L4949NG View Datasheet(PDF) - ON Semiconductor
Part Name
Description
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L4949NG Datasheet PDF : 10 Pages
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L4949, NCV4949
OPERATING DESCRIPTION
The L4949 is a monolithic integrated low dropout voltage
Vout
regulator. Several outstanding features and auxiliary
functions are implemented to meet the requirements of
supplying microprocessor systems in automotive
applications. Nevertheless, it is suitable also in other
Vout
applications where the present functions are required. The 5.0 V
modular approach of this device allows the use of other
features and functions independently when required.
Voltage Regulator
The voltage regulator uses an isolated Collector Vertical
PNP transistor as a regulating element. With this structure,
very low dropout voltage at currents up to 100 mA is
obtained. The dropout operation of the standby regulator is
maintained down to 3.0 V input supply voltage. The output
voltage is regulated up to the transient input supply voltage
of 35 V. With this feature no functional interruption due to
overvoltage pulses is generated.
The typical curve showing the standby output voltage as
a function of the input supply voltage is shown in Figure 14.
The current consumption of the device (quiescent current)
is less than 200 mA.
To reduce the quiescent current peak in the undervoltage
region and to improve the transient response in this region,
the dropout voltage is controlled. The quiescent current as
a function of the supply input voltage is shown in Figure 15.
Short Circuit Protection:
The maximum output current is internally limited. In case
of short circuit, the output current is foldback current limited
as described in Figure 13.
10
5.0
0
20
100
200
Iout (mA)
Figure 13. Foldback Characteristic of Vout
0 V 2.0 V
5.0 V
35 V
VCC
Figure 14. Output Voltage versus Supply Voltage
3.0
2.5
TJ = 25°C
2.0
1.5
1.0
RL = 100 W
0.5
RL = 5.0 k
0
0
5.0
10
15
20
25
30
VCC, SUPPLY VOLTAGE (V)
Figure 15. Quiescent Current versus Supply Voltage
Preregulator
To improve the transient immunity a preregulator
stabilizes the internal supply voltage to 6.0 V. This internal
voltage is present at Pin 3 (VZ). This voltage should not be
used as an output because the output capability is very small
(≤ 100 mA).
This output may be used as an option when better transient
behavior for supply voltages less than 8.0 V is required. In
this case a capacitor (100 nF − 1.0 mF) must be connected
between Pin 3 and GND. If this feature is not used Pin 3 must
be left open.
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