TECHNICAL DATA
5-V L
OW
-D
ROP
F
IXED
V
OLTAGE
R
EGULATOR
Functional Description
The device is a 5-V low-drop fixed-voltage regulator. The
maximum input voltage is 42 V (65 V,
≤400
ms). Up to an input
voltage of 26 V and for an output current up to 550 mA it regulates
the output voltage within a 2% accuracy. The short circuit
protection limits the output current of more than 650 mA.
The IC can be switched off via the inhibit input. An integrated
watchdog monitors the connected controller. The device
incorporates overvoltage protection and temperature protection
that disables the circuit at unpermissibly high temperatures.
Features
•
Output voltage tolerance
≤±
2%
•
Low-drop voltage
•
Integrated overtemperature protection
•
Reverse polarity protection
•
Input voltage up to 42 V
•
Overvoltage protection up to 65 V (≤ 400 ms)
•
Short-circuit proof
•
Suitable for use in automotive electronics
•
Wide temperature range
•
Adjustable reset and watchdog time
ILE4271-2
Pin Definitions and Functions
Pin
1
2
3
4
5
6
7
Symbol
I
INH
RO
GND
D
W
Q
Function
Input; block to ground directly on the IC with ceramic capacitor.
Inhibit
Reset Output; the open collector output is connected to the
5 V output via an integrated resistor of 30 kOhm
Ground
Reset Delay; connect a capacitor to ground for delay time adjustment.
Watchdog Input
5-V Output; block to ground with 22 uF capacitor, ESR < 3 Ohm.
1
ILE4271-2
Application Description
The IC regulates an input voltage in the range of 5.5 V < V
I
< 36 V to V
Qnom
= 5.0 V. Up to
26 V it produces a regulated output current of more than 550 mA. Above 26 V the save-
operating-area protection allows operation up to 36 V with a regulated output current of
more than 300 mA. Overvoltage protection limits operation at 42 V. The overvoltage
protection hysteresis restores operation if the input voltage has dropped below 36 V. The
IC can be switched off via the inhibit input, which causes the quiescent current to drop
below 50 uA. A reset signal is generated for an output voltage of VQ < 4.5 V. The
watchdog circuit monitors a connected controller. If there is no positive-going edge at the
watchdog input within a fixed time, the reset output is set to low. The delay for power-on
reset and the maximum permitted watchdog-pulse period can be set externally with a
capacitor.
Design Notes for External Components
An input capacitor CI is necessary for compensation of line influences. The resonant
circuit consisting of lead inductance and input capacitance can be damped by a resistor
of approx. 1 Ohm
in series with C
I
. An output capacitor CQ is necessary for the stability of
the regulating circuit. Stability is guaranteed at values of C
Q
≤22
uF and an ESR of <3
Ohm.
Circuit Description
The control amplifier compares a reference voltage, which is kept highly accurate by
resistance adjustment, to a voltage that is proportional to the output voltage and drives the
base of a series transistor via a buffer. Saturation control as a function of the load current
prevents any over-saturation of the power element.
If the output voltage decreases below 4.5 V, an external capacitor CD on pin 4 (D) will be
discharged by the reset generator. If the voltage on this capacitor VD drops below VDRL,
a reset signal is generated on pin 2 (RO), i.e. reset output is set low. If the output voltage
rises above 4.5 V, CD will be charged with constant current. After the power-on-reset time
V
D
reaches V
DU
and the reset output will be set high again. The value of the power-
on-reset time can be set within a wide range depending on the capacity of C
D
. The value of
the pull-up resistor at reset output is typically 30 kOhm.
After V
D
has reached the voltage V
DU
and reset was set to high, the watchdog circuit is
enabled and discharges C
D
with a constant current. If there is no positive-going edge
observed at watchdog input, C
D
will be discharged down to VDWL. Then reset will be set
low and the watchdog circuit will be disabled. C
D
will be charged with the current as at
power-on reset until V
D
reaches V
DU
and reset will be set high again.
If a watchdog pulse will be observed before C
D
is discharged down to V
DWL
, the watchdog
circuit will be enabled and CD will be charged too, but reset will not be set low. After V
D
has reached V
DU
, the periodical behavior starts again.
The IC also incorporates a number of internal circuits for protection against:
•
•
•
•
Overload
Overvoltage
Overtemperature
Reverse polarity
2
ILE4271-2
Maximum & Absolute Maximum Ratings
Maximum Ratings
Parameter Symbol
Junction temperature,
Т
J
Storage temperature,
Т
S
Input voltage, V
I
Inhibit voltage, U
INH
Input current, I
I
Output voltage, U
Q
Output current, I
Q
Current on common pin ,I
GND
Reset voltage, U
R
Reset current, I
R
Output voltage, U
Q
Output current, I
Q
Output voltage, U
Q
Output current, I
Q
Thermal resistance junction ambient
(P-TO-263-7-1), R
th ja
,
Thermal resistance junction case
(P-TO-263-7-1), R
th jc
Unit
o
o
C
C
V
V
A
min.
-40
-
-
-
6
-
-
4,9
-5
-
4,9
-5
-
-
-
-
-
-
V
mA
mA
V
A
V
mA
V
mA
o
C /W
°С/W
max.
125
-
-
-
36
-
internally
limited
5,1
internally
limited
-
5,1
internally
limited
-
-
-
-
70**
3**
Absolute Maximum
Ratings
min.
max.
-40
150
-50
150
-
-
-
-
-42
42
-
65*
-
internally
limited
-1
16
-5
internally
limited
-0.5
–
-1
16
-5
internally
limited
-0.3
7
-5
5
-0.3
7
-5
5
-
70**
-
3**
* Time of influence t
≤
400ms
** Thermal resistance junction ambient for IC with heat dissipater is calculated by formula:
R
th ja
= R
th jc
+ R
th ca
(1)
R
th jc
- thermal resistance junction case,
o
C /W.
Application circuit and heat dissipater have to provide T
J
≤
125
О
С.
Maximum power P
tot
,Вт, dissipated by IC for T
A
, is calculated by formula:
P
tot
= (125 - T
A
) / R
th ja
(2)
125 – maximum permitable operating junction temperature,
О
С.
4
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