AD637JQ Analog Devices Inc, AD637JQ Datasheet - Page 10

• 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

Figure 17 is a curve of additional reading error for the AD637
for a 1 V rms input signal with crest factors from 1 to 11. A
rectangular pulse train (pulse width 100 µs) was used for this
test because it is the worst-case waveform for rms measurement
(all the energy is contained in the peaks). The duty cycle and
peak amplitude were varied to produce crest factors from l to 10
while maintaining a constant 1 V rms input amplitude.
0.01
–0.5
–1.0
–1.5
0.1
1.5
1.0
0.5
10
1
0
0
1
1
Vp
Figure 16. AD637 Error vs. Pulse Width Rectangular Pulse
100
POSITIVE INPUT PULSE
µ
2
F
T
Figure 17. Additional Error vs. Crest Factor
C
AV
3
e
0
= 22 µ F
4
10
PULSE WIDTH ( µ s)
CREST FACTOR
e
5
η
CF = 1/
IN
= DUTY CYCLE =
(RMS) = 1 V RMS
6
η
7
100
100
T
8
µ
C
s
AV
CF = 10
9
= 22 µ F
CF = 3
10
1000
1
1
Rev. G | Page 13 of 20
CONNECTION FOR DB OUTPUT
Another feature of the AD637 is the logarithmic, or decibel,
output. The internal circuit that computes dB works well over a
60 dB range. Figure 19 shows the dB measurement connection.
The user selects the 0 dB level by setting R1 for the proper 0 dB
reference current, which is set to exactly cancel the log output
current from the squarer/divider circuit at the desired 0 dB
point. The external op amp is used to provide a more
convenient scale and to allow compensation of the +0.33%/°C
temperature drift of the dB circuit. The special TC resistor R3 is
available from Precision Resistor Inc., Largo, Fla (Model PT146).
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
Figure 18. Error vs. RMS Input Level for Three Common Crest Factors
0
0
0.5
CF = 7
CF = 10
V
IN
(V rms)
1.0
CF = 3
1.5
AD637
2.0