last update November 30, 2010 reference smtutin page 1/27 Features Provides interfacing for many types of sensor elements: Capacitors, platinum resistors, thermistors, Resistive bridges and potentiometers Measurement of multiple sensor elements Single 2.9 V - 5.5 V power supply, current consumption below 2.5 mA Resolution and linearity up to 14 bits and 13 bits Continuous auto-calibration of offset and gain Microcontroller-compatible output signal Tri-state output Typical measurement time 10 ms or 100 ms 2/3/4-wire measurement available for almost all measurements AC excitation voltage signal for all sensor elements Suppression of 50/60 Hz interference Power down mode Operating temperature range for DIL and SO -40C to 85C Operating temperature range for bare die -40C to 180C Applications Automotive, industrial and medical applications for Capacitive level sensing Position sensing Angle sensing Accurate temperature measurement (Platinum, NTC) Bridge sensors for pressure, force etc. 1. General Description The Universal Transducer Interface (UTI) is a complete analog front end for low frequency measurement applications, based on a period-modulated oscillator. Sensing elements can be directly connected to the UTI without the need for extra electronics. Only a single reference element, of the same kind as the sensor, is required. The UTI outputs a microcontroller-compatible period-modulated signal. The UTI can provide interfacing for: Capacitive sensors 0 - 2 pF, 0 -12 pF, variable range up to 300 pF Platinum resistors Pt100, Pt1000 Thermistors 1 kW - 25 kW Resistive bridges 250 W - 10 kW with maximum imbalance +/- 4% or +/- 0.25% Potentiometers 1 kW - 50 kW Combinations of the items mentioned above The UTI is ideal for use in smart microcontroller-based systems. All data is present on a single microcontroller compatible output, which reduces the number of connecting wires and reduces the number of last update November 30, 2010 reference smtutin page 2/27 couplers required in insulated systems. For information about insulated UTI applications, please see the relevant application notes in the support shop of our website. Continuous auto-calibration of offset and gain of the complete system is performed by using the three-signal technique. The low-frequency interference is removed by an advanced chopping technique. Selection of any of the sixteen operating modes takes place by setting four mode-bits. Functional block diagram V DD Driver UTI A B AMP/ Voltage to Frequency C MUX C-V/ Period Divider OUT D Divider Converter E F Logic control circuit SL1 SL2 SL3 SL4 CML SF PD V SS The UTI is available in a 16-pin plastic dual-in-line package (DIP) as well as a 18-lead small outline package (SOIC). Figure 1 shows the pin configurations of DIP and SOIC. The function of the pins is listed in Table 1. D V D 1 16 VDD 1 18 DD C 2 17 E C 2 15 E B 3 16 F B 3 14 F SL1 4 15 CML Name Function of the pin SL1 4 13 CML UTI UTI SL2 5 14 OUT Top View Top View SL2 5 12 OUT (Not to Scale) (Not to Scale) V , V Power supply DD ss SL3 6 13 PD SL3 6 11 PD A, B, C, D, E, F Sensor connections SL4 7 12 SF SL4 7 10 SF NC NC 8 11 SEL1..SEL4 Mode selection (see Table 2) V A SS 8 9 V 9 10 A SS OUT Output 16-pins DIL 18-pins SOIC SF Slow/fast mode selection CML CMUX02/CMUX12 mode selection PD Power Down (tri-state) Figure 1 pin configuration of DIL 16 and SOIC-18 Table 1. Function of the pins