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ST3917BD bảng dữ liệu(PDF) 3 Page - STMicroelectronics |
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ST3917BD bảng dữ liệu(HTML) 3 Page - STMicroelectronics |
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3 / 16 page  SEL (Input, Pin 4) This is an option selectable pin for four Flash duration. The four options are summarised in the table 2. For option 1, softswitch feature is inhibited. It means redialed by the LND key in pulse mode will not repeat the softswitch and subsequent digits, only pulse digits are dialed out. Table 2 : Options Selectable for Flash Duration Options SEL Flash (ms) Softswitch 1VDD 100 Inhibited 2 GND 600 Enable 3 Any Row 300 Enable 4 Any Col 100 Enable OSC (Input, Pin 5) Only one pin is needed to connect the ceramic resonator to the oscillator circuit. The other end of the resonator is connected to GND. The nominal resonator frequency is 3.579545MHz and any de- viation from this standard is directly reflected in the Tone output frequencies. The ceramic resonator provides the time reference for all circuit functions. A ceramic resonator with tolerance of ±0.25% is recommended. PULSE (Output, Pin 6) This is an output consisting of an open drain N- channel device. During on-hook, pulse output pin is in high impedance and once off-hook, it will be pulled high by external resistor. MODE/PT (Input, Pin 7) Input (MODE). MODE determines the dialer’s de- fault operating mode. When the device is powered up or the hookswitch input is switched from on- hook (VDD) to off-hook (GND), the default deter- mines the signalling mode. A VDD connection defaults to tone mode operation and a GND con- nection defaults to pulse mode operation. When dialing in the pulse mode, a softswitch fea- ture will allow a change to the tone mode whenever the * or softswitch key (TONE) is depressed. Sub- sequent * key inputs will cause the DTMF code for an * to be dialed. The softswitch will only switch from pulse to tone. The phone will be in pulse mode only after returning to on-hook and back to off- hook. Redialed by the LND key will repeat the softswitch unless the softswitch redial feature is inhibited. Output (PT). Pacifier Tone Output. In pulse mode, all valid key entries activate the pacifier tone. In tone mode, any non DTMF entry (FLASH, PAUSE, LND, TONE) activates the pacifier tone. The paci- fier tone provides audible feedback, confirmingthat the key has been properly entered and accepted. It is a 500Hz square wave activated upon accep- tance of valid key input after the 32ms debounce time. The square wave terminates after 75ms typically or when the valid key is no longer present. The pacifier tone signal is simultaneously sent to the earphone and the buzzer. The buzzer can be removed with- out affecting this function. The resistor value set on MODE/PT pin determines the level of the pacifier tone in the earphone. HKS (Input, Pin 8) This is the hookswitch input to the device. It is a CMOS input with a high pull up internal resistance and must be switched high or open for on-hook operation and low for off-hook operation. A transi- tion on this input causes the on-chip logic to initial- ize, terminating any operation in progress at the time. The signalling mode defaults to the mode selected at MODE/PT pin. Figures 2, 3 and 4, 5 illustrate the timing for this pin. GND (Pin 9) GND is the negative line terminal of the device.This is the voltage reference for all specifications. RXOUT, GRX, RXIN (Pins 10, 11 and 12) The receive amplifier has one input RXIN and a non inverting output RXOUT. Amplification from RXIN to RXOUT is typically 31dB and it can be adjusted between 21dB and 41dB to suit the sensitivity of the earphone used. The amplification is propor- tional to the external resistor connected between GRX and RXOUT. For the hearing impaired, a specific application to offer 17dB additional gain at 3kHz is permitted. IREF (Pin 13) An external resistor of 3.6k Ω connected between IREF and GND will set the internal current level. Any change of this resistor value will influence the microphone gain, DTMF gain, earphone gain and sidetone level. VCC (Pin 14) VCC is the positive supply of the speech network. It can be stabilized by a decoupling capacitor be- tween VCC and GND. The VCC supply voltage may also be used to supply external peripheral circuits. PIN DESCRIPTION (continued) ST3917A - ST3917B 3/16 |
Số phần tương tự - ST3917BD |
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Mô tả tương tự - ST3917BD |
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