TSH511 ST Microelectronics, Inc., TSH511 Datasheet - Page 14

• Manufacturer Part Number: TSH511
• Description: Hifi Stereo/mono Infrared Receiver Stereo Sub-carrier Demodulator
• Manufacturer: ST Microelectronics, Inc.

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
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
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GND
GND
AMP-IN2
AMP-IN2
VCC
VCC
LNA-OUT2
LNA-OUT2
VCC
VCC
LNA-IN
LNA-IN
GND
GND
LNA-OUT1
LNA-OUT1
VCC
VCC
AMP-IN1
AMP-IN1
DEC-LNA
DEC-LNA
10
10
11
11
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
amp.
amp.
amp.
amp.
44
44
12
12
LNA
LNA
43
43
13
13
42
42
14
14
limiter
limiter
limiter
limiter
41
41
15
15
RX2
RX2
TSH511
TSH511
RX1
RX1
40
40
16
16
FM demodulator
FM demodulator
FM demodulator
FM demodulator
39
39
17
17
38
38
18
18
37
37
19
19
Audio
Audio
buffers
buffers
36
36
Vref
Vref
20
20
Standby
Standby
35
35
21
21
SQUELCH
SQUELCH
34
34
22
22
33
33
32
32
31
31
30
30
29
29
28
28
27
27
26
26
25
25
24
24
23
23
GND
GND
SBY1
SBY1
SBY2
SBY2
BUF-OUT2
BUF-OUT2
VCC
VCC
DEC-OUT
DEC-OUT
GND
GND
BUF-OUT1
BUF-OUT1
MUTE-OUT
MUTE-OUT
MUTE-INT
MUTE-INT
MUTE-IN
MUTE-IN
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
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
1.6 MHz
1.7 MHz
2.3 MHz
2.8 MHz
IR frequency
AM mono
FM mono
FM right channel
FM left channel or mono
applications