TCM4400EPET datasheet(32/64 Pages) TI

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TCM4400E

GSM/DCS BASEBAND AND VOICE A/D

AND D/A RF INTERFACE CIRCUIT

SLWS082A – JULY 1999 – REVISED MARCH 2000

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

RF power control (continued)

When APCMODE is one (see Figure 13) the APC output is given by formula

APCout = ( Shape value * Level value ) + Offset

BULON

BENA

APC OUT

Level 1

Level 255

Level 0

Offset = 120 mV

Figure 13. APC Output When APCMODE = 1

Power down is controlled with two bits. The first bit (APCW of AUXCTL2 register) determines whether the APC

can be powered down by activating external GSM transmit window activation (BULON): The second bit (APCPD

of AUXCTL2 register) controls the activation of APC function. See the topic,

power-down functional description,

for more details about power-down control. The auxiliary analog functions of the GSM baseband A/D and D/A

conversions are independently powered from the AVDD5 terminal.

monitoring

The monitoring section includes a 10-bit A/D converter and one result register that allows 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 AUXCTL1

second bit (ADCPD of AUXCTL1 register) controls the activation of the A/D conversion function. See the topic,

power-down functional description, for more details about power-down control.

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. This

way the power consumption of the main parts of the converter is limited to the useful part of the conversion time.

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