TDA5235
Functional Description
2.4.6.5 Analog to Digital Converter (ADC)
In front of the AD converter there is a multiplexer so that also temperature and VDDD
can be measured (see Figure 10).
The default value of the ADC-MUX is RSSI (register ADCINSEL: 000 for RSSI; 001 for
Temperature; 010 for VDDD/2).
After switching ADC-MUX to a value other than RSSI in SLEEP Mode, the internal
references are activated and this ADC start-up lasts 100µs. So after this ADC start-up
time the readout measurements may begin. The chip stays in this mode until
reconfiguration of register ADCINSEL to setting RSSI. However, it is recommended to
measure temperature during SLEEP mode (This is also valid for VDDD).
Readout of the 10-bit ADC has to be done via ADCRESH register (the lower 2 bits in
ADCRESL register can be inconsistent and should not be used).
Typical the ADC refresh rate is 3.7 µs. Time duration between two ADC readouts has to
be at least 3.7 µs, so this is already achieved due to the maximum SPI rate (16 bit for
SPI command and address last 8µs at an SPI rate of 2MBit/s). The EOC bit (end of
conversion) indicates a successful conversion additionally. Repetition of the readout
measurement for several times is for averaging purpose.
The input voltage of the ADC is in the range of 1 .. 2 V. Therefore VDDD/2 (= 1.65 V
typical) is used to monitor VDDD.
Further details on the measurement and calibration procedure for temperature and
VDDD can be taken from the corresponding application note.
Data Sheet
34
V1.0, 2010-02-19
INFINEON [ Infineon ]
