MOTOROLA LM2574N-ADJ, LM2574N-3.3, LM2574N-015, LM2574N-012, LM2574DW-ADJR2 Datasheet

...

Device

Operating

Temperature Range

Package



SEMICONDUCTOR

TECHNICAL DATA

EASY SWITCHER

0.5 A STEP–DOWN

VOLTAGE REGULATOR

ORDERING INFORMATION

LM2574DW–ADJ

TA = –40° to +125°C

SO–16L

N SUFFIX

PLASTIC PACKAGE

CASE 626

(DIP–8)

PIN CONNECTIONS

Order this document by LM2574/D

DEVICE TYPE/NOMINAL OUTPUT VOLTAGE

LM2574–3.3 LM2574–5 LM2574–12 LM2574–15 LM2574–ADJ

3.3 V

5.0 V 12 V 15 V

1.23 V to 37 V

XX = Voltage Option, i.e, 3.3, 5, 12, 15 V; and ADJ for Adjustable Output.

* No internal connection, but should be soldered to

* PC board for best heat transfer.

(Top View)

Pwr Gnd

ON/OFF

* *

11 10

5 6 7 8

LM2574N–XX DIP–8

DW SUFFIX

PLASTIC PACKAGE

CASE 751G

(SO–16L)

* *

Sig Gnd

Output * V

15 14 13

1 2 3 4

(Top View)

Sig Gnd

/OFF

Pwr Gnd

Output *

7 6 5

1 2 3 4

      

The LM2574 series of regulators are monolithic integrated circuits ideally suited for easy and convenient design of a step–down switching regulator (buck converter). All circuits of this series are capable of driving a 0.5 A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3 V, 5.0 V, 12 V, 15 V, and an adjustable output version.

These regulators were designed to minimize the number of external components to simplify the power supply design. Standard series of inductors optimized for use with the LM2574 are offered by several different inductor manufacturers.

Since the LM2574 converter is a switch–mode power supply, its ef ficiency is significantly higher in comparison with popular three–terminal linear regulators, especially with higher input voltages. In most cases, the power dissipated by the LM2574 regulator is so low, that the copper traces on the printed circuit board are normally the only heatsink needed and no additional heatsinking is required.

The LM2574 features include a guaranteed ±4% tolerance on output voltage within specified input voltages and output load conditions, and ±10% on the oscillator frequency (±2% over 0°C to +125°C). External shutdown is included, featuring 60 µA (typical) standby current. The output switch includes cycle–by–cycle current limiting, as well as thermal shutdown for full protection under fault conditions.

Features

• 3.3 V, 5.0 V, 12 V, 15 V, and Adjustable Output Versions

• Adjustable Version Output Voltage Range, 1.23 to 37 V ±4% max over

Line and Load Conditions

• Guaranteed 0.5 A Output Current

• Wide Input Voltage Range: 4.75 to 40 V

• Requires Only 4 External Components

• 52 kHz Fixed Frequency Internal Oscillator

• TTL Shutdown Capability, Low Power Standby Mode

• High Efficiency

• Uses Readily Available Standard Inductors

• Thermal Shutdown and Current Limit Protection

Applications

• Simple and High–Efficiency Step–Down (Buck) Regulators

• Efficient Pre–regulator for Linear Regulators

• On–Card Switching Regulators

• Positive to Negative Converters (Buck–Boost)

• Negative Step–Up Converters

• Power Supply for Battery Chargers

 Motorola, Inc. 1999 Rev 2, 07/1999

LM2574

MOTOROLA ANALOG IC DEVICE DATA

Figure 1. Block Diagram and Typical Application

7.0 – 40 V

Unregulated

DC Input

330

Pwr Gnd

4ON/OFF3

Output 7

Feedback 1

D1 1N5819

out

220

Typical Application (Fixed Output Voltage Versions)

Representative Block Diagram and Typical Application

Unregulated

DC Input

out

Feedback

1.0 k Output

7 Pwr Gnd

/OFF

Reset

Latch

Thermal

Shutdown

52 kHz

Oscillator

1.235 V Band–Gap Reference

Freq Shift

18 kHz

Comparator

Fixed Gain Error Amplifier

Current

Limit

Driver

1.0 Amp Switch

/OFF

3.1 V Internal Regulator

out

Load

Output

Voltage Versions

3.3 V

5.0 V 12 V 15 V

(

Ω

)

1.7 k

3.1 k

8.84 k

11.3 k

For adjustable version R1 = open, R2 = 0

Ω

LM2574

5.0 V Regulated Output 0.5 A Load

Sig Gnd

ABSOLUTE MAXIMUM RATINGS (Absolute Maximum Ratings indicate limits beyond which

damage to the device may occur).

Rating

Symbol Value Unit

Maximum Supply Voltage V

45 V

ON/OFF Pin Input Voltage – –0.3 V ≤ V ≤ +V

V Output Voltage to Ground (Steady State) – –1.0 V DW Suffix, Plastic Package Case 751G

Max Power Dissipation P

Internally Limited W

Thermal Resistance, Junction–to–Air R

θJA

145 °C/W

N Suffix, Plastic Package Case 626 Max Power Dissipation P

Internally Limited W

Thermal Resistance, Junction–to–Ambient R

θJA

100 °C/W

Thermal Resistance, Junction–to–Case R

θJC

5.0 °C/W

Storage Temperature Range T

stg

–65°C to +150°C °C

Minimum ESD Rating – 2.0 kV

(Human Body Model: C = 100 pF, R = 1.5 kΩ)

Lead Temperature (Soldering, 10 seconds) – 260 ° C Maximum Junction Temperature T

150 ° C

NOTE: ESD data available upon request.

LM2574

MOTOROLA ANALOG IC DEVICE DATA

OPERATING RATINGS (Operating Ratings indicate conditions for which the device is

intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics).

Rating

Symbol Value Unit

Operating Junction Temperature Range T

–40 to +125 °C

Supply Voltage V

40 V

SYSTEM PARAMETERS ([Note 1] Test Circuit Figure 16)

ELECTRICAL CHARACTERISTICS

(Unless otherwise specified, Vin = 12 V for the 3.3 V, 5.0 V, and Adjustable version,

Vin = 25 V for the 12 V version, Vin = 30 V for the 15 V version. I

Load

= 100 mA. For typical values TJ = 25°C, for min/max values TJ is the

operating junction temperature range that applies [Note 2], unless otherwise noted).

Characteristic

Symbol Min Typ Max Unit

LM2574–3.3 ([Note 1] Test Circuit Figure 16)

Output Voltage (Vin = 12 V, I

Load

= 100 mA, TJ = 25°C) V

out

3.234 3.3 3.366 V

Output Voltage (4.75 V ≤ Vin ≤ 40 V, 0.1 A ≤ I

Load

≤ 0.5 A) V

out

V TJ = 25°C 3.168 3.3 3.432 TJ = –40 to +125°C 3.135 – 3.465

Efficiency (Vin = 12 V, I

Load

= 0.5 A) η – 72 – %

LM2574–5 ([Note 1] Test Circuit Figure 16)

Output Voltage (Vin = 12 V, I

Load

= 100 mA, TJ = 25°C) V

out

4.9 5.0 5.1 V

Output Voltage (7.0 V ≤ Vin ≤ 40 V, 0.1 A ≤ I

Load

≤ 0.5 A) V

out

= 25°C

4.8 5.0 5.2

= –40 to +125°C

4.75 5.25

Efficiency (Vin = 12 V, I

Load

= 0.5 A) η – 77 – %

LM2574–12 ([Note 1] Test Circuit Figure 16)

Output Voltage (Vin = 25 V, I

Load

= 100 mA, TJ = 25°C) V

out

11.76 10 12.24 V

Output Voltage (15 V ≤ Vin ≤ 40 V, 0.1 A ≤ I

Load

≤ 0.5 A) V

out

= 25°C

11.52 12 12.48

= –40 to +125°C

11.4 – 12.6

Efficiency (Vin = 15 V, I

Load

= 0.5 A) η – 88 – %

LM2574–15 ([Note 1] Test Circuit Figure 16)

Output Voltage (Vin = 30 V, I

Load

= 100 mA, TJ = 25°C) V

out

14.7 15 15.3 V

Output Voltage (18 V < Vin < 40 V, 0.1 A < I

Load

< 0.5 A) V

out

V TJ = 25°C 14.4 15 15.6 TJ = –40 to +125°C 14.25 15.75

Efficiency (Vin = 18 V, I

Load

= 0.5 A) η – 88 – %

LM2574 ADJUSTABLE VERSION ([Note 1] Test Circuit Figure 16)

Feedback Voltage Vin = 12 V, I

Load

= 100 mA, V

out

= 5.0 V , TJ = 25°C V

1.217 1.23 1.243 V

Feedback Voltage 7.0 V ≤ Vin ≤ 40 V, 0.1 A ≤ I

Load

≤ 0.5 A, V

out

= 5.0 V V

FBT

V TJ = 25°C 1.193 1.23 1.267 TJ = –40 to +125°C 1.18 1.28

Efficiency (Vin = 12 V, I

Load

= 0.5 A, V

out

= 5.0 V) η – 77 – %

NOTES: 1. External components such as the catch diode, inductor, input and output capacitors can af fect the switching regulator system

performance. When the LM2574 is used as shown in the Figure 16 test circuit, the system performance will be as shown in the system parameters section of the Electrical Characteristics.

2.Tested junction temperature range for the LM2574: T

low

= –40°C T

high

= +125°C

LM2574

MOTOROLA ANALOG IC DEVICE DATA

SYSTEM PARAMETERS ([Note 1] Test Circuit Figure 16)

ELECTRICAL CHARACTERISTICS

(continued) (Unless otherwise specified, Vin = 12 V for the 3.3 V, 5.0 V, and Adjustable version,

Vin = 25 V for the 12 V version, Vin = 30 V for the 15 V version. I

Load

= 100 mA. For typical values TJ = 25°C, for min/max values TJ is the

operating junction temperature range that applies [Note 2], unless otherwise noted).

Characteristic UnitMaxTypMinSymbol

ALL OUTPUT VOLTAGE VERSIONS

Feedback Bias Current V

out

= 5.0 V (Adjustable Version Only) I

nA TJ = 25°C – 25 100 TJ = –40 to +125°C – – 200

Oscillator Frequency (Note 3) f

kHz TJ = 25°C – 52 – TJ = 0 to +125°C 47 52 58 TJ = –40 to +125°C 42 – 63

Saturation Voltage (I

out

= 0.5 A, [Note 4]) V

sat

V TJ = 25°C – 1.0 1.2 TJ = –40 to +125°C – – 1.4

Max Duty Cycle (“on”) [Note 5] DC 93 98 – % Current Limit Peak Current (Notes 3 and 4) I

A TJ = 25°C 0.7 1.0 1.6 TJ = –40 to +125°C 0.65 – 1.8

Output Leakage Current (Notes 6 and 7), TJ = 25°C I

mA Output = 0 V – 0.6 2.0 Output = – 1.0 V – 10 30

Quiescent Current (Note 6) I

mA TJ = 25°C – 5.0 9.0 TJ = –40 to +125°C – – 11

Standby Quiescent Current (ON/OFF Pin = 5.0 V (“off”)) I

stby

µA TJ = 25°C – 60 200 TJ = –40 to +125°C – – 400

ON/OFF Pin Logic Input Level V

out

= 0 V V

TJ = 25°C 2.2 1.4 – TJ = –40 to +125°C 2.4 – –

Nominal Output Voltage V

TJ = 25°C – 1.2 1.0 TJ = –40 to +125°C – – 0.8

ON/OFF Pin Input Current µA

ON/OFF Pin = 5.0 V (“off”), TJ = 25°C I

– 15 30

ON/OFF Pin = 0 V (“on”), TJ = 25°C I

– 0 5.0

NOTES: 1. External components such as the catch diode, inductor, input and output capacitors can af fect the switching regulator system

performance. When the LM2574 is used as shown in the Figure 16 test circuit, the system performance will be as shown in the system parameters section of the Electrical Characteristics.

2.Tested junction temperature range for the LM2574: T

low

= –40°C T

high

= +125°C

3.The oscillator frequency reduces to approximately 18 kHz in the event of an output short or an overload which causes the regulated output voltage to drop approximately 40% from the nominal output voltage. This self protection feature lowers the average power dissipation of the IC by lowering the minimum duty cycle from 5% down to approximately 2%.

4.Output (Pin 2) sourcing current. No diode, inductor or capacitor connected to the output pin.

5.Feedback (Pin 4) removed from output and connected to 0 V.

6.Feedback (Pin 4) removed from output and connected to 12 V for the Adjustable, 3.3 V, and 5.0 V versions, and 25 V for the 12 V and 15 V versions, to force the output transistor OFF .

7.Vin = 40 V.

LM2574

MOTOROLA ANALOG IC DEVICE DATA

stby

, STANDBY QUIESCENT CURRENT ( A)

, QUIESCENT CURRENT (mA)

out

, OUTPUT VOLTAGE CHANGE (%)

TJ, JUNCTION TEMPERATURE (°C)

, OUTPUT CURRENT (A)

TJ, JUNCTION TEMPERATURE (°C)

Vin, INPUT VOLTAGE (V)

INPUT – OUTPUT DIFFERENTIAL (V)

TJ, JUNCTION TEMPERATURE (°C)

out

, OUTPUT VOLTAGE CHANGE (%)

Figure 2. Normalized Output Voltage

TJ, JUNCTION TEMPERATURE (°C)

Figure 3. Line Regulation

Vin = 20 V I

Load

= 100 mA

Normalized at TJ = 25

Figure 4. Dropout Voltage Figure 5. Current Limit

Figure 6. Quiescent Current Figure 7. Standby Quiescent Current

Load

= 100 mA

TJ = 25

3.3 V, 5.0 V and ADJ

12 V and 15 V

Vin = 25 V

Load

= 100 mA

Load

= 500 A

Vin = 12 V

Vin = 40 V

L = 300 µH

Load

= 500 mA

Load

= 100 mA

out

= 5.0 V Measured at Ground Pin TJ = 25

/OFF

= 5.0 V

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 16)

1.0

0.8

0.6

0.4

0.2 0

–0.2 –0.4 –0.6 –0.8 –1.0

1.4

1.2

1.0

0.8

0.6

0.4

0.2 0

–0.2 –0.4 –0.6

2.0

1.5

1.0

0.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

20 18 16 14 12 10

8.0

6.0

4.0

200 180 160

140 120 100

80 60 40 20

1251007560250–25–50 403530252015105.00

1251007560250–25–50 1251007560250–25–50

403530252015105.00 1251007560250–25–50

LM2574

MOTOROLA ANALOG IC DEVICE DATA

, INPUT VOLTAGE (V)V

sat

, SATURATION VOLTAGE (V)I

, FEEDBACK PIN CURRENT (nA)

s/DIV

TJ, JUNCTION TEMPERATURE (

SWITCH CURRENT (A)

s/DIV

TJ, JUNCTION TEMPERATURE (

NORMALIZED FREQUENCY (%)

Figure 8. Oscillator Frequency

TJ, JUNCTION TEMPERATURE (°C)

Figure 9. Switch Saturation Voltage

Figure 10. Minimum Operating Voltage Figure 11. Feedback Pin Current

Figure 12. Continuous Mode Switching Waveforms

out

= 5.0 V, 500 mA Load Current, L = 330 µH

Figure 13. Discontinuous Mode Switching Waveforms

out

= 5.0 V, 100 mA Load Current, L = 100 µH

Vin = 1.23 V I

Load

= 100 mA

Adjustable Version Only

Vin = 12 V Normalized at 25

Adjustable Version Only

A: Output Pin Voltage, 10 V/DIV. B: Inductor Current, 0.2 A/DIV . C: Output Ripple Voltage, 20 mV/DIV, AC–Coupled

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 16) (continued)

8.0

6.0

4.0

2.0 0

–2.0 –4.0 –6.0 –8.0

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

100

80 60 40 20

0 –20 –40 –60 –80

–100

1251007550250–25–50 0 0.1 0.2 0.3 0.4 0.5

1251007550250–25–50 1251007550250–25–50

20 V 10 V

0.6 A

0.4 A

0.2 A 0

20 mV

20 V 10 V

0.6 A

0.4 A

0.2 A 0

20 mV

–40°C

25°C

125°C

LM2574

MOTOROLA ANALOG IC DEVICE DATA

200

s/DIV200 µs/DIV

Figure 14. 500 mA Load Transient Response for

Continuous Mode Operation, L = 330 µH, C

out

= 300 µF

Figure 15. 250 mA Load Transient Response for

Discontinuous Mode Operation, L = 68 µH, C

out

= 470 µF

A: Output Voltage, 50 mV/DIV, AC Coupled B: 100 mA to 500 mA Load Pulse

A: Output Voltage, 50 mV/DIV, AC Coupled B: 50 mA to 250 mA Load Pulse

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 16) (continued)

50 mV

500 mA

50 mV

200 mA

100 mA

LM2574

MOTOROLA ANALOG IC DEVICE DATA

Figure 16. Test Circuit and Layout Guidelines

D1 1N5819

330

Output 7

Feedback

out

220

LM2574

Fixed Output

34ON

/OFFPwr

Gnd

Load

out

D1 1N5819

330

Output

Feedback

out

220

LM2574

Adjustable

Load

out

5.0 V

Fixed Output Voltage Versions

Adjustable Output Voltage Versions

out

ref

1.0

)

R2 R1

R2+R1

out

ref

–1.0

Where V

ref

= 1.23 V, R1

between 1.0 k

Ω

and 5.0 k

Ω

6.12 k

2.0 k

7.0 – 40 V

Unregulated

DC Input

2 Sig

Gnd

34ON/OFFPwr

Gnd

2 Sig

Gnd

7.0 V – 40 V Unregulated

DC Input

Cin–22 µF, 60 V, Aluminium Electrolytic C

out

– 220 µF, 25 V, Aluminium Electrolytic D1 – Schottky, 1N5819 L1 – 330 µH, (For 5.0 Vin, 3.3 V

out

, use 100 µH) R1 – 2.0 k, 0.1% R2 – 6.12 k, 0.1%

PCB LAYOUT GUIDELINES

As in any switching regulator, the layout of the printed circuit board is very important. Rapidly switching currents associated with wiring inductance, stray capacitance and parasitic inductance of the printed circuit board traces can generate voltage transients which can generate electromagnetic interferences (EMI) and affect the desired operation. As indicated in the Figure 16, to minimize inductance and ground loops, the length of the leads indicated by heavy lines should be kept as short as possible.

For best results, single–point grounding (as indicated) or ground plane construction should be used.

On the other hand, the PCB area connected to the Pin 7 (emitter of the internal switch) of the LM2574 should be kept to a minimum in order to minimize coupling to sensitive circuitry.

Another sensitive part of the circuit is the feedback. It is important to keep the sensitive feedback wiring short. To assure this, physically locate the programming resistors near to the regulator, when using the adjustable version of the LM2574 regulator.

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