CAV444 Datasheet, PDF (5/12 Pages) Analog Devices – C/V transmitter IC with adjustable output voltage for capacitive input signals

CAV444 – C/V transmitter IC
with adjustable output voltage
for capacitive input signals
TRANSFER FUNCTION (FULL-SCALE OUTPUT SIGNAL)
VTEMP
7
GND
10
R_A
RA
14
V_CC
V_B
VCC VB
11
3
Temperature-
Sensor
CAV444
Supply
CM
12 _Measurement
f/V
C_M
RCM
1
oszillator
converter
Lowpass
filter
Output-
stage
R_CM
16 2
15 13
4
CW
RCW CF1 CF2
GAIN
C_W
R C _CW
F1
C_F2
VREF ^VREF
6
C_VREF
VOUT ^VOUT
5
R₁
R₂
V_REF
Figure 3: CAV444 with circuitry for full-scale adjustment
Transfer function V_OUT* for the CAV444 full-scale output signal is expressed as:
V_OUT * = V_DIFF * +V_REF
(1)
where V_REF = reference voltage and V_DIFF * = G_LP ⋅V_TPAS
(2)
The
following
applies
to
G_LP:
G_LP
= 1+
R₁
R₂
(3)
and
to
the
output
voltage
after
the
lowpass:
V_TPAS
=
3 ⋅ C_M ⋅ ∆V_CM ⋅ R_CM
8 ⋅ C_W ⋅ R_CW
(4)
with ∆V_CM = 2.1V .
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
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Fax: [phone]
Internet: http://www.analogmicro.de
Email: [e-mail]
Mai 2010 - Rev 1.1 - Page 5/12