universal sensors and transducers interface USTI features ? 29 measuring modes and one generator mode ? 2 identical channels ? provides frequency (time)-to-digital conversion for many types of sensors and transducers ? provides interfacing for resistive (including platinum (pt), cuprum (cu) resistors and thermistors (ni)), capacitive sensing elements and resistive bridges ? frequency range from 0.05 hz up to 9 mhz without prescaling and 144 mhz with prescaling; ? programmable accuracy (relative error) for frequency (period) conversion from 1 % to 0.0005% ? relative quantization erro r is constant in all specified frequency range ? non-redundant conversion time ? scalable resolution ? internal reference clock 625 khz, 20 mhz @ 20 mhz quartz oscillator ? quartz-accurate automated calibration ? 3-wire serial interface (spi compatible) ? 2-wire interface (i 2 c compatible) ? rs-232/485 serial interface ? master and slave communication modes ? frequency generator mode 10 mhz with quartz crystal stability applications physical and chemical sensor systems digital sensors, soc, sip, biomems, lab-on-chip smart and intelligent sensors and systems industrial and process control data acquisition systems instrumentations customer electronics automotive general description the universal sensors and transducers interface (USTI) is a fully digital cmos integrated circuit of universal, 2-channel, high precision, multifunctional converter based on novel, advanced methods for frequency, period, its ratio, duty-cycle and phase-shift measurements. it is perfectly suited to any applications where frequency-time parameters but also sensors output signal, have to be measured with highest functional block diagram resolution and programmable accuracy during the non- redundant conversion time. the USTI covers a wide range of frequencies and accuracies for modern frequency-time domain sensors. in addition, the USTI provides interfacing for resistive (including platinum, cuprum resistors and thermistors), capacitive sensing elements and resistive bridges. by using this ic it is possible to build a wide variety of digital, smart sensors and intelligent sensor systems. the device represents a hi gh-resolution conversion and designed to support all range of frequency-time domain and digital sensor applications. it offers high performances with flexibility and requires minimum possible number of external components. the USTI can be easy included into digital environment, controlled by an external microcontroller (slave mode) or work independently as a separate measuring unit without an external control (master mode). the function selection can be configured in both software and hardware. the ic converts frequency-time domain signals, resistance and capacitance of sensing elements and resistance of sensor bridges into digital and provides digital, bus interface to mi crocontroller, daq or sensor system to read these digital results. sensing elements can be directly connected to the USTI without the need for extra electronics. only a single reference element, of the same kind as the sensor, is required. the USTI has 29 measuring and one generating modes. the measuring mode can be hardware- www..net
2 selected by using four selection external pins m0-m2 and the relative error by using four selection pins n0- n2 (rs232 master communication mode). the mode and accuracy can be also selected by using any of three possible interfaces (slave communication mode). a communication interface type (rs232, spi or i 2 c) can be automatically selected according to the circuit connection. measuring modes ? frequency, f x 0.05 hz ? 9 mhz directly and up to 144 mhz with prescaling ? period, t x 110 ns ? 20 s ? phase shift, ? x 0 - 360o at f xmax = 625 khz at 50 % duty-cycle ? time interval between start ? and stop-pulse, ? x 1.5 s ? 250 s ? duty-cycle, dc 0 ? 1 at f xmax 625 khz ? duty-off factor, q 1 10 -8 ? 810 6 at f xmax 625 khz ? frequency difference, f x2 ? f x2 with sign recognition, 0 ? 9 mhz ? period difference, t x1 ? t x2 with sign recognition, 0 ? 20 s ? frequency ratio, f x1 /f x2 5.510 -9 ? 1.810 8 ? period ratio, t x1 /t x2 4.010 -9 ? 210 8 ? rotation speed, n x = (f x 60)/z, where z is the number of encoder teeth ? pulse width, t p 1.5 s ? 250 s ? space interval, t s 1.5 s ? 250 s ? pulse number (events) counting, n x 0 ? 410 9 ? frequency deviation absolute d a1, 0-9 mhz ? frequency deviation relative d r1, 0-100 % ? resistance, r x 10 ? to 10 m ? with average relative error ? 0.47 % and ? 0.01 % error at splitting of the range into sub ranges ? capacitance, c x 50 pf to 100 ? f with average relative error ? 0.036 % and ? 0.7 % the worst case relative error ? resistive bridges, b x must not include any internal components other than 4 arms forming a bridge note: the USTI can also work with any voltage and current output sensors. it this case, any voltage?to- frequency converter (vfc) can be used. the accuracy of such system will be deter mined by sens or accuracy as well as by vfc accuracy. accuracy the USTI has programmable relative error from 1 to 0.0005 % in all specified range of frequencies for frequency and period measurements. this error is constant and does not depend on the measuring frequencies in all frequency ranges. the USTI has non-redundant conversion time . the higher conversion accuracy needs longer conversion time. however, it is non-redundant for any selected accuracy and frequency. for time interval, phase shift, pulse width and space measurements the relative error is determined mainly by measurnd and can be calculated according to the following equation: %, 100 10 20 1 6 ? ? ? ? x q t ? where t x is the appropriate measuring value of t p , t s or ? x depending on the mode. communication modes the USTI can work as an independent measuring unit (master mode), controlled by any external microcontroller (or embedded into a sensor), daq board or pc (slave mode). in the master mode, the conversion accuracy and measurement mode should be selected by external switches. in this mode the USTI works only through the rs232 interface in a unidirectional mode. in the slave mode (with an external microcontroller), all measuring modes and programmed accuracy can be set up by a data bus or through communication i/o ports of master microcontroller. this allows us use the USTI as a simple peripheral circuit for a microcontroller. a bidirectional data exchange is possible with any of three interfaces rs232, spi or i 2 c. the USTI works as a standard element in different systems with i 2 c bus architecture, or can be controlled through the rs232 or spi interfaces. the choice of interface can be performed automatically depend on the circuit connections. the selection of communication interface is performed automatically based on the st ate of is1 and is2 inputs at the power switch on: is1 is2 communication interface 0 0 spi slave 0 1 i2c slave 1 0 rs232 master 1 1 rs232 slave characteristics ? single power supply, v: 4.5 ? 5.5 ? external reference frequency, mhz: 20 ? internal reference frequency, khz: 625 ? conversion time, s: 0.00016 to 0.32 ? supply current (at 20 mhz, 4.5v, 25oc), ma: < 9.5 ? operating temperature range -40oc to +85oc ? storage temperature range -65c to +150c pin-out and housing the USTI is available in a 28-lead (0.300"/7.62 mm wide) plastic dual inline package (pdip); 32-lead 7 x 7 mm body size, 1.0 mm body thickness, 0.8 mm lead pitch small thin profile plastic quad flat package (tqfp); and 32-pad, 5 x 5 x 1.0 mm body,
3 lead pitch 0.50 mm, 3.10 mm exposed pad, micro lead frame package (mlf). pin function descriptions name pin descriptions vcc supply voltage gnd ground fx1, st1 input channel 1 fx2, st2 input channel 2 osc1, osc2 oscillator m0, m1, m2 mode selection (see table) n0, n1, n2 accuracy selection (see table) a0, a1, a2 address of i 2 c slave (for i 2 c bus communication) test calibration signal sck spi bus master clock input miso spi bus master input/slave output mosi spi bus master output/slave input ss spi bus master slave select scl two-wire (i 2 c compatible) serial bus clock line sda two-wire (i 2 c compatible) serial bus data input/output line rxd uart input txd uart output is0,is1 interface mode selection bn north port of bridge bw west port of bridge bs south port of bridge ce1 calibration element 1 ce2 calibration element 2 chrg, mes, smpl r x and c x measurement pins pdip 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 nc rxd txd/is1 fx1 fx2 st1 vcc gnd osc1 osc2 st2 ce2/bn smpl chrg scl sda/is0 m2/a2 m1/a1 m0/a0 mes/bs gnd nc vcc sck/n2 miso/n1 mosi/n0 ss/test ce1/bw tqfp/mlf top view 1 2 3 4 5 6 7 8 24 23 22 21 20 19 18 17 fx2 st1 gnd vcc gnd vcc osc1 osc2 m0/a0 mes/bs nc gnd nc nc vcc sck/n2 note: bottom pad for mlf package should be soldered to ground. this device can also be supplied in wafer form. please contact technology assistanc e bcna 2010 s. l. sales office for detailed ordering information and minimum quantities. for more detailed information, specifications and application notes the following document are strongly recommended: universal sensors and transducers interface (USTI): specification and application note technology assistance bcna 2010, s. l. riera de tena, no. 9 local 4, 08014, barcelona, spain tel.:+34 680 282 682 e-mail: info@techassist2010.com web: http://www. techassist2010.com
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