ADR439AR Analog Devices Inc, ADR439AR Datasheet - Page 17
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ADR439AR
Manufacturer Part Number
ADR439AR
Description
IC VREF PREC 4.5V 30MA 8-SOIC
Manufacturer
Analog Devices Inc
Series
XFET®r
Datasheet
1.ADR435BRZ-REEL7.pdf
(24 pages)
Specifications of ADR439AR
Rohs Status
RoHS non-compliant
Reference Type
Series
Voltage - Output
4.5V
Tolerance
±0.12%
Temperature Coefficient
10ppm/°C
Voltage - Input
6.5 ~ 18 V
Number Of Channels
1
Current - Quiescent
800µA
Current - Output
30mA
Operating Temperature
-40°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
8-SOIC (3.9mm Width)
Current - Cathode
-
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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.
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.
ADR43x
INPUT
GND
V
IN
V
TRIM
OUT
Figure 34. Output Trim Adjustment
470kΩ
R1
R2
10kΩ (ADR430)
15kΩ (ADR431)
R
10kΩ
OUTPUT
P
V
O
= ±0.5%
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
Rev. H | Page 17 of 24
NEGATIVE PRECISION REFERENCE WITHOUT
PRECISION RESISTORS
In many current output CMOS DAC applications, where the
output signal voltage must be of the same polarity as the reference
voltage, it is required to reconfigure a current-switching DAC
into a voltage-switching DAC by using a 1.25 V reference, an
operational amplifier, and a pair of resistors. Using a current-
switching DAC directly requires an additional operational amplifier
at the output to reinvert the signal. A negative voltage reference
is desirable because an additional operational amplifier is not
required for either reinversion (current-switching mode) or
amplification (voltage-switching mode) of the DAC output voltage.
In general, any positive voltage reference can be converted to a
negative voltage reference by using an operational amplifier and
a pair of matched resistors in an inverting configuration. The
disadvantage of this approach is that the largest single source of
error in the circuit is the relative matching of the resistors used.
ELECTRONICS
CONTROL
LASER BEAM
ACTIVATOR
LEFT
SOURCE FIBER
Figure 35. All Optical Router Network
AMPL
DAC
GIMBAL + SENSOR
MEMS MIRROR
PREAMP
ADC
GND
DSP
AMPL
DAC
ACTIVATOR
RIGHT
DESTINATION
FIBER
ADR431
ADR431
ADR431