AD654JRZ Analog Devices Inc, AD654JRZ Datasheet - Page 5

• Manufacturer Part Number: AD654JRZ
• Description: IC V-F CONVERTER MONO 8-SOIC
• Manufacturer: Analog Devices Inc
• Type: Voltage to Frequencyr

Specifications of AD654JRZ

• Frequency - Max: 500kHz
• Full Scale: ±50ppm/°C
• Linearity: ±0.2%
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Frequency: 500kHz
• Linearity %: 0.03%
• Supply Voltage Range: ± 5V To ± 18V
• Digital Ic Case Style: SOIC
• No. Of Pins: 8
• Svhc: No SVHC (18-Jun-2010)
• Operating Temperature Max: 85°C
• Operating Temperature: RoHS Compliant
• Converter Function: VFC
• Full Scale Frequency: 500
• Power Supply Requirement: Single/Dual
• Single Supply Voltage (typ): 5/9/12/15/18/24/28V
• Single Supply Voltage (max): 36V
• Single Supply Voltage (min): 4.5V
• Dual Supply Voltage (typ): ±9/±12/±15V
• Dual Supply Voltage (min): ±5V
• Dual Supply Voltage (max): ±18V
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Package Type: SOIC N
• Full Scale Range: 0kHz To 500kHz
• Rohs Compliant: Yes
• Bandwidth: 0.5MHz
• Base Number: 654
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

If the AD654’s 1 mV offset voltage must be trimmed, the trim
must be performed external to the device. Figure 3c shows an
optional connection for positive inputs in which R
R
source of 0.6 V applied to R
Similarly, a 0.6 V variable source is applied to R
ure 3d to trim offset for negative inputs. The 0.6 V bipolar
source could simply be an AD589 reference connected as shown
in Figure 3e.
FULL-SCALE CALIBRATION
Full-scale trim is the calibration of the circuit to produce the
desired output frequency with a full-scale input applied. In most
cases this is accomplished by adjusting the scaling resistor R
Precise calibration of the AD654 requires the use of an accurate
voltage standard set to the desired FS value and an accurate
frequency meter. A scope is handy for monitoring output wave-
shape. Verification of converter linearity requires the use of a
switchable voltage source or DAC having a linearity error below
mize count uncertainties. Since each AD654 is factory tested for
REV. B
Figure 3b. Bias Current Compensation—Negative Inputs
OFF2
0.005%, and the use of long measurement intervals to mini-
Figure 3d. Offset Trim Negative Input (–10 V FS)
add a variable resistance in series with R
Figure 3c. Offset Trim Positive Input (10 V FS)
+5V
–5V
Figure 3e. Offset Trim Bias Network
V
V
R
IN
R
10k
IN
20
OFF1
OFF2
AD589
10k
10k
10k
R1
R1
R2
0.6V
8.25k
V
(OPTIONAL)
IN
R1
5k
R
–
+
COMP
C
10k
5.6M
10k
R
R2
8.25k
OFF
5k
10k
10k
0.6V
OFF1
R3
R4
then adjusts the offset 1 mV.
AD654
AD654
100k
AD654
R5
0.6V
T
. A variable
OFF
OFF1
in Fig-
and
T
.
–5–
linearity, it is unnecessary for the end-user to perform this tedious
and time consuming test on a routine basis.
Sufficient FS calibration trim range must be provided to accom-
modate the worst-case sum of all major scaling errors. This
includes the AD654’s 10% full-scale error, the tolerance of the
fixed scaling resistor, and the tolerance of the timing capacitor.
Therefore, with a resistor tolerance of 1% and a capacitor tolerance
of 5%, the fixed part of the scaling resistor should be a maximum
of 84% of nominal, with the variable portion selected to allow
116% of the nominal.
If the input is in the form of a negative current source, the scaling
resistor is no longer required, eliminating the capability of trim-
ming FS frequency in this fashion. Since it is usually not practical
to smoothly vary the capacitance for trimming purposes, an
alternative scheme such as the one shown in Figure 4 is needed.
Designed for a FS of 1 mA, this circuit divides the input into two
and flowing into Pin 3; it constitutes the signal current I
converted. The second path, through another 100
carries the same nominal current. Two equal valued resistors
offer the best overall stability, and should be either 1% discrete
film units, or a pair from a common array.
Since the 1 mA FS input current is divided into two 500 A legs
(one to ground and one to Pin 3), the total input signal current
(I
same conversion scale factor, C
two. This results in a transfer unique to this hookup:
For calibration purposes, resistors R3 and R4 are added to the
network, allowing a 15% trim of scale factor with the values
shown. By varying R4’s value the trim range can be modified to
accommodate wider tolerance components or perhaps the cali-
bration tolerance on a current output transducer such as the
AD592 temperature sensor. Although the values of R1–R4 shown
are valid for 1 mA FS signals only, they can be scaled upward
proportionately for lower FS currents. For instance, they should
be increased by a factor of ten for a FS current of 100 A.
In addition to the offsets generated by the input amplifier’s bias
and offset currents, an offset voltage induced parasitic current
arises from the current fork input network. These effects are
minimized by using the bias current compensation resistor R
and offset trim scheme shown in Figure 3e.
Although device warm-up drifts are small, it is good practice to
allow the devices operating environment to stabilize before trim,
S
) is divided by a factor of two in this network. To achieve the
–V
Figure 4. Current Source FS Trim
I
1mA
FS
S
100
392
100
R2
R4
R1
f
I
R
R3
1k
(20 V ) C
*
T
0.6V
must be reduced by a factor of
I
R
100k
S
OFF
*OPTIONAL
OFFSET TRIM
T
AD654
f =
(20V) C
I
S
AD654
T
resistor R2,
T
to be
OFF