Motorola LM2574N Datasheet

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LM2574

Advance

Information

Easy

Switcher

0.5

A

Step-Down

Voltage

Regulator

EASY SWITCHER

The LM2574 series of regulators are monolithic integrated circuits ideally

0.5 A STEP±DOWN

VOLTAGE REGULATOR

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

SEMICONDUCTOR

output voltages of 3.3 V, 5.0 V, 12 V, 15 V, and an adjustable output version.

TECHNICAL DATA

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 efficiency

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

8

heatsinking is required.

1

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

N SUFFIX

included, featuring

60 μA

(typical) standby current. The output switch

PLASTIC PACKAGE

includes cycle±by±cycle current limiting, as well as thermal shutdown for full

CASE 626

protection under fault conditions.

Features

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

PIN CONNECTIONS

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

Line and Load Conditions

• Guaranteed 0.5 A Output Current

FB

1

8

*

• Wide Input Voltage Range: 4.75 to 40 V

Sig Gnd

2

7

Output

ON/OFF

3

6

*

• Requires Only 4 External Components

Pwr Gnd

4

5

Vin

• 52 kHz Fixed Frequency Internal Oscillator

(Top View)

• TTL Shutdown Capability, Low Power Standby Mode

• High Efficiency

* No internal connection, but should be soldered to

• Uses Readily Available Standard Inductors

* PC board for best heat transfer.

• 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

This document contains information on a new product. Specifications and information herein are subject to change without notice.

DEVICE TYPE/NOMINAL OUTPUT VOLTAGE

LM2574±3.3	3.3 V
LM2574±5	5.0 V
LM2574±12	12 V
LM2574±15	15 V
LM2574±ADJ	1.23 V to 37 V

ORDERING INFORMATION

	Operating
Device	Temperature Range	Package
LM2574N±XX	TA = ±40° to +125°C	DIP±8

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

Motorola, Inc. 1997

Rev 0

LM2574

Figure 1. Block Diagram and Typical Application

Typical Application (Fixed Output Voltage Versions)
						Feedback
7.0 ± 40 V	+Vin		LM2574			1	L1
Unregulated	5					Output	330 μH	5.0 V Regulated
DC Input
Cin						7	D1	Output 0.5 A Load
22 μF								Cout
	2	Sig	4	Pwr	3	ON/OFF	1N5819
		Gnd		Gnd				220 μF

Representative Block Diagram and Typical Application

Unregulated	+Vin			3.1 V Internal	ON/OFF		ON/OFF	Output		R2
DC Input	5			Regulator				Voltage Versions		(Ω)
							3
										1.7 k
	Cin							3.3 V
	1							5.0 V		3.1 k
								12 V		8.84 k
	Feedback				Current			15 V		11.3 k
								For adjustable version
		R2	Fixed Gain		Limit
			Error Amplifier Comparator					R1 = open, R2 = 0 Ω
		R1				Driver
			Freq		Latch
		1.0 k					Output	L1		Vout
			Shift
			18 kHz			1.0 Amp	7
	Sig Gnd	1.235 V
						Switch	Pwr Gnd	D1	Cout
				52 kHz
	2	Band±Gap			Reset	Thermal	4			Load
		Reference		Oscillator		Shutdown

ABSOLUTE MAXIMUM RATINGS (Absolute Maximum Ratings indicate limits beyond which damage to the device may occur).

		Rating	Symbol	Value	Unit
	Maximum Supply Voltage		Vin	45	V
	ON/OFF Pin Input Voltage		±	±0.3 V ≤ V ≤ +Vin	V
	Output Voltage to Ground (Steady State)		±	±1.0	V
	Power Dissipation		PD	Internally Limited	W
	Thermal Resistance, Junction±to±Ambient		RθJA	100	°C/W
	Thermal Resistance, Junction±to±Case		RθJC	5.0	°C/W
	Storage Temperature Range		Tstg	±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		TJ	150	°C

NOTE: ESD data available upon request.

2	MOTOROLA ANALOG IC DEVICE DATA

LM2574

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	TJ	±40 to +125	°C
Supply Voltage	Vin	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. ILoad = 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, ILoad = 100 mA, TJ = 25°C)	Vout	3.234	3.3	3.366	V
Output Voltage (4.75 V ≤ Vin ≤ 40 V, 0.1 A ≤ ILoad ≤ 0.5 A)	Vout				V
TJ = 25°C		3.168	3.3	3.432
TJ = ±40 to +125°C		3.135	±	3.465
Efficiency (Vin = 12 V, ILoad = 0.5 A)	η	±	72	±	%
LM2574±5 ([Note 1] Test Circuit Figure 16)
Output Voltage (Vin = 12 V, ILoad = 100 mA, TJ = 25°C)	Vout	4.9	5.0	5.1	V
Output Voltage (7.0 V ≤ Vin ≤ 40 V, 0.1 A ≤ ILoad ≤ 0.5 A)	Vout				V
TJ = 25°C		4.8	5.0	5.2
TJ = ±40 to +125°C		4.75		5.25
Efficiency (Vin = 12 V, ILoad = 0.5 A)	η	±	77	±	%
LM2574±12 ([Note 1] Test Circuit Figure 16)
Output Voltage (Vin = 25 V, ILoad = 100 mA, TJ = 25°C)	Vout	11.76	10	12.24	V
Output Voltage (15 V ≤ Vin ≤ 40 V, 0.1 A ≤ ILoad ≤ 0.5 A)	Vout				V
TJ = 25°C		11.52	12	12.48
TJ = ±40 to +125°C		11.4	±	12.6
Efficiency (Vin = 15 V, ILoad = 0.5 A)	η	±	88	±	%
LM2574±15 ([Note 1] Test Circuit Figure 16)
Output Voltage (Vin = 30 V, ILoad = 100 mA, TJ = 25°C)	Vout	14.7	15	15.3	V
Output Voltage (18 V < Vin < 40 V, 0.1 A < ILoad < 0.5 A)	Vout				V
TJ = 25°C		14.4	15	15.6
TJ = ±40 to +125°C		14.25		15.75
Efficiency (Vin = 18 V, ILoad = 0.5 A)	η	±	88	±	%
LM2574 ADJUSTABLE VERSION ([Note 1] Test Circuit Figure 16)
Feedback Voltage Vin = 12 V, ILoad = 100 mA, Vout = 5.0 V, TJ = 25°C	VFB	1.217	1.23	1.243	V
Feedback Voltage 7.0 V ≤ Vin ≤ 40 V, 0.1 A ≤ ILoad ≤ 0.5 A, Vout = 5.0 V	VFBT				V
TJ = 25°C		1.193	1.23	1.267
TJ = ±40 to +125°C		1.18		1.28
Efficiency (Vin = 12 V, ILoad = 0.5 A, Vout = 5.0 V)	η	±	77	±	%

NOTES: 1. External components such as the catch diode, inductor, input and output capacitors can affect 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: Tlow = ±40°C Thigh = +125°C

MOTOROLA ANALOG IC DEVICE DATA	3

LM2574

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. ILoad = 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
ALL OUTPUT VOLTAGE VERSIONS
	Feedback Bias Current Vout = 5.0 V (Adjustable Version Only)						Ib				nA
	TJ = 25°C							±	25	100
	TJ = ±40 to +125°C							±	±	200
	Oscillator Frequency (Note 3)						fO				kHz
	TJ = 25°C							±	52	±
	TJ = 0 to +125°C							47	52	58
	TJ = ±40 to +125°C							42	±	63
	Saturation Voltage (Iout = 0.5 A, [Note 4])						Vsat				V
	TJ = 25°C							±	1.0	1.2
	TJ = ±40 to +125°C							±	±	1.4
	Max Duty Cycle (ªonº) [Note 5]						DC	93	98	±	%
	Current Limit Peak Current (Notes 3 and 4)						ICL				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						IL				mA
	Output = 0 V							±	0.6	2.0
	Output = ± 1.0 V							±	10	30
	Quiescent Current (Note 6)						IQ				mA
	TJ = 25°C							±	5.0	9.0
	TJ = ±40 to +125°C							±	±	11
	Standby Quiescent Current (ON/OFF Pin = 5.0 V (ªoffº))						Istby				μA
	TJ = 25°C							±	60	200
	TJ = ±40 to +125°C							±	±	400
	ON/OFF Pin Logic Input Level										V
	Vout = 0 V						VIH
	TJ = 25°C							2.2	1.4	±
	TJ = ±40 to +125°C							2.4	±	±
	Nominal Output Voltage						VIL
	TJ = 25°C							±	1.2	1.0
	TJ = ±40 to +125°C							±	±	0.8
	ON/OFF Pin Input Current										μA
	ON/OFF P		in	= 5.0 V (ªoffº), T = 25°C			I	±	15	30
					J		IH
	ON/OFF P		in	= 0 V (ªonº), T = 25°C			I	±	0	5.0
					J		IL

NOTES: 1. External components such as the catch diode, inductor, input and output capacitors can affect 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: Tlow = ±40°C Thigh = +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.

4	MOTOROLA ANALOG IC DEVICE DATA

LM2574

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 16)

Figure 2. Normalized Output Voltage

Figure 3. Line Regulation

	1.0
(%)	0.8	Vin = 20 V
CHANGE	0.6	ILoad = 100 mA
		Normalized at TJ = 25°C
	0.4
VOLTAGE	0.2
	0
	±0.2
, OUTPUT
	±0.4
	±0.6
out	±0.8
V
	±1.0	±25	0	25	60	75	100	125
	±50
			TJ, JUNCTION TEMPERATURE (°C)

	1.4
(%)	1.2	ILoad = 100 mA
CHANGE
	1.0	TJ = 25°C
	0.8
			3.3 V, 5.0 V and ADJ
VOLTAGE	0.6
	0.4
	0.2
OUTPUT							12 V and 15 V
	0
	±0.2
,
out	±0.4
V
	±0.6	5.0	10	15	20	25	30	35	40
	0
				Vin, INPUT VOLTAGE (V)

Figure 4. Dropout Voltage

Figure 5. Current Limit

	2.0
(V)		L = 300 μH
DIFFERENTIAL	1.5			ILoad = 500 mA
	1.0
± OUTPUT
				ILoad = 100 mA
	0.5
INPUT
	0	±25	0	25	60	75	100	125
	±50
			TJ, JUNCTION TEMPERATURE (°C)

	1.4
(A)	1.3						Vin = 25 V
CURRENT	1.2
	1.1
, OUTPUT	1.0
	0.9
O
I
	0.8
	0.7
	±50	±25	0	25	60	75	100	125
			TJ, JUNCTION TEMPERATURE (°C)

Figure 6. Quiescent Current

Figure 7. Standby Quiescent Current

	20								A)
									(μ
							Vout = 5.0 V
QUIESCENTCURRENT (mA)	18								QUIESCENT CURRENT
							Measured at
	16						Ground Pin
	14						TJ = 25°C
	12				ILoad = 500 A
	10
	8.0		ILoad = 100 mA
,									STANDBY,
Q	6.0
I
	4.0								stby
									I
	0	5.0	10	15	20	25	30	35	40
				Vin, INPUT VOLTAGE (V)

200
180	VON/OFF = 5.0 V
160
140
120
100			Vin = 40 V
80
60			Vin = 12 V
40
20
0
±50	±25	0	25	60	75	100	125
		TJ, JUNCTION TEMPERATURE (°C)

MOTOROLA ANALOG IC DEVICE DATA	5

LM2574

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

Figure 8. Oscillator Frequency

	8.0
(%)	6.0	Vin = 12 V
	4.0	Normalized at 25°C
FREQUENCY
	2.0
	0
	±2.0
NORMALIZED
	±4.0
	±6.0
	±8.0
	10	±25	0	25	50	75	100	125
	±50
			TJ, JUNCTION TEMPERATURE (°C)

Figure 10. Minimum Operating Voltage

	5.0
	4.5				Adjustable Version Only
(V)	4.0
	3.5
VOLTAGE
	3.0
	2.5
,INPUT
	2.0
	1.5
in		Vin = 1.23 V
V	1.0
		ILoad = 100 mA
	0.5
	0	±25	0	25	50	75	100	125
	±50
			TJ, JUNCTION TEMPERATURE (°C)

Figure 12. Continuous Mode Switching Waveforms Vout = 5.0 V, 500 mA Load Current, L = 330 μH

		20 V
	A	10 V
		0
		0.6 A
	B	0.4 A
		0.2 A
		0
	C	20 mV
		AC
		5 μs/DIV

A:Output Pin Voltage, 10 V/DIV.

B:Inductor Current, 0.2 A/DIV.

C:Output Ripple Voltage, 20 mV/DIV, AC±Coupled

Figure 9. Switch Saturation Voltage

	1.3
(V)	1.2
	1.1
VOLTAGE
	1.0
	0.9	±40°C
, SATURATION
	0.8	25°C
	0.7
	0.6	125°C
	0.5
sat
V	0.4
	0.3
	0	0.1	0.2	0.3	0.4	0.5

SWITCH CURRENT (A)

	100	Figure 11. Feedback Pin Current
(nA)
	80				Adjustable Version Only
CURRENT
	20
	60
	40
PIN	0
FEEDBACK,
	±60
	±20
	±40
FB	±80
I
	±100	±25	0	25	50	75	100	125
	±50

TJ, JUNCTION TEMPERATURE (°C)

Figure 13. Discontinuous Mode Switching Waveforms Vout = 5.0 V, 100 mA Load Current, L = 100 μH

		20 V
	A	10 V
		0
		0.6 A
	B	0.4 A
		0.2 A
		0
	C	20 mV
		AC
		5 μs/DIV

A:Output Pin Voltage, 10 V/DIV.

B:Inductor Current, 0.2 A/DIV.

C:Output Ripple Voltage, 20 mV/DIV, AC±Coupled

6	MOTOROLA ANALOG IC DEVICE DATA

LM2574

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

Figure 14. 500 mA Load Transient Response for Continuous Mode Operation, L = 330 μH, Cout = 300 μF

	A	50 mV
		AC
	B	500 mA
		0
		200 μs/DIV

Figure 15. 250 mA Load Transient Response for Discontinuous Mode Operation, L = 68 μH, Cout = 470 μF

	A	50 mV
		AC
		200 mA
	B	100 mA
		0
		200 μs/DIV

A: Output Voltage, 50 mV/DIV, AC Coupled	A: Output Voltage, 50 mV/DIV, AC Coupled
B: 100 mA to 500 mA Load Pulse	B: 50 mA to 250 mA Load Pulse

MOTOROLA ANALOG IC DEVICE DATA	7

LM2574

Figure 16. Test Circuit and Layout Guidelines

Fixed Output Voltage Versions

						Feedback
		Vin		LM2574		1
						L1
				Fixed Output		330	μ
		1					H
						Output			Vout
7.0 ± 40 V						7
				4 Pwr 2	Sig 3	ON/OFF
Unregulated
	Cin			Gnd	Gnd
DC Input							Cout		Load
						D1
	22	μF					220	μF
						1N5819
		Cin	±	22 μF, 60 V, Aluminium Electrolytic
		Cout ±		220 μF, 25 V, Aluminium Electrolytic
		D1	±	Schottky, 1N5819
		L1	±	330 μH, (For 5.0 Vin, 3.3 Vout, use 100 μH)
		R1	±	2.0 k, 0.1%
		R2	±	6.12 k, 0.1%

Adjustable Output Voltage Versions

Feedback

Vin

LM2574

1

L1

Vout

1

Adjustable

Output

330 μH

5.0 V

7.0 V ± 40 V

7

R2

4

Pwr

2

Sig

3

ON/OFF

Unregulated

6.12 k

Cin

Gnd

Gnd

DC Input

Cout

Load

D1

22

μF

220 μF

R1

1N5819

2.0 k

Vout + Vref 1.0 )

R2

R1

R2 + R1

Vout

± 1.0

Vref

Where Vref = 1.23 V, R1

between 1.0 kΩ and 5.0 kΩ

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.

8	MOTOROLA ANALOG IC DEVICE DATA