RC4152N [FAIRCHILD]
Voltage-to-Frequency Converters; 电压 - 频率转换器
| 型号： | RC4152N |
| 厂家： | 
FAIRCHILD SEMICONDUCTOR |
| 描述： | Voltage-to-Frequency Converters |
| 文件： | 总12页 (文件大小：78K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
www.fairchildsemi.com
RC4 1 5 2
Vo lt a g e -t o -Fre q u e n c y Co n ve rt e rs
• Signal isolation:
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
– VFC—opto-isolaton—FVC
– ADC with opto-isolation
• Signal encoding:
– FSK modulation/demodulation
– Pulse-width modulation
• Frequency scaling
• DC motor speed control
• Single-ended input, referenced to ground
• V-F or F-V conversion
Description
• Voltage or current input
• Wide dynamic range
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.
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:
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.
– Current-to-Frequency
– Temperature-to-Frequency
– Pressure-to-Frequency
– Capacitance-to-Frequency
– Frequency-to-Current
Functional Block Diagram
4152
Switched
Current
Source
Switched
Current
Source Output
Voltage
Reference
1
-VS
8
Open Loop
Comparator
Switched
Reference
Output
Switched
Voltage
Reference
2
3
4
7
6
5
Comparator
Inputs
Open Collector
Output
Precision
One Shot
One Shot
Timing
Ground
Open Collector
Logic Output
Transistor
4152-01
Rev. 1.0.1
PRODUCT SPECIFICATION
RC4152
Pin Assignments
Pin Descriptions
Pin
1
Function
8
7
6
5
IOUT
RS
1
2
3
4
+VS
VIN
VTH
CO
Switched Current Source Output (IOUT
)
2
Switched Voltage Reference (RS)
3
Logic Output (Open Collector) (FOUT
)
FOUT
GND
4
Ground (GND)
5
One-Shot R, C Timing (CO)
6
Threshold (VTH)
4152-02
7
Input Voltage (VlN)
+VS
8
Absolute Maximum Ratings
Parameter
Min.
Typ.
Max.
+22
500
+VS
20
Units
V
Supply Voltage
Internal Power Dissipation
Input Voltage
mW
V
-0.2
-65
Output Sink Current
(Frequency Output)
mA
Output Short Circuit to Ground
Storage Temperature Range
Operating Temperature Range
RC4152
Continuous
+150
°C
0
+70
+85
°C
°C
RV4152N
-25
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
8-Lead Plastic DIP
+125°C
Small Outline SO-8
+125°C
Max. Junction Temp.
Max. PD TA<50°C
Therm. Res qJC
468 mW
300mW
—
—
Therm. Res qJC
160°C/W
6.25 mW/°C
240°C/W
4.17mW/°C
For TA>50°C Derate at
2
RC4152
PRODUCT SPECIFICATION
Electrical Characteristics
(VS = +15V, and TA = +25°C unless otherwise noted)
Parameters
Test Conditions
Min.
Typ.
Max.
Units
Power Supply Requirements (Pin 8)
Supply Current
VS = +15V
2.5
6.0
mA
V
Supply Voltage
+7.0
+15
+18
Input Comparator (Pins 6 and 7)
VOS
±2.0
-50
±10
-300
±100
VS-3
mV
nA
nA
V
Input Bias Current
Input Offset Current
Input Voltage Range
One Shot (Pin 5)
±30
0
VS-2
Threshold Voltage
0.65
0.67
-50
0.69
-500
0.5
VS
nA
Input Bias Current
Saturation Voltage
Drift of Timing vs. Temperature2
I = 2.2 mA
0.1
V
T = 75 ms over the specified
±30
±50
ppm/°C
temperature range
Timing Drift vs. Supply Voltage
Switched Current Source (pin 1)1
Output Current
Drift vs. Temperature2
Drift vs. Supply Voltage
Leakage Current
±100
ppm/V
RS = 16.7K
+138
±50
0.10
1.0
mA
over specified temperature range
±100 ppm/°C
%/V
Off State
50
nA
Compliance
Pin 1 = 0V to +10V
1.0
2.0
2.5
mA
Reference Voltage (Pin 2)
VREF
Drift vs. Temperature2
2.25
±50
0.1
2.5
V
over specified temperature range
ISINK = 3 mA
±100 ppm/°C
Logic output (Pin 3)
Saturation Voltage
0.5
V
V
ISINK = 10 mA
0.8
Leakage Current
Off State
0.1
1.0
mA
Nonlinearity Error
(Voltage Sourced Circuit of Figure 3)
1.0 Hz to 10 kHz
0.007
0.05
%
Temperature Drift Voltage2
FOUT = 10 kHz,
(Voltage Sourced Circuit of Figure 3)
over specified temperature range
±75
±150 ppm/°C
Notes:
1. Temperature coefficient of output current source (pin 1 output) exclusive of reference voltage drift.
2. Guaranteed but not tested.
3
PRODUCT SPECIFICATION
RC4152
Typical Performance Characteristics
10 KHz Current-Sourced VFC
Nonlinearity vs. Input Voltage
100 KHz Current-Sourced VFC
Nonlinearity vs. Input Voltage
+0.01
+0.06
+0.005
0
+0.03
0
-0.005
-0.03
-0.01
-0.06
-0.09
-0.015
1
1
0
2
3
4
5
6
7
8
9
10
2
3
4
5
6
7
8
9
10
0
VIN (V)
V
IN (V)
10 KHz Voltage-Sourced VFC
Nonlinearity vs. Input Voltage
100 KHz Voltage-Sourced VFC
Nonlinearity vs. Input Voltage
+0.01
+0.10
+0.005
0
+0.05
0
-0.005
-0.05
-0.01
-0.10
-0.15
-0.015
1
1
2
3
4
5
6
7
8
9
10
0
2
3
4
5
6
7
8
9
10
0
VIN (V)
VIN (V)
10 KHz Precision VFC
Nonlinearity vs. Input Frequency
100 KHz Precision VFC
Nonlinearity vs. Input Frequency
+0.01
+0.12
+0.005
0
+0.08
+0.04
0
-0.005
-0.01
-0.04
-0.08
-0.015
0
0
1
1
2
3
4
5
6
7
8
9
10
2
3
4
5
6
7
8
9
10
F
IN (kHz)
FIN (kHz)
4
RC4152
PRODUCT SPECIFICATION
(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.
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.
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.
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.
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.
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
Integrator
CB
4152
IOUT
Switched
Current
Source
+VS
Voltage
Reference
1
8
RB
Open Loop
Comparator
100K
VIN
Switched
Voltage
Reference
2
3
4
7
6
5
0 to +10V
0.01mF
RS
Current Setting Resistor
RS = 16.7K
Precision
One Shot
RO
Ground
RLOAD
One Shot
Timing
Open Collector
Logic Output
Transistor
F
OUT
CO
Open Collector Output
4152-04
Figure 1. Single Supply VFC
5
PRODUCT SPECIFICATION
RC4152
Applications
1
T = -------------
FOUT
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).
TP
VIN
-----
T
------------ = I OUT
RB
where TP = 1.1 ROCO
VREF
IOUT = -------------
RS
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.
By rearranging and substituting,
VIN RS
1
------------- ------ ----------------------
=
FOUT
VREF RB 1.1ROCO
Recommended component values for different operating
frequencies are shown in the table below.
Range
InputV
Output
Scale
Factor
F
R
C
C
R
B
IN
O
O
O
I
0 to -10V 0 to 1.0 kHz 0.1 KHz/V 6.8 kW 0.1 mF
0.05 mF 100 kW
Because the one-shot firing frequency is the same as the
open collector output frequency, the output frequency is
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
directly proportional to VIN
.
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.
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.
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.
Operating
Range
R
C
R
C
B
O
O
B
DC to 1.0 kHz
DC to 10 kHz
DC to 100 kHz
6.8 kW
6.8 kW
6.8 kW
0.1 mF
100 kW
100 kW
100 kW
10 mF
10 mF
10 mF
0.01 mF
0.001 mF
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.
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
Single Supply FVC
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.
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.
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.
6
RC4152
PRODUCT SPECIFICATION
CI
m
F
0.005
1N914
-VS
+VS
4
R B
100K
2
3
7
W
100
VIN
0 to -10V
6
OP-27
8
RL
10k
W
1
+VL
Offset
Adjust
RS = 16.7K
RB+
+VS
100 kW
RL
5.1K
+VS
2
1
I
FOUT
3
4
RS
8
OUT +VS
FOUT
Gnd
4152
VFC
Output Frequency
FO 10kHz
7
V
0
IN
VTH
CO
10 kW
6
5
5k
W
CO
m
F
0.01
m
F
1
+VS
RO
6.8 kW
4152-05
Figure 2. Precision Current Sourced VFC
CI
m
F
0.005
1N914
-VS
+VS
7
4
R B
100K
2
100W
VIN
0 to -10V
6
OP-27
3
8
RZ
1
10kW
Offset
Adjust
RS = 16.7K
RB+
100 kW
+VS
+VL
RL
5.1K
+VS
1
IOUT RS
2
3
4
8
7
FOUT
Output Frequency
+VS
VIN
FOUT
Gnd
4152
VFC
CO
VTH
0
FOUT 10kHz
10 kW
6
5
5 kW
CO
m
1
F
m
0.01
F
+VS
RO
6.8 kW
4152-06
Figure 3. Precision Voltage Sourced VFC
7
PRODUCT SPECIFICATION
RC4152
The input waveform must have fast slewing edges, and the
differentiated input signal must be less than the timing
period of the one-shot, 1.1 ROCO. A differentiator and
divider are used to shape and bias the trigger input; a nega-
tive going pulse at pin 6 will cause the comparator to fire the
one-shot. The input pulse amplitude must be large enough to
trip the comparator, but not so large as to exceed the ICs
input voltage ratings.
Precision FVC
Linearity, offset and response time can be improved by
adding one or more op amps to form an active lowpass filter
at the output. A circuit using a single pole active integrator is
shown in Figure 5.
The positive output current pulses are averaged by the invert-
ing integrator, causing the output voltage to be negative.
Response time can be further improved by adding a double
pole filter to replace the single pole filter. Refer to the graphs
under Typical Performance Characteristics that show
nonlinearity error versus input frequency for the
precision FVC circuit.
The output voltage is directly proportional to the input
frequency:
1.1ROC RBVREF
---------------------O-----------------------
FIN(Hz)
VOUT
=
RS
Output ripple can be minimized by increasing CB, but this
will limit the response time. Recommended values for
various operating ranges are shown in the following table.
Input
Operating
Rage
0 to 1.0 kHz 0.02 mF 6.8 kW 0.1 mF
0 to 10 kHz 0.002 mF 6.8 kW 0.01 mF 100 kW 10 mF 1.0 mV
C
R
C
R
C
Ripple
IN
O
O
B
B
100 kW 100 mF 1.0 mV
0 to 100 kHz 200 pF
6.8 kW 0.001 mF 100 kW 1.0 mF 1.0 mV
+15V
RO
6.8 kW
CO
10 k W
0.01 mF
Ÿ
W
10 k
5
7
CIN
0.022
VIN
VTH
+VS
4
3
CO
Gnd
m
F
4152
VFC
IOUT
6
FIN
FOUT
RS
Frequency
Input
1
8
2
5 kW
0
FIN
10kHz
10 k
RS = 16.7K
VOUT
W
+15V
RB
CB
m
F
100K
10
4152-07
Figure 4. Single Supply FVC
8
RC4152
PRODUCT SPECIFICATION
R O
6.8 kW
+15V
10 k
W
10 k W
CO
m
F
0.01
7
5
4
3
CO
CIN
0.022
VIN
Gnd
m
F
4152 VFC
6
FOUT
VTH
FIN
RS
2
IOUT
1
+VS
8
Frequency Input
FO 10kHz
W
5 k
0
RS = 16.7K
5.0 VP-P
Squarewave
10 kW
RB
100 kW
+15V
C I
5 pF
-VS
+VS
4
2
3
7
100
W
6
OP-27
VOUT
8
Voltage Output
-10V VO
R Z
10 kW
0
1
RB
100 kW
Offset
Adjust
+VS
4152-08
9
PRODUCT SPECIFICATION
RC4152
Schematic Diagram
10
RC4152
PRODUCT SPECIFICATION
Notes:
11
PRODUCT SPECIFICATION
RC4152
Ordering Information
Part Number
RC4152N
RC4152M
RV4152N
Package
Operating Temperature Range
0°C to +70°C
N
M
N
0°C to 70°C
-25°C to +85°C
Notes:
N = 8-lead plastic DIP
M = 8-lead plastic SOIC
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.
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6/25/98 0.0m 003
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Ó 1998 Fairchild Semiconductor Corporation
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