TSH512 TQFP44 TSH511 TSH512CF TSH512C TSH512CFT SMV1212 ZC833 - Datasheet Archive

 

HiFi stereo/mono infrared transmitter Stereo sub-carrier generator s s s s s s s s Supply voltage: 2.3V to 5.5V Carriers

 

TSH512 TSH512 HiFi stereo/mono infrared transmitter Stereo sub-carrier generator s s s s s s s s Supply voltage: 2.3V to 5.5V Carriers frequency range: 0.4 to 11 MHz High versatility: I/O pins for each section Two FM transmitters for stereo Sinusoidal carriers for high spectral purity Micro or line level preamplifiers with ALC VOX function to save on battery power Transmitter 2 Standby for mono operation PACKAGE DESCRIPTION s s s s s PIN CONNECTION (top view) 44 43 42 41 40 39 38 36 37 35 34 VCO 1 33 PEA 2 + APPLICATIONS F TQFP44 TQFP44 10 x 10 mm 3 32 + The TSH512 TSH512 is a 0.4 to 11 MHz dual FM transmitter. Access pins to each section give a high versatility and allow several applications: stereo headphone, multimedia headset, audio sub-carrier generator. The TSH512 TSH512 integrates in one chip: Low-noise audio preamplifiers with ALC (Automatic Level Control), frequency modulated oscillators, and linear output buffers to drive external transistors. The sinusoidal carriers facilitates the filtering and allows high performance audio transmission. The VOX (Voice Operated Transmit) circuitry disables the output buffer when there is no audio to save battery power. For MONO applications, the STAND-BY pin enables one transmitter only, reducing the supply current. The TSH512 TSH512 forms a chipset with the dual receiver TSH511 TSH511. ALC TX2 31 Output buffer LNA 4 30 TSH512 TSH512 29 5 Infrared HiFi stereo transmitter Infrared Headsets Stereo sub-carrier for video transmitters Voice operated wireless webcams FM IF transmit systems VOX 6 + - 7 Monostable 8 27 26 LNA 9 Output buffer TX1 + - ALC 25 + - 10 ORDER CODE 28 24 PEA 11 Temperature Range Package Conditionning TSH512CF TSH512CF -40°C to +85°C TQFP44 TQFP44 Tray TSH512C TSH512C TSH512CFT TSH512CFT -40°C to +85°C TQFP44 TQFP44 Tape & reel 23 VCO Marking TSH512C TSH512C Part Number December 2003 12 13 14 15 16 17 18 19 20 21 22 1/19 TSH512 TSH512 ABSOLUTE MAXIMUM RATINGS Symbol Vcc Toper Tstg Tj Rthjc Parameter Value 1) 7 V -40 to +85 -65 to +150 150 14 Supply voltage Operating free air temperature range Storage temperature Maximum junction temperature Thermal resistance junction to case °C °C °C °C/W Latch-up Class2) ESD sensitive device: handling precautions required ESD A HBM: Human Body Model3) 2 4) except pin CDM: Charged Device Model 20 & 36 1. 2. 3. 4. 5. Unit 1 kV 0.2 MM: Machine Model5) All voltages values, except differential voltage, are with respect to network ground terminal Corporate ST Microelectronics procedure number 0018695 ElectroStatic Discharge pulse (ESD pulse) simulating a human body discharge of 100 pF through 1.5k 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. OPERATING CONDITIONS Symbol Parameter Value 2.3 to 5.5 Supply voltage Unit V Vcc faudio Audio frequency range 20 to 20,000 Hz fcarrier Carrier frequency range 0.4 to 11 MHz DEC2 VCO-OUT2 39 VCO-B2 40 VCO-A2 41 VCO-BIAS2 ALC-INT2 42 VCC LNA-OUT2 43 PEA-INN2 LNA-INN2 44 38 37 36 35 34 PEA-OUT2 LNA-INP2 BLOC DIAGRAM Bias VCO 33 GND 32 BUF-IN2 31 BUF-OUT2 30 GND 29 VOX-TIMER 28 VOX-INTN 27 VOX-MUTE 26 1 VCC 25 BUF-OUT1 24 BUF-IN1 23 GND PEA 3 VCC 4 SBY 7 VCC 8 GND 9 TX2 6 VOX-SENS ALC 5 VOX-INTS + GND + MIC-BIAS2 2 MIC-BIAS1 Bias Output buffer TSH512 TSH512 VOX + - Monostable Bias LNA Output buffer TX1 + - ALC + - 10 DEC1 LNA 11 PEA 12 2/19 13 14 15 16 17 18 19 20 21 22 LNA-INP1 LNA-OUT1 ALC-INT1 PEA-INN1 PEA-OUT1 VCO-BIAS1 VCC VCO-A1 VCO-B1 VCO-OUT1 VCO LNA-INN1 Bias TSH512 TSH512 PIN DESCRIPTION related to direction1) Pin Pin name Pin description 1 2 3 4 5 6 7 8 9 10 11 DEC2 MIC-BIAS2 GND VCC SBY VOX-INTS VOX-SENS VCC GND MIC-BIAS1 DEC1 TX2 TX2 TX1 & TX2 TX1 & TX2 TX1 & TX2 TX1 TX1 O I O - Decoupling capacitor for internal voltage reference Microphone bias GROUND SUPPLY VOLTAGE Standby Control (INPUT pin) Time constant terminal for Audio Signal integrator in VOX Gain adjustment for VOX input sensitivity SUPPLY VOLTAGE GROUND Microphone bias Decoupling capacitor for internal voltage reference 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 LNA-INP1 LNA-INN1 LNA-OUT1 ALC-INT1 PEA-INN1 PEA-OUT1 VCO-BIAS1 VCC VCO-A1 VCO-B1 VCO-OUT1 GND BUF-IN1 BUF-OUT1 VCC VOX-MUTE VOX-INTN VOX-TIMER GND BUF-OUT2 BUF-IN2 GND VCO-OUT2 VCO-B2 VCO-A2 VCC VCO-BIAS2 PEA-OUT2 PEA-INN2 ALC-INT2 LNA-OUT2 LNA-INN2 LNA-INP2 TX1 TX1 TX1 TX1 TX1 TX1 TX1 TX1 TX1 TX1 TX1 TX1 TX1 & TX2 TX1 & TX2 TX1 & TX2 TX2 TX2 TX2 TX2 TX2 TX2 TX2 TX2 TX2 TX2 TX2 TX2 I I O I O O O I O O O I O O O I O I I LNA positive input LNA negative input LNA output Time constant terminal for integrator in ALC Pre-Emphasis Amplifier negative input Pre-Emphasis Amplifier output Bias for external VCO components Supply Voltage Oscillator component connection Oscillator component connection VCO output Ground Input to the output buffer Output of the output buffer Supply Voltage Mute control (Output pin) in VOX Time constant terminal for Noise integrator in VOX Rise time for timer in VOX Ground Output of the output buffer Input to the output buffer Ground VCO output Oscillator component connection Oscillator component connection Supply Voltage Bias for external VCO components Pre-Emphasis Amplifier output Pre-Emphasis Amplifier negative input Time constant terminal for internal peak detector in ALC LNA output LNA negative input LNA positive input 1. pin direction: I = input pin, O = output pin, - = pin to connect to supply or decoupling capacitors or external components 3/19 TSH512 TSH512 TYPICAL SCHEMATIC Stereo infrared transmitter 4/19 TSH512 TSH512 INFRARED STEREO TRANSMITTER APPLICATION (ie: stereo headphone) The HiFi stereo audio is amplified and level regulated by ALC. The carrier of each transmitter TX1 or TX2 of the TSH512 TSH512 is modulated in FM and bufferized to attack the LED final stage. IR stereo HiFi transmitter (Television) IR stereo HiFi receiver (Headphones) Vcc: 2.3 to 5.5V Current < 15 mA 2.3 MHz filter TSH512 TSH512 LNA + ALC TSH511 TSH511 Audio buffer2 buffer2 photodiode Vcc RX2 SBY Line inputs LNA VOX LED buffer1 TX1 LNA + ALC rs rrie : ca reo Hz st e .8 M Fi Hi & 2 2.3 20 mW / 16 RX1 SBY1 Left channel 20 mW / 16 SQUELCH TX2 SBY2 Right channel Audio buffer1 filter 2.8 MHz Power supply: 2.3 to 5.5V Icc < 20 mA stereo SUB-CARRIER GENERATOR APPLICATION: voice operated wireless camera Thanks to the operating frequency the TSH512 TSH512 offers the possibility to generate usual audio sub-carriers for video applications. The camera can be voice activated using the VOX-MUTE output of the TSH512 TSH512. The TSH512 TSH512 also provides bias, amplification, ALC for the electret microphone. Miniature camera Video FM 2.4 GHz transmitter Sub-carrier Stand-By Stand-By TSH512 TSH512 LNA + ALC buffer2 TX2 Vcc SBY MIC. BIAS Electret Condenser Microphone VOX-MUTE VOX MIC. BIAS buffer1 TX1 LNA + ALC 6 or 6.5 MHz 6 or 6.5 MHz Audio sub-carrier filter 5/19 TSH512 TSH512 MULTIMEDIA APPLICATION: HEADSET SIDE The TSH512 TSH512 is used in mono to transmit the signal of the Electret Condenser Microphone of the headset. The circuit is supplied by batteries and the VOX function switches off the output stages to spare energy. The usual working frequency is 1.7 MHz for infrared mono operation. TSH511 TSH511 & 512 supply: 2.3 to 5.5V, 25 mA HiFi stereo from the PC: 2x 20 mW /16 1.7 MHz reject filter TSH511 TSH511 buffer2 photodiode LNA Vcc SBY1 Audio buffer1 Vcc SBY2 RX1 TX2 SBY RX2 SQUELCH TSH512 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 TSH512 TSH512 transmits the HiFi stereo from the PC to the headset. TSH511 TSH511 & 512 supply: 2.3 to 5.5V, 24 mA HiFi stereo Voice from the headset microphone mono Rx: 1.7 MHz TSH511 TSH511 Audio buffer2 RX2 TSH512 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 6/19 1.7 MHz Band-pass Vcc Audio buffer1 TSH512 TSH512 ELECTRICAL CHARACTERISTICS Vcc = 2.7V, Tamb = 25°C, faudio = 1 kHz, fcarrier = 2.8 MHz (unless otherwise specified) Symbol Parameter Test condition Min Typ Max Unit Overall Circuit ICC_TOT Current consumption, TX1 on, TX2 on, MIC-BIAS1 and MIC-BIAS2 not used: VOX-MUTE=1, output buffers on 16 18.6 mA VOX-MUTE=0, output buffers off TX1 on, TX2 off, MIC-BIAS1 and MIC-BIAS2 not used: 11 12.8 mA Current consumption VOX-MUTE=1, output buffers on 10 11.5 mA VOX-MUTE=0, output buffers off ICC_SBY TX1 and TX2 are on. 7 8 mA No external load 7 MHz 30 k with TX2 in stand-by: SBY (pin5) active LNA Sections (for TX1 and TX2) GBPLNA RinLNA Gain Band Product Input Resistance on positive input: (LNA-INP1 pin 12 or LNA-INP2 pin 44) THDLNA Total Harmonic Distortion GLNA=0dB VoutLNA =700mVPP 0.01 0.05 % GLNA=40dB, at f=1kHz En Equivalent Input Noise Voltage 6 nV/Hz 20 Rs=390, Rfeedback= 39k dB Automatic Level Control (ALC) Section GALC VALC_OUT Voltage Gain Regulated Output Level 600 (At positive input of the PEA amplifier) 710 800 mVpp Pre-Emphasis Amplifier (PEA) Section GBPPEA VOpp-PEA Gain Band Product No Load (PEA-OUT1 pin17 or PEA-OUT2 pin39) Output voltage RL = 22k 9 MHz 550 mVpp Audio LNA+ALC+PEA sections Total Harmonic Distorsion THDALC GLNA = 0 dB, f =1kHz VinALC < 25mVrms (-30dBu) 0.05 0.15 % (Vin)ALC = 36mVrms (-27dBu) in linear region on PEA-OUT1 pin17 or PEA-OUT2 pin 39 1.3 1.7 % (Vin)ALC= 100mVrms (-18dBu) 3 4 % RL = 22 k tied to GND THDAGC Total Harmonic Distorsion in compression region RL = 22 k tied to GND Phase Margin at PEA PEA-OUT1 pin 17 or PEA-OUT2 pin 39 RL = 22 k LNA and PEA at unity gain 70 ° Vin = 40mV 7/19 TSH512 TSH512 Symbol Parameter Test condition Min Typ Max Unit 2.15 2.25 2.35 V Microphone Biasing Section VMIC-BIAS Microphone Biasing Voltage (see page 15) VMIC-BIAS VMIC-BIAS temperature coefficient IMIC-BIAS = 2.5 mA Over temperature range [0, 70°C] 260 [-40, 85°C] 460 ppm/°C IMIC-BIAS = 2.5 mA IMIC-BIAS MIC-BIAS current capability PSRRMIC-BIAS Power Supply Rejection Ratio of MIC-BIAS enMIC-BIAS Equivalent input noise of MIC-BIAS over VCC range [2.3V-5.5V] 2.5 @ 1kHz and mA 50 V ripple = 25mVRMS VCC=2.7V dB 22 VCC=5.0V nV/Hz 42 Vox Operated Switch (VOX) Section IVOX-TIMER Monostable Current Source (VOX-TIMER pin 29) Threshold voltage of the Monostable (Time Constant) Low Level Output Voltage (VOX-MUTE Pin27) High Level Output Voltage (VOX-MUTE Pin27) VTHVOX-TIMER VMUTE_L VMUTE_H Vcc = 2.7V 5 µA 1.4 V RL = 2 k RL = 2 k 0.2 Vcc-0.3 V V Standby Max. Low Level Input Voltage of Standby input (SBY Pin5) Min. High Level Input Voltage of Standby input (SBY Pin5) VSBY_IL max VSBY_IH min 0.1xVcc V 0.9xVcc V VCO Section VCO-BIAS output voltage VVCO-BIAS IVCO-BIAS (VCO-BIAS1 pin18 or VCO-BIAS2 pin 38) VCO-BIAS output current capability With No Load 1.43 1.47 1.51 VDC +265 ppm/°C [0, 70°C] Vcc=5.0V +356 ppm/°C +265 ppm/°C [-40, 85°C] Vcc=5.0V @ 1kHz, Phase Noise µA mV/V [-40, 85°C] Vcc=2.7V PNLO 40 8 [0, 70°C] Vcc=2.7V VVCO-BIAS VCO-BIAS voltage drift VVCO-BIAS > 1.38V 2.3V < Vcc < 5.5V +356 ppm/°C -80 dBc 43 dB 400 L = 120µH (Q=30) and RVCO no connected SVRVCO-BIAS ZVCO-OUT 8/19 Supply Voltage Rejection Ratio of VCO-BIAS VCO Output Impedance (VCO-OUT1 pin22 or VCO-OUT2 pin34) With No Load TSH512 TSH512 Symbol ZLVCO-OUT min Parameter Test condition Min Minimum Load Impedance Typ Max 1 Unit k L= 120µH (Q=30), VVCO-OUT VCO Output Level VCO ouput connected to Output Buffer input, RVCO = 100K 0.58 0.62 0.66 Vpp Output Buffer ZBUF-IN GOB VBUF-OUT AC Input Impedance (BUF-IN1 pin24 or BUF-IN2 pin32) Linear Voltage Gain 400 10 Output AC voltage at 1dB compression ZL=2k point k dB 1.3 Vpp Output AC voltage (BUF-OUT1 pin 25 or BUF-OUT2 pin 31) VBUF-OUT DC Output DC voltage H2BUF-OUT 2nd Harmonic Level H3BUF-OUT 3rd Harmonic Level ZL=2k VBUF-IN = 0.60Vpp DC Output current= 0.4 mA VBUF-OUT =1.2Vpp and ZL=2k VBUF-OUT =1.2Vpp and 1.35 1.5 1.7 1.25 VDC -40 dBc -30 dBc ZL=2k 9/19 TSH512 TSH512 Supply current vs. Supply voltage Supply current vs. Temperature 18 20 TX1+TX2+Buffers 16 12 10 ICC(mA) 14 TX1 12 V CC = 2.7V 16 TX1+Buffers 14 ICC(mA) 18 TX1+TX2 8 6 TX1+TX2 TX1+TX2+Buffers 10 8 TX1+Buffers 6 4 TX1 4 2 2 0 0 1 2 3 4 5 0 -40 6 -20 0 20 VCC(V) 40 60 80 TAMB(°C) AUDIO SECTION LNA Distorsion vs. Frequency LNA Distorsion vs. Frequency 1 10 V CC = 2.7V G LNA = 40dB V OUT-LNA = 700mV pp THDLNA+N (%) THDLNA+N (%) V CC = 2.7V G LNA = 0dB V OUT-LNA = 700mV pp 0.1 0.01 10 100 1000 1 0.1 10 10000 100 Frequency (Hz) LNA Distorsion vs. LNA Output Voltage 0.8 GLNA = 0dB VCC = 2.7V 0.7 VCC = 2.3V 0.6 VOUT-PEA(VPP) THDLNA+N (%) 10 1 0.1 VCC = 2.3V 0.5 VCC = 2.7V 0.3 RL-PEA = 22K GLNA = 0dB GPEA = 0dB 0.1 VCC = 5.5V 0 200 400 600 800 1000 VOUT-LNA(mVpp) 1200 1400 1600 VCC = 5.5V 0.4 0.2 0.01 10/19 10000 PEA Output Voltage vs. LNA Input Voltage 100 1E-3 1000 Frequency (Hz) 0.0 0.00 0.05 0.10 0.15 0.20 0.25 VIN-LNA(V pp) 0.30 0.35 0.40 TSH512 TSH512 PEA Output Voltage vs. Temperature MIC-BIAS Voltage vs. MIC-BIAS Current 800 2.4 700 2.2 V CC = 2.3V VCC = 2.7V 500 V CC = 5V 400 300 VMIC-BIAS(V) VOUT-PEA(VPP) 600 2.0 1.8 RL-PEA=22K GLNA = 0dB GPEA = 0dB 200 100 0 -40 -20 1.6 0 20 40 60 80 0 1 2 TAMB(°C) 3 PEA Output Voltage vs. Resistor Load LNA+ALC+PEA Distorsion vs. Input Voltage 600 10 THDLNA+ALC+PEA+N (%) VCC = 2.7V 500 VOUT-PEA(mVPP) 4 IMIC-BIAS(mA) 400 VCC = 2.7V 1 RL-PEA = 22K GLNA = 0dB GPEA = 0dB VCC = 2.3V 0.1 300 VCC = 5.5V 200 100 1k 10k 100k 0.01 1M 0.02 0.04 RL-PEA() 0.06 0.08 0.10 VIN(Vpp) MIC-BIAS Output Voltage vs. Supply Voltage MIC-BIAS Output Voltage vs. Temperature 2.4 VCC = 2.7V IMIC-BIAS = 2.5mA 4.5 IMIC-BIAS = 2.5mA 4.0 VMIC-BIAS(V) VMIC-BIAS(V) 2.3 3.5 3.0 2.2 2.5 2.0 1.5 2.0 2.5 3.0 3.5 4.0 VCC(V) 4.5 5.0 5.5 6.0 2.1 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 TAMB(°C) 11/19 TSH512 TSH512 MIC-BIAS Voltage vs. MIC-BIAS Current VOX Delay vs. CTRIG Capacitor 2.40 35 VCC=2.7V 2.35 25 VOXDelay(s) VMIC-BIAS(V) V CC = 2.7V 30 2.30 20 15 10 2.25 5 2.20 0 1 2 0 3 0 10 20 30 40 50 60 70 80 90 100 CTRIG(µF) IMIC-BIAS(mA) MIC-BIAS Voltage vs. MIC-BIAS Current Monostable Current Source vs. Temperature 7 4.8 V CC = 2.7V 6 VCC = 5.5V 4.6 IVOX-TIMER(µA) VMIC-BIAS(V) 5 4.4 4.2 4 3 2 4.0 1 3.8 0 1 2 3 IMIC-BIAS(mA) 12/19 4 5 6 0 -40.0 -20.0 0.0 20.0 TAMB(°C) 40.0 60.0 80.0 TSH512 TSH512 RF SECTION VCO Output Voltage vs. RVCO VCO-BIAS Voltage vs. Temperature 1.6 700 650 1.5 VVCO-BIAS(V) VVCO-OUT(mVPP) 600 VCC = 2.7V No Load VCC = 2.7V L = 120µH (Q=30) FCARRIER = 2.8MHz 550 500 450 1.4 400 350 300 10k 100k 1.3 -40 -30 -20 -10 1M 0 10 20 30 40 50 60 70 80 RVCO( ) TAMB(°C) VCO & Output Buffer Spectrum VCO-BIAS Voltage vs. VCO-BIAS Current 60 1.45 VCC = 2.7V Rfilter = 51 Cfilter = 470nF 50 VCC = 2.7V L = 120µH (Q=30) R VCO = no connected ZL = 2k BW = 200Hz FCARRIER = 2.8MHz VBUF-OUT(dBmV) 40 VVCO-BIAS(V) 1.40 1.35 30 20 10 0 -10 -20 2.805 2.804 2.803 2.802 50 2.801 40 2.800 30 2.799 20 2.798 10 2.797 0 2.796 1.30 2.795 -30 Frequency(MHz) IVCO-BIAS(mA) VCO & Output Buffer Spectrum 60 V CC = 2.7V RVCO = 22k ZL = 2k FCARRIER = 2.8MHz 50 VBUF-OUT(dBmV) 40 30 20 10 0 -10 -20 -30 3 6 9 12 15 18 Frequency(MHz) 13/19 TSH512 TSH512 GENERAL DESCRIPTION The TSH512 TSH512 is a 0.4 to 11 MHz dual FM analog transmitter. This circuit offers the functions needed for an advanced infrared STEREO transmitter. The access pins for each section allow a high versatility and therefore a lot of applications: mono infrared transmitter, stereo transmitter, mono/stereo sub-carrier generator for video transmissions (ie: popular 2.4GHz video links). 4 SBY VCC 8 GND VCO-BIAS2 VCC VCO-A2 VCO-B2 VCO-OUT2 36 35 34 PEA-OUT2 LNA-OUT2 ALC-INT2 LNA-INN2 37 VCO 9 33 GND 32 BUF-IN2 31 BUF-OUT2 30 GND VOX-TIMER 28 VOX-INTN 27 VOX-MUTE 26 7 The stand-by of the second transmitter reduces consumption in mono operation. For each transmitter, the audio source is connected to the LNA. The LNA stage is a low noise operationnal amplifier typically usable with a gain from 0dB to 40dB. 29 6 VOX-SENS 38 VCC 25 BUF-OUT1 24 BUF-IN1 23 5 VOX-INTS 39 Bias 3 VCC 40 2 GND 41 1 MIC-BIAS2 42 PEA-INN2 LNA-INP2 DEC2 43 The Voice Operated Transmit (VOX) function automatically detects when an audio signal appear over the background noise. LNA section: Low Noise Amplifier Figure 1 : TSH512 TSH512 bloc diagram 44 in multicarrier systems (see the chapter ' Applications'). GND PEA TX2 + LNA Bias Output buffer TSH512 TSH512 VOX + - Monostable Bias + - LNA Output buffer TX1 ALC + - 10 DEC1 + MIC-BIAS1 ALC 11 PEA LNA-OUT1 ALC-INT1 PEA-INN1 18 19 20 21 22 VCO-OUT1 LNA-INP1 17 VCO-B1 16 VCO-A1 15 VCC 14 PEA-OUT1 13 VCO-BIAS1 12 LNA-INN1 Bias VCO Each audio input is amplified with a Low Noise Amplifier (LNA section) allowing connection to line level sources or directly to a microphone. Built-in voltage references 'MIC BIAS' provide bias for Electret Condenser Microphones (ECM) with a high power supply rejection ratio. Each audio path includes also an Automatic Level Control (ALC) to limit the overmodulation and the distorsion on very high signal amplitudes. The following operationnal amplifier (PEA) allows a preamphasis transfer function before modulating the varicap diode. Built-in voltage references (VCO-BIAS) offers a regulated voltage to bias the varicap diodes. The Voltage Controlled Oscillator (VCO) is an integrated oscillator giving typically 600 mV peak to peak at 2.8 MHz. The Output Buffer section amplifies linearly the FM carrier to provide a sinusoidal output. This sinusoidal signals reduce the intermodulation products beetween the carriers, specially in two-way or 14/19 Figure 2 : LNA schematic The LNA gain is given by: GLNA (dB) = 20.Log(1+R LNA2/RLNA1) The High-pass cut-off frequency is: fHPF = 1/(2.RLNA1.C LNA1) The Lowpass filter cut-off frequency is: fLPF = 1/(2.RLNA2.CLNA2) If you connect an external circuit to the LNA output, the impedance of this external circuit should be higher than 10 M and the capacitance lower than 50 pF in order to keep a good stability. TSH512 TSH512 Electret Condenser Microphone source When a Electret Condenser Microphone (ECM) is used, a high gain LNA is recommanded, but low frequencies have to be attenuated. The ECM has to be biased with a stable and clean reference voltage.The TSH512 TSH512 offers you the LNA and the MIC-BIAS sections to perform this functions. (see MIC-BIAS chapter). Figure 3 : Electret Condenser Microphone source Moreover, the supply rejection ratio is guaranteed better than 50 dB without any decoupling capacitor. To address biasing of most of the microphones, the current drive capability is 2.5 mA. The MIC-BIAS voltage depend linearly on the supply voltage Vcc (refer to the curve 'MIC-BIAS vs. VCC'). ALC section: Automatic Level Control Both transmitters of the TSH512 TSH512 are including Automatic Level Control (ALC). When the level of the audio signal is too high, the ALC compress the signal in order to avoid overmodulation of the FM VCO. Therefore, the ALC reduces the distorsion and keep a reduced transmit spectrum with very high amplitude signals. Figure 4 : Automatic Level Control Schematic The capacitor C in serie with the microphone stops the DC coming from MIC-BIAS. The resistor R provides the DC from MIC-BIAS to supply the ECM. Thanks to the ALC (Automatic Level control), the great variations of amplitude will not overmodulate the transmitter (refer to the chapter on ALC). The self-adaptative VOX (Voice Operated Transmit) offers an automatic transmitting with a good discrimination of the background noise (see the chapter on VOX). MIC-BIAS section: microphone bias voltage The MIC-BIAS bias voltages are dedicated to the bias of Electret Condenser Microphones. These bias voltages on pin 10 for TX1 and pin 2 for TX2, exhibit a low voltage noise density of 22nV/ SQR(Hz). This allows more than 55 dB S/N considering a bandwith of 7 kHz. (see the figure in the 'Electret Condenser Microphone source' chapter). The MIC-BIAS voltage is related with VCC as follow (with I MIC-BIAS= 2.5 mA): VMIC-BIAS = 0.844.VCC-0.140 (Volts) The ALC features a 20dB gain and an output signal regulated to 700 mVpp in compression. The attack time is the response time of the ALC to go from the linear amplification to the compression region. The attack time mainly depends on CALC capacitor value. A typical value of CALC is 1µF with music as audio signal (refer to the 'application schematic'). The decay time is the response time of the ALC to recover a full gain amplifying mode from a compression mode. The decay time depends mainly on the RALC resistor value. A typical value of RALC is 470k with music as audio signal (refer to the 'application schematic'). 15/19 TSH512 TSH512 VOX description: Voice Operated Transmit The Voice Operated Transmit section (VOX) reduces consumption when there is no audio signal to transmit. When the VOX detects that no audio signal is present, it mutes the Output Buffers of TX1 and TX2 and provides the logic signal VOX-MUTE to switch-off external LED drivers if needed. The audio signal of TX1 is amplified with a gain depending on Rsens and Csens. Rsens and Csens are connected to pin 7. The high-pass filtering has the following cut-off frequency: fHPF = 1/(2.Rsens.C sens) Figure 5 : Vox delay and sensitivity schematic The self-adaptative VOX threshold consist in the constatation that the ambient background noise variation is slow compared to the voice or the music. On the pin 28, RCOMP and CCOMP integrates the amplitude to follow the background amplitude. Therefore, the comparator switches when an audio signal appears over the background noise. Refering to the 'application schematic', CCOMP will be typically a 100nF capacitor and RCOMP will be determined depending on the audio signal. As soon as an audio is detected, the output of the monostable switches to 'high' state and enables both output buffers. The output of the monostable is the pin 27 and is called 'VOX-MUTE'. The monostable holds the TSH512 TSH512 in transmit mode during a delay fixed by the value of CTRIG connected to pin 29 1.4V VOX DELAY = - Ctrig 5µA Please note that the VOX function is activated with the audio coming into the first transmitter TX1. When the application needs a permanent transmission, it is possible to inhibit the VOX function. Just remove CTRIG capacitor and connect pin 29 to ground. On pin 6, Rpeak and Cpeak integrate the rectified audio signal with a short time constant. This filtered signal follows the audio amplitude. Figure 6 : Vox integrator and monostable schematic As soon as the TSH512 TSH512 is powered-on, the internal reset circuitry sets the VOX-MUTE to high state to enable transmission. The transmission remains during the monostable timing and continue if an audio signal triggs the monostable Figure 7 : VOX state at power-on on POWER SUPPLY off high state if retriggered by audio 1 VOX-MUTE VOX Delay (Ctrig) 0 time 16/19 TSH512 TSH512 PEA section: Pre-Emphasis The amplitude regulated audio coming from the ALC feeds the postive input of the Operational Amplifier called PEA (Pre-Emphasis). The pre-emphasis consist in a high-pass filter in order to compensate the behavior of the FM transmission. The generated frequency can be set from 400 kHz to 11 MHz by external components. Refer to the table 1 for the usual frequencies in Infrared audio. The working frequency is: 1 fVCO = -2 ( L Ct ) Figure 8 : Pre-Emphasis schematic Ct is the total capacity of C L, Cp, C s and C v. Ct = 1/(1/Cc+1/CL) with Cc = C p+1/(1/C v+1/Cs) It's possible to use varicap diodes SMV1212 SMV1212 (Alpha Ind.) or ZC833 ZC833 (Zetex). Usual Infrared frequencies IR frequency applications 1.6 MHz RPEA1 and C PEA1 set the time constant of the pre-emphasis as: = RPEA1 . CPEA1 50 µs or 75µs time constant are generally used. Choosing the gain of the PEA stage allows also to set the right modulation level to the varicap diode. The gain in the pass-band is: GPEA = 1+ (RPEA2/R PEA1) VCO section: Voltage Controlled Oscillator Each TSH512 TSH512's transmitter has his own oscillator to generate the carrier. The audio signal is applied on the varicap diode to perform the Frequency Modulation. Thanks to the VCO-BIAS voltage reference, the DC bias of the varicap is stabilized. The high PSRR (Power Supply Rejection ratio) of the VCO-BIAS insure good immunity with the noise of the power supply. Figure 9 : VCO schematic AM mono 1.7 MHz FM mono 2.3 MHz FM right channel 2.8 MHz FM left channel or mono The output level of the VCO can be reduced by adding the resistor RVCO beetween pin 19 and pin 20 or beetween pin 36 and pin 37 for TX1 and TX2 respectively. Output Buffer section The output buffers are able to deliver a sinusoidal signal with 1.5Vpp amplitude in a 1K load. This impedance is compatible with popular biasing circuitry of external transistor drivers of IR LEDs. The VOX-MUTE logic signal can be used to control the external LED drivers. When the audio is not present on the TX1 input, VOX-MUTE is at 'Low' state, the TSH512 TSH512's internal buffers are muted, and external drivers can be switched off by controlling their bias. SBY pin: Standby for mono operation A high state on the Standby pin (SBY) sets the second transmitter TX2 in power-down. The SBY pin is typically used when the TSH512 TSH512 is used as a mono transmitter (ie: infrared microphone transmitter). 17/19 TSH512 TSH512 APPLICATION SCHEMATIC The audio signals are transmitted on the left and the right channels using a 2.8 & 2.3 MHz carriers. The VOX activates the transmitter TX1 when the audio signal is present. 18/19 TSH512 TSH512 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. Min. 1.60 0.15 1.45 0.40 0.20 0.002 0.053 0.012 0.004 0.75 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. 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