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ADR430BRZ View Datasheet(PDF) - Analog Devices

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ADR430BRZ Datasheet PDF : 24 Pages
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ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
APPLICATIONS INFORMATION
OUTPUT ADJUSTMENT
The ADR43x trim terminal can be used to adjust the output
voltage over a ±0.5% range. This feature allows the system designer
to trim system errors out by setting the reference to a voltage
other than the nominal. This is also helpful if the part is used in
a system at temperature to trim out any error. Adjustment of the
output has negligible effect on the temperature performance of the
device. To avoid degrading temperature coefficients, both the
trimming potentiometer and the two resistors need to be low
temperature coefficient types, preferably <100 ppm/°C.
INPUT
SOURCE FIBER
GIMBAL + SENSOR
LASER BEAM
ACTIVATOR
LEFT
MEMS MIRROR
DESTINATION
FIBER
ACTIVATOR
RIGHT
AMPL
PREAMP
AMPL
CONTROL
ELECTRONICS
DAC
ADC
DAC
ADR431
ADR431
ADR431
VIN
VOUT
ADR43x
TRIM
GND
R1
470k
OUTPUT
VO = ±0.5%
RP
10k
R2
10k(ADR430)
15k(ADR431)
Figure 34. Output Trim Adjustment
REFERENCE FOR CONVERTERS IN OPTICAL
NETWORK CONTROL CIRCUITS
In Figure 35, the high capacity, all optical router network
employs arrays of micromirrors to direct and route optical
signals from fiber to fiber without first converting them to
electrical form, which reduces the communication speed. The
tiny micromechanical mirrors are positioned so that each is
illuminated by a single wavelength that carries unique information
and can be passed to any desired input and output fiber. The
mirrors are tilted by the dual-axis actuators, which are controlled
by precision ADCs and DACs within the system. Due to the
microscopic movement of the mirrors, not only is the precision
of the converters important but the noise associated with these
controlling converters is also extremely critical. Total noise
within the system can be multiplied by the number of converters
employed. Therefore, to maintain the stability of the control
loop for this application, the ADR43x, with its exceptionally low
noise, is necessary.
GDNSDP
Figure 35. All Optical Router Network
HIGH VOLTAGE FLOATING CURRENT SOURCE
The circuit in Figure 36 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.
+VS
SST111
VISHAY
2
VIN
VOUT 6
ADR43x
GND
4
OP90
2N3904
RL
2.1k
–VS
Figure 36. High Voltage Floating Current Source
KELVIN CONNECTION
In many portable instrumentation applications, where printed
circuit board (PCB) 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, circuit interconnects can exhibit a typical line resistance
of 0.45 mΩ/square (for example, 1 oz. Cu). 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 of Figure 37 overcomes the problem by
including the wiring resistance within the forcing loop of the
operational amplifier.
Because the amplifier senses the load voltage, the operational
amplifier loop control forces the output to compensate for the
wiring error and to produce the correct voltage at the load.
Rev. J | Page 18 of 24
 

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