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analog microelectronics, inc. 1 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs n n n n n key features l 100 m v resolution l high impedance differential inputs l differential reference l drive lcd directly l three new convenient features (ame811a only) l low-battery indication l integration status indication l de-integration status indication n n n n n applications l digital multimeter l ph meter l capacitance meter l thermometer l digital panel meter l photometer n n n n n general description the ame811 family are high performance, low power. 3-1/2 digit, dual-slope integrating a/d converters, with on-chip display drivers. the ame811 is designed for a single battery operated system, will drive non-multi- plexed lcd display directly. these a/d converters are inherently versatile and ac- curate. they are immune to the high noise environ- ments. the true differential high impedance inputs and differential reference are very useful for making ratiometric measurement, such as resistance, strain gauge and bridge transducers. the built-in auto-zero feature automatically corrects the system offset with- out any external adjustments. low-battery flag, integration and de-integration status flags are three additional features which are available in the 44-pin package, ame811ackw. n n n n n typical operating circuit * for the operating circuit of the reverse-pins version, please refer to pin configuration on page 4 and pin description on page 5 & 6. analog c ref+ v ref+ v ref- v ref c ref- in p u t in hi lcd display segment drive in lo pol bp v+ com minus sign backplane drive buf a/z int v ref fu ll scale in put 200.0mv 100.0m v to analog common (p32) v- osc osc 21 35 31 2-19 22-25 30 20 21 38 36 9v 33 26 40 39 20pf 10pf v+ v+ 32 28 29 27 34 1m 47k 24k 1k 0.01 0.1 0.47 0.22 20m 40khz 470k
analog microelectronics, inc. 2 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs n n n n n absolute maximum ratings ame811 static sensitive device. unused devices must be stored in the conductive material. protect device from static discharge and static field. stresses exceed the above absolute maximum ratings may cause permanent damage to the device. exposure to absolute maximum rating conditions for extended periods may affect the reliability of the device. n n n n n ordering information supply voltage (v+ to v-) 12v analog input voltage (either inputs) v+ to v- reference input voltage (either inputs) v+ to v- clock input test to v+ power dissipation 800mw operating temperature 0 o c to 70 o c storage temperature -55 o c to 150 o c lead temperature (soldering 60 seconds) 300 o c part number display marking package pin layout temp.range ame811cpl lcd ame811cpl yyww 40 pin pdip normal 0 o c to 70 o c AME811RCPL lcd AME811RCPL yyww 40 pin pdip reverse 0 o c to 70 o c ame8 1 1 ac kw l c d ame8 1 1ackw yyww 44 pin pqfp normal 0 o c to 70 o c
analog microelectronics, inc. 3 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs notes: 1. input voltage may exceed the supply voltages provided the input current is limited to 100 m a. 2. dissipation rating assumes a device is mounted with all leads soldered to printed circuit board. parameter conditions min typ max unit vin = 0v -0 w 0 +0 digital reading full-scale = 200.0mv ratiometric reading vin = vref = 100.0mv 999 999/1000 1000 digital reading roll-over error (difference in reading for equal positive and negative reading near full-scale) linearity (max. deviation from best straight line fit) common-mode vcm = 1v, vin =0v rejection ratio full-scale = 200.0mv noise (pk-pk value not vin = 0v exceeded 95% of time) full-scale = 200.0mv leakage current at input vin = 0v 1 10 pa zero reading drift vin = 0v, 0 o c to 70 o c0.21 m v/ o c analog common voltage 25k w between (with respect to v+) common and v+ temp. coeff. of analog 25k w between common (with respect to v+) common and v+ 0 o c m t a m 70 o c low battery flag v+ to v- 6.3 7.0 7.7 v test pin voltage with respect to v+ 4 5 6 v lcd segment drive voltage v+ to v- = 9v 4 5 6 v backplane drive voltage v+ to v- = 9v 4 5 6 v counts +1 0.2 -1 m v m v/v -1 0.2 +1 counts 50 v 50 75 ppm/ o c zero input reading 2.8 3 3.2 15 -vin = +vin ? 200.0mv full-scale = 200.0mv unless otherwise noted, ame811 is specified at ta = 25 o c, fclock = 48khz. supply voltage = 9v (v+ to v-) n n n n n electrical characteristics
analog microelectronics, inc. 4 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs n n n n n pin configurations
analog microelectronics, inc. 5 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs n n n n n pin description 40-pin dip 40-pin dip 44-pin pqfp symbol description pin number (reverse) pin number 1 (40) 8 hold hold pin, logic 1, holds display 2 (39) 9 d1 units-digit d-segment driver 3 (38) 10 c1 units-digit c-segment driver 4 (37) 11 b1 units-digit b-segment driver 5 (36) 12 a1 units-digit a-segment driver 6 (35) 13 f1 units-digit f-segment driver 7 (34) 14 g1 units-digit g-segment driver 8 (33) 15 e1 units-digit e-segment driver 9 (32) 16 d2 tens-digit d-segment driver 10 (31) 17 c2 tens-digit c-segment driver 11 (30) 18 b2 tens-digit b-segment driver 12 (29) 19 a2 tens-digit a-segment driver 13 (28) 20 f2 tens-digit f-segment driver 14 (27) 21 e2 tens-digit e-segment driver 15 (26) 22 d3 hundreds-digit d-segment driver 16 (25) 23 b3 hundreds-digit b-segment driver 17 (24) 24 f3 hundreds-digit f-segment driver 18 (23) 25 e3 hundreds-digit e-segment driver 19 (22) 26 ab4 thousands-digit, b&c segments driver 20 (21) 27 pol negative-polarity driver 21 (20) 28 bp lcd backplane driver 22 (19) 29 g3 hundreds-digit g-segment driver 23 (18) 30 a3 hundreds-digit a-segment driver 24 (17) 31 c3 hundreds-digit c-segment driver 25 (16) 32 g2 tens-digit g-segment driver w 33 lb low-battery flag segment driver 26 (15) 34 v- negative power supply voltage 27 (14) 35 int integrator output. connection point for integration capacitor. 28 (13) 36 buf integrator resistor connection-point. 29 (12) 37 a/z auto-zero capacitor connection-point 30 (11) 38 inlo analog-input low 31 (10) 39 inhi analog-input high 32 (9) 40 com analog-common 33 (8) 41 vref- analog-reference input, negative terminal
analog microelectronics, inc. 6 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs n n n n n pin description (cont.) n n n n n function description 40-pin dip 40-pin dip 44-pin pqfp symbol description pin number (reverse) pin number 34 (7) 42 cref- reference capacitor, negative terminal 35 (6) 43 cref+ reference capacitor, positive terminal 36 (5) 44 vref+ analog-reference input, positive terminal w 1 deen de-integration status flag w 2 inten integration status flag 37 (4) 3 test display-test pin, when pulled to v+, display should read -1888. 38 (3) 4 v+ positive supply voltage w 5 osc3 buffered osc1 39 (2) 6 ocs2 crystal oscillator output 40 (1) 7 ocs1 crystal oscillator input
analog microelectronics, inc. 7 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs the a/d conversion has the following three phases: 1. auto-zero phase 2. integration phase 3. de-integration phase auto-zero phase the inhi and inlo are shorted to analog common in- ternally. the reference capacitor is charged to the ref- erence voltage. a feedback loop is closed around the system to cancel the offset voltage of buffer, integrator and comparator. signal integration phase the converter integrates the differential voltage across the inhi and inlo for a fixed time, 1000 system clocks. the polarity of the signal is determined at the end of this phase. reference integration phase inlo is internally connected to the analog common, inhi is connected across the reference capacitor with appropriate polarity determined by the control circuit. the integrator output will then return to zero. the time it takes to return to zero, 1000 x vin /vref, is the digi- tal representation of the analog signal. differential signal inputs (inhi & inlo) the ame811 has true differential inputs and accepts input signals within the input common mode voltage range (vcm). typical range is from 1v above the v- to 1v below the v+. the integrator output can swing within 0.3 v of v+ or v- without increasing linearity errors. care must be exercised to make sure the integrator output does not saturate. in a typical application, the common mode is eliminated by connecting the inlo to com, analog common. differential reference (vref+ & vref-) the reference voltage can be generated anywhere within the v+ to v-. under a large common mode volt- age, reference capacitor can gain charge during the de-integration of a positive signal. the reference ca- pacitor will lose charge when de-integrating a negative input signal. the difference in reference voltage for positive or negative input voltages can cause the rollover error. to prevent rollover error from being in- duced by large common-mode voltages, reference ca- pacitor should be large compared to stray node capaci- tance. analog common (com) the analog common is to set a common mode volt- age for the analog signal. the analog common is typi- cally 3.0v below v+, set primary for the battery oper- ated application. analog common is capable to sink 20 ma. its source current is limited to 10 m a. analog common is therefore easily pulled to a more negative voltage to override the internal reference. when sup- ply voltage is greater than 7v, analog common can be used as reference source with temperature coefficient of typically 50 ppm/ o c.
analog microelectronics, inc. 8 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs n n n n n digital block diagrams
analog microelectronics, inc. 9 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs n n n n n digital section digital ground ame811 generates an internal digital ground, typically 5v below the v+. clock circuit the clock can be generated in either of the following three methods. 1. an external oscillator connected to osc1 2. a crystal between pins osc1 and osc2 3. a r-c oscillator using osc1, osc2 and osc3 notes: there is no on-chip feedback resister across osc1 and osc2. systems timing the oscillator frequency is divided by 4 prior to clock- ing the internal decade counters. each conversion takes 4000 counts or 16000 oscillator clock pulses. the timing of each phase are as follows: for signals less than full-scale, the unused reference integration time is assigned to the autozero phase. segment drivers the backplane frequency is 1/800 of the oscillator clock frequency. for example if the oscillator frequency is 48 khz (3 conversions per second) the backplane fre- quency will be 60 hz. the segment and backplane are at the same frequency with a nominal 5 volt amplitude. the segment is visible (on) when the segment and the backplane are out of phase, otherwise it is invisible (off). the polarity segment is on for negative ana- log inputs. when the test pin on the ame811 is pulled to v+, all segments are turned on. the display reads -1888. during this mode the lcd segments have a constant dc voltage impressed. do not leave the display in this mode for more than sev- eral minutes! lcd displays may be destroyed if operated with dc levels for extended periods. auto-zero phase: 1000 to 3000 counts signal integration phase: 1000 counts (fixed) reference integration phase : 0 to 2000 counts
analog microelectronics, inc. 10 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs test when the test is pulled to v+ all segments and the minus sign will be activated. the test pin is tied to the internally generated digital ground through a 500 w resistor in the ame811. it is typically 5v lower than v+. test pin may be used as the negative power supply for external cmos logic at the maximum current of 1 ma. data hold when the hold pin is connected to v+ the conversion result will not be updated. the conversion is still free running during the hold mode. integration status (inten) the inten is an output signal of the converter, it is high during the signal integration phase. this signal can be used as a status indicator or a control to con- nect the analog signal to the converter for processing. it is available in 44 pin package. de-integration status (deen) the deen is an output signal of the converter, it is high during the reference de-integration phase. the period of the deen is proportional to the conversion result. users may calculate the conversion result by counting the number of clock pulse on the osc3 pin when deen is high. the conversion result is equal to (n /4) - 1/2 where n is the number of the pulse at the osc3 pin. it is available in 44 pin package. n n n n n component value selection auto-zero capacitor (caz) the caz capacitor size has some influence on system noise. a 0.47 m f capacitor is recommended for 200 mv full-scale applications. a 0.047 m f capacitor is rec- ommended for 2.0v full-scale applications. a mylar dielectric capacitor is adequate. reference capacitor (cref) a 0.1 m f capacitor is acceptable when inlo is tied to analog common. if a large common-mode voltage exists and the application requires 200 mv full-scale, increase cref to 1.0 m f. a mylar dielectric capacitor is adequate.
analog microelectronics, inc. 11 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs integrating capacitor (cint) cint should be selected to maximize the integrator out- put voltage swing without causing output saturation. a 2v full-scale integrator output swing is recommended if analog common is used as signal reference. for 3 readings/second (fosc = 48 khz) a 0.22 m f value is suggested. if a different oscillator frequency is used, cint must be changed in inverse proportion to maintain the nominal 2v integrator swing. an exact expres- sion for cint is: cint = [(4000)(1/fosc)(vfs/rint)] / vint where: fosc= oscillator clock frequency vfs = full-scale input voltage rint = integrating resistor vint = desired full-scale integrator output swing cint must have low dielectric absorption to minimize rollover error. a polypropylene capacitor is recom- mended. integrating resistor (rint) the input buffer amplifier and integrator both have a class a output stage with 100 m a quiescent current. the integrator and buffer can supply 20 m a drive cur- rents with negligible linearity errors. rint is chosen to keep the output stage in the linear region. for a 200mv full-scale, it is 47k w ; 2.0v full-scale requires 470k w . summary of component selection: note: fosc = 48 khz oscillator components r-c oscillator a 100 k w rosc is recommended for all frequencies. cosc is selected by using the equation: fosc = 0.45/(rc) for fosc of 48khz, cosc is 100pf nominally. to achieve maximum line noise rejection, the signal- integrate period should be a multiple of line period. the optimum oscillator frequencies for 60 hz and 50 hz rejection are listed as follows: for 60 hz rejection: 40khz, 48khz, 60khz etc. for 50 hz rejection: 40khz, 50khz, 66-2/3khz etc. reference voltage selection a full-scale reading (2000 counts) requires the input signal be twice the reference voltage. in some applications a scale factor other than unity may exist between a transducer output voltage and the re- quired digital reading. assume, for example, a pres- sure transducer output is 600 mv for 2000 ib/in 2 . rather than dividing the input voltage by three the reference voltage should be set to 300 mv. this permits the trans- ducer input to be used directly. the integrator resistor would be 120k w . in some temperature and weighting system with variable tare, the offset reading can be generated by connecting the voltage transducer be- tween inhi and common and the variable offset volt- age between common and inlo. low battery flag (lb) the low battery flag is set when the supply voltage (v+ to v-) is lower than seven volts, typical. once the lb is set, the waveform of the lb will be out of phase with the bp (back plane) to turn on a low battery annuncia- tor for ame811. full sca le 200.0m v 2.000v caz 0.47 m f 0.047 m f rint 47 k w 470 k w cint 0.22 m f 0.22 m f v ref 100.0m v 1.000v full-scale voltage vref 200.0 m v 100.0 m v 2.000 v 1.000 v
analog microelectronics, inc. 12 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs n n n n n typical applications
analog microelectronics, inc. 13 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs
analog microelectronics, inc. 14 ame811/ame811a/ame811r 3-1/2 digit a/d converter - low power with hold and differential reference inputs
life support policy: these products of analog microelectronics, inc. are not authorized for use as critical components in life- support devices or systems, without the express written approval of the president of analog microelectronics, inc. analog microelectronics, inc. reserves the right to make changes in the circuitry and specifications of its devices and advises its customers to obtain the latest version of relevant information. ? analog microelectronics, inc. , july 2001 document: 1021-duc-b-0704 corporate headquarters asia pacific headquarters analog microelectronics, inc. ame, inc. 3100 de la cruz blvd. suite 201 2f, 187 kang chien road, nei-hu district santa clara, ca. 95054-2046 taipei 114, taiwan, r.o.c. tel : (408) 988-2388 tel : 886 2 2627-8687 fax: (408) 988-2489 fax : 886 2 2659-2989 www.analogmicro.com e-mail: info@analogmicro.com

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