Panasonic KX-TCD700GB / KX-TCD700GH Service Manual ▷ View online
6.1.6. BUZZER CIRCUIT (SEE Fig. 25)
A square-wave signal from IC1 pin 68 is used to sound the buzzer via switching transistor T4. Various tones and cadences are
used dependent on function. Buzzer volume is varied by changing the duty cycle of the drive waveform. D10 provides
quenching of back-emf generated when T4 turns off.
used dependent on function. Buzzer volume is varied by changing the duty cycle of the drive waveform. D10 provides
quenching of back-emf generated when T4 turns off.
6.1.7. AUDIO PATH - TX AUDIO (SEE Fig. 25)
The audio signal from the microphone (TP23) enters the BBIC at pin 44. RF decoupling and signal conditioning are provided
by C17, R21, C14 and C25.
by C17, R21, C14 and C25.
In the BBIC the signal passes through the analogue section where it is amplified and converted to a digital audio stream signal.
The burst mode controller processes this stream performing encryption and scrambling, adding the various other fields to
produce the GAP standard DECT frame, assigning to a time slot and channel etc. to emerge on pin 14 as TXDA.
The burst mode controller processes this stream performing encryption and scrambling, adding the various other fields to
produce the GAP standard DECT frame, assigning to a time slot and channel etc. to emerge on pin 14 as TXDA.
6.1.8. AUDIO PATH - RX AUDIO (SEE Fig. 25)
Audio from the receiver RXDA enters the BBIC on pin 10 as GAP standard DECT frames. It passes through the decoding
section burst mode controller where it separates out the frame information and performs de-encryption and de-scrambling as
required. It then goes to the DSP where it is turned back into analogue audio. This is amplified by the analogue front end and
emerges at pin 40 and 41. The telephone speaker is driven directly from the BBIC output ports.
section burst mode controller where it separates out the frame information and performs de-encryption and de-scrambling as
required. It then goes to the DSP where it is turned back into analogue audio. This is amplified by the analogue front end and
emerges at pin 40 and 41. The telephone speaker is driven directly from the BBIC output ports.
On 700 models the ring alarm is provided by means of a buzzer BUZ1 which is switched by T4 from pin 68. IC5, J6 and the
HF_AM1 are not fitted.
HF_AM1 are not fitted.
705 models use the hands-free loudspeaker at SP+ and SP- to generate the ring alarm, so the buzzer BUZ1 is not fitted. IC5
is used to switch off the telephone loudspeaker while the HF_AM1 amplifier is used to drive the hands-free loudspeaker. They
are selected mutually exclusively using the SP_CTR line from pin 93 of the BBIC. The 2.5mm headset jack is also exclusive to
the 705 model.
is used to switch off the telephone loudspeaker while the HF_AM1 amplifier is used to drive the hands-free loudspeaker. They
are selected mutually exclusively using the SP_CTR line from pin 93 of the BBIC. The 2.5mm headset jack is also exclusive to
the 705 model.
6.1.9. CLOCK GENERATION (SEE Fig. 25)
A single clock generator in the BBIC uses an external crystal X1 to derive all clock frequencies used in the handset. The crystal
is tuned to the exact frequency of 10.368 MHz during manufacture.
is tuned to the exact frequency of 10.368 MHz during manufacture.
The BBIC provides a reference clock signal SYRI (pin 21, TP101) which is used to drive the PLL circuitry in the RF module. The
basic data rate for TXDA (pin 14) and RXDA (pin 10) is 1.152 Mbits/s, which is 10.368MHz divided by 9.
basic data rate for TXDA (pin 14) and RXDA (pin 10) is 1.152 Mbits/s, which is 10.368MHz divided by 9.
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KX-TCD700GB / KX-TCD700GH
Circuit Diagram
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KX-TCD700GB / KX-TCD700GH
6.1.10. KEYBOARD (SEE Fig. 26)
The keyboard “On” button is connected directly to pin 33 and 28 of the BBIC. When pressed it turns the handset on and off.
All other keys are connected in a row/column matrix. They are scanned in five rows using scan pulses (only active when keys
are pressed) from IC1 pins 15 to 19. The five key matrix columns are input to the BBIC on pins 51, 52, 53, 57 and 58.
All other keys are connected in a row/column matrix. They are scanned in five rows using scan pulses (only active when keys
are pressed) from IC1 pins 15 to 19. The five key matrix columns are input to the BBIC on pins 51, 52, 53, 57 and 58.
6.1.11. LCD DISPLAY, AND DISPLAY DRIVER (SEE Fig. 26)
The LCD display receives data via a serial interface. Serial data is sent to the display on pin 4 of the J7 socket, with control lines
at pin1 thru 3.
at pin1 thru 3.
Circuit Diagram
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KX-TCD700GB / KX-TCD700GH
6.1.12. BATTERY SUPPLY (SEE Fig. 27)
A switch mode boost converter is used to provide a 3.8V supply from the battery. This supply is sensed by the BBIC through
pin 26 (TP14) so that the switching rate can be controlled by a FET (T3) driven from pin 24 (TP13). A resistor on the Source
of the FET provides a current sense at pin 25 (TP12).
pin 26 (TP14) so that the switching rate can be controlled by a FET (T3) driven from pin 24 (TP13). A resistor on the Source
of the FET provides a current sense at pin 25 (TP12).
T3 switches the current through L1. When T3 switches off the back emf conducts through D16 and charges the reservoir cap
C4.
C4.
6.1.13. 2.65V REGULATOR (SEE Fig. 27)
A 2.65V supply is provided for the BBIC and is regulated by the BBIC’s on board control signal LRB (pin 37).
This reference is fed to the base of T6 to keep the “VREG+” line at 2.65V.
6.1.14. BATTERY CHARGING CIRCUIT (SEE Fig. 27)
The supply for the battery comes from the charge terminals at J3 and J4. Battery charge rate is controlled by switching the
current through T7 such that the average charging current is 170mA. The current flow is monitored at pin 49 of the BBIC by
measuring the voltage across R56.
current through T7 such that the average charging current is 170mA. The current flow is monitored at pin 49 of the BBIC by
measuring the voltage across R56.
D21 protects against the high voltage present on the charge contacts (J3 and J4) when there is no battery in the handset. R42
and C50 provide a signal to the BBIC (pin 27) to detect that the handset has been placed on the base charger.
and C50 provide a signal to the BBIC (pin 27) to detect that the handset has been placed on the base charger.
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KX-TCD700GB / KX-TCD700GH
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