One Chip Telephone Circuit
Description
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TELEFUNKEN Semiconductors
U3750BM
One Chip Telephone Circuit
Description
TELEFUNKEN microelectronic’s one chip telephone circuit, U 3750 BM, is BICMOS integrated circuit that performs all the speech and line interface functions required in an electronic telephone set, the tone ringer, the pulse and DTMF dialling with redial, a keyboard interface with the possibility to interface with an external microcontroller using the internal serial bus, and a power supply for peripherals.
Features
D Adjustable dc slope characteristic D Adjustable automatic line length receiving and sending gain control (not used in DTMF) with the possibility of fixed gain (PABX) D Adjustable dynamic impedance D Stabilized power supply for peripherals D Confidence level during pulse and DTMF dialling D Receiving amplifier for dynamic or piezo-electric ear pieces D High-impedance microphone inputs (80 kW in symmetrical and 40 kW in asymmetrical) suitable for dynamic, magnetic, piezo-electric or electret microphone D Dynamic limiting in sending (anticlipping) prevents distortion of line signal and sidetone D Ringing balanced output in HVMOS for higher power capability D Four ringing tones adjustable without external components D Internal speed up circuit permits a faster charge of VCC and VRAM capacitors D Logic bounce elimination D Pulse dialling 66/33 or 60/40 or DTMF dialling selectable by programming pin D Adjustable flashing duration D Pause function D Confidence tone (440 Hz) D Last number redial up to 23 digits D Standard low-cost ceramic 455 kHz D Binary data input in serial mode D Test-mode capability
Benefits
D Low number of external components D High quality through one chip solution
Rev.
A1: 16.
07.
1996
1 (20)
U3750BM
Block Diagram
TELEFUNKEN Semiconductors
2 (20)
Rev.
A1: 16.
07.
1996
TELEFUNKEN Semiconductors
U3750BM
Pin Description
Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Symbol C4 C3 FLASH DC/FV OL RESET TEEIN SHEN NC VRAM VCC VL OSCAB EC Function Keyboar...
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