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ST3917A 数据表(PDF) 4 Page - STMicroelectronics |
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ST3917A 数据表(HTML) 4 Page - STMicroelectronics |
4 / 16 page LED (Output, Pin 15) When the MU/MFI pin is connected to either VDD or GND, the LED connected to the LED pin, which functions as a keyboard illumination or off-hook indicator, will light up when the telephone is off- hook. When the MU/MFI pin is connected to any row pins, the LED connected to LED pin functions as a tone mode indicator. From minimum operating line current up to 20mA, ILN-ICC is sourced into the LED with a maximum current limit of 18mA. For line current more than 20mA, this sourced current is limited at 18mA (typical). ILINE (Pin 16) A recommended external resistor of 20 Ω is con- nected between ILINE and GND. Changing this resistor value will influence the microphone gain, DTMF gain, sidetone, maximum output swing on LN and 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 charac- teristics can be changed with an external resistor connected between LN and REG or between REG and ILINE. GTX, MIC-, MIC+ (Pins 19, 20, 21) The device has a symmetrical microphone inputs. The amplification from microphone inputs to LN is 51dB at 15mA line current and it can be adjusted between 43 and 51dB. The amplification is propor- tional to the external resistor connected between GTX and REG. GDTMF (Pin 22) When the DTMF input is enabled, the microphone inputs and the receive amplifier input will be muted and the dialing tone will be sent on the line. The voltage amplification from GDTMF to LN is 40dB. Final output level on the LN can be adjusted via the external resistor connected between GDTMF and GND through a decoupling capacitor. A confidence tone is sent to the earphone during tone dialing. The attenuation of the confidence tone from LN to RXOUT is -32dB typically. The level of the confi- dence tone in the earphone can be increased by adjusting the resistor connected between GDTMF and GRX pins, the possible range is 20dB. VDD (Pin 23) VDD is the positive supply for the dialing circuit and it must meet the maximum and minimum voltage requirements. MU/MFI (Input, Pin 24) A logic low input to this pin will disable the transmit amplifier of the speech circuit. MUTE efficiency is greater than 60dB. An open circuit to this pin will enable the transmit amplifier. In this case, LED is used for keypad lighting. A connection to any row will disable the transmit mute function and the LED connected to the LED pin is used for tone mode indication. Table 3 : Logic of MU/MFI Pin Indicator MU/MFI Pin Transmit Muting LED at Pin 15 OPEN Active Lighted Dial Indicator GND Muted Lighted Dial Indicator Any Row Not Available Tone Mode Indicator PIN DESCRIPTION (continued) ST3917A - ST3917B 4/16 |
类似零件编号 - ST3917A |
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类似说明 - ST3917A |
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