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TSH511(2002) データシートの表示(PDF) - STMicroelectronics

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TSH511 Datasheet PDF : 18 Pages
First Prev 11 12 13 14 15 16 17 18
TSH511
GENERAL DESCRIPTION
The TSH511 is a 0.4 to 11 MHz dual FM analogue
receiver. The incoming signal is amplified with a
22 dB Low Noise Amplifier (LNA section). The
good noise performance of the LNA allows the
photodiode for infrared applications to be connect-
ed directly to the TSH511 without any external
preamplifier. The access pins for each section and
the two standby configurations allow a high versa-
tility for many applications: HiFi stereo infrared re-
ceiver, mono/stereo subcarrier receiver, power
line carrier audio.
Figure 1 : TSH511 block diagram
44 43 42 41 40 39 38 37 36 35 34
GND
1
AMP-IN2
2
VCC
3
LNA-OUT2 4
VCC
5
LNA-IN
6
GND
7
LNA-OUT1 8
VCC
9
AMP-IN1 10
DEC-LNA 11
amp.
LNA
amp.
33 GND
limiter
FM demodulator
RX2
Standby
32 SBY1
31 SBY2
30 BUF-OUT2
TSH511
Audio
buffers
29 VCC
28 DEC-OUT
27 GND
RX1
limiter
Vref
FM demodulator
26 BUF-OUT1
25
SQUELCH
24
MUTE-OUT
MUTE-INT
23 MUTE-IN
12 13 14 15 16 17 18 19 20 21 22
The LNA is common to both receivers but the out-
put is split in two: one for each receiver. Each LNA
output can be connected to a first optional filter for
bandpass or reject filtering.
The filtered signal is amplified with an intermedi-
ate Amplifier (AMP section) followed by a second
filter. The AMP sections have 20 dB typical gain.
Finally, the signal is amplified and limited in the
Limiter (LIM section). The 60 dB amplifier-limiter
LIM provides a constant amplitude signal to the
demodulator. It reduces AM parasitics demodula-
tion in the FM demodulator.
The FM demodulator is a classical quadrature de-
tector using an external tank.
The demodulated signal can be amplified by the
Audio Buffer section after de-emphasis. Each Au-
dio Buffer can drive a 16 ohms headphone with 20
mW power.
The two standby pins SBY1 & SBY2 allow the sec-
ond receiver RX2 to be put into standby for mono
operation. In mono, it is possible to use both Audio
14/18
Buffers or only one depending on the combination
on SBY1 & SBY2.
To avoid noise at the audio output, a Squelch sec-
tion mutes the Audio Buffers when no carrier is re-
ceived. The Squelch Section uses the demodulat-
ed signal of the first receiver (RX1). This signal is
highpass filtered, rectified and compared to a
threshold to produce the Mute signal (pin 25).
When no carrier is received on RX1, the wideband
’FM noise’ on the demodulator increases and the
Mute signal mutes the both Audio Buffers. When
the carrier is present, the wideband noise on the
demodulator output decreases, enabling the Au-
dio Buffers.
Figure 2 : Infrared audio frequencies
IR frequency
1.6 MHz
1.7 MHz
2.3 MHz
2.8 MHz
applications
AM mono
FM mono
FM right channel
FM left channel or mono
LNA section: Low Noise Amplifier
The Low Noise Amplifier (LNA) has a typical gain
of 22 dB to amplify the incoming RF signal from
the photodiode. The LNA is common to both re-
ceivers sections RX1 and RX2.
Figure 3 : LNA schematic

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