M761E

M761E STMICROELECTRONICS | Alldatasheet

Document overview

• Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
• PDF pages: 9

Technical content

{77 SGS-THOMsON MICROELECTRONICS M761E DUAL TONE MULTIFREQUENCY GENERATOR = 2.4 TO 4V SUPPLY RANGE = VERY LOW POWER CONSUMPTION = ON-CHIP CRYSTAL CONTROLLED OSCILLA- TOR (fo = 4.433619 MHz) WITH INTEGRATED FEEDBACK RESISTOR AND LOAD CAPACI- TORS : = LOW HARMONIC DISTORTION ( < 2 %) i pipis = FIXED PRE-EMPHASIS ON HIGH-GROUP 1 iatus, TONES 1 af « FAST START-UP TIME = LOW POWER CONSUMPTION IN STANDBY MODE » MUTE OUTPUT » ONE CONTACT PER KEY ORDER CODE :M761EBt DESCRIPTION The M761 can be interfaced with the speech circuit The M761 provides all the tone frequency pairs re-_ family LS156, LS356, LS656 with MF interface avoi- quired for a DTMF Dialling System. Tones are ob- —_ding the need of the common spring set. tained from an inexpensive TV crystall (fo = — The M761 utilizes low voltage CMOS technology

4.433619 MHz) followed by two independent pro- and is available in 18 pin dual in-line plastic

grammable dividers. The dividing ratio is controlled package. by the selected key. Keyboard format is 4 rows x 4 columns and a key is valid when a column and a row are connected together. PIN CONNECTION (top view) Intemal logic prevents the transmission of illegal tones when more than one key is pressed. If no key is selected the oscillator tums off and the linear parts are strobed to decrease the total power consump- : wD) Yoo tion. ose. q: wf) Fuser w As any buttomis pressed row and column inputs are _ scanned internally, to identity the activated ones. aff ssf) Fuser our | Electrically, row and column inputs are activated on | high level voltage couuns | 7H! ssf) mure out | Single tone output cannot be emitted by a "1" an a CS) | "row or column only. For single tone emission see cals safe “Single tone procedure”. “f I ows _ Adebounce output is available to indicate that a key Ne vee | has been selected. D/A conversion is accomplished wren our ffe wife by a capacitive network allowing very low power | consumption, very low distortion and an exceptional Yes le wo) our ee stability of tone level against temperature variations. ow |The tones are mixed in a resistive network ; a unity gain amplifier is provided to realize a two pole ac- | tie fiter with only four external passive compo- nents. November 1988 a) | ar

. [4 = Sihymoene kan | comes wos’ | — ABSOLUTE MAXIMUM RATINGS [Symboi] Parameter Value Unit Supply Voltage = 05 to +55 Input Voltage = 03 to Voo + 05 [Ber Power Dispaion oo Storage Temperature Range THERMAL DATA [Rin-am» | Thermal Resistance Junction-ambient Max [00s | so yy SessTHomson

ELECTRICAL CHARACTERISTICS (all parameters are tested at Tams = 25 °C) Test Conditions ee ed DC CHARACTERISTICS Voo Voltage Supply Vv suph Voltage PPly fino Operating Supply | Voo = 24 V mA Current Ippo Stand-by Supply Vooo = 2.55 V mA Current [Input Votage teves | TTT Vin Logical "1" 80 % of v Row and (Vo0-Vss) Column inputs|Vi, Logical "0" Ves | 20%of | V =03V | (Voo-Vss) Cin Input Capacitance Any 75 Pin Iw High Levei Input Von =25V Vw =25V 1 WA Current T._Low Level input Vo =25V Vi =0V HA | Oscillator Current [on High Level Oust [Von =28V Von =v |-100] -s00 | | | : lo. Low Level Output Voo=25V Vor =05V pA Current Digt. [lor Low Level Output | Voo=25V Vor =1V nA Freq. Current Outp. (open drain output) Vo Output DC Voltage | Vo = 25 V mv Without Tones Vo Output DC + AC Voo = 25 V (see note 2) 0.84 Vv Voltage with (see fg. 1)

2 Tones 1

| Ton Output Orve Gureni_[Vou=@8V Vou =18v [100] |_| wr | Notes : 1, This dovico has boon designed tobe connected othe DTMF interface of the speech crcuit family LS156, LS356, LSB56 rom which ittakes a Voo = 2.4 V min. Therefore many parameters are tested at this value. 2. Tho value of DC output component at two diferent conditons of supply voltage, wth two tones activated, can be related as follows Voo'= Voe ~. 3. The value of AC output components (Vir, Vie) at two different conditions of supply voltages can be related as follows Vr= Ve a Vie = Var ze oo oo | ‘The values are measured with two tone at the output Fe scs-tosson SY7 machomscraomics

ELECTRICAL CHARACTERISTICS (all parameters are tested at Tams = 25 °C) Test Conditions ee ee AC CHARACTERISTICS Re Feedback Oscillator Resistance Gi Input Capacitance 95 to Voo Co Output Capacitance 105, pF to Voo Zo: Output Dynamic Von =25V Ka Impedance with

2 Tones

Zo2 Output Dynamic Voo =25V Filter Impedance with AF Max. Oulput Tone | At Crystal Frequency F Derivation from f= 4.433619 MHZ Standard Rt 697 Hz +05 | % R2 770 Hz -02 | % RO 852 Hz +05 | % Ra 941 Hz -08 | % Ct 1209 Hz +06 | % G2 1396 Hz -04 | % C3 1477 Hz -03 % C4 1633 Hz +t | % Vir Low Frequency Tones | Von =25V (see note 3) | 124 mVee Amplitude at Filter Out (see fig. 2) Vur High Frequency Tones| Von =25V (see note 3) | 157 187 | mVpp Amplitude at Filter Out (see fig. 2) Tone ogt——Prvemphasis [es |e rs | oe | (Characteristics wanted Frequency Components at f =3.4 KHz dBm at f =50 KHz dBm Total Harminic Vop =25V % Distortion for a Single Frequency ts Start-up Time Vo + 25V (see fig. 4) (see fig. 5) t; Supply Voltage Rise |Vop = 25V Time Notes : 1. This device has been designed to be connected the DTMF interface of he speech crcultfamily LS 186, L S356, L S656 rom which itakes a Vio = 24 V min, Therfore many parameters are tasted ats valu 2. The value of DC output component at two different conditions of supply voltage, with two tones activated, can be related as toiows Voo= Voc Ye Voo 3. The value of AC output component (Vir, Vie) at wo dtferent conditions of supply voages canbe relatod as flows Vien Vir Ym. Var = Vie M00. Voo Voo “The values are measured with two tone atthe output — k SGS-THOMSON —0 7 iaicromncrromcs

OSCILLATOR (OSC. IN - OSC. OUT) is switched off and the current consumption is redu- The oscillator circuit has been designed to work C24 to 2/3 of the initial value. with a4,433619 MHz crystal ensuringbothfaststart- Feedback resistance and load capacitances are in- up time and low current consumption. tegrated on the chip ensuring good temperature per- _ When Voo is applied and a key is activated two in- formance. verters are paralleled (see fig. below) to decrease —_ when the device is supplied but no key is activated, the total ron resistance. the oscillator is in the stand-by mode to minimize po- After oscillations have started one of the two buffers. wer consumption. Yoo Yoo 1 of scm T ose.out toon oon, THREE, STATE TNPU s-3008 _ KEYBOARD INPUTS MIXER OUTPUT (C1, C2, C3, C4- Rt, R2, R3, R4) The two reconstructed sine waves are buffered then Each keyboard input has an intemal protection cir-___mixedin a resistive array network that also restores ~ cuit ; when a button is pressed, the oscillator starts the DC output level. and dynamic scanning of keyboard is realised. This allows to the detection of which button has been pressed. When two or more column or row inputs are activa- ororrat ted no tone is generated. FREQUENCY 7 9 J ourpur DIGITAL FREQUENCY OUTPUT a This output is intended for testing only ; when a sin- 53-3006 gle tone is activated, at this output is available a di- Gital signal whose frequency is 16 times the selected output tone frequency. This output is an open col- lector N-channel transistor. Yoo Yoo Yoo Yoo poKn 20K. iF ANALOGUE Hi UI LE ANALOGUE TW ch, : INPUT | 20K WKN 1OKN 20Kn SY micnosscraomcs

FILTER (Filter Input, Filter Output) The following values are suggested : A unity gain amplifier is available to realize atwo = R1= S6KQ42% pole active filter (see fig. below). The output of this R2= 33KQ+2% amplifier is held low untitones are valid, itthanrises C1 = 2.2 nF +10 % to about 0.85 V at Voo = 2.5 V. 2 = 0.56 nF + 10% T it hi ‘ones are superimposed on tis DC. MuTE ouTPUT The output DC component is very precise and sta- ble to allow DC coupling with the LS156 speech cir- Mute output becomes active when a key is activa cuit with MF interface. ted eliminating keyboard bounces and remains ac The output dynamic impedance ofthe fiteris about We forall the duration of tone transmission, 25 Ka. If the key is released before the oscillator produces the correct control signals, mute output is disabled y SINGLE TONE PROCEDURE

50 This is accomplished through the following steps :

15kO 1) Activate simultaneously R1, R4, C1, C4 inputs appling logic 1'S. This implies the use of logic le vel sources. The single contact keyboard does not allow this procedure. 2) The device enters the "test mode" Now any sin ~ gle row or column frequency (or both) can be S-3808 activated at output applying logic "1" to corres: pondant input (inputs). The following equivalent circuit should be applied _ 3) To get out from “test mode" reply Rt, R4, C1, C4 during fiter design : activation or power otf/power on. A ona as {mp PRTEMIMPUT asKn fi = Aut itis evident that 1 and R2 should be kept high to —o4__. avoid undue influence of Mixer and Filter output im- pedances. 8/9 G77 SSS:THOMSON SY/ imcromscraowics

Figure 3: THD Measurement Test Set. vy | rs po ! FY | ' | ! 1 a tN PEAK D.U.T. o b> v > i F2 i DETECTOR our s-a80mn High pass fiters characteristics : F1 :fo= 1400 Hz 100 dBidec F2 f= 2500 Hz 100 dB/dec THD measurement is made by sensing the level of harmonic components after suppression of the fundamental. ‘Two different high pass fiters are used for low and high frequency tones. Figure 4 : Start-up time Measurement Test Set. Figure 5 : Start-up time Definition. wv FROM TEST MACHINE amA FROM ama TEST ~ - ~~~ i MACHINE ¢ Lama 00 4IV. Out. Me

0.1 F [oun | our

oo {jj SGs-THomson mu ‘Y/ facromscrmomcs

Figure 6 : M761 appiication circuit with electronic speech circuit. il oa. st fo Ve |i an fs fo i ‘23, ‘ah cf 2 o- 2 “ le « es . ‘| : ie r . s os 32 = a i } | Mm alt | E| Ed Bs ” S|} | gees ene n | TT | (<Te[eTo} iofoto [at Occ Els]-[¢}— | — | pe 2 2 | \\ | ‘SGS-THOMSON 89 i SSS