tda7513t STMicroelectronics, tda7513t Datasheet - Page 32

• Manufacturer Part Number: tda7513t
• Description: Single-chip Fm/am Tuner With Stereo Decoder And Audio Processor
• Manufacturer: STMicroelectronics

Functional description
3.3.10
3.4
3.4.1
3.4.2
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If the comparison result is good the IF counter output changes from LOW to HIGH and is
made available outside at the pin #SD (after a NAND operation with the signal strength
evaluation circuit). The following relationships apply:
where
Counting succesful:
Count failed:
where
The IF counter can be started only by inlock information from the PLL, and it is enabled by
software (IFENA).
Adjustment of the measurement time and frequency window
The measurement precision is adjustable by controlling the width of the frequency
discrimination window through control registers EW0 to EW2. The center frequency of the
discrimination window is adjustable by the control register CF0 to CF4. The measurement
time per cycle is adjustable by setting the registers IFS0 - IFS2.
Audio processor
Input multiplexer
CD quasi differential 1
CD quasi differential 2
Stereodecoder input (for both FM and AM signals).
Input stages
The quasi-differential input stages (see
CD players in the market having a significant high source impedance which affects strongly
the common-mode rejection of "normal" differential input stages. The additional buffer of the
CD input avoids this drawback and offers the full common-mode rejection even with those
CD players. The quasi-differential input can also be used with normal stereo single-ended
output signal sources such as TAPEOUT.
t
t
t
t
t
t
t
t
t
TIM
CNT
CNT
TIM
CNT
CNT
TIM
TIM
ERR
> t
< t
= IF timer cycle time (sampling time)
= (IRC + 1) / f
= (CF + 1697) / f
= (CF + 448) / f
= IF counter cycle time
- t
= discrimination window (controlled by the EW registers)
CNT
CNT
ERR
+ t
- t
= t
ERR
ERR
TIM
OSC
= t
IF
IF
CNT
(AM mode)
(FM mode)
+ t
ERR
Figure
2.) have been designed to cope with some
TDA7513T