ADR423BR Analog Devices Inc, ADR423BR Datasheet - Page 18

• Manufacturer Part Number: ADR423BR
• Description: IC VREF PREC 3V 10MA OUT 8-SOIC
• Manufacturer: Analog Devices Inc
• Series: XFET®r

Specifications of ADR423BR

• Rohs Status: RoHS non-compliant
• Design Resources: 40 Channels of Programmable Output Span Using AD5371 (CN0149)
• Reference Type: Series
• Voltage - Output: 3V
• Tolerance: ±0.04%
• Temperature Coefficient: 3ppm/°C
• Voltage - Input: 5 ~ 18 V
• Number Of Channels: 1
• Current - Quiescent: 500µA
• Current - Output: 10mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Current - Cathode: -

ADR420/ADR421/ADR423/ADR425
HIGH VOLTAGE FLOATING CURRENT SOURCE
The circuit in Figure 43 can be used to generate a floating
current source with minimal self-heating. This particular
configuration can operate on high supply voltages determined
by the breakdown voltage of the N-channel JFET.
KELVIN CONNECTIONS
In many portable instrumentation applications where PC board
cost and area are important considerations, circuit intercon-
nects are often narrow. 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 flow-
ing through wiring resistance produce an error (V
at the load. However, the Kelvin connection in Figure 44
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.
Figure 43. High Voltage Floating Current Source
ADR420/
ADR421/
ADR423/
ADR425
GND
V
2
4
IN
V
OUT
6
OP09
+V
–V
2N3904
S
S
SST111
VISHAY
R
2.10kΩ
L
ERROR
= R × I
Rev. H | Page 18 of 24
L
)
DUAL-POLARITY REFERENCES
Dual-polarity references can easily be made with an op amp and
a pair of resistors. In order not to defeat the accuracy obtained
by the ADR42x, it is imperative to match the resistance toler-
ance and the temperature coefficient of all components.
V
IN
+10V
1µF
Figure 46. +2.5 V and −2.5 V Reference Using ADR425
Figure 45. +5 V and −5 V Reference Using ADR425
Figure 44. Advantage of Kelvin Connection
ADR420/
ADR421/
ADR423/
ADR425
0.1µF
GND
V
GND
V
2
IN
4
ADR425
2
4
IN
V
OUT
V
GND
U1
2
IN
4
ADR425
TRIM
6
V
OUT
U1
V
TRIM
A1 = OP191
6
5
OUT
A1
5.6kΩ
5.6kΩ
V
IN
R1
R2
6
5
R
+2.5V
–2.5V
LW
10kΩ
5kΩ
R3
R
R1
LW
OP1177
OP1177
+10V
–10V
U2
–10V
V
SENSE
V
FORCE
R
V+
V–
V +
V –
OUT
OUT
L
U2
10kΩ
R2
+5V
–5V