View IC-WT_3391393.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

IC-WT incremental encoder features applications differential scanning for track a and b constant-light-evaluated scanning for the index track z with adjustable relative threshold photocurrent amplifier with high cut-off frequency current comparators with hysteresis index track z selectable gated by tracks a and b current-limited and short-circuit-proof push-pull outputs outputs ttl compatible adjustable led current control for constant optical receiver power integrated 50ma driver for the transmit led led current monitoring and error message upon violating the control range low current consumption from single 5v power supply option: enhanced temperature range -40..125 c photocurrent evaluation for incremental linear or angular position measuring systems packages so16n block diagram ?1997 rev a0 photodiodes array codewheel +5v +5v out_a out_b out_z error driver led led current control error track a track b track z dpb dpa dz rled 68 w rlr 15k w dnb dna clr 10nf 15k w rz led 16 agnd 3 a 7 led 6 nerr 4 b 5 z 2 vcc 1 gnd 11 dz 14 dpa 15 dna 12 dpb 13 dnb 8 clr 10 ilr 9 IC-WT iz ic-or ic-haus gmbh tel +49-6135-9292-0 integrated circuits fax +49-6135-9292-192 am kuemmerling 18, d-55294 bodenheim http://www.ichaus.com
IC-WT incremental encoder rev a0, page 2/13 description the device IC-WT is an evaluator ic for optical increment linear and rotary motion sensors, e.g. glass scales or shaft encoders. a photodiodes array supplies the input signals for the monolithically integrated amplifiers, comparators and the ttl compatible push-pull output drivers. two tracks, a and b, are evaluated differentially, the index track z as a constant light. an integrated led current control with driver stage enables the direct connection of a transmit led with series resistor and ensures a constant optical receive power. two external resistors are used to set the relative index track comparator threshold and to determine the receive photocurrents. the internally available logical and operation of index track z to tracks a and b can be switched off for adjustment. a monitor circuit triggers an error message when the led current control range is violated. the fault output designed as an open collector is low active and simultaneously functions as an input to turn off the and operation of the index track. all connections are protected against damage due to esd. the outputs are short-circuit proof. packages so16n to jedec standard pin configuration so16n pin functions (top view) no. name function 1 gnd ground 2 vcc +5v supply voltage 3 a track a ttl output 4 b track b ttl output 5 z track z ttl output 6 nerr fault output / and gate disable 7 led cathode led 8 clr capacitor for led current control 9 iz threshold for index track 10 ilr current control adjust 11 dz cathode photodiode index track z 12 dpb cathode photodiode track b+ 13 dnb cathode photodiode track b- 14 dpa cathode photodiode track a+ 15 dna cathode photodiode track a- 16 agnd common anode for all photodiodes, connected to gnd internally
IC-WT incremental encoder rev a0, page 3/13 absolute maximum ratings values beyond which damage may occur; device operation is not guaranteed. item symbol parameter conditions fig. unit min. max. g001 vcc supply voltage 0 7 v g002 i(dpx) i(dnx) current in inputs dpa, dna, dpb, dnb -1 1 ma g003 v(a,b,z) voltage at outputs a, b, z 0 vcc g004 i(a,b,z) current in outputs a, b, z v(a,b,z)< 0v or v(a,b,z)> vcc -4 4 ma g005 i(dz) current in input dz -1 1 ma g006 i(ilr) i(iz) current in ilr, iz -6 1 ma g007 i(clr) current in clr -1 1 ma g008 i(led) current in led v(led)> vcc -1 1 ma g009 i(led) current in led v(led) vcc -1 60 ma g010 v(nerr) voltage at nerr 0 vcc g011 i(nerr) current in nerr v(nerr)< 0 or v(nerr)> vcc -4 4 ma tg1 tj junction temperature -30 130 c tg2 ts storage temperature -30 130 c thermal data operating conditions: vcc= 5v 10% item symbol parameter conditions fig. unit min. typ. max. t1 ta operating ambient temperature range (extended temperature range on request) -25 125 c t2 rthja thermal resistance chip to ambient smd mounting, without special cooling 125 k/w all voltages are referenced to ground unless otherwise noted. all currents into the device pins are positive; all currents out of the device pins are negative.
IC-WT incremental encoder rev a0, page 4/13 electrical characteristics operating conditions: vcc= 5v 10%, tj= -25..125 c, unless otherwise noted item symbol parameter conditions tj fig. unit c min. typ. max. total device 001 vcc permissible supply voltage 4.5 5.5 v 002 i(vcc) supply current in vcc, outputs a, b, z hi closed led control: r(ilr/agnd)= 15k w , i(led) ? 3ma, nerr= hi; i(a,b,z)= 0, r(rz/agnd)= 15k w , i(dz,dpx)= -400na, i(dnx)= -40..0na, (x= a,b) 10 ma 003 i(vcc) supply current in vcc, outputs a, b, z lo closed led control: r(ilr/agnd)= 15k w , i(led) ? 3ma, nerr= hi; i(a,b,z)= 0, r(rz/agnd)= 15k w , i(dz,dpx)= -40..0na i(dnx)= -400na 27 5.5 12 ma ma 004 fo cut-off frequency for tracks a and b sinusoidal waveform, i(dpx)= -20..-400na, i(dnx)= -400..-20na 500 khz 005 fo cut-off frequency for index track z rectangular waveform, i(dz)= -20..-400na, threshold 200na 250 khz 006 d tp() propagation delay deviation track vs.track at a, b, z 100 ns differential photocurrent amplifier, track a and b 101 i(dpx) i(dnx) permissible sensor current at dpa, dna, dpb, dnb -600 0 na 102 cm(p/n) common mode dpa vs. dna, dpb vs. dnb 0.85 1 1.15 comparator, track a and b 201 hys hysteresis refered to [i(dpx) + i(dnx)] / 2 i(dpx,dnx)= -400..0na 15 20 25 % photocurrent amplifier, index track z 401 i(dz) permissible sensor current at dz -600 0 na comparator, index track z 801 hys hysteresis refered to i(dz) i(dz)= -400..0na 7 10 13 % push-pull outputs a, b, z 301 vs()hi saturation voltage hi vs()hi= vb-v(); i()= -400 m a -25 27 70 125 0.9 0.8 0.75 0.7 1.1 1.0 0.9 0.9 v v v v 302 vs()hi saturation voltage hi vs()hi= vb-v(); i()= -1.6ma -25 27 70 125 1.2 1.1 1.05 1.05 1.5 1.4 1.3 1.3 v v v v 303 vs()lo saturation voltage lo i()= 0.8ma 0.4 v 304 vs()lo saturation voltage lo i()= 1.6ma 0.5 v 305 isc()hi short-circuit current hi v()= 0v..2.8v 27 -8 -3.5 -1.7 ma ma
IC-WT incremental encoder rev a0, page 5/13 electrical characteristics operating conditions: vcc= 5v 10%, tj= -25..125 c, unless otherwise noted item symbol parameter conditions tj fig. unit c min. typ. max. push-pull outputs a, b, z (continued) 306 isc()lo short-circuit current lo v()= 1v..vcc 27 2 6 13 ma ma 307 vc()hi clamp voltage hi vc()hi= v()-vcc; i()= 4ma 0.4 1.5 v 308 vc()lo clamp voltage lo i()=-4ma -1.5 -0.4 v led current control, pins clr, ilr, iz, led 601 isum permissible total sensor current at dpa, dna, dpb, dnb isum= i(dpa)+i(dna) +i(dpb) +i(dnb); -1500 -50 na 602 i(led) permissible driver current in led 0.1 50 ma 603 vs(led) saturation voltage lo at led i(led)= 50ma, i(ilr)> 5 m a, isum= 0 27 0.4 0.8 1.2 v v 604 v(ilr) v(iz) voltage at ilr, iz i(ilr,iz)= -150..-5 m a 1.15 1.22 1.28 v 606 isc(ilr) isc(iz) short-circuit current in ilr, iz v(ilr)= 0, v(iz)= 0 27 -5 -2.4 ma ma 607 cr(ilr) current ratio i(ilr)/isum closed led control, isum= -800..-50na 80 100 125 608 cr(iz) current ratio i(iz)/i(dz) closed led control, i(dz)= -400..-10na 320 400 500 609 vc()hi clamp voltage hi at led, clr, ilr, iz vcc= 0v, i()= 1ma 0.4 1.0 v 610 vc()lo clamp voltage lo at led, clr, ilr, iz vcc= 0v, i()=-1ma -1.0 -0.4 v error detection, and gate select, input/output nerr 501 r(nerr) internal pull-up resistor 20 30 45 k w 502 vt()gate and gate turn-off threshold gate disabled if v(nerr)< 0.4v 27 0.4 0.5 1 v v 701 vs()lo saturation voltage lo i(nerr)= 1.6ma 27 0.15 0.4 v v 702 vs()lo saturation voltage lo i(nerr)= 5ma 27 0.25 0.8 v v 703 isc()lo short-circuit current lo v(nerr)= 2v..vcc 27 5 15 30 ma ma 704 vc()hi clamp voltage hi vc()hi= v(nerr)-vcc; nerr=hi, i(nerr)= 4ma 0.4 1.5 v 705 vc()lo clamp voltage lo nerr=lo, i(nerr)=-4ma -1.5 -0.4 v
IC-WT incremental encoder rev a0, page 6/13 applications information figure 1 illustrates the layout of the entire electronic system of an incremental rotary encoder. the devices ic-or (photodiodes array), IC-WT (incremental encoder) and ic-we (line driver) from ic-haus are used. the rotary encoder requires the supply voltages vcc= +5v and vb= +5v to +30v (line driver) and supplies the conditioned signals of tracks a and b and index track z at the outputs. it's possible to transmit these signals over directly connected lines of 100m length. the system's upper cut-off frequency is 500khz for track a/b. internal monitoring functions are available for the chip temperature of the line driver, for the supply voltages and for the led current control. the error port provides an error message signal which can be logically linked to other, external error signals by simple connection. fig. 1: incremental rotary encoder description of functions the photodiodes array ic-or comprises two diodes each for tracks a and b (differential evaluation) and one diode for track z (index pulse for constant-light evaluation) in the layout typical for an incremental encoder. a reference diode is not required since the threshold for the index signal is generated from the signals of tracks a and b. it is also possible to use the ic-haus device ic-ws or the siemens device kom 2100. the incremental encoder IC-WT evaluates the currents of the photodiodes and generates ttl-compatible information. the zero pulse is logically linked to the tracks a and b with an and operation. this operation can be cancelled for adjustment purposes by applying a low level to the error message output nerr (combined input and output). an integrated transmit-current drive circuit makes the adjustment to a constant summation photoelectric current at inputs a/b which is specified as the reference current at ilr by means of the external resistor rlr. the external capacitor clr stabilizes this adjustment. using a further reference current at iz which is set with rz it is possible to specify the constant-light evaluation threshold for the zero pulse at a controlled and, consequently, constant illuminance. with identical geometries and homogeneous illumination of all photodiodes, ilr and iz can operate on a common resistor. the resistor rled limits the maximum possible current through the led. the transmit-current control features an error detector which sets the output nerr to low (open collector) when the permissible working area is exited. the error message detector is activated, for example, in case of a defect of the led, when the code discs are dirty or steamed, or in the case of excessive influence of lights from an external source.
IC-WT incremental encoder rev a0, page 7/13 the line driver ic-we possesses short-circuit-proof push-pull output stages for the tracks a, b and z. the drivers typically supply 300ma at vb= 24v and are internally adapted for a characteristic impedance of 75 w . the outputs can be inverted via input inv (active-high). consequently, when two line drivers are used, a balanced activation of the line is also possible. tri-state switching of the output stages is possible to support bus systems (input tri). an error detector monitors the chip temperature as well as the supply voltages vcc and vb. in the event of a fault, the open-collector output ner is switched low and the output stages are switched to high impedance to prevent destruction. the error signal of the incremental encoder IC-WT can be switched through to the output ner via the error input tner. dimensioning adjusting the led current control since the photodiodes dpa to dna and dpb to dnb have anti-phase illumination, the following applies for the control parameter i sum as a function of the photocurrent peak value i ph,max. of a photodiode: i sum i ( dpa ) i ( dna ) i ( dpb ) i ( dnb ) 2 i ph , max multiplied by the current transmission factor of the led current control cr(ilr), the current to be set at ilr is (see electrical characteristics, no.607): i ilr i sum cr ( ilr ) 2 i ph ,max cr ( ilr ) this current can be set with a resistor r lr connected to agnd. due to the reference voltage v(ilr) being applied to pin ilr, this produces: r lr v ( ilr ) i ( ilr ) v ( ilr ) 2 i ph ,max cr ( ilr ) example: as a setpoint, the photodiodes should be illuminated so brightly that it conducts a photocurrent i ph,max = 400na at a maximum. with the electrical characteristics no.604 for v(ilr) and no.607 for cr(ilr) the result is: r lr 1.22 2 400 na 100 15.25 k w adjusting the index track comparator threshold the comparator threshold for the index signal is defined via a further reference current. the photocurrent i ph,max is also obtained as the maximum for the photodiode dz in the event of homogeneous illumination and same photodiodes for track a/b and track z. the maximum signal-to-noise ratio is attained with the constant-light evaluation threshold: i th i ph , max 2 analogue to the calculation of r lr , it follows that: i iz i th cr ( iz ) r z v ( iz ) i ( iz ) v ( iz ) i th cr ( iz ) example: as a setpoint, the threshold i th should be 200na. with the electrical characteristics no.604 for v(iz) and no.608 for cr(iz) the result is: r z 1.22 v 200 na 400 15.25 k w
IC-WT incremental encoder rev a0, page 8/13 if the current from ilr is the same as the current from iz, a common resistor with the value r lr,z =r lr /2=r z / 2 can be utilized (in the example, 15.25 k w / 2 = 7.625 k w ). ilr is connected directly to iz. limiting the current for the transmit led the resistance r led limits the maximum current through the led. it is calculated with the minimum forward voltage v fw,min of the led used for illumination, the minimum saturation voltage of the led pin vs(led) (electrical characteristics no.603) and the permissible transmit current for the driver output i(led) max (electrical characteristics no.602): r led vcc max v fw , min vs ( led ) min i ( led ) max example: r led = (5.5v - 1.2v - 0.4v) / 50ma = 78 w the lowest value for the current limiting is obtained by inserting the maximum saturation voltage of the led pin vs(led) max and the maximum led forward voltage v fw,max : i ( led ) lim 3 vcc min v fw , max vs ( led ) max r led example: i(led) lim = (4.5v - 1.5v - 1.2) / 78 w? 19ma the limiting value inserted for the saturation voltage vs(led) max of 1.2v is not achieved by currents under 50ma. the real minimum value for current limiting is therefore a little higher. capacitor at clr the value of capacitor c lr is not critical. the bottom of the permissible value range is restricted by the stability of control. the following applies: c lr , min 1 nf 15 k w r lr upwardly, the value is limited by the dead time t of the led current control after switching on the supply voltage: c lr , max 0.25 t r lr example: t = 100ms, r lr = 15k w :c lr,max = (0.25 100ms) / 15k w? 1.5 m f printed circuit board layout the following aspects should be noted when creating the pcb layout: - short connections between photodiodes array and IC-WT to minimize couplings and interference on the small photocurrents. - short-circuit the anodes of the photodiodes to pin agnd of the IC-WT. the connection to gnd is made exclusively inside the chip. - switch r lr ,r z ,c lr to agnd too. - do not run the printed conductors of the outputs of IC-WT and ic-we in the vicinity of the connections between photodiodes array and IC-WT or decouple by means of a gnd conductor between them. - connecting point of a metal reticle for the photodiodes array is gnd on the IC-WT.
IC-WT incremental encoder rev a0, page 9/13 demo board the demonstration board provides a survey over the properties of the IC-WT simply and easily. the encoder ic is already connected to the necessary external components. in addition, the board contains subunits which can be utilized to have measurements performed - even without a rotary encoder. figures 2 to 4 show the wiring as well as the top and bottom layout of the test pcb. fig. 2: schematic diagram of the demo board fig. 3: demo board (components side) fig. 4: demo board (solder dip side)
IC-WT incremental encoder rev a0, page 10/13 measurements with the demo board the IC-WT can be examined at three different levels: 1. static wiring of the sensor inputs with constant currents (using dip switches) 2. dynamic wiring of the sensor inputs using function generator and current mirror circuit 3. dynamic wiring of the sensor inputs using a rotary encoder with photodiodes array a regulated power supply of +5v dc must be applied between vcc and gnd for all measurements. since the IC-WT operates with very low sensor currents, the work surface should possess an insulated screen (e.g. a single sided copper-clad plate) which is connected to gnd. agnd is pulled down to gnd inside the IC-WT and should not be interconnected externally. the transmit led of the rotary encoder can be connected between led and vcc. for the visual check in case of measurements without rotary encoder a colored led is recommended. 1.1 static function of a, b and z shut off the and operation of index signal z with a and b by connecting the combined input/output nerr to ground; the red control led will light up. the two trimming potentiometers should be in the middle position initially, the dip switches opened. closing a dip switch of no.4 to no.8 connects the corresponding sensor input to agnd via a resistor (r4 to r8). since each input is at constant (but temperature-dependent!) voltage potential v(t), a constant current results of the magnitude: i= v(t) / r. the result at room temperature is about: i= 1.8v / 4.3m w = 420na this current is supposed to simulate the photocurrent of an illuminated photodiode. an open switch simulates a diode which is not illuminated (i= 0). the tracks a and b are evaluated differentially. the corresponding output is high (low) when current is only flowing from the p(ositive) (n(egative)) input. if the two inputs are conducting no current or the same current, the output remains in its old state due to hysteresis. track z is compared to a current threshold set using the trimmer rz. if the input current is higher, the output z is high. the current flowing from iz is specified with rz: i iz = v(iz) / rz the current threshold set is obtained with the aid of the current transmission factor cr(iz) as: i th = v(iz) / (cr(iz) rz) when the trimmer is at the middle setting, the following applies: i th = 1.22v / (400 12.5k w ) = 244na the resistance value set with rz can be measured after removing the jumper jz. 1.2 led current control and error output the function of the current control can be checked with an led connected between led and vcc. the voltage at nerr is displayed by the red led on the demo board. it lights up when nerr is active, i.e. low. the setpoint of the receive power is set at pin ilr by using trimmer rlr. the resistance value can be measured after removing the jumper jlr. the receive power is defined as the sum of the currents at the input pins dpa, dna, dpb and dnb. the setpoint i sum is: i sum = v(ilr) / (rlr cr(lr)) or: rlr= v(ilr) / (i sum cr(lr))
IC-WT incremental encoder rev a0, page 11/13 if two of the dip switches no.4 to no.7 are closed, the actual value of i sum is: i sum =2 420na = 840na, correspondingly, for the resistance rlr: rlr= 1.22v / (840na 100) = 14.5k w if the resistance set with the trimmer rlr is smaller, the result is a setpoint which is larger than the actual value. the control attempts to compensate for this by increasing the transmit led current. since the control loop is not closed, the control moves to the top stop and the transmit led lights up brightly. if the resistance set with the trimmer rlr is smaller, the result is a setpoint smaller than the actual value. the control attempts to compensate for this by reducing the transmit led current. since the control loop is not closed, the control moves to the bottom stop and the transmit led is extinguished. between these extremes is a linear range in which the transmit led is operated with a current proportional to the control difference. in this range the output nerr is moved to vcc potential via a pull-up resistor inside the ic and the error display is not lit. if the control is at a stop, nerr is low and the error led is lit. 1.3 and-operation of index track z with a and b the measuring set-up is identical to the one in 1.2. the led current control is set as the normal operating condition such that it operates in the linear range, i.e. nerr is high. the and-operation of index track z with a and b is now activated. with rz at the middle setting the output z can only be switch high via dip switch no.8 if a and b are also high (dip switches no.5 and 7 closed, 4 and 6 open). if a or b or both are low, the high state of z is only advanced to its output if the combined input/output nerr is connected to gnd (and gate disabled). this situation also exists if an error condition of the led current control exists. in actual operation this situation is insignificant, since the condition of tracks a and b are undefined anyway in the event of an error. 2.1 dynamic activation to check the dynamic operation, inputs must be stimulated with a function generator. tracks a and b are identical in construction, so only a and z have to be studied. the signal is injected for track a at the demo board via pin aca. a function generator connected between aca and agnd should generate a delta or sinusoidal signal of variable frequency. dip switches no.2 and 3 are closed, and no.4 and 5 are opened. via r3 the aca signal reaches a current mirror consisting of two npn transistors, ic2a and ic2e, which prepare the input signal for the differential activation. with v aca as the input voltage, the following applies for the current through r3 and consequently the current from dpa: i dpa =(v aca -v be )/r3 the result for the current from dna is: i dna =(v dna -v aca )/r2 with r2= r3, the input currents assume the same value for a symmetrical activation via v aca as the medium voltage between v dna and v be : v aca =(v dna +v be )/2 ? 1.16v i dpa = {(v dna +v be )/2-v be }/r3 ={v dna /2-v be /2}/r3 = {1.8 v/2- 0.52v / 2} / 3m w = 213na i dna ={v dna -(v dna +v be )/2}/r2 ={v dna /2-v be /2}/r2 = {1.8 v/2- 0.52v / 2} / 3m w = 213na
IC-WT incremental encoder rev a0, page 12/13 modulating aca around its mean value functions like a linear differential activation of the inputs dpa and dna. the modulation limits are v be and b dna . an appropriate rectangular signal can be picked off at output a with an oscilloscope. for a pulse duty factor of 1:1 it may be necessary to readjust the temperature-dependent medium voltage at aca. in addition, at high frequencies over 200khz the parasitic capacities of the test circuit affect the activation and thus the output signal. index track z can be measured by closed dip switch no.1 and opening no.8. the signal is injected via acz, r1 and the 1:1 current mirror ic2b, ic2d. the specifications for track a apply appropriately. the comparison threshold is set at rz (no differential activation). if the and operation is activated, outputs a and b must be high in order for output z to switch. 3.1 activation with rotary encoder the demonstration board can be activated by a rotary encoder with a photodiodes array. the connection between encoder and demo board can be made using a shielded cable. after the dip switch is removed, the plug supplied can be installed. figures 5 and 6 show the connection. fig. 5: connector configuration fig. 6: connecting a photodiodes array
IC-WT incremental encoder rev a0, page 13/13 ordering information type package order designation IC-WT wt demo board so16n IC-WT-so16n wt demo board for information about prices, terms of delivery, options for other case types, etc., please contact: ic-haus gmbh tel +49-6135-9292-0 am kuemmerling 18 fax +49-6135-9292-192 d-55294 bodenheim http://www.ichaus.com germany this specification is for a newly developed product. ic-haus therefore reserves the right to modify data without further notice. please contact us to ascertain the current data. the data specified is intended solely for the purpose of product description and is not to be deemed guaranteed in a legal sense. any claims for damage against us - regardless of the legal basis - are excluded unless we are guilty of premeditation or gross negligence. we do not assume any guarantee that the specified circuits or procedures are free of copyrights of third parties. copying - even as an excerpt - is only permitted with the approval of the publisher and precise reference to source.

▲Up To Search▲

Price & Availability of IC-WT

	To Download IC-WT Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .