AD CAV424

CAV424 - C/U transducer IC
with adjustable output voltage
PRINCIPLE FUNCTION
Capacitance/Voltage converter IC with an adjustable, differential output,
integrated temperature sensor
VCC = 5V + 5%
Measurement capacitance
(0...0,5 pF bis 0...1 nF)
Reference capacitance
(10 pF ... 1 nF)
CAV424
VOUT = 1,1 ... 3,9 V
Temperature
8mV / K
Typical applications
CAV424 is an analog linear transducer. The IC is suitable for all capacitive measurements which
require a voltage output signal which is proportional to the change in the capacitance to be
measured. It can be used for:
!
!
!
!
!
!
Distance measurement
Pressure sensing
Humidity measurement
Level sensing
Measurement of strength
As a capacity input circuit for microprocessors or as a stand-alone device
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 1/16
CAV424 - C/U transducer IC
with adjustable output voltage
CONTENTS
PRINCIPLE FUNCTION
1
CONTENTS
2
FEATURES
3
GENERAL DESCRIPTION
3
BLOCK DIAGRAMM
3
PRINCIPLE OF MEASUREMENT
4
HOW CAV424 WORKS
4
Oscillator function
Capacitive integrators
Signal conditioning
5
5
7
STANDARD DIMENSIONING
10
BOUNDARY CONDITIONS
10
DIMENSIONING PROCEDURE
10
INITIAL OPERATION
10
OUTPUT VOLTAGES
10
EXAMPLE APPLICATIONS
10
Application: EMC protection for CAV424
10
BLOCK DIAGRAM AND PINOUT
10
DELIVERY
10
ADDITIONAL EQUIPMENT
10
FURTHER READING
10
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 2/16
CAV424 - C/U transducer IC
with adjustable output voltage
FEATURES
GENERAL DESCRIPTION
! High detection sensitivity
! Wide capacitor measuring range:
5% – 100% relative to the reference
capacitor, 0.5pF to 1nF.
! Detection frequency of up to 2kHz
! Adjustable output offset
! Adjustable full scale output signal
! Differential output
! High voltage immunity
! Temperature output signal
! Wide temperature range:
-40°C...+105°C
! Supply voltage: 5V ± 5%
! Ratiometric output voltage
! Simple calibration (Excel program)
! RoHS compliant
CAV424 is an integrated C/V converter circuit
which contains full signal conditioning electronics for almost any source of capacitive signal.
For measurement capacitor CM CAV424
detects the relative change in capacitance !CM
= CM,max– CM,min in relation to that of a given,
fixed reference capacitor CR.
The IC has been optimized for reference
capacitors of between 10pF and 1nF where the
change in capacitance !CM can be 5% to 100%
of the basic capacitance CM,min.
The differential voltage output has been
specially designed for connection to an A/D
converter. Together with the integrated
temperature sensor and a processor
calibratable systems can be assembled. A
simple Excel program simplifies the
dimensioning of CAV424.
BLOCK DIAGRAMM
VTEMP
RCR
RCM
RCOSC
7
2
3
1
CAV424
11
VCC
T Sensor
Current reference
COSC
CR
CM
12
Reference
oscillator
16
Integrator 1
14
Integrator 2
6
VM
Signal conditioning
5
10
GND
15
CL1
13
LPOUT
4
CL2 RL
Figure 1: Block diagram CAV424
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 3/16
CAV424 - C/U transducer IC
with adjustable output voltage
PRINCIPLE OF MEASUREMENT
CAV424 is an integrated C/U converter circuit which contains full signal conditioning electronics
for capacitive signal sources.
VCC
IM IR
CAV424
UOUT
CM CR
Current sources IM and IR are integrated in CAV424
Figure 2: Principle of capacitance measurement using CAV424
The principle of measurement with the CAV424 entails recording a change in capacitance in a
sensor bridge comprising two adjustable current sources and two capacitors, the measurement
capacitance (CM) of which can be altered by the amount !CM = CM,max– CM,min. The second
capacitor is defined as a reference (CR, see Figure 2). CM,min is the basic capacitance of CM. The
change in measurement capacitance is compared to the fixed reference capacitance CR and the
resulting signal converted into an output voltage signal.
HOW CAV424 WORKS
The CAV424 IC functions according to the following principle. An adjustable oscillator, the
frequency of which is set using capacitor COSC, drives two symmetrical integrators which are phaselocked and clock-synchronized (see Figure 3). The amplitudes of the two driven integrators are
determined by capacitors CR and CM. With high common-mode rejection and a high resolution, the
difference between the two amplitudes produces a signal which corresponds to the difference in
capacitance between CR and CM (rectifier effect). This difference signal is then filtered in an
ensuing active low pass. The resulting voltage signal passes on to an adjustable amplifier stage
which sets the output signal to the required value.
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 4/16
CAV424 - C/U transducer IC
with adjustable output voltage
If capacitors CM and CR are the same, following rectification and filtering (see Figure 5) a DCvoltage signal is generated with a value of 0. Should CM change (measurement capacitor), a DCvoltage signal is produced which is proportional to !CM .
If CM and CR are not the same, when !CM = 0 an offset would be generated at the output which is
superimposed onto the actual direct voltage signal.
Oscillator function
The integrated oscillator charges up and then discharges the external oscillator capacitor COSC (see
Figure 3).
The oscillator current IOSC is determined by external resistor ROSC and reference voltage VM:
I OSC "
VM
ROSC
(1)
The oscillator frequency fOSC is calculated
as:
f OSC "
I OSC
2 # $VOSC # COSC
(2)
VOSC
VOSC,HIGH
VOSC
(2)
VOSC,LOW
where $VOSC is the difference between
the thresholds of the internal oscillator
time t
T
(VOSC,HIGH and VOSC,LOW). $VOSC is
T
2T
2
defined via internal resistors in the IC and
has a value of 2.1V @ VCC = 5V (see Figure 3: Oscillator voltage curve
Figure 3). The oscillator frequency can
thus be specified by the choice of ROSC and COSC; the relevant maximum and minimum values are
given in Table 1.
Capacitive integrators
The built-in capacitive integrators function works in the same way as the oscillator. One difference
lies in the discharge time, which here is half the length of the charge-up period. Furthermore, the
minimum oscillator voltage for the integrators is internally clamped to a value of VCLAMP = 1.2 V
(see Figure 4).
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 5/16
CAV424 - C/U transducer IC
with adjustable output voltage
VOSC
CR < CM
ICR = ICM
VCLAMP
VCR
VCM
T
2
T
2T
time t
Figure 4: Integrator oscillator voltage
The capacitive integrator currents ICR and ICM are set by external resistors RCM , RCR and reference
voltage VM:
V
V
(3)*, (4)*
I CM " M and I CR " M
RCM
RCR
Capacitors CM and CR are charged up to a maximum voltage of VCM and VCR respectively and can
be calculated as follows:
I CM
VCM "
% VCLAMP
(5)
2 # f OSC # C M
VCR "
I CR
2 # f OSC # C R
% VCLAMP
(6)
The two voltages VCM and VCR are subtracted from one another in the circuit's signal conditioning
unit. Via this subtraction, which is tantamount to a rectification of the procedure, VCLAMP is
eliminated and a direct voltage of VTPAS is produced as an output signal after filtering.
Should ICR and ICM be the same for CM,min (i.e. should the reference capacitance be the same as the
basic value of the measurement capacitance), on subtraction and filtering at the signal conditioning
output a value of zero is obtained (see Figure 5).
* The equations apply to RCX = 0 (see Figures 7 and 8). Should RCX "0 for the resistor due to better
thermal coupling, alternative calculations are provided in the Excel spreadsheets Kali1_cav424.exc
and Kali2_cavV424.xls.
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 6/16
CAV424 - C/U transducer IC
with adjustable output voltage
VTEMP
7
CAV424
RCR
RCM
RCOSC
3
2
1
11
VCC
T Sensor
Current reference
COSC
12
CR
CM
Referenceoszillator
6
VM
Integrator 1
16
14
Signal conditioning
Integrator 2
5
LPOUT
10
GND
15
CL1
13
CL2
4
RL
Figure 5: Block diagram and signal pattern
Signal conditioning
The filtered and smoothed voltage has a value of VTPAS:
3
VTPAS " # &VCR ( VCM '
8
(7)
Signal VTPAS can be boosted using the follow-on internal operational amplifier, with the
amplification GLP being determined by resistors RL1 and RL2. GLP is calculated as:
R
GLP " 1 % L1
(8)
RL 2
With (7), this results in:
3
V DIFF " G LP # VTPAS " G LP # # &VCR ( VCM '
8
For the output signal reference to ground (GND) it thus follows that:
VLPOUT " VDIFF % VM
(9)
VLPOUT = f(CM, (CR), fosc, ICM, ICR), where the basic values of CM and CR must be placed in a fixed
ratio. fosc or ICM, ICR act as parameters.
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 7/16
CAV424 - C/U transducer IC
with adjustable output voltage
The overall transfer function (9) is accrued from equations (5) and (6). It becomes evident
that the output signal is a function of capacitors CM and CR, of oscillator frequency fOSC and
of the integrator charging currents ICM and ICR.
U LPOUT
VM 2,5V
CM
CM
CM Max
CM Min
Figure 6: Output signal VLPOUT with CM > CR referenced to ground
A voltage is provided (9) as an output variable which is relative to the average voltage VM. As this is
ratiometric to the supply voltage, in effect a differential ratiometric output signal is obtained.
ROSC
RCM
RCX
RCR
7
CAV424
2
1
3
VCC
11
T Sensor
Current reference
12
Reference
oscillator
16
Integrator 1
14
Integrator 2
COSC
CR
CM
VM
6
CVM
Signal conditioning
VLPout
5
10
13
15
CL 1
CL2
RL1
4
RL3
VDIFF
CRL1
RL2
RA
RB
GND
Figure 7: Functional diagram for CAV424 (with charging currents ICM
and ICR constant)
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 8/16
CAV424 - C/U transducer IC
with adjustable output voltage
Figure 7 assumes that the charging currents ICM and ICR are constant. This means that with a change
in the basic value of the measurement capacitance CM,min (as is the case when different objects are
measured, for example) the oscillator frequency must be adjusted to the new measurement with the
alternate CM,min value.
If oscillator frequency fosc is to be set as a parameter, when CM,min is altered the two values ICM and
ICR must also be adjusted. It is recommended that ICM = ICR. Both procedures are equally effective;
the choice thereof depends on the conditions stipulated by the application.
A functional diagram is shown in Figure 8.
ROSC
RCX RCM
RCR
7
CAV424
2
1
3
VCC
11
T Sensor
Current reference
12
Reference
oscillator
16
Integrator 1
14
Integrator 2
COSC
CR
CM
VM
6
CVM
Signal conditioning
VLPout
5
10
13
15
CL 1
CL2
RL1
4
RL3
VDIFF
CRL1
RL2
RA
RB
GND
Figure 8: Functional diagram for CAV424 (with fosc constant)
If fosc = constant and ICM, ICR = f(CM, CR) the same equations (1 to 9) apply as for the case that ICM
and ICR = constant and fosc = f(CM, CR).
For dynamic measurements with periodically changeable measurement capacitances the various
frequencies must be taken into account. Among other things, the following applies:
f det << f osc
fdet is the detection frequency which gives the change in measurement capacity per unit of time.
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 9/16
CAV424 - C/U transducer IC
with adjustable output voltage
ELECTRICAL SPECIFICATIONS
Tamb = 25°C, VCC = 5V (unless otherwise stated)
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Unit
Supply
Supply Voltage
VCC
Ratiometric range
4.75
5.00
5.25
V
Quiescent Current
ICC
Tamb = -40 ... 105°C, GLP = 1
0.6
1.0
1.4
mA
Temperature Specifications
Operating
Tamb
-40
105
°C
Storage
Tst
-55
125
°C
COSC = 1.6 # CM
16
1600
pF
ROSC = 250k)
9.5
Oscillator
Oscillator Capacitor Range
COSC
Oscillator Frequency Range
fOSC
Oscillator Current
IOSC
1
10
130
kHz
10.75
*A
1000
pF
5.38
*A
Capacitive Integrator 1 and 2
10
Reference Capacitor Range
CR
Reference Capacitive Integrator Current
IR
RCR = 500k)
Measurement Capacitor Sensitivity
$ CM
$CM = (CM,max(CM,min )/CM,min
5
100
%
Measurement Capacitor Range
CM
CM,min ! CM ! CM,max
10
2000
pF
Measurement Capacitor Integrator
Current
IM
RCM = 500k)
5.38
*A
Detection Frequency
fDET
CL1 = CL2 =1nF
2
kHz
4.75
4.75
5
5
Low Pass Stage
Adjustable Gain
GLP
Output Voltage
VLPOUT
VLPout = VDiff + VM ,
Corner Frequency 1
fC1
R01 = 20k), CL1 =1nF
Corner Frequency 2
fC2
R02 = 20k), CL2 =1nF
Resistive Load at PIN LPOUT
RLOAD
Capacitive Load at PIN LPOUT
CLOAD
Output voltage shift
VDIFF
Temperature Coefficient VDIFF (together
with Input Stages)
dVDIFF /dT
Internal Resistor 1 and 2
R01, R02
Temperature Coefficient R01,02
dR01,02 /dT
[email protected]*
Tamb = -40 ... 105°C
VM
VM vs. Temperature
Current
IVM
Ratiometric Error of VLPOUT
1
10
1.1
VCC – 1.1
V
8
kHz
8
kHz
200
k)
50
VM = 2.5V
-1.4
1.4
+100
Tamb = -40 ... 105°C
pF
V
ppm/°C
20
k)
1.9
10-3/°C
0.11
%FS
Ratiometric to VCC
2.5
V
dVM /dT
Tamb = -40...+105°C
+20
+50
ppm/°C
IVM
Source
16
*A
Sink
-16
*A
Voltage Reference VM
Voltage
Load Capacitance
CVM
Ratiometric Error of VM
[email protected]**
80
100
0.007
120
nF
%FS
* RAT @ VDIFF = 2 [1.05 VDIFF(VCC = 5V) – VDIFF(VCC = 5.25V)]/[VDIFF(VCC = 5V) + VDIFF(VCC = 5.25V)]
** RAT @ VM = 2 [1.05 VM(VCC = 5V) – VM(VCC = 5.25V)]/[VM(VCC = 5V) + VM(VCC = 5.25V)]
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 10/16
CAV424 - C/U transducer IC
with adjustable output voltage
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Unit
2.20
2.32
2.45
V
Temperature Sensor VTEMP
RTEMP , 50M)
Voltage
VTEMP
Sensitivity
dVTEMP/dT
RTEMP , 50M)
RTEMP , 50M), end point method
Thermal Nonlinearity
8
mV/°C
0.5
%FS
Table 1: Specifications for CAV424
Note:
1) The oscillator capacity has to be chosen using COSC = 1.6 # CM,Min
2) The capacitor range of CM and CR can be extended, whereby the system performance is reduced
and the electrical limits are exceeded.
3) Currents flowing into the IC are negative.
4) RTEMP is the minimum load resistance at pin VTEMP.
The system performance over temperature forces resistors RCR, RCM and ROSC to have the same
temperature coefficient; this also requires that the components are placed very close together in the
circuit. Capacitors CR, CM and COSC are also obliged to have the same temperature coefficient and a
very close proximity on the circuit board.
STANDARD DIMENSIONING
For external elements which do not have to be altered dependent on the measurement capacity the
following standard values apply:
Parameter
Symbol
Min.
Typ.
Output Stage Resistor (1%)
RL2 , RL3
100
Offset Resistor (1%)
RB
100
Reference Voltage Capacity (VM = 2.5V)
CVM
Filter Capacitance
CRL1
80
Max.
Unit
k)
k)
100
120
nF
2.2
nF
Table 2: Standard values for external components
BOUNDARY CONDITIONS
Symbol
Parameter
Condition
Min.
Typ.
Max.
Unit
17
V
130
kHz
Maximum Supply Voltage
VCCmax
Oscillator Frequency Range
fOSC
Reference Capacitive Integrator Current
IR
RCR = 500k)
5.38
*A
Measurement Capacitor Integrator Current
IM
RCM = 500k)
5.38
*A
1
Table 3: Boundary conditions
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 11/16
CAV424 - C/U transducer IC
with adjustable output voltage
DIMENSIONING PROCEDURE
Programs Kali1_cav424.xls and Kali2_cav424.xls can be used for dimensioning purposes.
The dimensioning process takes the following scenarios into account:
a) Kali1_cav424.xls – The integrator charging currents ICM and ICR are given and constant.
Oscillator frequency fosc must be adjusted to suit the minimum value of measurement
capacitance CM,min.
b) Kali2_cav424.xls – Oscillator frequency fosc is given and determined and integrator
charging currents ICM and ICR must be adjusted to suit the minimum value of measurement
capacitance CM,min.
In a) the dimensioning process assumes that in addition to measurement capacitors CM and CR
parasitic capacitances in both the IC and measurement circuit also influence the signal pattern.
When dimensioning on the basis of the given equations a deviation from the theoretical value in the
output characteristic must thus be reckoned with.
For this reason a calibration algorithm has been developed (Kali1_cav424.xls) which at constant
integrator charging currents (ICM and ICR) calculates a suitable oscillator frequency of fosz
depending on the minimum value of CM,min (basic capacitance). It then dimensions the resistors for
the offset and signal span in such a way that the output signal adopts the required values.
Compensation of the sensor system is carried out in two stages. In stage one a calibration operating
point is defined, during which process oscillator frequency fosc is calculated depending on
minimum measurement capacitance CM,min. To this end the minimum and maximum values (CM,min
and CM,max) are entered in the Excel spreadsheet. The oscillator frequency, oscillator capacitance
COSC and oscillator resistance ROSC are then output.
In addition low pass filter capacitances CL1 and CL2 are calculated which are dependent on the
oscillator frequency. It is sufficient if these values are computed once for the largest expected value
of minimum basic capacitance CM,min (for example during one production batch) and the relevant
capacitors added to the circuit. The maximum signal frequency is also determined by which the
measurement capacitance is permitted to change.
Taking the given and calculated external components and particularly predefined precision resistors
RL1(mess) and RL2(mess) we can calculate the output voltage VLPOUT(mess).
NB: RL1(mess) and RA(mess) must both be 100kOhm precision resistors with a tolerance of 0.1%
maximum.
Output signal values VLPOUT(mess) are now entered in stage two of the calibration program. Using the
measured values the algorithm now calculates the setpoint for the two calibration resistors RL1 and
RA which replace precision resistors RL1(mess) and RL2(mess) and must be individually mounted.
Depending on the accuracy requirements of the setup their values should match those calculated as
closely as possible.
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 12/16
CAV424 - C/U transducer IC
with adjustable output voltage
Once the two calibration resistors RL1 and RA have been replaced by precision resistors RL1(mess) and
RL2(mess) the system is calibrated to the required output value – with all parasitic effects and
tolerances taken into account.
In stage one of b), at a given fixed oscillator frequency calibration spreadsheet Kali2_cav424.xls
calculates the values of integration currents ICM and ICR which can be achieved by setting resistors
RCM and RCR. Using these values and the other external elements output voltage VLPOUT(mess) is
measured and the value entered into the calibration program. The rest of stage two is identical to the
calibration procedure described in a).
INITIAL OPERATION
Initial operation is described in detail in the description of the calibration program (see
Kali1_cav424.xls and Kali2_cav424.xls).
OUTPUT VOLTAGES
The following applies for the output voltage (9):
VLPOUT " VDIFF % VM
V (Volt)
VCC
5
4
VLP O UT , max
+Vdiff
2,5
-Vdiff
1
VM
VLP O UT , min
0
Figure 9: Output voltages
If VM = 2.5V, according to the specifications the schematic shown in Figure 9 is generated.
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 13/16
CAV424 - C/U transducer IC
with adjustable output voltage
EXAMPLE APPLICATIONS
Application: EMC protection for CAV424
VTEMP
7
CAV424
RCX1 RCX2 RCOSC
2
3
1
11
VCC
T Sensor
COSC
CR
Stromreferenz
12
ReferenzOszillator
16
Integrator 1
6
VM
Signalverarbeitung
CM
CR
REMVM
5
LPOUT
100mV
REMVR
100mV
14
CM
Figure 10: Protective EMC circuitry for CAV 424
When measuring capacitance the electrodes are receptive to high-frequency disturbances such as
aerials. Measures must thus be taken to protect these high impedance inputs.
To protect against EMC resistors REMVM and REMVR are plugged into the supply lines servicing
external capacitors CM and CR. Together with the parasitic and internal capacitances these act as low
passes and thus suppress high-frequency disturbance factors.
The following applies:
REMVM "
0.1V
0.1V
and REMVR "
I CM
I CR
Further protective EMC measures are not required for industrial applications.
As CAV424 has been manufactured using bipolar technology the IC is robust with regard to ESD.
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 14/16
CAV424 - C/U transducer IC
with adjustable output voltage
BLOCK DIAGRAM AND PINOUT
VTEMP
RCR
RCM
RCOSC
7
2
3
1
CAV424
11
T Sensor
COSC
CR
CM
12
Reference
oscillator
16
Integrator 1
14
Integrator 2
VCC
Current reference
6
VM
Signal conditioning
5
10
15
GND
CL1
13
LPOUT
4
CL2 RL
Figure 11: Block diagram of CAV424
PIN
NAME
DESCRIPTION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
RCOSC
RCR
RCM
RL
LPOUT
VM
VTEMP
N.C.
N.C.
GND
VCC
COSC
CL2
CM
CL1
CR
Oscillator current definition
Current setting for integrator CR
Current setting for integrator CM
Gain setting
Output
Reference voltage 2.5V
Temperature sensor
Not connected
Not connected
IC ground
Supply voltage
Oscillator capacitance
Low pass 2, corner frequency
Measurement capacitance
Low pass 1, corner frequency
Reference capacitance
RCOSC
RCR
RCM
RL
LPOUT
VM
VTEMP
N.C.
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
CR
CL1
CM
CL2
COSC
VCC
GND
N.C.
Figure 12: CAV424 pinout
Table 4: CAV424 pinout
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 15/16
CAV424 - C/U transducer IC
with adjustable output voltage
DELIVERY
CAV424 is available as:
! SO16 (n)
! Dice on 5" blue foil
! For sample batches CAV424 can be supplied on a DIL16 SO16 adapter (CAV424Adapt)
Package dimensions: see http://www.analogmicro.de/products/analogmicro.de.en.package.pdf
ADDITIONAL EQUIPMENT
For design purposes, by way of support Analog Microelectronics GmbH can also supply a
breadboard (BBCAV424) which has been assembled for a set of parameters but which can also be
used for individual measurements.
FURTHER READING
Please see our website for further information (www.analogmicro.de):
[1] AN1008 application notes
[2] PR1009 press release
AMSYS reserves the right to amend any dimensions, technical data or other information contained herein without prior notification.
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: [email protected]
July 2007 - Rev 1.2 - Page 16/16