TDA7540B Datasheet, PDF (34/75 Pages) STMicroelectronics – AM/FM Car Radio Tuner IC with Stereo Decoder and Intelligent Selectivity System (ISS)

Functional description
TDA7540B
This is detected by a control logic and an external search stop output is changing from LOW
to HIGH. The frequency range inside which a successful count result is adjustable by the
EW bits.
t_CNT = (CF + 1696+1) / f_IF FM mode
t_CNT = (CF + 10688+1) / f_IF AM up conversion mode
t_CNT = (CF + 488+1) / f_IF AM mode
Counter result succeeded:
t_TIM ≥ t_CNT - t_ERR
t_TIM ≤ t_CNT + t_ERR
Counter result failed:
t_TIM > t_CNT + t_ERR
t_TIM < t_CNT - t_ERR
t_TIM = IF timer cycle time (sampling time)
t_CNT = IF counter cycle time
t_ERR = discrimination window (controlled by the EW registers)
The IF counter is only started by inlock information from the PLL part. It is enabled by
software (IFENA).
Adjustment of the measurement sequence time
The precision of the measurements is adjustable by controlling the discrimination window.
This is adjustable by programming the control registers EW.
The measurement time per cycle is adjustable by setting the registers IFS.
Adjust of the Frequency Value
The center frequency of the discrimination window is adjustable by the control registers CF.
4.5
4.5.1
4.5.2
I²C-Bus interface
The TDA7540 supports the I²C-Bus protocol. This protocol defines any device that sends
data onto the bus as a transmitter, and the receiving device as the receiver. The device that
controls the transfer is a master and device being controlled is the slave. The master will
always initiate data transfer and provide the clock to transmit or receive operations.
Data transition
Data transition on the SDA line must only occur when the clock SCL is LOW. SDA transitions
while SCL is HIGH will be interpreted as START or STOP condition.
Start condition
A start condition is defined by a HIGH to LOW transition of the SDA line while SCL is at a
stable HIGH level. This "START" condition must precede any command and initiate a data
transfer onto the bus. The device continuously monitors the SDA and SCL lines for a valid
START and will not response to any command if this condition has not been met.
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