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PDF VFC320 Data sheet ( Hoja de datos )
| Número de pieza | VFC320 | |
| Descripción | Voltage-to-Frequency and Frequency-to-Voltage CONVERTER | |
| Fabricantes | Burr-Brown Corporation | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de VFC320 (archivo pdf) en la parte inferior de esta página. Total 9 Páginas | ||
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® VFC320
Voltage-to-Frequency
and Frequency-to-Voltage
CONVERTER
FEATURES
q HIGH LINEARITY, 12 to 14 bits
±0.005% max at 10kHz FS
±0.03% max at 100kHz FS
±0.1% typ at 1MHz FS
q V/F OR F/V CONVERSION
q 6-DECADE DYNAMIC RANGE
q 20ppm/°C max GAIN DRIFT
q OUTPUT TTL/CMOS COMPATIBLE
APPLICATIONS
q INEXPENSIVE A/D AND D/A CONVERTER
q DIGITAL PANEL METERS
q TWO-WIRE DIGITAL TRANSMISSION
WITH NOISE IMMUNITY
q FM MOD/DEMOD OF TRANSDUCER
SIGNALS
q PRECISION LONG TERM INTEGRATOR
q HIGH RESOLUTION OPTICAL LINK FOR
ISOLATION
q AC LINE FREQUENCY MONITOR
q MOTOR SPEED MONITOR AND CONTROL
+VCC
VOUT
DESCRIPTION
The VFC320 monolithic voltage-to-frequency and fre-
quency-to-voltage converter provides a simple low
cost method of converting analog signals into digital
pulses. The digital output is an open collector and the
digital pulse train repetition rate is proportional to the
amplitude of the analog input voltage. Output pulses
are compatible with TTL, and CMOS logic families.
High linearity (0.005%, max at 10kHz FS) is achieved
with relatively few external components. Two exter-
nal resistors and two external capacitors are required
to operate. Full scale frequency and input voltage are
determined by a resistor in series with –In and two
capacitors (one-shot timing and input amplifier inte-
gration). The other resistor is a non-critical open
collector pull-up (f to +V ). The VFC320 is avail-
OUT
CC
able in three performance/temperature grades and two
package configurations. The TO-100 versions are her-
metically sealed, and specified for the –25°C to +85°C
and –55°C to +125°C ranges, and the dual-in-line
units are specified from –25°C to +85°C.
fIN
–In
+In
Comparators
Flip-
flop
fOUT
–7.5V Ref
One-shot
–VCC
C1
Common
International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111
Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©1982 Burr-Brown Corporation
PDS-483J
Printed in U.S.A. August, 1993
1 page  
Input Resistor
R1
2
e1 IIN 1
e2
C2
Integrating
Capacitor
VOUT
10
7 fIN
Input
Amp
Constant
IA Current Sinks
(1mA)
Switch
IB
–7.5V
Ref
+VCC
9
A
Comparators
B
Flip-
flop
One-shot
Q1
+VPULL-UP (VPU)
(5V to 15V Typically)
Pull-up
Resitor
6
fOUT
R2
fOUT =
VIN
7.5 R1 C1
3
–VCC
VIN:
For Postive Input Voltages use e1, short e2.
For Negative Input Voltages use e2, short e1.
For Differental Input Voltages use e1 and e2.
4
C1 One-shot
Capacitor
FIGURE 4. Functional Block Diagram of the VFC320.
8 Common
Pin numbers shown for “M” package (TO-100)
begins to ramp down again before the input amplifier has a
chance to saturate. In effect the comparators and flip-flop
form a one-shot whose period is determined by the internal
reference and a 1mA current sink plus the external capacitor,
C1. After the one-shot resets, fOUT changes back to logic 0
and the cycle begins again.
The transfer function for the VFC320 is derived for the
circuit shown in Figure 4. Detailed waveforms are shown in
Figure 5.
1
fOUT = t1 + t2
(1)
0V
–7.5V
∆VOUT
t1
t2
FIGURE 5. Integrator and VFC Output Timing.
In the time t1 + t2 the integrator capacitor C2 charges and
discharges but the net voltage change is zero.
Thus ∆Q = 0 = IIN t1 + (IIN – IA) t2
So that IIN (t1 + t2) = IA t2
1 VIN
But since t1 + t2 = fOUT and IIN = R1
(2)
(3)
(4), (5)
VIN
fOUT = IA R2 R2
(6)
In the time t1, IB charges the one-shot capacitor C1 until its
voltage reaches –7.5V and trips comparator B.
CIN 7.5
Thus t2 =
IB
VIN
Using (7) in (6) yield fOUT = 7.5 R1 C1
Since IA = IB the result is
X IB
IA
(7)
(8)
VIN
fOUT = 7.5 R1 C1
(9)
Since the integrating capacitor, C2, affects both the rising
and falling segments of the ramp voltage, its tolerance and
temperature coefficient do not affect the output frequency. It
should, however, have a leakage current that is small com-
pared to IIN, since this parameter will add directly to the gain
error of the VFC. C1, which controls the one-shot period,
should be very precise since its tolerance and temperature
coefficient add directly to the errors in the transfer function.
®
5 VFC320
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet VFC320.PDF ] | |
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