¡ Semiconductor
MSM7502
TPAI, TPAO
The transmit pre-amplifier input and output.
TPAI is the input and TPAO is the output. TPAI should be connected to the microphone of
handset via an AC-coupling capacitor if the DC offset appears at a transmit signal (offset from
SGT). The transmit path from TPAI to TPAO is always active regardless of processor control.
During the whole system power down mode, TPAO is at an analog ground level. The gain
between TPAI and TPAO is fixed to 20 dB.
SGT
Transmit path signal ground.
SGT outputs half the supply voltage. During the whole power down mode, SGT is in a high
impedance state.
SGC
Bypass capacitor connecting pin for signal ground level.
Insert a 0.1 mF high performance capacitor between SGC and AG.
VA, VD
+5 V power supply.
VA is for an analog circuit and VD is for digital supply. Connect both VA and VD to the +5 V
analog path of the system.
CAI, CAO
CODEC analog input and output.
CAI is the analog input of CODEC to be connected to the TO pin. If the DC offset voltage on the
TO signal is great, CAI should be connected via AC-coupling capacitor. At this time, insert an
about 100 kW bias resistor between CAI and SGT.
CAO is the analog output of CODEC. CAO should be connected to R1I via AC-coupling
capacitor. AbiasresistorisnotrequiredtoR1I. DuringthewholesystemorCODECpowerdown
mode, CAO is at the SG voltage level.
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