ST L5970D User Manual

L5970D

Up to 1A step down switching regulator

Features

■Up to 1A output current

■Operating input voltage from 4.4V to 36V

■3.3V / (±2%) reference voltage

■Output voltage adjustable from 1.2V to 35V

■Low dropout operation: 100% duty cycle

■250KHz Internally fixed frequency

■Voltage feedforward

■Zero load current operation

■Internal current limiting

■Inhibit for zero current consumption

■Synchronization

■Protection against feedback disconnection

■Thermal shutdown

SO8

Description

The L5970D is a step down monolithic power switching regulator capable to deliver up to 1A at output voltages from 1.2V to 35V.

The device uses an internal P-Channel D-MOS transistor (with a typical Rdson of 250mΩ) as switching element to minimize the size of the external components.

An internal oscillator fixes the switching frequency at 250KHz.

Applications

■Consumer: STB, DVD, TV, VCR, car radio, LCD monitors

■Networking: XDSL, modems, DC-DC modules

■Computer: printers, audio/graphic cards, optical storage, hard disk drive

■Industrial: changers, car battery, DC-DC converters

Having a minimum input voltage of 4.4V only, it is particularly suitable for 5V bus, available in all computer related applications.

Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection.

Figure 1. Test application circuit

	3.3V	VREF	6		OUT	L1 33 H		VOUT=3.3V
VIN = 4.4V to 35V		VCC			1
			8			D1
				L5970D			R1
	SYNC.		2			STPS2L40U
					FB		5.6K	C2
		COMP						100 F
C1				3	5
	C4		4		7			10V
10 F			INH.		GND
35V	22nF						R2
	C3
CERAMIC		R3					3.3K
	220pF
		4.7K
					D98IN954C
October 2007					Rev 16			1/16
								www.st.com

Contents	L5970D

Contents

1	Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		3
	1.1	Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	3
	1.2	Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	3
2	Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		4

2.1 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3	Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 5
4	Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 7
5	Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	9
6	Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	11
7	Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	12
8	Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	14
9	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	15

2/16

L5970D	Pin settings

1 Pin settings

1.1Pin connection

Figure 2. Pin connection (top view)

1.2Pin description

Table 1. Pin description

N°	Type	Description
1	OUT	Regulator output.
2	SYNC	Master/slave synchronization.
		A logical signal (active high) disables the device. If INH not used the pin
3	INH	must be grounded. When it is open an internal pull-up disable the
		device.
4	COMP	E/A output for frequency compensation.
		Feedback input. Connecting directly to this pin results in an output
5	FB	voltage of 1.23V. An external resistive divider is required for higher
		output voltages.
6	VREF	3.3V VREF. No cap is requested for stability.
7	GND	Ground.
8	VCC	Unregulated DC input voltage.

3/16

Electrical data	L5970D

2 Electrical data

2.1Maximum ratings

Table 2. Absolute maximum ratings

Symbol	Parameter	Value		Unit
V8	Input voltage	40		V
V1	Output DC voltage	-1 to	40	V
	Output peak voltage at t = 0.1µs	-5 to	40	V
I1	Maximum output current	int. limit.
V4, V5	Analog pins	4		V
V3	INH	-0.3V to VCC
V2	SYNC	-0.3 to 4		V
PTOT	Power dissipation at TA ≤ 60°C	0.75		W
TJ	Operating junction temperature range	-40 to	150	°C
TSTG	Storage temperature range	-55 to	150	°C

2.2Thermal data

Table 3. Thermal data

Symbol	Parameter	SO8	Unit
RthJA	Maximum thermal resistance junction-ambient	120 (1)	°C/W

1. Package mounted on board

4/16

L5970D	Electrical characteristics

3 Electrical characteristics

Table 4. Electrical characteristics

( TJ = 25°C, VCC = 12V, unless otherwise specified)

	Symbol	Parameter	Test condition		Min	Typ	Max	Unit
	VCC	Operating input	Vo = 1.235V; Io = 2A	(1)	4.4		36	V
		voltage range
	RDS(on)	Mosfet on		(1)		0.250	0.5	Ω
		Resistance
	Il	Maximum limiting	VCC = 4.4V to 36V		1.5	1.87	2.25	A
		current
	fs	Switching frequency		(1)	212	250	280	KHz
					225	250	275	KHz
		Duty cycle			0		100	%
	Dynamic characteristics (see test circuit ).
	V5	Voltage feedback	4.4V < VCC < 36V,		1.220	1.235	1.25	V
			20mA < IO < 2A	(1)	1.198	1.235	1.272	V
	h	Efficiency	VO = 5V, VCC = 12V			90		%
	DC characteristics
	Iqop	Total operating		(1)		3	5	mA
		quiescent current
	Iq	Quiescent current	Duty cycle = 0;				2.5	mA
			VFB = 1.5V
		Total stand-by	Vinh > 2.2V	(1)		50	100	µA
	Iqst-by
			VCC = 36V;
		quiescent current		(1)		80	150	µA
			Vinh > 2.2V
	Inhibit
		INH threshold	Device ON				0.8	V
		voltage	Device OFF		2.2			V
	Error amplfier
	VOH	High level output	VFB = 1V		3.5			V
		voltage
	VOL	Low level output	VFB = 1.5V				0.4	V
		voltage
	Io source	Source output	VCOMP = 1.9V;		200	300		µA
		current	VFB = 1V

5/16