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 |
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SO-8 |
SO-20 |
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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 |
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Package |
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Order codes |
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Tube |
Tape and reel |
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SO-8 |
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L4979D |
L4979D013TR |
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SO-20 |
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L4979MD |
L4979MD013TR |
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March 2012 |
Doc ID 10262 Rev 8 |
1/22 |
This is information on a product in full production. |
www.st.com |
Contents |
L4979D, L4979MD |
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Contents
1 |
Block diagram and pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . |
. 5 |
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2 |
Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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2.1 |
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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2.2 |
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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3 |
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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3.1 Voltage regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3 Watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4 |
Package and PCB thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
12 |
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4.1 |
SO-8 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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4.2 |
SO-20 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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5 |
Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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5.1 |
ECOPACK® . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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5.2 |
SO-8 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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5.3 |
SO-20 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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6 |
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
21 |
2/22 |
Doc ID 10262 Rev 8 |
L4979D, L4979MD |
List of tables |
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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
Doc ID 10262 Rev 8 |
3/22 |
List of figures |
L4979D, L4979MD |
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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
4/22 |
Doc ID 10262 Rev 8 |
L4979D, L4979MD |
Block diagram and pin descriptions |
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6I 6S
6CW |
#TW |
WATCHDOG |
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6OLTAGEEREFERENCE
6CR
RESET
#TR
6 M 6O
#O
GND
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2ES |
'!0'#&4
Table 2. |
Pin function |
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SO8 |
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SO20 |
Pin name |
Function |
pin number |
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Enable input If high, regulator, watchdog and reset are |
1 |
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1 |
En |
operating. If low, regulator, watchdog and reset are shut |
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down. |
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2 |
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4 |
gnd |
Ground reference |
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5,6,15,16 |
gnd |
Ground These pins are to be connected to a heat |
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spreader electrically grounded |
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3 |
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7 |
Res |
Reset output. It is pulled down when output voltage |
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drops below Vo_th or frequency at Wi is too low. |
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Vcr |
Reset timing adjust A capacitor between Vcr pin and |
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gnd sets the reset delay time (trd) |
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Vcw |
Watchdog timer adjust A capacitor between Vcw pin and |
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gnd sets the time response of the watchdog monitor. |
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Wi |
Watchdog input. If the frequency at this input pin is too |
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low, the Reset output is activated. |
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Vo |
Voltage regulator output Output capacitor >100 nF is |
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needed for regulator stability |
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Doc ID 10262 Rev 8 |
5/22 |
Block diagram and pin descriptions |
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L4979D, L4979MD |
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Table 2. |
Pin function (continued) |
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SO8 |
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SO20 |
Pin name |
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Function |
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pin number |
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pin number |
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20 |
Vs |
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Supply voltage Supply capacitor (e.g. 200 nF) is needed |
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for regulator stability. |
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2, 3, 8, 9, |
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12, 13, 18, |
N. C. |
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Not connected |
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19 |
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Figure 2. |
Pins connection (top view) |
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6#2 |
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7#7 |
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6/22 |
Doc ID 10262 Rev 8 |
L4979D, L4979MD |
Electrical specifications |
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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 |
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Symbol |
Parameter |
Value |
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Unit |
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Vvsdc |
DC supply voltage |
-0.3 to 40 |
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Ivsdc |
Input current |
Internally limited |
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Vvo |
DC output voltage |
-0.3 to 6 (1) |
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Ivo |
DC output current |
Internally limited |
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Vwi |
Watchdog input voltage |
-0.3 to Vvo +0.3 |
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Vod |
Open drain output voltage (RES) |
-0.3 to Vvo +0.3 |
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Iod |
Open drain output current (RES) |
Internally limited |
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Vcr |
Reset delay voltage |
-0.3 to Vvo +0.3 |
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Vcw |
Watchdog delay voltage |
-0.3 to Vvo +0.3 |
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Ven |
Enable input voltage |
-0.3 to 40 |
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Tj |
Junction temperature |
-40 to 150 |
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°C |
VESD |
ESD voltage level (HBM-MIL STD 883C) |
±2 |
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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 |
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Symbol |
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Parameter |
SO8 |
SO16+2+2 |
Unit |
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Rth j-amb |
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Thermal resistance junction to ambient |
130 to 180 |
50 to 80 |
°C/W |
Doc ID 10262 Rev 8 |
7/22 |