LHC4913
SERIES
3A POSITIVE LOW DROP VOLTAGE REGULATOR
WITH INHIBIT FUNCTION
ADVANCE DATA
s
s
s
s
s
s
s
s
LOW OUTPUT CAPACITANCE: 1µF
LOW DROP VOLTAGE:
0.5V @ I
O
=1A
1.5V @ I
O
=3A
OVERTEMPERATURE PROTECTION
OVERCURRENT PROTECTION
OUTPUT SHORT CIRCUIT MONITORING,
SIGNALLED BY TTL OUTPUT
ON/OFF EXTERNAL CONTROL BY MEANS
OF TTL COMPATIBLE INPUT
ADJUSTABLE CURRENT LIMITATION
PROTECTS OUTPUTS FROM DAMAGING
SHORTCIRCUITS
REMOTE SENSING OPERATION
PowerSO-20 slug-up
DESCRIPTION
The LHC4913 is a positive Voltage Regulator
family including both fixed and adjustable
versions. Housed into SO-20 slug-up package
with stand off zero, it is specifically intended for
applications in rugged environments, such as
Nuclear Physics, in which it has to withstand large
amounts of radiation doses during operating life.
The fixed output voltages available are 2.5, 3.0,
3.3, 5.0 and 8.0V. Input voltage ranges from 3 to
12V.
SCHEMATIC DIAGRAM
August 2002
This is preliminary information on a new product now in development. Details are subject to change without notice.
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LHC4913 SERIES
APPLICATION DIAGRAM FOR REMOTE SENSINS OPERATION FOR ADJUSTABLE VERSION
FUNCTIONAL DESCRIPTION
ADJUSTABLE VERSION
The ADJUST pin shall be set at 1.225V with the
adequated fraction of V
O
generated by a resistive
divider inserted between V
O
and GND. The
ADJ-GROUND resistor value must not be greater
than 2.5 KΩ. For a given V
O
the following holds:
V
O
=V
ADJ
(1+R
2
/R
1
).
OVERTEMPERATURE PROTECTION OPTION
The LHC4913 is protected by a junction-
temperature detection circuit, turning the device
“OFF” when the temperature attains 175°C. The
recovery of the ON mode occurs with a hysteresys
of 40 °C.
OVERCURRENT PROTECTION
The device is equipped with a circuit having the
purpose of limiting the maximum load current, in
order to protect the output stage against possible
overcurrent-related damages. Its threshold can be
modified externally by means of a resistor put
between the pins SH-CNTRL and V
I
.
For this characteristic, when the load current gets
close to the above threshold, the regulation is
inhibited. Thus, an excellent operation is granted
only up to 66% of preset maximum current.
SHORT CIRCUIT MONITORING / SIGNALLING
In the event of an overcurrent at the output, a
voltage level of 0.4V is present at the OCM pin. In
others conditions, this voltage equals V
I
.
REMOTE SENSING FOR ADJ VERSION
As pointed out in the pin configuration plot, V
O
and
SENSE are not linked to each other in order to get
a regulation with a load located far away from the
chip. Under ordinary applications, the SENSE
shall be connected to both V
O1
& V
O2
. To obtain
the best performances it is recommended to be
compliant with the configuration shown in the
figure at top page.
What can degrade the regulation performances of
this configuration is the variable voltage drop
between the chip ground and the load termination
Lv.
This is brought mostly by the current Ib coming
from the output power base and going to ground
through the driver stage. The degradation amount
to (1+R
2
/R
1
) x R
W1
x I
Bmax
+ R
W2
x I
Bmax
APPLICATION INFORMATION
Recommended V
I
=12V Max, V
O
= 1.225V Min.
The device is designed to operate with any V
I
-V
O
value according to above mentioned and thermal
dissipation limits.
An input filtering capacitor of 100nF is always
mandatory.
The two V
I
pins shall always be connected in
parallel, this applies also for the four V
O
pins.
Device stability is granted in any circumstance
with a 1µF output capacitor.
The device operation is guaranteed with any
Vin-Vout dropout under the above thermal
constraints.
Although two embedded protections first
mentioned (the overtemperature and the
overcurrent) ensure the L4913 integrity against
any fault load condition, it is recommended to
comply with the specified absolute maximum
ratings also in applications involving fast switching
of output currents.
To achieve this, a polyester capacitor of at least
470nF, put close to the regulator between input
and ground, improves the L4913 reliability by
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