TSH511 HiFi stereo/mono infrared receiver Stereo sub-carrier demodulator ■ ■ ■ ■ ■ ■ ■ ■ Supply voltage: 2.3V to 5.5V Carriers frequency range: 0.4 to 11 MHz Two FM receivers for stereo Integrated audio buffers Audio outputs: 20 mW into 16 ohms High sensitivity: 4µV @12dB SINAD Flexibility: access pins for each section Receiver 2 Standby for mono operation PACKAGE DESCRIPTION The TSH511 is a 0.4 to 11 MHz dual FM receiver. This circuit offers the functions needed for a highly sensitive infrared HiFi STEREO receiver. Featuring high input sensitivity and high input dynamic range, each receiver integrates a RF front-end LNA, an intermediate amplifier with 2 external filters, a voltage limiter, a quadrature FM demodulator, and finally an audio buffer. The integrated audio buffers are able to drive directly a 16 ohms headphone with 20mW. A SQUELCH circuit mutes both audio amplifiers. Access pins to each section makes the TSH511 suited for a wide field of applications. For MONO applications, the STANDBY pin enables one receiver only, reducing the supply current. The TSH511 forms a chipset with the dual transmitter TSH512. APPLICATIONS ■ ■ ■ ■ ■ F TQFP44 10 x 10 mm PIN CONNECTION (top view) 44 42 41 40 39 38 37 36 35 34 1 33 2 32 Standby 3 amp. 31 FM demodulator limiter RX2 4 5 Infrared HiFi stereo receiver Infrared Multimedia Headsets Stereo sub-carrier demodulator FM IF receiver systems Power Line Carrier Intercoms 43 30 29 LNA TSH511 6 Audio buffers 28 7 27 8 26 RX1 Vref 9 limiter amp. 25 FM demodulator SQUELCH 10 24 11 23 ORDER CODE Temperature Range Package Conditionning Marking TSH511CF -40°C to +85°C TQFP44 Tray TSH511C TSH511CFT -40°C to +85°C TQFP44 Tape & reel TSH511C Part Number 12 December 2002 13 14 15 16 17 18 19 20 21 22 1/18 TSH511 ABSOLUTE MAXIMUM RATINGS Symbol Vcc Parameter Toper Tstg Tj Rthjc Supply Operating free air temperature range Storage temperature Maximum junction temperature Thermal resistance junction to case ESD HBM: Human Body Model2) except CDM: Charged Device Model3) for pin 6 ESD only for pin 6 Value voltage1) 7 V -40 to +85 -65 to +150 150 14 °C °C °C °C/W 2 1.5 kV 0.2 Model4) MM: Machine HBM: Human Body Model 1 CDM: Charged Device Model 1 MM: Machine Model kV 0.1 Latch-up Class5) 1. 2. 3. 4. 5. Unit A All voltages values, except differential voltage, are with respect to network ground terminal ElectroStatic Discharge pulse (ESD pulse) simulating a human body discharge of 100 pF through 1.5kΩ Discharge to Ground of a device that has been previously charged. ElectroStatic Discharge pulse (ESD pulse) approximating a pulse of a machine or mechanical equipment. Corporate ST Microelectronics procedure number 0018695 OPERATING CONDITIONS Symbol Parameter Value Supply voltage Unit Vcc faudio 2.3 to 5.5 V Audio frequency range 20 to 20,000 Hz fcarrier Carrier frequency range 0.4 to 11 MHz GND BUF-IN2 39 MIX-OUT2 40 MIX-IN2 41 VCC 42 DEC-LIM2A LIM-IN2 43 DEC-LIM2B GND 44 LIM-OUT2 AMP-OUT2 BLOC DIAGRAM 38 37 36 35 34 GND 1 33 GND AMP-IN2 2 32 SBY1 Standby VCC 3 LNA-OUT2 4 VCC 5 LNA-IN 6 GND 7 27 GND LNA-OUT1 8 26 BUF-OUT1 VCC 9 25 MUTE-OUT amp. FM demodulator limiter RX2 LNA TSH511 Audio buffers RX1 31 SBY2 30 BUF-OUT2 29 VCC 28 DEC-OUT Vref limiter amp. FM demodulator SQUELCH 2/18 12 13 14 15 16 17 18 19 20 21 22 LIM-OUT1 DEC-LIM1B MIX-IN1 VCC MIX-OUT1 GND BUF-IN1 MUTE-IN DEC-LIM1 MUTE-INT 23 LIM-IN1 24 11 GND 10 DEC-LNA AMP-OUT1 AMP-IN1 TSH511 PIN DESCRIPTION related to direction1) Pin Pin name Pin description 1 GND - - GROUND 2 3 4 5 6 7 8 AMP-IN2 VCC LNA-OUT2 VCC LNA-IN GND LNA-OUT1 RX2 RX2 RX1 & RX2 RX1 I O I O Intermediate amplifier input SUPPLY VOLTAGE Low Noise Amplifier output SUPPLY VOLTAGE Low Noise Amplifier input GROUND Low Noise Amplifier output 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 VCC AMP-IN1 DEC-LNA AMP-OUT1 GND LIM-IN1 DEC-LIM1A LIM-OUT1 DEC-LIM1B MIX-IN1 VCC MIX-OUT1 GND BUF-IN1 MUTE-IN MUTE-INT MUTE-OUT BUF-OUT1 GND DEC-OUT VCC BUF-OUT2 SBY2 SBY1 GND BUF-IN2 GND MIX-OUT2 VCC MIX-IN2 DEC-LIM2A LIM-OUT2 DEC-LIM2B LIM-IN2 GND AMP-OUT2 RX1 RX1 & RX2 RX1 RX1 RX1 RX1 RX1 RX1 RX1 RX1 RX1 & RX2 RX1 & RX2 RX1 & RX2 RX1 RX1 & RX2 RX2 RX1 & RX2 RX1 & RX2 RX2 RX2 RX2 RX2 RX2 RX2 RX2 RX2 I O I O I O I I O O O I I I O I O I O SUPPLY VOLTAGE Intermediate amplifier input Decoupling capacitor Intermediate amplifier input GROUND Limiter input Decoupling capacitor Limiter output Decoupling capacitor Mixer input SUPPLY VOLTAGE Mixer output (demodulated audio signal) GROUND Audio buffer input Noise amplifier input (Squelch circuit) Capacitor connection of the noise rectifier Capacitor connection (ramp generator to mute the audio) Audio buffer output GROUND Decoupling capacitor of Audio buffers SUPPLY VOLTAGE Audio buffer output Standby 2 Standby 1 GROUND Audio buffer input GROUND Mixer output SUPPLY VOLTAGE Mixer input Decoupling capacitor Limiter output Decoupling capacitor Limiter input GROUND Intermediate amplifier output 1. pin direction: I = input pin, O = output pin, - = pin to connect to supply or decoupling capacitors or external components 3/18 TSH511 TYPICAL SCHEMATIC Stereo infrared receiver 4/18 TSH511 INFRARED STEREO HEADPHONE APPLICATION The right side of the figure shows the block-diagram of an infrared stereo receiver using the TSH511. The sensitive LNA directly connected to the photodiode does not require an external pre-amplifier. After filtering, the amplified signals are limited and demodulated with quadrature demodulators. The two integrated audio buffers directly drive the stereo headphones. The audio power reaches 2x20mW in two 16Ω loads. The built-in squelch function fades-out the audio when the incoming infrared signal is low. The standby inputs SBY1 and SBY2 enable only one receiver for the mono applications. IR stereo HiFi transmitter (Television) IR stereo HiFi receiver (Headphones) Vcc: 2.3 to 5.5V Current < 15 mA 2.3 MHz filter TSH512 LNA + ALC TSH511 Audio buffer2 buffer2 photodiode Vcc RX2 SBY Line inputs LNA VOX LED buffer1 TX1 LNA + ALC rs rrie o: z ca e r H st e .8 M Fi Hi & 2 2.3 20 mW / 16 Ω RX1 SBY1 Left channel 20 mW / 16 Ω SQUELCH TX2 SBY2 Right channel Audio buffer1 filter Power supply: 2.3 to 5.5V Icc < 20 mA stereo 2.8 MHz 5/18 TSH511 MULTIMEDIA APPLICATION: HEADSET SIDE The TSH511 receives the HiFi stereo sound from the computer through 2.3 and 2.8 MHz stereo infrared carriers. The access pins to the RF amplifiers allow the use of a 1.7 MHz reject filter to cancel the transmitted signal of the microphone. The wide supply range (2.3 to 5.5 V) allows battery operation. TSH511 & 512 supply: 2.3 to 5.5V, 25 mA HiFi stereo from the PC: 2x 20 mW /16 Ω 1.7 MHz reject filter TSH511 buffer2 photodiode LNA Vcc SBY1 Audio buffer1 Vcc SBY2 RX1 TX2 SBY RX2 SQUELCH TSH512 MIC. BIAS filter Audio buffer2 Voice transmitted to the PC LNA + ALC 2.3 MHz Band-pass VOX filter MIC. BIAS 1.7 MHz reject LED buffer1 filter 2.8 MHz Band-pass TX1 Stereo Rx: 2.3 & 2.8 MHz Microphone Tx: 1.7 MHz carrier LNA + ALC 1.7 MHz filter Band-pass MULTIMEDIA APPLICATION: COMPUTER SIDE In multimedia application, the TSH511 receives the voice of the user through the 1.7 MHz infrared carrier. The standby pins can disable the unused receiver and audio amplifier to reduce the supply current. TSH511 & 512 supply: 2.3 to 5.5V, 24 mA HiFi stereo Voice from the headset microphone mono Rx: 1.7 MHz TSH511 Audio buffer2 RX2 TSH512 LNA LNA + ALC buffer2 TX2 SBY1 RX1 SBY LED SBY2 HiFi stereo Tx: 2.3 & 2.8 MHz SQUELCH photodiode VOX filter buffer1 LNA + ALC TX1 6/18 1.7 MHz Band-pass Vcc Audio buffer1 TSH511 ELECTRICAL CHARACTERISTICS Vcc = 2.7V, Tamb = 25°C, faudio = 1 kHz, fcarrier = 2.8 MHz, frequency deviation = +/-75 kHz (unless otherwise specified) Symbol Parameter Test condition Min Typ Max Unit 15 18 mA 11 13 mA 9.5 11.5 mA Overall Circuit (refering to typical application schematic, without reject filters) ICC_OX Current consumption, RX1 is on, RX2 is on. SBY1 = ’Low’, SBY2 = X (X = don’t care) Current consumption ICC_10 RX1 is on, RX2 is off SBY1 = ’High’, RX1 audio buffer is on SBY2 = ’Low’ RX2 audio buffer is on Current consumption ICC_11 RX1 is on, RX2 is off SBY1 = ’High’, RX1 audio buffer is on, SBY2 = ’High’ RX2 audio buffer is off MAUS SNOUT Vi THD Maximum Usable Average Sensitivity Output audio signal to noise ratio Input limiting voltage Total Harmonic Distortion with audio SINAD=12 dB, audio BW=30 kHz 4 with audio SINAD=26 dB, audio BW=30 kHz 19 Vcarrier = 1 mVRMS, with psophometric filter µVRMS 58 output S/N reduced by 3dB, in BW = 30kHz 80 output S/N reduced by 3dB, psophometric filter 60 Vcarrier = 1 mVRMS, with psophometric filter dB µVRMS 0.6 % Low Noise Amplifier (LNA) Section GLNA LNA voltage gain ZL= 2 kΩ, fcarrier = 10 MHz 18 22 28 dB BWLNA -3dB LNA Bandwidth ZL = 2 kΩ 20 MHz En_LNA Equivalent input noise voltage Rs = 0 Ω 3.4 nV/√Hz In_LNA Equivalent input noise current Rs = 0 Ω 0.6 pA/√Hz Input impedance definied as RLNA_IN 30 kΩ RLNA_IN in paralell with CLNA_IN CLNA_IN 2 pF 200 Ω ZL= 2 kΩ 127 ZLNA_IN ZLNA_OUT P1dB_LNA IIP3LNA Output impedance 1dB compression point Input 3rd order interception point ZL= 2 kΩ, fcarrier=10 MHz 95 ZL= 2 kΩ 30 ZL= 2 kΩ, fcarrier=10 MHz 22 mVRMS mVRMS 7/18 TSH511 Symbol Parameter Test condition Min Typ Max Unit Amplifier Voltage Gain ZL=2 kΩ, fcarrier =10 MHz 16 20 dB Input impedance defined as RAMP_IN 10 kΩ RAMP_IN in parallel with CAMP_IN CAMP_IN 2 pF 350 Ω Amplifier (AMP) Section GAMP ZAMP_IN ZAMP_OUT Output impedance ZL = 2 kΩ P1dBAMP 1dB compression point -3dB AMP Bandwidth mVRMS ZL = 2 kΩ, fcarrier=10 MHz BWAMP 560 220 ZL = 2 kΩ 380 11 MHz Limitor (LIM) Section GLIM ZLIM_IN VLIM_OUT Voltage gain ZL=15kΩ tied to GND Input impedance defined as RLIM_IN 15 RLIM_IN in parallel with CLIM_IN CLIM_IN 2 pF 170 mVpp Output Voltage 50 ZL = 15 kΩ tied to GND 54 60 dB kΩ FM Demodulator Section +-75 kHz FM deviation VDEM Output voltage typical application schematic 700 800 900 mVRMS ZL = 4 kΩ 100 Ω 65 dB 2 kΩ 9 mVRMS 1 mVRMS Voltage on pin 25 = 1.7V 24 µA Voltage on pin 25 = 1.7V 14 µA ZDEM_OUT Output impedance Squelch Section ATT ZN_IN Audio attenuation on each receiver when audio buffers are muted. RX1 and RX2 audio buffers muted ZL = 16 Ω on both audio buffers Noise Amplifier Input impedance 55 from MUTED to UNMUTED state, VN_TH Comparator threshold RMUTE = 22 kΩ, fIN = 100 kHz VN_HYS Comparator hysteresis Current sinked on pin 25 to discharge CMUTE capacitor: ramp generator controlling the attenuation from ON to OFF states of audio buffers. Current sourced on pin 25 to charge IMUTE_SOU CMUTE capacitor: ramp generator conRCE trolling the attenuation from OFF to ON states of audio buffers. IMUTE_SINK 8/18 RMUTE = 22 kΩ, fIN = 100 kHz TSH511 Symbol Parameter Test condition Min Typ Max Unit Audio Buffers ZOD-IN BW1dB POUT_OD THDOD THDOD Input Impedance -1dB bandwith Output power Distortion in Line Driver mode Distortion in Power Amplifier mode ZL = 16 Ω ZL= 16Ω VOD_IN = 70mVRMS 15 Vout = 0.5 VRMS, ZL= 10kΩ with decoupling capacitor CDEC = 1µF/ceramic on pin 28. 200 kΩ 35 kHz 20 mW 0.2 0.3 % 0.35 0.8 % Pout = 20 mW, ZL = 16Ω VISOL Crosstalk: isolation between the two Audio Buffers Pout = 20 mW, ZL = 16Ω 51 dB Standby VSBY_L Low level input voltage of Standby inputs (Pins 31 & 32) VSBY_H High level input voltage of Standby inputs (Pins 31 & 32) TON Turn-on time from Standby mode to Active mode 0.5 µs TOFF Turn-off time from Active mode to Standby mode 0.5 µs 0.1xVCC 0.9xVcc V V 9/18 TSH511 OVERALL CIRCUIT Squelch Threshold vs. RMUTE Input Resistor Supply current vs. Supply voltage 20 60 RX1+RX2+Buffers 18 16 VCC = 2.7V 50 RX1+Buffers FIN = 100 kHz VN_TH(mVRMS) ICC(mA) 14 12 10 8 RX1+ (RX1 Buffer) 6 40 30 20 FIN = 1 MHz 4 10 2 0 0 1 2 3 4 5 0 6 1 10 VCC(V) 100 RMUTE(kΩ ) S/N vs. 2.8 MHz Input Level Supply current vs. Temperature 60 20 50 V CC = 2.7V 18 PSOPH TX1+TX2 14 30 BW = 30 kHz ICC(mA) Total S/N (dB) 16 40 20 TX1+TX2+Buffers 12 10 8 TX1+Buffers 6 10 2 0 1 10 100 TX1 4 VCC = 2.7 V Deviation = +/-75 kHz 1000 0 -40 Input Level (µV) -20 0 20 40 60 TAMB(°C) PSOPH: Signal on Noise Ratio curve measured with a CCITT standard psophometric bandpass characteristic. It approximates the response of human hearing. Sensitivity vs. Supply Voltage Sensitivity (µV) @ 26 dB SINAD 25 20 15 10 0 10/18 FCARRIER = 2.8MHz FMOD = 1 kHz Deviation = +/- 75kHz BW = 30 kHz 5 2 3 4 VCC(V) 5 80 TSH511 AUDIO BUFFERS Output THD+N vs. Output Power (RL = 16 Ω) Output THD+N vs. Output Power (RL = 16 Ω) 10 10 F = 20 kHz VCC = 2.7V THD+NBUFFER (%) THD+NBUFFER (%) VCC = 2.3V VCC = 5.5V 1 1 F = 1 kHz RL = 16 Ω F = 1 kHz BW = 30 kHz 0.1 1 10 0.1 100 1 10 POUT-BUF(mW) Output THD+N vs. Output Power (RL = 32 Ω) 10 VCC = 2.3V VCC = 2.7V THD+NBUFFER (%) THD+NBUFFER (%) RL = 32 Ω F = 1 kHz BW = 30 kHz 100 POUT-BUF(mW) Output THD+N vs. Output Power (RL = 32 Ω) 10 RL = 16 Ω VCC = 2.7 V F = 20 Hz 1 F = 20 kHz 1 F = 1 kHz F = 20 Hz RL = 32 Ω VCC = 2.7 V VCC = 5.5V 0.1 1 10 0.1 100 1 10 POUT-BUF(mW) 100 POUT-BUF(mW) Output THD+N vs. Output Power (RL = 600 Ω) Output THD+N vs. Output Power (RL = 600 Ω) 10 VCC = 2.3V 1 THD+NBUFFER (%) THD+NBUFFER (%) VCC = 2.7V VCC = 5.5V RL = 600 Ω F = 1 kHz BW = 30 kHz 0.1 0.1 1 POUT-BUF(mW) 10 F = 20 kHz 1 F = 20 Hz F = 1 kHz RL = 600 Ω VCC = 2.7 V 0.1 0.1 1 POUT-BUF(mW) 11/18 TSH511 Output THD+N vs. Output Voltage (RL = 10kΩ) Output THD+N vs. Output Voltage (RL = 10kΩ) 10 10 RL = 10 kΩ F = 1 kHz BW = 30 kHz RL = 10 kΩ VCC = 2.7 V VCC = 2.3V THD+NBUFFER (%) THD+NBUFFER (%) VCC = 2.7V 1 VCC = 5.5V 0.1 1 F = 1 kHz F = 20 Hz 0.1 0.1 1 0.1 1 VOUT-BUF(Vrms) VOUT-BUF(Vrms) Output THD+N vs. Frequency (RL = 16 Ω) Output THD+N vs. Frequency (RL = 32 Ω) 10 10 THD+NBUFFER (%) THD+NBUFFER (%) VCC = 2.7 V Vin = 50 mVrms RL = 16 Ω 1 0.1 20 100 1000 VCC = 2.7 V Vin = 50 mVrms RL = 32 Ω 1 0.1 20 10000 100 Output THD+N vs. Frequency (RL = 600 Ω) 10 VCC = 2.7 V Vin = 50 mVrms RL = 600 Ω THD+NBUFFER (%) THD+NBUFFER (%) 10000 Output THD+N vs. Frequency (RL = 10 kΩ) 10 1 100 1000 Frequency (Hz) 12/18 1000 Frequency (Hz) Frequency (Hz) 0.1 20 F = 20 kHz 10000 VCC = 2.7 V Vin = 50 mVrms RL = 10 kΩ 1 0.1 20 100 1000 Frequency (Hz) 10000 TSH511 Output Power vs. Temperature 24 POUT-BUF(mW) 22 20 18 16 14 VCC = 2.7V RL = 16 Ω VIN = 70 mVRMS 12 10 -40 -20 0 20 40 60 80 TAMB(°C) 13/18 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 connected directly to the TSH511 without any external preamplifier. The access pins for each section and the two standby configurations allow a high versatility for many applications: HiFi stereo infrared receiver, mono/stereo subcarrier receiver, power line carrier audio. GND BUF-IN2 39 MIX-OUT2 40 MIX-IN2 41 VCC 42 DEC-LIM2A LIM-IN2 43 DEC-LIM2B GND 44 LIM-OUT2 AMP-OUT2 Figure 1 : TSH511 block diagram 38 37 36 35 34 Buffers or only one depending on the combination on SBY1 & SBY2. To avoid noise at the audio output, a Squelch section mutes the Audio Buffers when no carrier is received. The Squelch Section uses the demodulated 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 Audio Buffers. Figure 2 : Infrared audio frequencies GND 1 33 GND AMP-IN2 2 32 SBY1 VCC 3 31 SBY2 30 BUF-OUT2 29 VCC 28 DEC-OUT 27 GND 26 BUF-OUT1 IR frequency applications Standby amp. FM demodulator limiter 1.6 MHz AM mono 1.7 MHz FM mono 2.3 MHz FM right channel 2.8 MHz FM left channel or mono RX2 LNA-OUT2 4 VCC 5 LNA-IN 6 GND 7 LNA-OUT1 8 VCC 9 LNA TSH511 Audio buffers RX1 Vref 25 MUTE-OUT AMP-IN1 10 24 MUTE-INT DEC-LNA 11 23 MUTE-IN limiter amp. FM demodulator SQUELCH LNA section: Low Noise Amplifier 22 BUF-IN1 21 GND 20 MIX-OUT1 19 VCC 18 MIX-IN1 17 DEC-LIM1B 16 LIM-OUT1 15 DEC-LIM1 14 LIM-IN1 13 GND AMP-OUT1 12 The LNA is common to both receivers but the output 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 intermediate 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 demodulation in the FM demodulator. The FM demodulator is a classical quadrature detector using an external tank. The demodulated signal can be amplified by the Audio Buffer section after de-emphasis. Each Audio Buffer can drive a 16 ohms headphone with 20 mW power. The two standby pins SBY1 & SBY2 allow the second receiver RX2 to be put into standby for mono operation. In mono, it is possible to use both Audio 14/18 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 receivers sections RX1 and RX2. Figure 3 : LNA schematic TSH511 The LNA output is directly connected to LNA-OUT1 and LNA-OUT2 pins in parallel (pin 8 and 4 respectively). As the LNA minimum impedance load is 1 kΩ, the load impedance on each pin LNA-OUT1 or LNA-OUT2 must be 2 kΩ minimum. The series 50 Ω resistor and the 100 nF capacitor decouple the LNA supply voltage (pin 5), improving noise performance. AMP and LIM sections: Amplifier and Limitor The first filter output is connected to the intermediate amplifier AMP. The gain of AMP is typically 20 dB. The second filter is connected between the output of AMP and the input of the limitor LIM. The 60 dB limitor LIM provides a constant amplitude signal to the FM demodulator. It reduces the AM parasitic effects into the FM demodulator. allows to adjustment of the demodulation characteristic. For a given transmitting deviation, a lower value of Rlo gives a lower demodulated amplitude and reduces the distortion. The AC amplitude on pin 18 must not exceed 300 mVRMS to prevent clipping by the internal ESD diodes of the circuit. The low output impedance of the demodulator (MIX-OUT pins) drives the external volume control and the de-emphasis filter. Figure 5 : FM demodulator schematic Figure 4 : AMP and LIM schematic SQUELCH section FM demodulator section The FM demodulator is a classical quadrature demodulator based on a multiplier. The quadrature is performed with the tank circuit Llo inductor and Clo capacitor. The tank circuit is tuned on the receiving frequency. The Rlo resistor is connected in parallel with Llo and Clo to reduce the Q factor of the tank circuit. It 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 serie 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. 15/18 TSH511 The comparator and the CMUTE capacitor generate the fade-in and fade-out control ramps for the audio buffers. The Squelch has been designed with particular attention to avoid audio pop-noise. Figure 6 : Squelch schematic The Audio Buffers can also drive the other usual impedances used in audio: 32Ω, 600Ω and 10kΩ (see the corresponding distorsion curves). The high input impedances of the Audio Buffers reduce the coupling capacitors to less than 0.1 µF allowing space and cost saving. Standby section Depending on the states of the logic inputs SBY1 and SBY2, RX2 and the Audio Buffer2 can be disabled separately. The TSH511 receiver can adapt to different applications by using SBY1 & SBY2 standby pins: The squelch section is driven by the receiver RX1 but controls both audio buffers. Audio Buffer sections The audio signal from a FM demodulator enters into the 6dB/octave low-pass filter for de-emphasis. 50µs and 75µs are standard de-emphasis values. After the de-emphasis network, the potentiometer controls the volume. The Rail-to-Rail output stage of each Audio Buffer is able to drive 20 mW into 16Ω at 2.3V supply voltage. In this condition, the distortion is typically 0.3% before saturation. 16/18 RX1 & audio buffer1 RX2 audio buffer 2 typical use High ON ON ON stereo High Low ON OFF ON mono on the two outputs High High ON OFF OFF mono on one output SBY1 pin 32 SBY2 pin 31 Low Low Low In the standard stereo mode, the configuration is: SBY1 = SBY2 = ’Low’ In mono mode with one load(example: a single loadspeaker), RX2 and Audio Buffer 2 are disabled, the configuration is SBY1 = SBY2 = ’High’. In mono mode with a stereo load (example: a stereo headphone), the configuration is SBY1 = ’high’, SBY2 = ’Low’. A pin connected to Vcc is at ’High’ state, and if connected to GND is at ’Low’ state. TSH511 APPLICATION SCHEMATIC The infrared carriers are detected by the photodiode and the signal is directly amplified by the TSH511. Optional reject filters can be added in each channel to improve crosstalk performances. Each receiver has a standard bandpass filter (filters F1 & F3) to select the 2.3 and 2.8 MHz carriers. After the FM demodulators, the potentiometers P1 and P2 control the volume levels. The stereo headphones are directly connected to the integrated audio buffers. The potentiometer P3 allows adjustment of the sensitivity of the Squelch. The Squelch function fade-in and fade-out the audio signal depending on the level of the 2.8 MHz carrier. 17/18 TSH511 PACKAGE MECHANICAL DATA 44 PINS - PLASTIC PACKAGE A A2 e 44 A1 34 33 11 23 E3 E1 E B 1 0,10 mm .004 inch SEATING PLANE c 22 L D3 D1 D L1 12 K Dimensions Millimeters Min. A A1 A2 B C D D1 D3 e E E1 E3 L L1 K 0,25 mm .010 inch GAGE PLANE 0.05 1.35 0.30 0.09 0.45 Typ. 1.40 0.37 12.00 10.00 8.00 0.80 12.00 10.00 8.00 0.60 1.00 Inches Max. 1.60 0.15 1.45 0.40 0.20 0.75 Min. 0.002 0.053 0.012 0.004 0.018 Typ. 0.055 0.015 0.472 0.394 0.315 0.031 0.472 0.394 0.315 0.024 0.039 Max. 0.063 0.006 0.057 0.016 0.008 0.030 0° (min.), 7° (max.) Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is a registered trademark of STMicroelectronics © 2002 STMicroelectronics - All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - China - Finland - France - Germany - Hong Kong - India - Italy - Japan - Malaysia - Malta - Morocco Singapore - Spain - Sweden - Switzerland - United Kingdom http://www.st.com 18/18