ST3917A |
RFQ for ST3917A Required Field |
 |
| Product | Manufacturers | Pack | D/C |
| ST3917A | - | SOP28 | - |
The device consists of thespeech and the dialer functions. It provides the DCline interfacecircuit that terminates the telephone line, analog amplifier for speech transmission and necessary signals for either DTMF and pulse ialing.When mated with a tone ringer, a completetelephonecanbe producedwith just two ICs. The DC lineinter face circuit develop sitsown line voltage across the device andit is adjus tablebyexternal resistor to suit different country's specification. A built-in LED driver can deliver excess line current to external LED indicator(s) during dialing and speech mode. The LED(s) can be used either for keyboard illumination purpose or for tone mode indication during softswitch andmixedmode dialing by connectingMU/MFI pin to VDDandGNDoranyrowrespectively.TheLEDcurrent is limited to 17mA(typical).
The speechnetwork provides the two to fourwires interface, electronic switching between dialing and speech and automatic gaincontrol ontransmit andreceive.
The dialing network buffersup to32 digits into the LND memorythatcanbelaterredialedwithasinglekeyinput. Users can store all 13 signalling keys and access severaluniquefunctionswith single key entries.These functions include : Pause, Last NumberDialled (LND), Softswitch and Flash. (see Figure 1).
TheFLASHkey simulatesa hookflashto transfercalls or to activate other special features provided by the PABXor central office.
The PAUSE key stores a timed pause in the number sequence.Redial is then delayeduntil an outside line can be accessed or some other activities occur before normal signalling resumes. A LND key automatically redials the last number dialed.
AdedicatedpinMU/MFI is used toselect themutingfor transmit amplifier and lighted dial LED for keyboard illumination ora LEDindicator for tonemode indication. The SEL pin allows selection of any one of the four possible Flash duration opti
Features |
| SPEECH CIRCUIT. 2 TO4 WIRES CONVERSION. PRESENT THE PROPERDC PATH FOR THE LINE CURRENT AND THE FLEXIBILITY TO ADJUST IT ANDALLOWPARALLELPHONEOPERATION·SYMMETRICAL HIGH IMPEDANCE MICROPHONE INPUTS SUITABLE FOR DYNAMIC,ELECTRETORPIEZOELECTRICTRANSDUCER· ASYMMETRICAL EARPHONE OUTPUT SUIT. ABLE FOR DYNAMIC TRANSDUCER · LINE LOSS COMPENSATION FIXED INTER NALLY BY A.G.C.·INTERNAL MUTING TO DISABLE SPEECH DURING DIALING AND EXTERNAL MUTING TO DISABLE TRANSMIT AMPLIFIER DURING CONVERSATIONMODE· LED INDICATOR EITHER FOR KEYBOARDILLUMINATION (OR ON-LINE INDICATION) DURING DIALING AND CONVERSATION OR FOR TONE MODE INDICATION, THROUGH MU/MFI PINDIALER CIRCUIT · STORE UP TO 32 DIGITS FOR LAST NUMBER REDIAL BUFFER, LNR IS INHIBITED IF THERE. AREMORE THAN 32 DIGITS STORED . ALLOWMIXEDMODE DIALINGIN PULSEMODE· PACIFIER TONE PROVIDES AUDIBLE INDICATION OF VALID KEY PRESSED IN A BUZZ ER OR/AND IN THE EARPHONE. TIMED PABX PAUSE / 10PPS PULSE RATE · MAKE/BREAK RATIO : 40/60 (ST3917A) AND 33/67 (ST3917B) · 4 SELECTABLE OPTIONS ON FLASH DURATION AND SOFTSWITCH INHIBITION IN ONE OF THE OPTION WITH 100ms FLASH TIMING· 2 SELECTABLE OPTIONS : TRANSMIT MUTE TOGETHERWITH LED FORKEYBOARDILLUMI NATIONORLEDFOR TONEMODE INDICATION· CONTINUOUS TONE FOR EACH DIGIT UNTIL KEYRELEASE· |
| Symbol | Parameter |
Value |
Unit |
| VLN | Positive Line Voltage Continuous |
12 |
V |
| ILN | Line Current |
140 |
mA |
| VDD | Logic Voltage |
7 |
V |
| VI | Maximum Voltage on PULSE, SEL, HKS, MODE, Ri, Ci, MU/MFI and OSC Pins |
GND(-0.3) VDD(+0.3) |
V |
| Toper | Operating Temperature |
-25, +70 |
°C |
| Tstg | Storage Temperature |
-40, +125 |
°C |
| Ptot | Total Power Dissipation |
700 |
mW |
