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ADR293FR View Datasheet(PDF) - Analog Devices

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Description
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ADR293FR Datasheet PDF : 12 Pages
First Prev 11 12
APPLICATIONS
KELVIN CONNECTIONS
In many portable instrumentation applications where PC board
cost and area go hand-in-hand, circuit interconnects are very often
of dimensionally minimum width. These narrow lines can cause
large voltage drops if the voltage reference is required to provide
load currents to various functions. In fact, a circuit’s interconnects
can exhibit a typical line resistance of 0.45 mΩ/square (1 oz. Cu,
for example). Force and sense connections, also referred to as
Kelvin connections, offer a convenient method of eliminating
the effects of voltage drops in circuit wires. Load currents flowing
through wiring resistance produce an error (VERROR = R × IL) at
the load. However, the Kelvin connection in Figure 23 overcomes
the problem by including the wiring resistance within the forcing
loop of the op amp. Because the op amp senses the load voltage,
op amp loop control forces the output to compensate for the
wiring error and to produce the correct voltage at the load.
VIN
RLW
+VOUT
2
VIN
SENSE
ADR293
VOUT 6
1µF
A1
100k
RLW
+VOUT
FORCE
RL
GND
4
Figure 23. Advantage of Kelvin Connection
ADR293
VOLTAGE REGULATOR FOR PORTABLE
EQUIPMENT
The ADR293 is ideal for providing a stable, low cost, and low
power reference voltage in portable equipment power supplies.
Figure 24 shows how the ADR293 can be used in a voltage
regulator that not only has low output noise (as compared to
switch mode design) and low power, but also a very fast
recovery after current surges. Some precautions should be taken
in the selection of the output capacitors. Too high an ESR
(effective series resistance) could endanger the stability of the
circuit. A solid tantalum capacitor, 16 V or higher, and an
aluminum electrolytic capacitor, 10 V or higher, are recom-
mended for C1 and C2, respectively. In addition, the path from
the ground side of C1 and C2 to the ground side of R1 should
be kept as short as possible.
CHARGER
INPUT 0.1µF
2
VIN
ADR293
6V
LEAD-ACID +
BATTERY
VOUT 6
GND
4
R1
402k
1%
R3
510k
2
7
OP20 6
3
4
IRF9530
R2
402k
1%
5V, 100mA
C1 +
68µF
TANT
+ C2
1000µF
ELECT
Figure 24. Voltage Regulator for Portable Equipment
Rev. D | Page 11 of 12
 

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