AD637JQ Analog Devices Inc, AD637JQ Datasheet - Page 9

• Manufacturer Part Number: AD637JQ
• Description: IC RMS/DC CONV PRECISION 14-CDIP
• Manufacturer: Analog Devices Inc

Specifications of AD637JQ

• Rohs Status: RoHS non-compliant
• Current - Supply: 2.2mA
• Voltage - Supply: ±3.0V ~ 18V
• Mounting Type: Through Hole
• Package / Case: 14-CDIP (0.300", 7.62mm)
• Accuracy %: 0.25%
• Bandwidth: 200kHz
• Supply Current: 2.2mA
• Power Dissipation Pd: 108mW
• Supply Voltage Range: ± 3V To ± 18V
• Digital Ic Case Style: DIP
• No. Of Pins: 14
• Input Type: RMS
• Module Type: Converter
• Output Type: DC
• Voltage, Supply: ± 18 VDC
• For Use With: AD637-EVALZ - BOARD EVALUATION FOR AD637
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD637
Table 5. Practical Values of C
Input Waveform
and Period
A
B
C
D
FREQUENCY RESPONSE
The frequency response of the AD637 at various signal levels is
shown in Figure 15. The dashed lines show the upper frequency
limits for 1%, 10%, and ±3 dB of additional error. For example,
note that for 1% additional error with a 2 V rms input, the
highest frequency allowable is 200 kHz. A 200 mV signal can be
measured with 1% error at signal frequencies up to 100 kHz.
To take full advantage of the wide bandwidth of the AD637,
care must be taken in the selection of the input buffer amplifier.
To ensure that the input signal is accurately presented to the
converter, the input buffer must have a −3 dB bandwidth that is
wider than that of the AD637. Note the importance of slew rate
in this application. For example, the minimum slew rate
required for a 1 V rms, 5 MHz, sine wave input signal is
44 V/µs. The user is cautioned that this is the minimum rising
or falling slew rate and that care must be exercised in the
selection of the buffer amplifier, since some amplifiers exhibit a
two-to-one difference between rising and falling slew rates. The
AD845 is recommended as a precision input buffer.
Sine Wave with dc Offset
Symmetrical Sine Wave
Pulse Train Waveform
T
T
T
T
T
T
2
2
0V
0V
0V
0V
Absolute Value
Circuit Waveform
and Period
T
T
T
T
T
AV
2
2
1/2T
and C2 for Various Input Waveforms
Minimum
R × C
1/2T
T
10 (T − T
10 (T − 2T
AV
Time Constant
2
)
2
)
Rev. G | Page 12 of 20
Recommended C
for 1% Averaging Error @ 60 Hz with T = 16.6 ms
Recommended
Standard Value C
0.47 µF
0.82 µF
6.8 µF
5.6 µF
AC MEASUREMENT ACCURACY AND CREST FACTOR
Crest factor is often overlooked in determining the accuracy of
an ac measurement. Crest factor is defined as the ratio of the peak
signal amplitude to the rms value of the signal (CF = Vp/V rms).
Most common waveforms, such as sine and triangle waves, have
relatively low crest factors (≤2). Waveforms that resemble low
duty cycle pulse trains, such as those occurring in switching
power supplies and SCR circuits, have high crest factors. For
example, a rectangular pulse train with a 1% duty cycle has a
crest factor of 10 (CF = 1 η ).
0.01
0.1
10
1
1k
100mV RMS INPUT
100mV RMS INPUT
7V RMS INPUT
2V RMS INPUT
1V RMS INPUT
AV
AV
and C2 Values
10k
Figure 15. Frequency Response
INPUT FREQUENCY (Hz)
Recommended
Standard Value C2
1.5 µF
2.7 µF
22 µF
18 µF
100k
1%
10%
1M
1% Settling
Time
181 ms
325 ms
2.67 sec
2.17 sec
±3dB
10M