU 3.3V –40°C to +85°C 5-lead TO-263
MIC4575-5.0BU 5.0V –40°C to +85°C 5-lead TO-263
MIC4575BU Adjustable –40°C to +85°C 5-lead TO-263

Pin Configuration

5 SHDN
4FB

TAB

3 GND
2SW
1V

IN

TAB

Pin Description

Pin Number Pin Name Pin Function

1V
2 SW Switch (Output): Emitter of NPN output switch. Connect to external storage

3, TAB GND Ground

4 FB Feedback (Input): Output voltage feedback to regulator. Connect to output

5 SHDN Shutdown (Input): Logic low enables regulator. Logic high (> 2.4V) shuts

IN

5-Lead TO-220 (T)

5 SHDN
4FB
3 GND
2SW
1V

IN

5-Lead TO-263 (U)

Supply Voltage (Input): Unregulated +4V to +40V supply voltage.

inductor and Shottky diode.

of supply for fixed versions. Connect to 1.23V tap of resistive divider for
adjustable versions.

down regulator.

4

April 1998• 4-107

MIC4575 Micrel

Absolute Maximum Ratings

Supply Voltage (VIN) Note 1 .......................................+40V

Shutdown Voltage (V

Output Switch (VSW) steady state.................................–1V

Storage Temperature (TS) ......................... –65°C to 150°C

) .......................... –0.3V to +36V

SHDN

Operating Ratings

Supply Voltage (VIN) ...................................................+24V

Junction Temperature ............................................. +150°C

Package Thermal Resistance

TO-220, TO-263 (θJA) .........................................65°C/W

TO-220, TO-263 (θJA) ...........................................2°C/W

Electrical Characteristics

VIN = 12V; I

Parameter Condition Min Typ Max Units
MIC4575 [Adjustable]

Feedback Voltage 1.217 1.230 1.243 V
Feedback Voltage 8V ≤ V

Efficiency I
Feedback Bias Current 50 100 nA

MIC4575-3.3

Output Voltage 3.234 3.3 3.366 V
Output Voltage 6V ≤ V

Efficiency I

MIC4575-5.0

Output Voltage 4.900 5.0 5.100 V
Output Voltage 8V ≤ V

Efficiency I

MIC4575 / -3.3 / -5.0

Oscillator Frequency 180 200 220 kHz
Saturation Voltage I

Maximum Duty Cycle (On) FB connected to 0V 90 95 %
Current Limit Peak Current, t

Output Leakage Current V

Quiescent Current 510mA
Standby Quiescent Current SHDN = 5V (regulator off) 50 200 µA
SHDN Input Logic Level V

SHDN Input Current SHDN = 5V (regulator off) 4 30 µA

= 200mA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +85°C; unless noted.

LOAD

≤ 24V, 0.2A ≤ I

IN

= 1A, V

LOAD

≤ 24V, 0.2A ≤ I

IN

= 1A 72 %

LOAD

≤ 24V, 0.2A ≤ I

IN

= 1A 77 %

LOAD

= 1A 1 1.3 V

OUT

= 24V, FB connected to 0V

IN

Output = 0V 0 2 mA

= 5V 77 %

OUT

≤ 3µs 1.7 2.2 3.0 A

ON

≤ 1A 1.193 1.230 1.267 V

LOAD

≤ 1A 3.168 3.3 3.432 V

LOAD

≤ 1A 4.800 5.0 5.200 V

LOAD

Output = –1V 7.5 30 mA

= 0V (regulator off) 2.2 1.4 V

OUT

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

V

OUT

SHDN = 0V (regulator on) –10 0.01 10 µA

1.180 1.280 V

500 nA

3.135 3.465 V

4.750 5.250 V

1.5 V

1.3 3.2 A

2.4 V

0.8 V

General Note: Devices are ESD protected, however, handling precautions are recommended.
Note 1: The MIC4575 is not guaranteed to survive a short circuit to ground for input voltage above 24V.

4-108 April 1998•

MIC4575 Micrel

Block Diagrams

+24V max.

V

Shutdown
Enable

SHDN

Internal

Regulator

200kHz

Oscillator

Thermal

Shutdown

Current

Limit

IN

C

IN

Shutdown
Enable

SHDN

Driver

1.23V

Bandgap

R1

R2
GND

1A
Switch

MIC4575-x.x

Com-

parator

Error
Amp.

Block Diagram with External Components

Fixed Step-Down Regulator

+24V max.

V

IN

Internal

Regulator

200kHz

Oscillator

MIC4575

Com-

parator

[Adjustable]

Thermal

Shutdown

Error
Amp.

Driver

1.23V

Bandgap

Current

Limit

GND

1A
Switch

SW

FB

SW

FB

L1

D1

C

IN

V

OUT VREF

R1 R2

L1

D1

R1

R2

V

OUT

C

OUT

4

R1

+ 1

R2

V

OUT

1

V

REF

V

OUT

C

OUT

Block Diagram with External Components

Adjustable Step-Down Regulator

April 1998• 4-109