5-V Low-Drop Fixed Voltage Regulator
TLE 4279
Features
•
•
•
•
•
•
•
•
•
Output voltage tolerance
≤ ±
2 %
Very low current consumption
Early warning
Reset output low down to
V
Q
= 1 V
Overtemperature protection
Reverse polarity proof
Settable reset threshold
Very low-drop voltage
Wide temperature range
Ordering Code Package
on request
Q67006-A9225
P-DIP-8-4
P-DSO-8-1 (SMD)
P-DSO-14-4 (SMD)
P-DSO-20-6 (SMD)
P-DSO-8-1
P-DIP-8-4
Type
TLE 4279 A
TLE 4279 G
w
TLE 4279 GM Q67006-A9307
TLE 4279 GL Q67006-A9306
w
New type
Functional Description
This device is a voltage regulator with a fixed 5-V output,
e.g. in a P-DSO-8-1 package. The maximum operating
P-DSO-20-6
voltage is 45 V. The output is able to drive a 150 mA
load. It is short circuit protected and the thermal
shutdown switches the output off if the junction
temperature is in excess of 150
°C.
A reset signal is
generated for an output voltage of
V
Q
< 4.6 V. The reset
threshold voltage can be decreased by external
connection of a voltage divider. The reset delay time can
be set by an external capacitor. If the application
requires pull up resistors at the logic outputs (Reset,
P-DSO-14-4
Sense Out) the TLE 4269 with integrated resistors can
be used. It is also possible to supervise the input voltage by using an integrated
comparator to give a low voltage warning.
Semiconductor Group
1
1998-11-01
TLE 4279
Circuit Description
The control amplifier compares a reference voltage, made highly accurate by resistance
balancing, with a voltage proportional to the output voltage and drives the base of the
series PNP transistor via a buffer. Saturation control as a function of the load current
prevents any over-saturation of the power element.
In the reset generator block a comparator compares a reference voltage independent of
the input voltage with the scaled-down output voltage. If the output voltage reaches 4.6 V
the reset delay capacitor is discharged and the reset output is set to low. This low is
guaranteed down to an output voltage of 1 V. As the output voltage increases again,
from 4.6 V onward the reset delay capacitor is charged with constant current. When the
capacitor voltage reaches the upper switching threshold
V
dt
, the reset returns to high. By
choosing the value of this capacitor, the reset delay time can be selected over a wide
range. With the reset threshold input RE it is possible to lower the reset threshold
V
rt
. If
pin RE is connected to pin Q via a voltage divider, for example, the reset condition is
reached when this voltage is decreased below the switching threshold
V
re
of 1.35 V.
Another comparator compares the signal of the pin SI, normally fed by a voltage divider
from the input voltage, with the reference and gives an early warning on the pin SO. It is
also possible to superwise an other voltage e.g. of a second regulator, or to build a
watchdog circuit with few external components.
Application Description
The input capacitor
C
I
is necessary for compensating line influences. Using a resistor of
approx. 1
Ω
in series with
C
I
, the oscillating circuit consisting of input inductivity and input
capacitance can be damped. The output capacitor
C
Q
is necessary for the stability of the
regulating circuit. Stability is guaranteed at values
≥
10
µF
and an ESR
≤
10
Ω
within the
operating temperature range. Both reset output and sense output are open collector
outputs and have to be connected to 5 V output via external pull-up resistors
≥
10 kΩ.
For small tolerances of the reset delay the spread of the capacitance of the delay
capacitor and its temperature coefficient should be noted.
Semiconductor Group
5
1998-11-01
Embedded System
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