TSH511CF datasheet(20/25 Pages) STMICROELECTRONICS

Part #	TSH511CF

Description	Hi-fi stereo/mono infrared receiver and stereo sub-carrier demodulator

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

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General description

TSH511

20/25

The low output impedance of the demodulator (MIX-OUT pins) drives the external volume

control and the de-emphasis filter.

Figure 28.

FM demodulator schematics

8.4

Squelch section

To avoid audio FM noise at the speakers when no carrier is received, the TSH511 has a

built-in squelch circuit. The squelch detects the wideband FM noise on the demodulated

output and fades out the audio of both audio buffers.

The audio is filtered from the FM noise using the high-pass RC filter. The cut-off frequency is

typically 100kHz. The squelch level depends on the value of the RMUTE resistor in series

with the input pin of the noise amplifier MUTE-IN (pin 23). The detected noise is integrated

with the Cpeak capacitor connected to MUTE-INT pin. The DC voltage on this pin follows the

amplitude of the noise.

The comparator and the CMUTE capacitor generate the fade-in and fade-out control ramps

for the audio buffers. The squelch was designed with particular attention to avoid audio pop-

noise.

TSH511CF Datasheet(PDF) 20 Page - STMicroelectronics