TCM4400 Datasheet, PDF (44/72 Pages) Texas Instruments – GSM/DCS BASEBAND AND VOICE A/D AND D/A RF INTERFACE CIRCUIT

BULON
BENA
Level 255
APC OUT
Level 1
Level 0
Offset = 120 mV
Figure 4–8. APC Output When APCMODE = 1
Power down is controlled with two bits. The first bit (APCW of the AUXCTL 2 register) determines whether
the APC can be powered down by activating external GSM transmit window activation (BULON); the second
bit (APCPD of the AUXCTL 2 register) controls the activation of APC function. For more information about
power-down control, see Section 4.8 in this document. The auxiliary analog functions of the GSM baseband
A/D and D/A conversions are independently powered from the AV_DD3/5 terminal. The APC output voltage
swing is programmable to provide the largest voltage range. This configuration is programmed with bit
APCSWG of the AUXCTRL 2 register.
4.3.4 Monitoring
The monitoring section includes a 10-bit A/D converter and one result register that allow monitoring of five
external analog values, such as the temperature and the battery voltage. The selection of the input and
reading of the control registers is done using the serial interfaces.
The selection of the input channel is done with the bits ADCCH0 – ADCCH2 of the AUXCTL1 register; the
data is read from the AUXADC register. Power down is controlled with two bits. The first bit (ADCPN of the
AUXCTL1 register) determines whether the A/D converter can be powered down from the external PWRDN
terminal; the second bit (ADCPD of the AUXCTL1 register) controls the activation of the A/D conversion
function. For more information about power-down control, see Section 4.8 in this document.
Conversion is started with a write access to the AUXCTL1 register. During the conversion, the ADCEOC
bit of BSTATUS register stays at 1 and resets to 0 when the converted data is loaded into the AUXADC
register. The power consumption of the main parts of the converter is limited to the useful part of the
conversion time.
4.4 Voice Codec
The voice coder/decoder (codec) circuitry processes analog audio components in the uplink path and
applies this signal to the voice signal interface for eventual baseband modulation. In the downlink path, the
codec circuitry changes voice-component data received from the voice serial interface into analog audio.
The following paragraphs describe these uplink/downlink functions in more detail.
4–8