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PDF L4979MD Data sheet ( Hoja de datos )
| Número de pieza | L4979MD | |
| Descripción | LOW DROP VOLTAGE REGULATOR | |
| Fabricantes | STMicroelectronics | |
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L4979D
L4979MD
LOW DROP VOLTAGE REGULATOR
1 FEATURES
■ OPERATING DC SUPPLY VOLTAGE RANGE
5.6V TO 31V
■ LOW QUIESCENT CURRENT
(6µA Typ. @ 25°C with Enable Low)
■ HIGH PRECISION OUTPUT VOLTAGE (2%)
■ LOW DROPOUT VOLTAGE LESS THAN 0.5V
■ RESET CIRCUIT SENSING THE OUTPUT
VOLTAGE DOWN TO 1V
■ 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
Figure 2. Block Diagram
Figure 1. Packages
SO-8
Table 1. Order Codes
Part Number
L4979D
L4979MD
L4979D13TR
L4979MD13TR
SO-20
Package
SO-8
SO-20
SO-8 Tape & Reel
SO-20 Tape & Reel
Vi Vs
5V, 150 mA
Vo
Co
Vcw
Ctw
Wi
watchdog
Voltage reference
Vcr
Ctr
reset
gnd
En
Res
October 2004
Rev. 5
1/10
1 page  
L4979MD L4979D
ELECTRICAL CHARACTERISTICS (continued)
Pin Symbol
Parameter
Test Condition
Min. Typ. Max. Unit
Vcw Icwc Charge current
Vs = 13.5V, Vcw = 0.1V
4 7.5 14 µA
Vcw Icwd Discharge current
Vs = 13.5V, Vcw = 2.5V
1.0 2.4 4.5 µA
Vcw Twop Watchdog period
Vs = 13.5V, Ctw = 47nF
25 50 90 ms
Res twol Watchdog output low time Vs = 13.5V, Ctw = 47nF
6 10 22 ms
ENABLE
En Ven_l Enable input low voltage
1V
En Ven_h Enable input high voltage
3V
En Ven_hy Enable input hysteresis
700 1000 1100 mV
En I_leak Pull down current
En = 5V
2 10 20 µA
Note:
1. see fig4 (behavior of output current versus regulated voltage Vo)
2. guaranteed by design
3. When Vo becomes lower than 4V, the reset reaction time decreases down to 2µs assuring a faster reset condition in this particular
case.
2 VOLTAGE REGULATOR
The voltage regulator uses a p-channel MOS transistor as a regulating element. With this structure a low drop-
out voltage at current up to 150mA is achieved. The output voltage is regulated up to transient input supply volt-
age of 40V. No functional interruption due to over-voltage pulses is generated. The high precision of the output
voltage is obtained with a pre-trimmed reference voltage. A short circuit protection to GND is provided.
Figure 4. Behavior of output current versus regulated voltage Vo (see a.m. Note 1)
Vo
Vo_ref
Ishort Ilim Iout
3 RESET
The reset circuit monitors the output voltage Vo. If the output voltage drops below Vo_th then Res becomes low
with a delay time trr. Real trr value changes as a non-linear function of delta (Vo-th - Vo). The reset low signal is
guaranteed for an output voltage Vo greater than 1V.
When the output voltage becomes higher than Vo_th then Res goes high with a delay trd. This delay is obtained
by 512 periods of an oscillator (see fig. 5). The oscillator period is given by:
5/10
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