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L3934AN Datasheet(PDF) 4 Page - STMicroelectronics |
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L3934AN Datasheet(HTML) 4 Page - STMicroelectronics |
4 / 15 page IREF Pin 13. An external resistor of 3.6kOhm con- nected between IREF and GND will set the inter- nal current level. Any change of this resistor value will influence the microphone gain, DTMF gain, earphone gain and sidetone. VCC Pin 14, VCC is the positive supply of the speech network. It is stabilized by a decoupling capacitor between VCC and GND. The VCC supply voltage may also be used to supply external peripheral circuits. LED Pin 15. The LED connected to this pin will start to blink when the HOLD key is pressed and will turn off if the HOLD key is pressed again. Otherwise, it will continue to blink at 1Hz frequency when the phone is on-hooked and then turn off when the parallel phone goes off-hook. ILINE Pin 16. A recommended external resistor of 20ohm is connected between ILINE and GND. Changing this resistor value will have influence on microphone gain, DTMF gain, sidetone, maximum output swing on LN and on the DC characteristics (especially in the low voltage region). LN Pin 17. LN is the positive line terminal of the device. REG Pin 18. The internal voltage regulator has to be decoupled by a capacitor from REG) to GND). The DC characteristics can be changed with an external resistor connected between LN and REG or between REG and ILINE . GTX, MIC–, MIC+ GTX (pin 19), MIC– (pin 20) and MIC+ (pin 21). The one chip phone has symmetrical microphone inputs. The amplification from microphone inputs to LN is 51.5dB and it can be adjusted between 43.5 and 51.5dB. The amplification is proportional to ex- ternal resistor connected between GTX and REG. GDTMF Pin 22. When the DTMF input is enabled, the mi- crophone inputs and the receive amplifier input will be muted and the dialing tone will be sent to the line. The voltage amplification from GDTMF to LN is 40dB. Final output level on LN can be adjusted via the external resistor connected between GDTMF and GND through a decoupling capaci- tor. A confidence tone is sent to the earphone during tone dialing. The attenuation of the confi- dence tone from LN to Vear is –32dB typically. VDD Pin 23. VDD is the positive supply for the dialing network and must meet the maximum and mini- mum voltage requirements. DEVICE OPERATION During on-hook all keypad inputs are high imped- ance internally and it requires very low current for memory retention. At anytime, Row and Column inputs assume opposite states at off-hook. The circuit verifies that a valid key has been entered by alternately scanning the Row and Column in- puts. If the input is still valid following 32ms of de- bounce, the digit is stored into memory, and dial- ing begins after a pre-signal delay of approximately 40ms (measured from the initial key closure). Output tone duration is shown in Ta- ble 1. The device allows manual dialing of an indefinite number of digits, but if more than 32 digits are di- aled, it will ”wrap around”. That is, the extra digits beyond 32 will be stored at the beginning of LND buffer, and the first 32 digits will no longer be available for redial. Table 2: DTMF Output Frequency Key Input Stadard Frequency Actual Frequency % Deviation ROW 1 ROW 2 ROW 3 ROW 4 697 770 852 941 699.1 766.2 847.4 948.0 +0.31 –0.49 –0.54 +0.74 COL 1 COL 2 COL 3 1209 1336 1477 1215.9 1331.7 1471.9 +0.57 –0.32 –0.35 NORMAL DIALING D1 D2 D3 ....etc Normal dialing is straighforward, all keyboard en- tries will be stored in the buffer and signaled in succession. PROGRAMMING AND REPORTORY DIALING To program, enter the following: PROG D1 D2 Dn MEM (location 0-9) or PROG D1 D2 Dn E1-E3 During programming, dialing is inhibited. FUNCTION PIN DESCRIPTION (continued) L3914A - L3924A - L3934A 4/15 |
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