ST L4979D, L4979MD User Manual

L4979D

L4979MD

Low drop voltage regulator

Features

■Operating DC supply voltage range 5.6 V to 31 V

■Low quiescent current (6 µA typ. @ 25 °C with enable low)

■High precision output voltage (2%)

■Low dropout voltage less than 0.5 V

■Reset circuit sensing the output voltage down to 1 V

■Programmable reset pulse delay with external capacitor

■Watchdog

■Programmable watchdog timer with external capacitor

■Thermal shutdown and short circuit protection

■Automotive temperature range (Tj = -40 °C to 150 °C)

■Enable input for enabling/disabling the voltage regulator output

Datasheet −production data

'!0'#&4	'!0'#&4
SO-8	SO-20

Description

L4979D and L4979MD are low dropout linear regulators with microprocessor control functions such as low voltage reset, watchdog, on/off control. Typical quiescent current is 100 µA in very low output current mode and enabled regulator. The devices drop to 6 µA with not enabled regulators.

On chip trimming results in high output voltage accuracy (2%). Accuracy is kept over wide temperature range, line and load variation.

The maximum input voltage is 40 V. The max output current is internally limited. Internal temperature protection disables the voltage regulator output.

Table 1.	Device summary
Package		Order codes
		Tube	Tape and reel
SO-8		L4979D	L4979D013TR
SO-20		L4979MD	L4979MD013TR

March 2012

Doc ID 10262 Rev 8

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This is information on a product in full production.

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Contents	L4979D, L4979MD

Contents

1	Block diagram and pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . .		. 5
2	Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. 7
	2.1	Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7
	2.2	Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	8
3	Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		10

3.1 Voltage regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3 Watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4	Package and PCB thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		12
	4.1	SO-8 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	12
	4.2	SO-20 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	14
5	Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		17
	5.1	ECOPACK® . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 17
	5.2	SO-8 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
	5.3	SO-20 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	19
6	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		21

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L4979D, L4979MD	List of tables

List of tables

Table 1. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Table 2. Pin function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Table 3. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Table 4. Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Table 5. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 6. Voltage regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 7. Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 8. Watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Table 9. Enable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Table 10. Reset time diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Table 11. SO-8 thermal parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Table 12. SO-20 thermal parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Table 13. SO-8 mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Table 14. SO-20 mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Table 15. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

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List of figures	L4979D, L4979MD

List of figures

Figure 1. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Figure 2. Pins connection (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 3. Behavior of output current versus regulated voltage Vo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Figure 4. Watchdog time diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 5. SO-8 PC board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Figure 6. Rthj-amb vs PCB copper area in open box free air condition. . . . . . . . . . . . . . . . . . . . . . . 12 Figure 7. SO-8 thermal impedance junction ambient single pulse . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 8. Thermal fitting model of Vreg in SO-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Figure 9. SO-20 PC board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 10. Rthj-amb vs PCB copper area in open box free air condition. . . . . . . . . . . . . . . . . . . . . . . 15 Figure 11. SO-20 thermal impedance junction ambient single pulse . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 12. Thermal fitting model of Vreg in SO-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Figure 13. SO-8 package dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 14. SO-20 package dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

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L4979D, L4979MD	Block diagram and pin descriptions

1 Block diagram and pin descriptions

Figure 1. Block diagram

6I 6S

6CW

	#TW	WATCHDOG
		7I

6OLTAGEEREFERENCE

6CR

RESET

#TR

6 M 6O

#O

GND

%N

2ES

'!0'#&4

Table 2.	Pin function
SO8		SO20	Pin name	Function
pin number		pin number
				Enable input If high, regulator, watchdog and reset are
1		1	En	operating. If low, regulator, watchdog and reset are shut
				down.
2		4	gnd	Ground reference
		5,6,15,16	gnd	Ground These pins are to be connected to a heat
				spreader electrically grounded
3		7	Res	Reset output. It is pulled down when output voltage
				drops below Vo_th or frequency at Wi is too low.
4		10	Vcr	Reset timing adjust A capacitor between Vcr pin and
				gnd sets the reset delay time (trd)
5		11	Vcw	Watchdog timer adjust A capacitor between Vcw pin and
				gnd sets the time response of the watchdog monitor.
6		14	Wi	Watchdog input. If the frequency at this input pin is too
				low, the Reset output is activated.
7		17	Vo	Voltage regulator output Output capacitor >100 nF is
				needed for regulator stability

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Block diagram and pin descriptions									L4979D, L4979MD
	Table 2.	Pin function (continued)
	SO8		SO20	Pin name					Function
	pin number		pin number
	8		20	Vs		Supply voltage Supply capacitor (e.g. 200 nF) is needed
						for regulator stability.
			2, 3, 8, 9,
			12, 13, 18,	N. C.		Not connected
			19
	Figure 2.	Pins connection (top view)
							%.			63
							. #			. #
	%.				63		. #			. #
							'.$			6/
	'.$				6/
							'.$			'.$
	2%3	3/			7)
							'.$		3/	'.$
	6#2				6#7
							2%3			7)
				'!0'#&4			. #			. #
							. #			. #
							6#2			7#7
										'!0'#&4

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L4979D, L4979MD	Electrical specifications

2 Electrical specifications

2.1Absolute maximum ratings

Stressing the device above the ratings listed in Table 3 may cause permanent damage to the device. These are stress ratings only and operation of the device at these or any other conditions above those indicated in the operating sections of this specification is not implied. Exposure to the conditions reported in this section for extended periods may affect device reliability. Refer also to the STMicroelectronics SURE program and other relevant quality documents.

Table 3.	Absolute maximum ratings
Symbol	Parameter	Value		Unit
Vvsdc	DC supply voltage	-0.3 to 40		V
Ivsdc	Input current	Internally limited
Vvo	DC output voltage	-0.3 to 6 (1)		V
Ivo	DC output current	Internally limited
Vwi	Watchdog input voltage	-0.3 to Vvo +0.3		V
Vod	Open drain output voltage (RES)	-0.3 to Vvo +0.3		V
Iod	Open drain output current (RES)	Internally limited
Vcr	Reset delay voltage	-0.3 to Vvo +0.3		V
Vcw	Watchdog delay voltage	-0.3 to Vvo +0.3		V
Ven	Enable input voltage	-0.3 to 40		V
Tj	Junction temperature	-40 to 150		°C
VESD	ESD voltage level (HBM-MIL STD 883C)	±2		kV

1.Using the typical application schematic with Cout= 10 µF and Iout=0 A, when the regulator is switched-on, an overshoot exceeding 6 V could occur.This behavior does not impact the reliability of the regulator.

Table 4.	Thermal data
Symbol		Parameter	SO8	SO16+2+2	Unit
Rth j-amb		Thermal resistance junction to ambient	130 to 180	50 to 80	°C/W

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