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RV4152N Schematic ( PDF Datasheet ) - Fairchild Semiconductor

Teilenummer RV4152N
Beschreibung Voltage-to-Frequency Converters
Hersteller Fairchild Semiconductor
Logo Fairchild Semiconductor Logo 




Gesamt 12 Seiten
RV4152N Datasheet, Funktion
RC4152
Voltage-to-Frequency Converters
www.fairchildsemi.com
Features
• Single supply operation
• Pulse output DTL/TTL/CMOS compatible
• Programmable scale factor (K)
• High noise rejection
• Inherent monotonicity
• Easily transmittable output
• Simple full scale trim
• Single-ended input, referenced to ground
• V-F or F-V conversion
• Voltage or current input
• Wide dynamic range
Applications
• Precision voltage-to-frequency converters
• Pulse-width modulators
• Programmable pulse generators
• Frequency-to-voltage converters
• Integrating analog-to-digital converters
• Long-term analog integrators
• Signal conversion:
– Current-to-Frequency
– Temperature-to-Frequency
– Pressure-to-Frequency
– Capacitance-to-Frequency
– Frequency-to-Current
• Signal isolation:
– VFC—opto-isolaton—FVC
– ADC with opto-isolation
• Signal encoding:
– FSK modulation/demodulation
– Pulse-width modulation
• Frequency scaling
• DC motor speed control
Description
The RC4152 is a monolithic circuit containing all of the
active components needed to build a complete voltage-to-
frequency converter. Circuits that convert a DC voltage to a
pulse train can be built by adding a few resistors and capaci-
tors to the internal comparator, one-shot, voltage reference,
and switched current source. Frequency-to-voltage convert-
ers (FVCs) and many other signal conditioning circuits are
also easily created using these converters.
The RC4151 was the first monolithic VFC available and
offers guaranteed temperature and accuracy specifications.
The converter is available in a standard 8-pin plastic DIP.
Functional Block Diagram
Switched
Current 1
Source Output
Switched
Reference 2
Output
Open Collector
Output
3
Ground 4
4152
Switched
Current
Source
Switched
Voltage
Reference
Voltage
Reference
8 -VS
Open Loop
Comparator
7
Comparator
Inputs
Precision
One Shot
Open Collector
Logic Output
Transistor
6
One Shot
5 Timing
4152-01
Rev. 1.0.1






RV4152N Datasheet, Funktion
PRODUCT SPECIFICATION
RC4152
Applications
Single Supply VFC
The stand-alone voltage-to-frequency converter is one of the
simplest applications for the RC4152. This application uses
only passive external components to create the least expen-
sive VFC circuit (see Figure 1).
The positive input voltage VIN is applied to the input com-
parator through a low pass filter. The one-shot will fire repet-
itively and the switched current source will pump out current
pulses of amplitude VREF/RS and duration 1.1 ROCO into the
integrator. Because the integrator is tied back to the inverting
comparator input, a feedback loop is created. The pulse repe-
tition rate will increase until the average voltage on the inte-
grator is equal to the DC input voltage at pin 7. The average
voltage at pin 6 is proportional to the output frequency
because the amount of charge in each current pulse is
precisely controlled.
Because the one-shot firing frequency is the same as the
open collector output frequency, the output frequency is
directly proportional to VIN.
The external passive components set the scale factor. For
best linearity, RS should be limited to a range of 12 kW to
20 kW
The reference voltage is nominally 2.25V for the RC4152.
Recommended values for different operating frequencies are
shown in the table below.
Operating
Range
DC to 1.0 kHz
DC to 10 kHz
DC to 100 kHz
RO
6.8 kW
6.8 kW
6.8 kW
CO
0.1 mF
0.01 mF
0.001 mF
RB
100 kW
100 kW
100 kW
CB
10 mF
10 mF
10 mF
The single supply VFC is recommended for uses where
dynamic range of the input is limited, and the input does not
reach 0V. With 10 kHz values, nonlinearity will be less than
1.0% for a 10 mV to 10V input range, and response time will
be about 135 ms.
Precision Current Sourced VFC
This circuit operates similarly to the single supply VFC,
except that the passive R-C integrator has been replaced by
an active op amp integrator. This increases the dynamic
range down to 0V, improves the response time, and
eliminates the nonlinearity error introduced by the limited
compliance of the switched current source output.
The integrator algebraically sums the positive current pulses
from the switched current source with the current VIN/RB.
To operate correctly, the input voltage must be negative, so
that when the circuit is balanced, the two currents cancel.
T = ------1-------
FOUT
--V-----I-N----
RB
=
IOUT
T----P-
T
where TP = 1.1 ROCO
IOUT
=
V-----R----E---F-
RS
By rearranging and substituting,
FOUT
=
--V-----I--N---- -R----S- -----------1-----------
VREF RB 1.1ROCO
Recommended component values for different operating
frequencies are shown in the table below.
Range
Output
Input VIN
FO
Scale
Factor
RO
CO
0 to -10V 0 to 1.0 kHz 0.1 KHz/V 6.8 kW 0.1 mF
CI RB
0.05 mF 100 kW
0 to -10V 0 to 10 kHz 1.0 KHz/V 6.8 kW 0.01 mF 0.005 mF 100 kW
0 to -10V 0 to 100 kHz 10 KHz/V 6.8 kW 0.001 mF 500 pF 100 kW
The graphs shown under Typical Performance Characteris-
tics show nonlinearity versus input voltage for the precision
current sourced VFC. The best linearity is achieved by using
an op amp having greater than 1.0 V/ms slew rate, but any op
amp can be used.
Precision Voltage Sourced VFC
This circuit is identical to the current sourced VFC, except
that the current pulses into the integrator are derived directly
from the switched voltage reference. This improves tempera-
ture drift at the expense of high frequency linearity.
The switched current source (pin 1) output has been tied to
ground, and RS has been put in series between the switched
voltage reference (pin 2) and the summing node of the op
amp. This eliminates temperature drift associated with the
switched current source. The graphs under the Typical
Performance Characteristics show that the nonlinearity error
is worse at high frequency, when compared with the current
sourced circuit.
Single Supply FVC
A frequency-to-voltage converter performs the exact oppo-
site of the VFCs function; it converts an input pulse train into
an average output voltage. Incoming pulses trigger the input
comparator and fire the one-shot. The one-shot then dumps a
charge into the output integrator. The voltage on the integra-
tor becomes a varying DC voltage proportional to the
frequency of the input signal. Figure 4 shows a complete
single supply FVC.
6

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RV4152N pdf, datenblatt
PRODUCT SPECIFICATION
Ordering Information
Part Number
RC4152N
RC4152M
RV4152N
Package
N
M
N
Notes:
N = 8-lead plastic DIP
M = 8-lead plastic SOIC
Operating Temperature Range
0°C to +70°C
0°C to 70°C
-25°C to +85°C
RC4152
LIFE SUPPORT POLICY
FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES
OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR
CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body,
or (b) support or sustain life, and (c) whose failure to
perform when properly used in accordance with
instructions for use provided in the labeling, can be
reasonably expected to result in a significant injury of the
user.
2. A critical component in any component of a life support
device or system whose failure to perform can be
reasonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
www.fairchildsemi.com
6/25/98 0.0m 003
Stock#DS30004152
Ó 1998 Fairchild Semiconductor Corporation

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