austriamicrosystems AG is now ams AG The technical content of this austriamicrosystems application note is still valid. Contact information: Headquarters: ams AG Tobelbaderstrasse 30 8141 Unterpremstaetten, Austria Tel: +43 (0) 3136 500 0 e-Mail: [email protected] Please visit our website at www.ams.com Application note AN533 AN533 AS2533…6 Single Chip Telephone Demoboard PRELIMINARY APPLICATION NOTE • Receive volume reset to default volume after off-hook (AS2533,AS2535) • Key Features • Receive volume remains at last setting after off-hook (AS2534B,AS2536) 4 direct memories, 10 indirect memories (AS2533,AS2536) • • Versatile applications, same chip for all countries in the world Easily adaptable for different PTT demands • Same board layout for every country • Very few external low cost components • • CMOS technology, far less sensitive to EMC EN55024 (electromagnetic irradiation) approved • Side Tone and Return Loss adjustable independent of each other • Real and complex AC impedance programmable by one resistor and one capacitor Sidetone programmable by two resistors and one capacitor • • 12 direct memories (AS2535) • Centrex (ABCD) keys (AS2533, AS2534B,AS2536) • Tone / Pulse switch (AS2533, AS2534B,AS2536) Modular connectors for handset and line cord, line connector a/b- terminals selectable by jumper • lv High performance telephone with speech circuit, DTMF/Pulse dialer and tone ringer am lc s on A te G nt st il • • • Overvoltage & overcurrent protection installed Several hook transistor options • Layout prepared for metering pulses blocking filter • 32-key SPST Keyboard on board Applications DTMF level adjustable by two resistors (voltage divider) feature telephones • Ringer volume and melody programmable by keypad • • Ring frequency discrimination Different dialing modes selectable by jumper PTT spec conformity • Line loss compensation selectable by jumper • Different flash timings selectable by 3 flash keys • • 31-digit last number redial Sliding cursor protocol and pause key • Pacifier tone and flashing LED during programming and mute • One-touch repeat dialing (AS2533, AS2534B,AS2536) Receive volume control by either one toggle or two volume +/- keys (AS2533, AS2535.AS2536) The application notes hereafter should be understood as guidelines for other designs based on the AS253x circuit. No guarantee can be given for completeness or full conformity to PTT specification requirements. As requirements differ from country to country, each required parameter must be individually tested and adjusted, if necessary. Further guidelines for adjustment is given in the documents, listed in cpt.Other applicable documents and papers. Te ch ni ca • • al id This application note describes the use of the Single Chip Telephone IC´s AS2533...6, based on the multi standard demo board DB533. Revision D01 Page 1 of 16 Application note AN533 Data Sheet AS2533/4B/5/6: Multi-Standard CMOS Single Chip Telephone IC with Dual Soft Clipping • „Speakerphone“ with 8Ω loudspeaker amplifier: AN2202 SCT with on-hook-dialing, loudhearing and music-onhold with auto-release: AN2203 • Keyboard entry via microcontroller: Application Note AN3010 • SCT: Power extraction for external loads: AN3020 • SCT: Using dynamic microphone as tone ringer: AN3021 • Application Notes AN500-1: PSTN Telephone & Line Interface ICs basics AMS PSTN Telephone & Line Interface ICs Basics The AN500-1 application note covers all the basics, which are common to all AMS PSTN telephone and line interface bases ICs. It covers the following parameters and features: Synthesising the AC impedance Calculation of the total AC impedance • Generating the DC characteristics • • Calculation of the total DC drop Sidetone cancellation • Interdependence of return loss and sidetone cancellation Transmitting and receiving frequency shaping ca • • • ni • Hook switch transistor options For all the above information, please refer to application note AN500-1 Further Applications Te ch Applications based on the AS2533...6 are continuously updated. Ask your local distributor or Austria Mikro Systeme sales office for the latest revisions or visit our home-page: http: //www.austriamicrosystems.com Revision D01 Rev.: D01 Rev.: D01 Rev.: D01 Revision history: Rev. D01 is the first issue of AN533. It is based on the previous application note AN2201, with excluded common features, which are now covered by AN500-1. The application note AN2201 was the documentation for the previos demoboard revision DB2201 B01. The now available demo-kit DB533 contains the following parts: AS2533…6 Single Chip Telephone demoboard with handset, application note and AS2533…6 datasheet. am lc s on A te G nt st il • AN533 Application Note (this document): DB533 Demo Board Schematic DB533 Demo Board Layout al id • Revision status lv Other applicable documents and papers General description The AS253x family was developed to provide a multistandard “plug & play” solution for POTs, emphasizing high performance voice transmission and reception. In spite of the fact that voice transmission and reception are the most vital features in telephony, they are very often ignored or given lower priority compared with some more or less useless non-voice features. No compromises were accepted during the design phase of the AS253x speech circuit which supersedes even the hardest PTT requirements worldwide. The dialer part is based on a long history of producing a wide range of dialer circuits with user-friendly features in compliance with various national PTT regulations. This knowledge enabled us to develop a multi-standard dialer circuit compatible to all PSTN and PABX systems worldwide which became an important part of the AS253x. The last piece in the puzzle to complete the full picture of the first CMOS single chip POT was the tone ringer. A ring frequency discrimination circuit was implemented to avoid false “bell-tinkle” during pulse dialing from a parallel telephone. The 3-tone melody generator is userprogrammable via the keyboard providing different ringer melodies and levels. Note: all the subsequent component numbering is referenced to the AN2201 schematic, shown in pt. XXX Page 2 of 16 Application note AN533 Demo board configuration The AS253x family is the rare combination of advanced technology and down-to-earth simplicity providing easy and uncomplicated design effort for the telephone manufacturer. No fussing around: Simply go by the straight forward guidelines supplied by the highly experienced AMS application group. No technology stress but appealing functionality. See Fig. 1 for configuration locations: J6: line loss compensation J12,J13: line onnector al id selector a/b terminal selector 6pin modular phone R11,R12,C5: line connector side tone network P1: DTMF lv 4pin modular level adjust handset connector am lc s on A te G nt st il mute/program LED J3: dial mode selector Fig. 1: Demo board configuration ca Setting a/b line connection outer two pins (optional) A handset connected at Z2 should have the following connections: ch ni inner two pins (default) Connecting a handset Te J12,J13 allow selection of a/b line terminals to easily adapt the demo board to various PTT line connections: Revision D01 remark: observe polarity of the electret microphone Page 3 of 16 Application note AN533 Setting AC impedance al id Line loss compensation = line current dependent gain setting of Tx and Rx amplifiers can be set by jumper setting to 3 different modes : high, low and no LLC (=default). Please refer to AS2533...6 data sheet for exact values The default setting on the demo board is 600Ω AC impedance. Please refer to AN 500 for changing the AC impedance of the board. am lc s on A te G nt st il By J3, a selection of 7 different dialing modes can be made, 5 pulse (=LD) dialing modes and 2 DTMF dialing modes. 10,20 pps = 10 or 20 pulses per second 33/66 = make/break ratio 1:2 40/60 = make/break ratio 2:3 MF 82/82ms = DTMF; 82ms tone, 82ms inter digit pause (default setting) MF 82/164ms = DTMF; 82ms tone, 164ms inter digit pause if none of the 7 dialing modes is selected, the keyboard is disabled Setting line loss compensation (AGC) lv Setting dialing mode When switching to temporary MF by pressing the *-key all entries following the *-key will be dialed out as DTMF tones, as long as the temporary MF state is not terminated. Mode 5 (LD 10pps 33/66 temp. MF) however, will also immediately send the DTMF-tone for the *-key invoking the temporary MF mode (=PTT requirement in France). ca Setting DTMF level Te ch ni DTMF level is set by a DC voltage at Pin #2 = MFL. This voltage is usually set by a voltage divider, connected from AGND to V SS . To allow easy setting of the full DTMF level range on the Demoboard, the voltage divider is replaced by a potentiometer. The DTMF level is increased by clockwise turn. Please refer to AS2533...6 data sheet for exact levels. Revision D01 Description of keyboard functions The user-friendly operating procedures comply with different PSTN and PABX systems worldwide. By choosing between the total of 32 keys it is possible to fit the AS253x into any telephone design. The keyboard is connected to 8 pins of the AS253x (C1...C4, R1...R4) by a n*m SPST keyboard matrix. To double the number of rows, 4 diodes (D8..D11) are added. This arrangement allows detection of 32 keys on a 4*8 matrix. Three groups of keyboard functions (AS2533=AS2536, AS2534B, AS2535) are available. They differ in the functions for the keys connected at rows 6..8 (number of direct/indirect memories) , while the connection of rows 1..5 (number keys, P/M key, flash, LNR and Volume keys) remains the same. This configuration allows easy upgrade/downgrade of a telephone family set by just changing the IC type and function key lettering without a need to change the PCB ! Numeric keys The numeric keys (1..0,*,#) are standard number dial keys for both DTMF and pulse dialing (* and # only DTMF). Additionally the *-key can be used for temporary MF switching. Page 4 of 16 Application note AN533 Program/Mute key (P/M) Repeat dialing (RP) The P/M key is used to enter the Program/Mute state. Depressing the P/M key mutes the speech circuit and the device is in the programming state, indicated by the flashing LED (connected at pin #22) . To exit the P/M state, press the key again (LED switches off). Remark: the LED will also switch off, when an invalid key sequence is entered. This error-condition is also indicated by an error-message (tone sequence) in the earpiece. AS2533, AS2534B, AS2536 Pause key (PS) AS2533, AS2534B, AS2536 Tone / Pulse switching (T/P) am lc s on A te G nt st il Flash timing is selected by choosing one of the 3 flash keys :R1=100ms, R2=270ms and R3=600ms. This key is to insert a pause in a digit string when programming memories. See Sliding cursor protocol and pause insertion for programming procedures. lv Flash keys (R1,R2,R3) al id The last dialed number can be repeated without manually going on-hook by pressing the RP key. If ,for example, a called number is engaged, pressing the RP key will break the line (= t rp =1.6 sec., to get a new dial tone) and after a pause (=t ap = 2.05sec) the number will be repeated. Last number redial key (LNR) The last number redial facility allows redialing of the last manually entered number by one keystroke. LNR is repeatable after each off-hook. The LNR key also supports the sliding cursor protocol to allow convenient redialing with PABX systems. Volume keys (VOL, Vol+, Vol-) Volume control of the receive channel can be chosen as a one-key toggle function (VOL key toggles between 0 / +5.4 dB) or a two-key up/down function (VOL+, VOL- keys allow 5.4......+8.1dB range of receive volume setting) When any of the LD dialing modes is selected (see cpt.Setting dialing mode), a switch to temporary MF can be performed by either pressing the *-key to get into DTMF mode and one of the flash (R)-keys to get back to pulse dialing or using the T/P key as a toggle function to switch back and forth between pulse dialing and (temporary) MF. Remark: temporary MF and Tone/Pulse switching respectively, can only be activated, when the initial dialing mode selected by J3 (see cpt.Setting dialing mode) is one of the 5 pulse dialing modes. M.. and MR keys AS2533, AS2535, AS2536 Keys M1...M12 are direct memory keys and key MR is for invoking one of the 10 indirect memories (MR 1 .... MR0; AS2533 only). ni ca After off-hook, the volume is reset to 0dB for the AS2533 and AS2535, while it remains at the last setting for the AS2534B and AS2536. AS2533, AS2534B, AS2536 Centrex keys (ABCD) ch AS2533, AS2534B, AS2536 Te The alphanumeric keys accommodate easy use of Centrex services. They are only valid in DTMF mode and cannot be stored. Revision D01 Page 5 of 16 Application note AN533 Summary of AS2533...6 keyboard functions direct memories (1-key) indirect memories (2-key) sum of storable numbers Program / mute key 3 flash keys LNR key VOL keys Vol. setting after off-hook Centrex keys Repeat dialing Pause key T/P key 4 10 14 yes yes yes yes reset yes yes yes yes AS2536 last setting AS2534B AS2535 0 0 0 yes yes yes no last setting yes yes yes yes 12 0 12 yes yes yes yes reset no no no (pause with LNR) no (temp MF with * and R) al id AS2533 lv function keys: AS2533/6 am lc s on A te G nt st il The AS2533...6 family is a set of pin-to-pin compatible IC´s, the only difference is the amount of Repertory memories and some extra functions invoked by keyboard: AS2534B A RP M2 LNR A RP Vol B PS M3 Vol B PS + C T/P M4 + C T/P - D M1 MR - D ca LNR Te ch ni By default, the DB2201 demo board is delivered with an AS2533 installed and the key functions are according to that chip. If AS2534 or AS2535 chips are installed, the key lettering of Rows 5..8 can be changed by replacing the key cap label (simply click off the transparent cover) with the following symbols: Revision D01 AS2535 LNR M1 M5 M9 Vol M2 M6 M10 + M3 M7 M11 - M4 M8 M12 Page 6 of 16 Application note AN533 Programming procedures al id These procedures are also described in the AS2533/4B/5/6 data sheet, below is a quick reference for storing numbers and ringer melody/volume (bold letters indicate keys to be pressed): Programming direct memories P/M --- Mx*) --- Enter number**) --- P/M lv Programming indirect memories P/M --- MR ---n***) --- Enter number**) --- P/M Mx = one of the direct memory keys: M1......M12 valid keys are: 1,2,3,4,5,6,7,8,9,0,*,#,PS,LNR(=pause),R1,R2,R3, maximum length = 21 digits n: indirect memory locations are 1,2,3,4,5,6,7,8,9 or 0 am lc s on A te G nt st il *) **) ***) Programming ringer melody / volume Ringer melody and volume can be programmed for 3 different repetition rates (=melodies) and 3 different volumes per melody: P/M --- # --- code*) --- P/M *) if the telephone is connected to the PTT line for the first time or after V DD has been completely discharged, the ringer melody/volume is set to default (=code 6) , therefore re-programming of the ringer is only necessary, if a setting other than the default setting is desired. Melody codes: -16dB (min Vol) -7dB 0dB (max Vol) Repetition rate = 1 (slow) 1 2 3 Repetition rate = 4 4 5 6 (default) 7 8 9 Repetition rate = 10 (fast) ringer off**) ca 0 Te ch ni **) when code=0 is selected, the ringer is off until next off-hook, where the ringer melody/volume is reset to the last programmed code prior to code 0. Revision D01 Page 7 of 16 Application note AN533 ≈1.2V. The POR will: • • clear all memories clear the last number redial (LNR) • reset the ringer melody to default (Code 6) • reset the Rx volume to default (middle) P/M --- M1 --- 0 1 PS 2 3 4 5 6 --- P/M P/M --- M1 --- 0 1 LNR 2 3 4 5 6 --- P/M or example2: dial up- services: desired (service) number 1-800-1234567, after request from the other party the caller has to enter his code = 001. This complete string should be stored at indirect memory location 1. After dialing the number, dialing should be stopped until the dial-up service requests for the user code. Then, with one keytouch the remaining number should be dialed out: am lc s on A te G nt st il A POR can only be executed in off-hook state. Normally, a POR occurs, when a telephone is plugged into the PSTN line for the first time (all voltages are discharged) by an off-hook / on-hook action. If VDD is applied externally, before a POR has been executed, the internal RAM registers, which hold the setup parameters (Ringer code, Rx volume) and memories (LNR, etc..) are not reset and can have purely accidental contents. In this case, it is advised to discharge VDD by either disconnecting the unit from the PSTN line for 24..48hrs (depends on VDD buffer cap size) or simply discharging the VDD buffer cap via a series resistor of example1: automatic dialing behind a PABX: desired number 0123456 (where 01 is the access code) should be stored with a pause after the access code at location M1: al id A Power-On-Reset occurs, when VDD is discharged and the AS253x goes off-hook. The POR circuit is supplied by VLI and will generate a POR, when VDD is rising above lv Power-On-Reset When storing memories, pauses can be inserted at any location by pressing PS or LNR . Each pause is 2 sec. when inserted within the first 5 digits of the stored number. Pauses can be cascaded. If the pause is inserted after the 5th digit of the stored number, dialing will be held until the PS or LNR is pressed: ≈1kΩ (by a pushbutton, for example). It is also possible to re-program e.g. the ringer code by the programming sequences using the P/M key. Sliding cursor protocol and pause insertion ni ca To accommodate easy and uncomplicated redialing behind a PABX, a sliding cursor protocol is implemented: if a manually entered digit string matches the contents of the LNR memory, pressing LNR will only dial out the remaining digits : example: desired number 0123456 (where 01 is the access code) ch off-hook, manual entry = 01 ⇒wait for dial tone ⇒23456 ⇒ line is busy⇒ on-hook (LNR contents is 0123456) Te off-hook, manual entry = 01⇒ wait for dial tone⇒ press LNR key: LNR dials out the remaining digits: 23456 Revision D01 P/M ⇒ MR 1 ⇒ 1 8 0 0 1 2 3 4 5 6 7 PS 0 0 1 ⇒ P/M result: when calling up the memory by pressing MR 1, the numbers 1 8 0 0 1 2 3 4 5 6 7 are dialed out and dialing is stopped, until either PS or LNR are pressed. Then, 0 0 1 is dialed out. Dual Soft clipping: The dual soft clipping circuit prevents harsh distortion and acoustic shock in both directions by limiting the maximum output of the Tx/Rx amplifiers at a level which still maintains a non-distorted signal (see V AGC levels in data sheet). If the output of the amplifier is already at the soft clip level and the input level is further increased, then the amplifier’s gain is reduced, so that the output level remains non-distorted at the soft clip level. Even fast input signal peaks are detected because of the fast attack time (see t ATTACK ) of the soft clip circuit. Instabilities are prevented by using a long decay time (see t DECAY in data sheet). Page 8 of 16 Application note AN533 If filtering of metering pulses (typ. 12 or 16kHz ) is required (for example in Germany) two blocking filters can be installed: LBF1 , CBF1 as notch filter at the line input and LBF2 ,CBF2 as notch filter at the Rx amplifier input Note: since CBF1 is connected at the line side, it must be a .../250V capacitor and LBF1 must be able to drive the The application AN2201, shown with two resonators, gives adequate attenuation of the metering pulses signal. The benefit of this application is, that only one filter (LBF1,CBF1) is used on the high voltage/high current side, while the second notch filter (LBF2,CBF2) is connected at a low voltage/low current node, enabling use of low cost components. Equation to calculate CBF with a given LBF: C= 1 / (ϖ 2 • L where: C= CBF value in Farad, L= LBF value in Henry, ϖ = 2 • π • f Res ca Off-Hook conditions & DC mask Speech mode ch ni In speech mode, shunt regulation (by Q3) is active and line current flows as described in application note AN500-1. At the same time, both Tx and Rx amplifiers and 2 wire-4 wire conversion circuits are active. DTMF dialing Te During DTMF dialing the same line conditions as in Speech mode apply, except that speech is muted in both directions and a confidence tone is sent to the Rx amplifier. Revision D01 With pulse dialing, the line has to be interrupted during “break” periods and short circuited during “make” periods. For example, “LD 60/40 10pps” means: break/make ratio is 60:40 with 10 pulses per second = The dialing pulse is a 60ms break (line interrupt) followed by a 40ms make (line short circuit). Dialing number “1” will result in one dialing pulse, total time = 100ms. dialing number “0” will result in 10 dialing pulses, total time = 10*100ms = 1sec. am lc s on A te G nt st il maximum line current (≈100mA) without saturation. LBF2 and CBF2 however, can be low voltage, low current components . On the current layout, LBF1 is short circuited by a PCB trace ! Before installing an inductor at LBF1, the trace underneath the coil must be opened ! Pulse dialing al id Metering pulses filtering The DTMF signal is modulated to the line by controlling the shunt transistor, Q3. During inter-digit pauses speech is also muted. DTMF level is adjusted by a DC voltage at the MFL input (pin #2, see cpt.0). lv Further Adjustments Line break pulses are performed by Q1 being switched off. The on-off control signal is output from the HS/DP pin (#10) switching Q2 (and in turn Q1) on and off. Make pulses are performed by Q3 with Q1 being switched on. The base of Q3 (=pin CS, #25) is pulled to V SS , resulting in V LI = V BE ≈ 0.7V. Pin CS is pulled low during the complete dialing period of one digit, which means in worst case (dialing number “0”) the circuit cannot be supplied from line and must be buffered by the V DD -cap, C8. Therefore C8 must be big enough to supply the active circuit for 1 second. Pre-digit, Inter-digit ,inter-tone and access pauses During pulse and DTMF dialing, several pauses must be added (see also: data sheet): pre-digit pause (PDP): Pause between CS=low and first break (pulse dialing only) inter-digit pause (IDP): Pause between pulse dialed numbers, from last “make” to next PDP inter-tone pause (ITP): Pause between DTMF dialed numbers access pause (AP): manually inserted pause in a digit string (see cpt. 0) Page 9 of 16 Application note AN533 On-hook conditions In on-hook state the circuit is supplied by a very small current to maintain the stored numbers and the ringing melody. The hook transistor is off and the HS pin (#10) is forced to zero by R7 and R8//Q2 B,E . The IC is powered down, only a very small current flows from line to maintain V DD and thus retention of stored memories and ringing melody. The DC resistance of the application in this state is >5MΩ (= the value of R1). La ⇒ R1 (determines on hook DC resistance) ⇒ RB1 ⇒ R19 ⇒ V DD (C8 // D7) V SS ⇒ RB1 ⇒ Lb If the telephone is disconnected from line, memories are not lost since the charged C8 holds V DD for a limited period of time. The absolute time span depends on the quality (internal discharge) of C8 and the leakage resistance of D7. Ringing mode ni ca The tone ringer provides 4 different “melodies” which can be selected by the user in order to distinguish between several telephones in the same office. The level of the tone ringer can also be programmed from the keyboard by the user, so no expensive micro-switches are needed. The frequency discrimination assures that the tone ringer is activated only when a valid ring signal is applied and not due to pulsedialing from a parallel telephone (false “belltinkle”). Ringing frequency comparator ch The ring signal is checked at pin FCI (#21) for a valid ringing frequency. As soon as a signal is applied to the line, the internal “ring frequency detector” will start, provided that the signal level at FCI is above the trigger Te threshold (≈ 2/3 V DD ) . If the frequency is within the specified range, the melody generator will send a bitstream out of MO (#8), charging the piezo ringer via Q4 and discharging it via D5 and the internal high voltage open Revision D01 La ⇒ C1 ⇒ R2 ⇒ RB1 ⇒ C10//D6 (piezo ringer supply) ⇒ C8//D7 (V DD ) V SS ⇒ RB1 ⇒ Lb another path exists from C1 ⇒ D2 ⇒ R15 to FCI // C2 // R16 for the ringing frequency detector input (anti- aliasing filter). Oscillator input A 3.58MHz ceramic resonator (recommended type MuRata CSA 3.58MHz ) must be connected at OSC (#11). The parallel capacitor C17 is to trim the oscillation frequency (not required with the recommended resonator type). am lc s on A te G nt st il Quiescent current path Ringing signal path: al id Q4 is used to switch the piezo ringer on and off, it can be any NPN single or darlington transistor capable of driving 100mA at 25V U CE . drain transistor. As soon as a non-valid or missing ring signal is detected, the bitstream is stopped and the circuit returns to standby. lv Ringer Transistors Note: The exact resonance frequency should not be measured at the OSC input directly, because the capacitive load of the Oscilloscope probe will shift the oscillation frequency. DTMF frequencies are derived from the resonant frequency, if these frequencies (see DTMF frequency standards or data sheet) are not centered, the oscillator must be trimmed. EMC & RFI issues EMC (electromagnetic compatibility) and RFI (radio frequency interference) is a major concern in most PTT approvals. And due to the digital networks (GSM, CDMA, DECT) also a feature which can be “heard” by the user. Therefore it is a major headache for telephone designers, since EMC testing is generally done with finished designs and failing EMC tests may result in adding expensive components, like coils, chokes etc. Much can be done by considering EMC from the very beginning ! The most important factors are IC technology, layout and placement of EMC blocking components: Technology Due to AMS´s unique CMOS technology the circuits show far less sensitivity to RFI than bipolar circuits which makes EMC a much easier task. Page 10 of 16 Application note AN533 Additionally, long distances between LI (#27) and the Emitter of the shunt transistor (Q3) should be avoided. Therefore, Q3 should be placed near the IC pins : collector = pin #26 =Vss, base = pin #25 = CS, emitter = pin #27 = LI. EMC blocking parts The DB533 Demo Board has been approved to conform the EN 55024) (electromagnetic irradiation) specification required for CE-approval in the European Community (EC) market! Te ch ni ca am lc s on A te G nt st il Connections for blocking components, preferably ceramic capacitors (far less cost than coils) should be already considered in the layout design. These capacitors should be connected as close to the IC (or line/handset connetor) pins as possible with a low-ohmic connection to V SS . SMD caps have best performance for EMC blocking because al id As a common rule, V SS ground planes should be as large as possible. “Bottlenecks” and long distances in the ground path should be avoided. of short leads and they can be placed directly underneath the IC at the solder junction. If the use of SMD components is not possible, leaded ceramic capacitors can be connected at top PCB side as shown in the demo board’s layout. Refer to EC1..EC7 on both schematic and layout. The actual number of required EMC blocking components in the customer’s design cannot be predicted, since EMC performance is influenced by many other factors, like telephone assembly, wire lengths etc. lv Layout hints Revision D01 Page 11 of 16 Application note AN533 Te ch ni ca am lc s on A te G nt st il lv al id Board schematic: Revision D01 Page 12 of 16 Application note AN533 Te ch ni ca am lc s on A te G nt st il lv al id Board Layout Revision D01 Page 13 of 16 Application note AN533 Part list Rating 250V 10V 10V 10V 10V 10V 10V 6V 6V 30V 6V 10V 10V 10V 6V 6V 10V 10V 50V Ringer Capacitor Anti-aliasing filter, ring frequency detector DC-AC separation, Rx amplifier DC-AC separation, AC impedance Side tone network DC-AC separation, Rx amplifier AC impedance capacitor for complex impedance (if required) V DD supply capacitor, buffer during pulse dialing Analogue ground filter Filter and buffer for ringer supply Electret handset microphone supply filter Tx response shaping (high pass) , DC-AC separation Tx response shaping (high pass), DC-AC separation Tx response shaping (low pass) Rx response shaping (high pass), DC-AC separation Rx response shaping (low pass) ceramic; Oscillator fine tuning (if required) Buffer for Power extraction AC path for current limiter Surge protection 0.5W minimum ringing voltage setpoint 0.5W Gate voltage protection for Q1 (MOSFET hook transistor option) 1.3W Surge protection 0.5W Piezo ringer discharge 0.5W Ringer voltage limitation 0.25W V DD limitation 0.5W Keyboard 0.5W Power extraction (optional) 10V ceramic; EMC blocking capacitors 10V ceramic; EMC blocking capacitors 10V ceramic; EMC blocking capacitors 10V ceramic; EMC blocking capacitors (place directly over mircophone capsule in Handset 10V ceramic; EMC blocking capacitors 250V ceramic; EMC blocking capacitors Single chip telephone IC Line connector pin selection Dialing mode selector Ground for connecting measurement tools Piezo ringer connector Line loss compensation (AGC) selector Output for power Extraction disable current limiter enable current limiter Keyboard PGM/Mute indicator 0.1W DTMF level setting (replaced by 2 resistors in user’s final application) Hook transistors for PNP darlington option Hook transistor for Single PNP option Hook transistor for MOSFET option Driver transistor for Q1X Line current shunt transistor Ringer driver transistor Current limiter Current limiter Transistor for low LI-Voltage Power extraction circuit 0.1W Leakage current limitation 0.4W Ringing impedance 0.1W Pull-up resistor for Q1 Te ch ni ca am lc s on A te G nt st il C1 680n C2 10n C3 10µ C4 10µ C5 C6 1µ C7 CCI C8 470µ C9 100µ C10 10µ C11 100µ C12 10n C13 10n C14 10n C15 10µ C16 C17 C18 100uF C29 10uF V1 BR211-180 D2 12V D3 12V D4 10V D5 1N4148 D6 18V D7 5V1 D8..D11 1N4148 D12 1N4148 EC1 100nF EC3..6 100pF EC2,EC13..14 10nF EC12 4.7nF EC8,EC9 1nF EC10,11 1n IC1 AS2533...6 J12,J13 line J3 mode J4 VSS J5 Ringer J6 LLC J5A Power extraction J5A current limiter J5B current limiter K1..K32 SPST LED1 low-current LED P1 100k Q1A,B n.c. =MPSA92 Q1D n.c. =2SA1209 Q1C n.c. =BSS92 Q2 2N5551 Q3 BC327-16 Q4 BC547B Q5 BC557 Q6 BC327 Q7 n.c. =BC547 Q8 n.c. =BC327-40 R1 5M1 R2 2k2 R4 100k Description al id Value lv Part Revision D01 Page 14 of 16 10k 220k 150k 1M 0.1W 0.1W 0.1W 0.1W Base/gate series resistor for Q1 Pull-up resistor, HS input current limitation Base resistor for Q2 Base shunt resistor for Q2 30Ω 0.5W Sensing resistor for DC-mask, Line current and AC impedance 300Ω 1k8 7k5 1k5 15k 330k 220k 100k 0.1W 0.1W 0.1W 0.1W 0.1W 0.1W 0.1W 0.1W Side tone balance bridge resistor, must be 10x R8 Side tone network Side tone network Real AC-impedance setting (if required) Side tone balance for R14A,must be 10xR14A FCI input protection and voltage divider Voltage divider, FCI input Pull-up resistor for Q4 R18 R19 R20 R21 R22 R23 510Ω 330k 2k2 1k8 1k8 n.c. 0.1W 0.1W 0.1W 0.1W 0.1W 0.1W Low pass filter for ringer capacitance Leakage current supply during on-hook Filter for electret handset microphone supply Supply for electret microphone, microphone gain setting Supply for electret microphone, microphone gain setting Microphone gain setting (attenuator) R24 R25 R26 R27A R27B R28 R29 R30 RB1 SW1 X1 Z1 Z2 390Ω 13R 10k 1.2k 1.2k 22k 82k 5k1 4x1N4004 250V Hook-Sw. DPDT 3.58MHz LINE HANDSET 0.1W 0.1W 0.1W 0.25W 0.25W 0.1W 0.1W 0.1W Rx handset earpiece gain setting Current Limiter Current Limiter Current Limiter Current Limiter Resistor for Low DC-Mask Resistor for Low DC-Mask Power extraction circuit Resistor Rectifier bridge Hook Switch Ceramic Resonator, oscillator for IC1 AMP modular connector AMP modular connector am lc s on A te G nt st il R9 R10 R11 R12 R14A R14B R15 R16 R17 lv R5 R6 R7 R8 al id Application note AN533 Related Standards ni ca The product, AS25xx, is designed to be in compliance with ETSI standards for connection to the analogue PSTN of terminal equipment including voice telephony services or other voice band communication when installed into a properly designed system. The specification of the product is based on following standards and requirements: Note: Some national PTT authorities may have additional requirements exceeding the above standards and requirements. Such additional requirements have only been respected to the extent that they were known to Austria Mikro Systeme prior to designing the product. However, Austria Mikro Systeme shall not be liable to recipient or any third party in connection with the approval procedures of applications in which the AS25xx is used. Approvals EN55022 EMC ( Electro Magnetic Compatibility) IEC 1000-4-3 Electromagnetic Irradiation (CE approval) Since the AS25xx is a component and not a complete system, it can not be approved as a stand alone part by the standards bodies. Hence, full conformance to above standards is depending on the application in which the AS25xx is being used, and therefore, approvals by the standards Te ch NET 4 ETS 300 001, PSTN basic access; analogue terminal equipment general requirements, March 1996. Revision D01 Page 15 of 16 Application note AN533 bodies are the responsibility of the customer and Austria Mikro Systeme will not have tested the product to meet the above standards. austriamicrosystems AG A 8141 Schloss Premstätten, Austria T. +43 (0) 3136 500 0 F. +43 (0) 3136 525 01 [email protected] Copyright al id Contact Te ch ni ca am lc s on A te G nt st il lv Copyright © 2001 austriamicrosystems. Trademarks registered ®. All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. To the best of its knowledge, austriamicrosystems asserts that the information contained in this publication is accurate and correct. Revision D01 Page 16 of 16