Datasheet

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last update
November 30, 2010
reference
smtutin
page
4/27
4.1 Output
The UTI outputs a microcontroller-compatible period-modulated signal and excitation signals to drive the
sensing elements. Table 3 shows some output specifications of the UTI. Because all UTI data is present on
one single digital output, only four wires are needed to make a versatile insulated front end. For information
about insulated use of UTI please go to the relevant application notes in the support shop of our website.
Parameter Value Unit Conditions
Vol, output voltage low
0,4 V
Voh, output voltage high
Vdd-0,6 V
Rout, output resistance
60 
Maximum Iout
8 mA Vdd= 5 V.
output resistance at B - F
800  used as outputs in capacitive modes
maximum Iout at E and F
20 mA for resistive and bridge modes
Rise time
14 ns
Fall time
13 ns
propagation delay PD-OUT
30 ms in fast mode 8 times smaller
propagation delay SELi-out
30 ms in fast mode 8 times smaller
Table 3. Output specifications of the UTI
4.2 Analog inputs
Various sensing elements can be directly connected to the inputs of the UTI. The connections of
the sensing elements with the UTI for various modes are described in section 8. Table 4 shows
some input specifications of the UTI.
Parameter Value Unit conditions
Input capacitance 20 pF
Capacitance leakage between A to B,C,D,E and F 30 x 10E-3 pF DIL package
Suppression of 50/60 Hz dB
Table 4. some input specifications of the UTI @ VDD = 5 V, TA = +25 ° C
4.3 Control lines
As described in section 4.1, the UTI has 16 operating modes. These modes are selected by using
four selection pins, SEL1, SEL2, SEL3 and SEL4. In Table 2 , a ‘1’ corresponds to V
DD
and ‘0’ to
GND. Some special functions are available, such as, Slow/fast selection and power-down. These
modes are set by SF and PD, respectively.
The pin SF is used to set the measurement speed. When SF = 1, the UTI is working in the fast
mode. In this mode the duration of one complete cycle of the output signal is about 10 ms. When
SF = 0, the UTI is working in the slow mode and the duration of one complete cycle of the output
signal is about 100 ms.