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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
4152-01
4152
1
2
3
4
5
6
7
8
-V
S
Comparator
Inputs
One Shot
Timing
Switched
Current
Source
Switched
Voltage
Reference
Voltage
Reference
Precision
One Shot
Open Collector
Logic Output
Transistor
Open Loop
Comparator
Switched
Current
Source Output
Switched
Reference
Output
Open Collector
Output
Ground
RC4152
Voltage-to-Frequency Converters
Rev. 1.0.1
PRODUCT SPECIFICATION
RC4152
2
Pin Assignments
Pin Descriptions
1
2
3
4
I
OUT
R
S
F
OUT
GND
+V
S
V
IN
V
TH
C
O
5
6
7
8
4152-02
Pin
Function
1
Switched Current Source Output (I
OUT
)
2
Switched Voltage Reference (R
S
)
3
Logic Output (Open Collector) (F
OUT
)
4
Ground (GND)
5
One-Shot R, C Timing (C
O
)
6
Threshold (V
TH
)
7
Input Voltage (V
lN
)
8
+V
S
Absolute Maximum Ratings
Note:
1. "Absolute maximum ratings" are those beyond which the safety of the device cannot be guaranteed. They are not meant to
imply that the device should be operated at these limits. If the device is subjected to the limits in the absolute maximum ratings
for extended periods, its reliability may be impaired. The tables of Electrical Characteristics provides conditions for actual
device operation.
Thermal Characteristics
Parameter
Min.
Typ.
Max.
Units
Supply Voltage
+22
V
Internal Power Dissipation
500
mW
Input Voltage
-0.2
+V
S
V
Output Sink Current
(Frequency Output)
20 mA
Output Short Circuit to Ground
Continuous
Storage Temperature Range
-65
+150
C
Operating Temperature Range
RC4152 0
+70
C
RV4152N -25
+85
C
8-Lead Plastic DIP
Small Outline SO-8
Max. Junction Temp.
+125
C
+125
C
Max. P
D
T
A
<50
C
468 mW
300mW
Therm. Res
q
JC
--
--
Therm. Res
q
JC
160
C/W
240
C/W
For T
A
>50
C Derate at
6.25 mW/
C
4.17mW/
C
RC4152
PRODUCT SPECIFICATION
3
Electrical Characteristics
(V
S
= +15V, and T
A
= +25
C unless otherwise noted)
Notes:
1. Temperature coefficient of output current source (pin 1 output) exclusive of reference voltage drift.
2. Guaranteed but not tested.
Parameters
Test Conditions
Min.
Typ.
Max.
Units
Power Supply Requirements (Pin 8)
Supply Current
V
S
= +15V
2.5
6.0
mA
Supply Voltage
+7.0
+15
+18
V
Input Comparator (Pins 6 and 7)
V
OS
2.0
10
mV
Input Bias Current
-50
-300
nA
Input Offset Current
30
100
nA
Input Voltage Range
0
VS-2
VS-3
V
One Shot (Pin 5)
Threshold Voltage
0.65
0.67
0.69
V
S
Input Bias Current
-50
-500
nA
Saturation Voltage
I = 2.2 mA
0.1
0.5
V
Drift of Timing vs. Temperature
2
T = 75
m
s over the specified
temperature range
30
50
ppm/
C
Timing Drift vs. Supply Voltage
100
ppm/V
Switched Current Source (pin 1)
1
Output Current
R
S
= 16.7K
+138
m
A
Drift vs. Temperature
2
over specified temperature range
50
100
ppm/
C
Drift vs. Supply Voltage
0.10
%/V
Leakage Current
Off State
1.0
50
nA
Compliance
Pin 1 = 0V to +10V
1.0
2.5
m
A
Reference Voltage (Pin 2)
V
REF
2.0
2.25
2.5
V
Drift vs. Temperature
2
over specified temperature range
50
100
ppm/
C
Logic output (Pin 3)
Saturation Voltage
I
SINK
= 3 mA
0.1
0.5
V
I
SINK
= 10 mA
0.8
V
Leakage Current
Off State
0.1
1.0
m
A
Nonlinearity Error
(Voltage Sourced Circuit of Figure 3)
1.0 Hz to 10 kHz
0.007
0.05
%
Temperature Drift Voltage
2
(Voltage Sourced Circuit of Figure 3)
F
OUT
= 10 kHz,
over specified temperature range
75
150
ppm/
C
PRODUCT SPECIFICATION
RC4152
4
Typical Performance Characteristics
1
2
3
4
5
6
7
8
9
10
+0.01
+0.005
0
-0.005
-0.01
1
2
3
4
5
6
7
8
9
10
+0.06
+0.03
0
-0.03
-0.06
1
2
3
4
5
6
7
8
9
10
+0.01
+0.005
0
-0.005
-0.01
1
2
3
4
5
6
7
8
9
10
V
IN
(V)
+0.10
+0.05
0
-0.05
-0.10
1
2
3
4
5
6
7
8
9
10
F
IN
(kHz)
+0.01
+0.005
0
-0.005
-0.01
1
2
3
4
5
6
7
8
9
10
4152-03
NL (% Error)
+0.12
+0.08
+0.04
0
-0.04
0
-0.015
0
-0.015
0
-0.015
0
-0.15
0
-0.08
0
-0.09
F
IN
(kHz)
V
IN
(V)
V
IN
(V)
10 KHz Current-Sourced VFC
Nonlinearity vs. Input Voltage
100 KHz Current-Sourced VFC
Nonlinearity vs. Input Voltage
10 KHz Voltage-Sourced VFC
Nonlinearity vs. Input Voltage
100 KHz Voltage-Sourced VFC
Nonlinearity vs. Input Voltage
10 KHz Precision VFC
Nonlinearity vs. Input Frequency
100 KHz Precision VFC
Nonlinearity vs. Input Frequency
V
IN
(V)
NL (% Error)
NL (% Error)
NL (% Error)
NL (% Error)
NL (% Error)
RC4152
PRODUCT SPECIFICATION
5
Principles of Operation
The RC4152 contains the following components: an open
loop comparator, a precision one-shot timer, a switched volt-
age reference, a switched current source, and an open collec-
tor logic output transistor. These functional blocks are
internally interconnected. Thus, by adding some external
resistors and capacitors, a designer can create a complete
voltage-to-frequency converter.
The comparator's output controls the one-shot (monostable
timer). The one-shot in turn controls the switched voltage
reference, the switched current source and the open collector
output transistor. The functional block diagram shows the
components and their interconnection.
To detail, if the voltage at pin 7 is greater than the voltage at
pin 6, the comparator switches and triggers the one-shot.
When the one-shot is triggered, two things happen. First, the
one-shot begins its timing period. Second, the one-shot's
output turns on the switched voltage reference, the switched
current source and the open collector output transistor.
The one-shot creates its timing period much like the popular
555 timer does, by charging a capacitor from a resistor tied
to +VS. The one-shot senses the voltage on the capacitor
(pin 5) and ends the timing period when the voltage reaches
2/3 of the supply voltage. At the end of the timing period, the
capacitor is discharged by a transistor similar to the open
collector output transistor.
Meanwhile, during the timing period of the one-shot, the
switched current source, the switched voltage reference, and
the open collector output transistor all will be switched on.
The switched current source (pin 1) will deliver a current
proportional to both the reference and an external resistor,
RS. The switched reference (pin 2) will supply an output
voltage equal to the internal reference voltage (2.25V). The
open collector output transistor we be turned on, forcing the
logic output (pin 3) to a low state. At the end of the timing
period all of these outputs will turn off. The switched voltage
reference has produced an off-on-off voltage pulse, the
switched current source has emitted a quanta of charge, and
the open collector output has transmitted a logic pulse.
To summarize, the purpose of the circuit is to produce a cur-
rent pulse, well-defined in amplitude and duration, and to
simultaneously produce an output pulse which is compatible
with most logic families. The circuit's outputs show a pulse
waveform in response to a voltage difference between the
comparators inputs.
Figure 1. Single Supply VFC
4152-04
4152
1
2
3
4
5
6
7
8
+V
S
Switched
Current
Source
Switched
Voltage
Reference
Voltage
Reference
Precision
One Shot
Open Collector
Logic Output
Transistor
Open Loop
Comparator
Ground
LOAD
R
O
C
O
0.01 F
m
V
IN
0 to +10V
C
Integrator
B
R
B
R
S
Current Setting Resistor
R
S
= 16.7K
R
I
OUT
F
Open Collector Output
OUT
One Shot
Timing
100K
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