AD654JNZ Analog Devices Inc, AD654JNZ Datasheet - Page 7

• Manufacturer Part Number: AD654JNZ
• Description: IC V-F CONVERTER MONO 8-DIP
• Manufacturer: Analog Devices Inc
• Type: Voltage to Frequencyr

Specifications of AD654JNZ

• Frequency - Max: 500kHz
• Full Scale: ±50ppm/°C
• Linearity: ±0.2%
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Frequency: 500kHz
• Full Scale Range: 0kHz To 500kHz
• Linearity %: 0.03%
• Supply Voltage Range: ± 6V To ± 18V
• Digital Ic Case Style: DIP
• No. Of Pins: 8
• Input Voltage Primary Min: -14V
• 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: PDIP
• Calibration Error Fs Typ: 10%
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

TWO-WIRE TEMPERATURE-TO-FREQUENCY
CONVERSION
Figure 8 shows the AD654 in a two-wire temperature-to-frequency
conversion scheme. The twisted pair transmission line serves the
dual purpose of supplying power to the device and also carrying
frequency data in the form of current modulation.
The positive supply line is fed to the remote V/F through a
140
current of the AD654 will cause less than one V
As the V/F oscillates, additional switched current is drawn through
R
rent causes Q1 to saturate, and thus regenerates the AD654’s
output square wave at the collector. The supply voltage to the
AD654 then consists of a dc level, less the resistive line drop, plus a
one V
This ripple is reduced by the diode/capacitor combination.
To set up the receiver circuit for a given voltage, the R
resistances are selected as shown in Table I. CMOS logic stages
can be driven directly from the collector of Q1, and a single TTL
load can be driven from the junction of R
K 10 V –
At the V/F end, the AD592C temperature transducer is inter-
faced with the AD654 in such a manner that the AD654 output
frequency is proportional to temperature. The output frequency
can be sealed and offset from K to C or F using the resistor
REV. B
C 10 V 6.49k 4.02k
F 10 V 6.49k 4.42k
L
when Pin 1 goes low. The peak level of this additional cur-
(+V
15 V –
15 V 12.7k 4.02k
15 V 12.7k 4.42k
BE
resistor. This resistor is selected such that the quiescent
S
p-p square wave at the output frequency of the AD654.
) R1 ( ) R2 ( ) R3 ( ) R4 ( ) R5 ( )
+V
10 V
15 V
S
–
–
AD589
R
270
680
–
–
1k
1k
1k
1k
Table II.
S
Table I.
( )
1 A/k
+
–
AD592
100k
100k
95.3k
78.7k
154k
105k
Figure 8. Two-Wire Temperature-to-Frequency Converter
R2
R3
R1
S
R
1.8k
2.7k
127k
127k
22.6k F = 10 Hz/ C
36.5k
22.6k F = 5.55 Hz/ F
36.5k
and R6.
L
R4
R5
( )
BE
to be dropped.
F = 10 Hz/K
S
and R
f =
(10V) C
L
1 F
I
DRIVER
AD654
0.01 F
T
OSC/
–7–
1N4148
C
T
T
values shown in Table II. Since temperature is the parameter of
interest, an NPO ceramic capacitor is used as the timing capaci-
tor for low V/F TC.
When scaling per K, resistors R1–R3 and the AD589 voltage
reference are not used. The AD592 produces a 1 A/K current
output which drives Pin 3 of the AD654. With the timing
capacitor of 0.01 F this produces an output frequency scaled to
10 Hz/K. When scaling per C and F, the AD589 and resistors
R1–R3 offset the drive current at Pin 3 by 273.2 A for scaling
per C and 255.42 A for scaling per F. This will result in fre-
quencies sealed at 10 Hz/ C and 5.55 Hz/ F, respectively.
OPTOISOLATOR COUPLING
A popular method of isolated signal coupling is via optoelec-
tronic isolators, or optocouplers. In this type of device, the signal is
coupled from an input LED to an output photo-transistor, with
light as the connecting medium. This technique allows dc to be
transmitted, is extremely useful in overcoming ground loop
problems between equipment, and is applicable over a wide
range of speeds and power.
Figure 9 shows a general purpose isolated V/F circuit using a
low cost 4N37 optoisolator. A +5 V power supply is assumed for
both the isolated (+5 V isolated) and local (+5 V local) supplies.
The input LED of the isolator is driven from the collector out-
put of the AD654, with a 9 mA current level established by R1
for high speed, as well as for a 100% current transfer ratio.
(0V TO 1V)
V
IN
R
T
R
1k
T
Figure 9. Optoisolator Interface
AD654
140
(10V TO 15V)
220
R
R6
S
V
DRIVER
(ISOLATED)
1000pF
S
OSC/
Q1
2N3906
C
T
5V
390
R1
CMOS
OUTPUT
TTL
OUTPUT
(1 LOAD)
ISOLATED
OPTO-ISOLATOR
4N37
LOCAL
R2
120
GRN
LED
(LOCAL)
AD654
5V
Q1
2N3904
R3
270
74LS14
V/F OUTPUT
FS = 100kHz
TTL