TSH512CF

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 The 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 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 forms a chipset with the dual receiver TSH511. APPLICATIONS F TQFP44 10 x 10 mm PIN CONNECTION (top view) 44 43 42 41 40 39 38 37 36 35 34 1 PEA ALC VCO 33 32 3 LNA 4 5 6 7 8 LNA 9 10 11 TSH512 VOX + Monostable s s s s s Infrared HiFi stereo transmitter Infrared Headsets Stereo sub-carrier for video transmitters Voice operated wireless webcams FM IF transmit systems + - ALC ORDER CODE Part Number TSH512CF TSH512CFT Temperature Range -40°C to +85°C -40°C to +85°C Package TQFP44 TQFP44 Conditionning Tray Tape & reel Marking TSH512C TSH512C 12 13 14 15 16 December 2002 + + + 2 + TX2 Output buffer 31 30 29 28 27 26 TX1 + PEA Output buffer 25 24 23 VCO 17 18 19 20 21 22 1/19 TSH512 ABSOLUTE MAXIMUM RATINGS Symbol Vcc Toper Tstg Tj Rthjc voltage1) Parameter Supply Operating free air temperature range Storage temperature Maximum junction temperature Thermal resistance junction to case Value 7 -40 to +85 -65 to +150 150 14 A 2 1 0.2 kV Unit V °C °C °C °C/W Latch-up Class2) ESD sensitive device: handling precautions required ESD HBM: Human Body Model3) Model4) except pin CDM: Charged Device 20 & 36 5) MM: Machine Model 1. 2. 3. 4. 5. 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 1.5kΩ 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. OPERATING CONDITIONS Symbol Vcc faudio fcarrier Supply voltage Audio frequency range Carrier frequency range Parameter Value 2.3 to 5.5 20 to 20,000 0.4 to 11 Unit V Hz MHz BLOC DIAGRAM VCO-BIAS2 LNA-OUT2 PEA-OUT2 LNA-INN2 ALC-INT2 PEA-INN2 LNA-INP2 VCO-A2 VCO-B2 35 VCO-OUT2 34 VCC 37 VCO 44 43 42 41 40 39 38 36 DEC2 MIC-BIAS2 GND VCC SBY VOX-INTS VOX-SENS VCC GND MIC-BIAS1 DEC1 1 Bias PEA ALC LNA Bias 33 32 GND BUF-IN2 BUF-OUT2 GND VOX-TIMER VOX-INTN VOX-MUTE VCC BUF-OUT1 BUF-IN1 GND 3 4 5 6 7 8 9 10 11 TSH512 VOX + Monostable Bias LNA + - ALC 12 LNA-INP1 13 LNA-INN1 14 LNA-OUT1 15 ALC-INT1 16 PEA-INN1 VCC VCO-BIAS1 VCO-A1 VCO-B1 2/19 VCO-OUT1 PEA-OUT1 + 2 + TX2 Output buffer 31 30 29 28 27 26 TX1 + PEA Bias Output buffer 25 24 23 VCO 17 18 19 20 21 22 TSH512 PIN DESCRIPTION Pin 1 2 3 4 5 6 7 8 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 Pin name DEC2 MIC-BIAS2 GND VCC SBY VOX-INTS VOX-SENS VCC GND MIC-BIAS1 DEC1 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 related to TX2 TX2 TX1 & TX2 TX1 & TX2 TX1 & TX2 TX1 TX1 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 direction1) O I O I I O I O O O I O O O I O O O I O I I Pin description 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 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 TYPICAL SCHEMATIC Stereo infrared transmitter . Rbias2 Clna1 PRE-EMPHASIS NETWORK LNA GAIN : 0dB to 40dB ATTACK-DECAY TIME Rbias1 47k 100nF Cpen1 47k Varicap Cv Cp Cs CL Rlna1 Ralc Calc 51 Clna2 Rpen1 AUDIO IN TX2 44 1 OUTPUT BUFFER MICRO BIAS TX2 2 3 Vcc 4 30 STANDBY 5 29 Cpeak VOX Delay + Rpeak 6 28 Rcomp + + VOX Sensitivity 7 Rsens Csens Vcc 8 26 OUTPUT BUFFER 9 MICRO BIAS TX1 10 Varicap BIAS 11 12 PRE-EMPHASIS NETWORK LNA GAIN : 0dB to 40dB Rpen1 Clna2 Rlna1 Ralc Calc AUDIO IN TX1 ATTACK-DECAY TIME Cpen1 47k Rbias2 + Clna1 47k 100nF . 4/19 Rbias1 + Rlna2 43 42 L Vcc Rvco 51pF 36 35 51pF 34 51pF Rpen2 40 39 38 37 41 Vcc 33 Varicap BIAS + + + PEA VCO TX2 32 IR ALC Transmitter 2 (TX2) LNA 31 BIAS TSH512 Varicap Pulse Width Adjust Ctrig 1M Ccomp 10µF Vcc 27 MONO STABLE VOX-MUTE Vcc IR 25 BIAS ALC LNA Transmitter 1 (TX1) 24 PEA VCO TX1 23 13 Rlna2 14 15 16 Rpen2 17 18 Vcc 19 Rvco 20 51pF 21 51pF 22 51 Cs Cp L 51pF Varicap Cv CL 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 is modulated in FM and bufferized to attack the LED final stage. IR stereo HiFi transmitter Headphone side Vcc: 2.3 to 5.5V Current < 15 mA 2.3 MHz TSH512 Right channel LNA + ALC filter TSH511 Audio amp2 20 mW / 16 Ω buffer2 TX2 Vcc SBY photodiode Line inputs VOX Left channel buffer1 LNA SQUELCH RX2 TX1 LNA + ALC rs rrie : ca reo Hz te i s .8 M HiF & 2 3 2. LED Audio Audio amp1 SBY2 RX1 SBY1 20 mW / 16 Ω filter Power supply: 2.3 to 5.5V Icc < 20 mA stereo 2.8 MHz SUB-CARRIER GENERATOR APPLICATION: voice operated wireless camera Thanks to the operating frequency the 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. The TSH512 also provides bias, amplification, ALC for the electret microphone. Miniature camera Video Σ Sub-carrier FM 2.4 GHz transmitter Stand-By Stand-By TSH512 TSH512 LNA + ALC buffer2 TX2 Vcc SBY MIC. BIAS Electret Condenser Microphone VOX MIC. BIAS VOX-MUTE buffer1 TX1 LNA + ALC 6 or 6.5 MHz 6 or 6.5 MHz Audio sub-carrier filter 5/19 TSH512 MULTIMEDIA APPLICATION: HEADSET SIDE The 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 & 512 supply: 2.3 to 5.5V, 25 mA HiFi stereo from the PC: 2x 20 mW /16 Ω 1.7 MHz reject filter 2.3 MHz Band-pass filter TSH511 Voice transmitted to the PC Audio amp2 SQUELCH RX2 LNA photodiode TSH512 TSH512 LNA + ALC buffer2 SBY2 Vcc MIC. BIAS SBY Vcc Audio amp1 VOX MIC. BIAS LED SBY1 filter 1.7 MHz reject TX2 RX1 filter 2.8 MHz Band-pass buffer1 TX1 LNA + ALC 1.7 MHz filter Band-pass Stereo Rx: 2.3 & 2.8 MHz Microphone Tx: 1.7 MHz carrier MULTIMEDIA APPLICATION: COMPUTER SIDE In multimedia application, the TSH512 transmits the HiFi stereo from the PC to the headset. TSH511 & 512 supply: 2.3 to 5.5V, 24 mA HiFi stereo Voice from the headset microphone mono Rx: 1.7 MHz TSH511 photodiode Audio amp2 LNA TSH512 LNA + ALC SQUELCH SBY1 Vcc SBY2 HiFi stereo Tx: 2.3 & 2.8 MHz buffer2 RX2 TX2 Audio amp1 RX1 SBY LED VOX filter LNA + ALC 1.7 MHz Band-pass buffer1 TX1 6/19 TSH512 ELECTRICAL CHARACTERISTICS Vcc = 2.7V, Tamb = 25°C, faudio = 1 kHz, fcarrier = 2.8 MHz (unless otherwise specified) Symbol Overall Circuit TX1 on, TX2 on, MIC-BIAS1 and MIC-BIAS2 not used: VOX-MUTE=1, output buffers on VOX-MUTE=0, output buffers off TX1 on, TX2 off, MIC-BIAS1 and MIC-BIAS2 not used: VOX-MUTE=1, output buffers on VOX-MUTE=0, output buffers off LNA Sections (for TX1 and TX2) GBPLNA RinLNA THDLNA Gain Band Product Input Resistance on positive input: (LNA-INP1 pin 12 or LNA-INP2 pin 44) Total Harmonic Distortion GLNA=0dB VoutLNA =700mVPP GLNA=40dB, at f=1kHz En Equivalent Input Noise Voltage Rs=390Ω, Rfeedback= 39kΩ 6 0.01 0.05 % nV/√Hz No external load 7 30 MHz kΩ 16 11 18.6 12.8 mA mA Parameter Test condition Min Typ Max Unit ICC_TOT Current consumption, TX1 and TX2 are on. Current consumption ICC_SBY with TX2 in stand-by: SBY (pin5) active 10 7 11.5 8 mA mA Automatic Level Control (ALC) Section GALC VALC_OUT Voltage Gain Regulated Output Level (At positive input of the PEA amplifier) Gain Band Product 20 600 710 800 dB mVpp Pre-Emphasis Amplifier (PEA) Section GBPPEA VOpp-PEA No Load (PEA-OUT1 pin17 or PEA-OUT2 pin39) Output voltage RL = 22kΩ GLNA = 0 dB, f =1kHz VinALC < 25mVrms (-30dBu) RL = 22 kΩ tied to GND (Vin)ALC = 36mVrms (-27dBu) THDAGC Total Harmonic Distorsion in compression region (Vin)ALC= 100mVrms (-18dBu) RL = 22 kΩ tied to GND Phase Margin at ΦΜPEA PEA-OUT1 pin 17 or PEA-OUT2 pin 39 RL = 22 kΩ LNA and PEA at unity gain Vin = 40mV 7/19 70 ° 1.3 3 1.7 4 % % 0.05 0.15 % 9 550 MHz mVpp Audio LNA+ALC+PEA sections Total Harmonic Distorsion THDALC in linear region on PEA-OUT1 pin17 or PEA-OUT2 pin 39 TSH512 Symbol Parameter Test condition Min Typ Max Unit Microphone Biasing Section VMIC-BIAS Microphone Biasing Voltage (see page 15) IMIC-BIAS = 2.5 mA Over temperature range [0, 70°C] [-40, 85°C] IMIC-BIAS = 2.5 mA IMIC-BIAS PSRRMIC-BIAS 2.15 2.25 2.35 V ∆VMIC-BIAS VMIC-BIAS temperature coefficient 260 460 ppm/°C MIC-BIAS current capability Power Supply Rejection Ratio of MIC-BIAS Equivalent input noise of MIC-BIAS over VCC range [2.3V-5.5V] @ 1kHz and V ripple = 25mVRMS VCC=2.7V VCC=5.0V Vcc = 2.7V 2.5 mA 50 22 42 dB nV/√Hz enMIC-BIAS Vox Operated Switch (VOX) Section IVOX-TIMER VTHVOX-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) Max. Low Level Input Voltage of Standby input (SBY Pin5) Min. High Level Input Voltage of Standby input (SBY Pin5) VCO-BIAS output voltage 5 1.4 µA V 0.2 V V VMUTE_L VMUTE_H Standby VSBY_IL max RL = 2 kΩ RL = 2 kΩ Vcc-0.3 0.1xVcc 0.9xVcc V V VSBY_IH min VCO Section VVCO-BIAS IVCO-BIAS (VCO-BIAS1 pin18 or VCO-BIAS2 pin 38) VCO-BIAS output current capability With No Load VVCO-BIAS > 1.38V 2.3V < Vcc < 5.5V [0, 70°C] Vcc=2.7V δVVCO-BIAS VCO-BIAS voltage drift [0, 70°C] Vcc=5.0V [-40, 85°C] Vcc=2.7V [-40, 85°C] Vcc=5.0V @ 1kHz, PNLO SVRVCO-BIAS 1.43 1.47 40 8 +265 +356 +265 +356 -80 1.51 VDC µA mV/V ppm/°C ppm/°C ppm/°C ppm/°C dBc Phase Noise Supply Voltage Rejection Ratio of VCO-BIAS VCO Output Impedance (VCO-OUT1 pin22 or VCO-OUT2 pin34) L = 120µH (Q=30) and RVCO no connected With No Load 43 400 dB Ω ZVCO-OUT 8/19 TSH512 Symbol ZLVCO-OUT min Parameter Minimum Load Impedance Test condition Min Typ 1 Max Unit kΩ L= 120µH (Q=30), VVCO-OUT VCO Output Level VCO ouput connected to Output Buffer input, RVCO = 100K Output Buffer ZBUF-IN GOB VBUF-OUT AC 0.58 0.62 0.66 Vpp Input Impedance (BUF-IN1 pin24 or BUF-IN2 pin32) Linear Voltage Gain Output AC voltage at 1dB compression ZL=2kΩ point 400 10 1.3 kΩ dB Vpp Output AC voltage (BUF-OUT1 pin 25 or BUF-OUT2 pin 31) VBUF-OUT DC Output DC voltage ZL=2kΩ VBUF-IN = 0.60Vpp DC Output current= 0.4 mA VBUF-OUT =1.2Vpp and ZL=2kΩ VBUF-OUT =1.2Vpp and ZL=2kΩ 1.35 1.5 1.25 1.7 VDC H2BUF-OUT 2nd Harmonic Level -40 dBc H3BUF-OUT 3rd Harmonic Level -30 dBc 9/19 TSH512 Supply current vs. Supply voltage 18 16 14 12 ICC(mA) 10 8 6 4 2 0 0 1 2 3 VCC(V) 4 5 6 TX1+TX2+Buffers TX1+TX2 TX1+Buffers Supply current vs. Temperature 20 18 16 14 ICC(mA) 12 10 8 6 4 2 0 -40 -20 0 20 TAMB(°C) 40 60 80 TX1 TX1+Buffers TX1+TX2+Buffers V CC = 2 .7V TX1+TX2 TX1 AUDIO SECTION LNA Distorsion vs. Frequency 1 V CC = 2 .7V G LNA = 0dB V OUT-LNA = 700mV pp LNA Distorsion vs. Frequency 10 V CC = 2.7V G LNA = 4 0dB V OUT-LNA = 7 00mV pp THDLNA+N (%) 0.1 THDLNA+N (%) 100 1000 10000 1 0.01 10 0.1 10 100 1000 10000 Frequency (Hz) Frequency (Hz) LNA Distorsion vs. LNA Output Voltage 100 GLNA = 0dB 10 VCC = 2.3V VCC = 2.7V PEA Output Voltage vs. LNA Input Voltage 0.8 0.7 0.6 VCC = 2.3V 0.5 0.4 0.3 0.2 VCC = 5.5V 0.1 1400 1600 0.0 0.00 0.05 0.10 0.15 0.20 0.25 RL-PEA = 22KΩ GLNA = 0dB GPEA = 0dB 0.30 0.35 0.40 VCC = 2.7V VCC = 5.5V THDLNA+N (%) 1 0.1 0.01 1E-3 0 200 400 600 800 1000 1200 VOUT-LNA(mVpp) VOUT-PEA(VPP) VIN-LNA(V pp) 10/19 TSH512 PEA Output Voltage vs. Temperature 800 700 600 VOUT-PEA(VPP) VMIC-BIAS(V) 2.2 V CC = 2 .3V MIC-BIAS Voltage vs. MIC-BIAS Current 2.4 500 400 300 200 100 0 -40 RL-PEA=22K Ω GLNA = 0dB GPEA = 0dB VCC = 2.7V V CC = 5V 2.0 1.8 1.6 -20 0 20 TAMB(°C) 40 60 80 0 1 2 3 4 IMIC-BIAS(mA) PEA Output Voltage vs. Resistor Load LNA+ALC+PEA Distorsion vs. Input Voltage 600 VCC = 2.7V 10 RL-PEA = 22KΩ GLNA = 0dB GPEA = 0dB THDLNA+ALC+PEA+N (%) 500 VCC = 2.7V 1 VCC = 2.3V VOUT-PEA(mVPP) 400 0.1 300 VCC = 5.5V 200 100 1k 10k 100k 1M 0.01 0.02 0.04 0.06 0.08 0.10 RL-PEA(Ω) VIN(Vpp) MIC-BIAS Output Voltage vs. Supply Voltage MIC-BIAS Output Voltage vs. Temperature 2.4 4.5 IMIC-BIAS = 2.5mA 4.0 VCC = 2 .7V IMIC-BIAS = 2 .5mA 2.3 VMIC-BIAS(V) 3.5 3.0 2.5 2.0 1.5 2.0 VMIC-BIAS(V) 2.2 2.5 3.0 3.5 4.0 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) VCC(V) 11/19 TSH512 MIC-BIAS Voltage vs. MIC-BIAS Current VOX Delay vs. CTRIG Capacitor 2.40 VCC=2.7V 2.35 35 30 25 V CC = 2 .7V VMIC-BIAS(V) VOXDelay(s) 0 1 2 3 20 15 10 5 2.30 2.25 2.20 0 0 10 20 30 40 50 60 70 80 90 100 IMIC-BIAS(mA) CTRIG(µF) MIC-BIAS Voltage vs. MIC-BIAS Current Monostable Current Source vs. Temperature 7 V CC = 2.7V 4.8 VCC = 5.5V 6 5 4.6 4.4 IVOX-TIMER(µA) VMIC-BIAS(V) 4 3 2 4.2 4.0 1 3.8 0 1 2 3 4 5 6 0 -40.0 -20.0 0.0 20.0 TAMB(°C) 40.0 60.0 80.0 IMIC-BIAS(mA) 12/19 TSH512 RF SECTION VCO Output Voltage vs. RVCO 700 650 600 VCC = 2.7V L = 120µH (Q=30) FCARRIER = 2.8MHz VCO-BIAS Voltage vs. Temperature 1.6 VCC = 2 .7V No Load VVCO-OUT(mVPP) 1.5 550 500 450 400 350 300 10k 100k 1M VVCO-BIAS(V) 1.4 1.3 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 TAMB(°C) RVCO(Ω ) VCO-BIAS Voltage vs. VCO-BIAS Current VCO & Output Buffer Spectrum 1.45 VCC = 2.7V Rfilter = 51Ω Cfilter = 470nF 1.40 60 50 40 VCC = 2 .7V L = 120µH (Q=30) R VCO = n o connected ZL = 2k Ω BW = 200Hz FCARRIER = 2 .8MHz VBUF-OUT(dBmV) 30 20 10 0 VVCO-BIAS(V) 1.35 -10 -20 -30 2.795 2.796 2.797 2.798 2.799 2.800 2.801 2.802 2.803 2.804 1.30 0 10 20 30 40 50 IVCO-BIAS(mA) Frequency(MHz) VCO & Output Buffer Spectrum 60 50 40 V CC = 2 .7V RVCO = 22kΩ ZL = 2kΩ FCARRIER = 2 .8MHz VBUF-OUT(dBmV) 30 20 10 0 -10 -20 -30 3 6 9 12 15 18 Frequency(MHz) 13/19 2.805 TSH512 GENERAL DESCRIPTION The 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). Figure 1 : TSH512 bloc diagram VCO-BIAS2 LNA-OUT2 PEA-OUT2 LNA-INN2 ALC-INT2 PEA-INN2 LNA-INP2 VCO-B2 VCO-A2 VCO-OUT2 in multicarrier systems (see the chapter ’ Applications’). The Voice Operated Transmit (VOX) function automatically detects when an audio signal appear over the background noise. The stand-by of the second transmitter reduces consumption in mono operation. LNA section: Low Noise Amplifier 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. 44 43 42 41 40 39 38 37 VCC 36 35 34 DEC2 MIC-BIAS2 GND VCC SBY VOX-INTS VOX-SENS VCC GND MIC-BIAS1 DEC1 1 Bias PEA ALC LNA Bias VCO 33 32 GND BUF-IN2 BUF-OUT2 GND VOX-TIMER VOX-INTN VOX-MUTE VCC BUF-OUT1 BUF-IN1 GND 3 4 5 6 7 8 9 10 11 TSH512 VOX + Monostable Bias LNA ALC + - 12 LNA-INP1 13 LNA-INN1 14 LNA-OUT1 15 ALC-INT1 16 PEA-INN1 VCO-BIAS1 PEA-OUT1 VCC VCO-B1 VCO-A1 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 VCO-OUT1 14/19 + 2 TX2 Output buffer 31 30 29 28 27 26 Figure 2 : LNA schematic + TX1 + PEA Bias Output buffer 25 24 23 VCO 17 18 19 20 21 22 The LNA gain is given by: GLNA (dB) = 20.Log(1+R LNA2/RLNA1) The High-pass cut-off frequency is: fHPF = 1/(2.πRLNA1.C LNA1) The Lowpass filter cut-off frequency is: fLPF = 1/(2.πRLNA2.CLNA2) If you connect an external circuit to the LNA output, the impedance of this external circuit should be higher than 10 MΩ and the capacitance lower than 50 pF in order to keep a good stability. 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 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 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 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.πRsens.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 in transmit mode during a delay fixed by the value of CTRIG connected to pin 29 1.4 V V OX 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. As soon as the 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 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 on POWER SUPPLY off high state if retriggered by audio 1 VOX-MUTE 0 time VOX Delay (Ctrig) 16/19 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. 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 (Alpha Ind.) or ZC833 (Zetex). Usual Infrared frequencies IR frequency 1.6 MHz applications AM mono FM mono FM right channel FM left channel or mono 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 ⋅ π ⋅ ( L ⋅ Ct ) RPEA1 and C PEA1 set the time constant of the pre-emphasis as: τ = 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’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 1.7 MHz 2.3 MHz 2.8 MHz 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 1KΩ 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’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 is used as a mono transmitter (ie: infrared microphone transmitter). 17/19 TSH512 APPLICATION SCHEMATIC The Electret Condenser Microphone is biased with MIC-BIAS1 voltage. The audio signal is transmitted on the left channel using a 2.8 MHz carrier. The VOX activates the transmitter TX1 when the audio signal is present. The audio signal at line level is attenuated and is transmitted by the second transmitter TX2 at 2.3 MHz. . TX2 = 2.3MHz SMV1212 C23 1uF 33K R27 C24 2nF2 R5 270K 50K 1K R28 P3 100K R33 C19 1uF C18 1uF 470K R31 C25 470pF D1 C49 12pF 39pF 4-25pF L3 120uF C45 680pF C6 100nF R6 47K R7 100K 470pF C37 C39 56pF C43 56pF C56 nc Reject filter 2.8MHz (optional) 390 R35 INPUT LINE TX2 (RIGHT) RCA R1 10K R2 1K C4 100nF 390 R37 C26 nc 51 R45 C11 470nF C35 C55 nc 470nF C12 VCC 37 36 35 34 VCC R43 22K VCC-LED nc L5 D3 TSFP5400 44 43 42 40 39 41 38 J7 PEA-INN2 VCO-BIAS2 LNA-INP2 LNA-OUT2 ALC-INT2 VCO-OUT2 PEA-OUT2 VCO-A2 LNA-INN2 VCO-B2 VCC 56pF C40 C52 22nF 1uF C20 1 DEC2 R13 4K7 IC? Q1 BC847 32 31 30 29 28 27 VCC 26 25 24 C53 23 22nF 56pF R18 3K3 C41 C15 470nF R17 4K7 C57 10uF R14 3K3 GND 33 VCC B A ON OFF C8 VCC 3 4 5 PEA BUF-OUT2 A J20 VCC SBY VOX-INTS VOX-SENS VCC GND MIC-BIAS1 LNA-INP1 DEC1 TSH512 VOX + Monostable GND VOX-TIMER VOX-INTN VOX-MUTE VCC BUF-OUT1 P5 220K C58 100nF VCC-LED D4 TSFP5400 B 220nF C16 R26 33K 1K R24 6 470nF C9 470nF VCC C10 C17 1uF 9 10 11 3K9 R25 R25 7 8 LNA + LNA-OUT1 LNA-INN1 ALC PEA + VCO-BIAS1 PEA-OUT1 PEA-INN1 VCO-A1 VCO-B1 BUF-IN1 VCO-OUT1 GND 22 R16 Q2 BC847 L6 nc C59 nc nc Reject filter 2.3MHz (optional) 22 R20 J20 TX2 2 470nF MIC-BIAS2 LNA GND ALC TX1-LEFT MICRO MIC1 ALC-INT1 VCC 12 13 14 15 16 17 18 19 20 21 C5 100nF 51 R46 C27 nc R38 390 R36 VCC C13 470nF C32 VCC 470nF R44 22K C42 56pF 39pF C36 C38 4-25pF C44 56pF L4 120uF C50 SMV1212 12pF C46 82pF 39k C22 C14 C28 R8 100K C21 1uF 470k R32 1uF 470pF R34 100K C7 100nF 47K R9 R10 270K 33K 1K P4 50K R29 R30 22 C33 1uF . 18/19 + + C34 2nF2 + + - BUF-IN2 TSH512-B D2 TX1 = 2.8MHz TSH512 PACKAGE MECHANICAL DATA 44 PINS - PLASTIC PACKAGE A A2 44 e A1 34 0,10 mm .004 inch SEATING PLANE B 11 23 c 1 33 12 D3 D1 D 22 L1 L E3 E1 E K 0,25 mm .010 inch GAGE PLANE Dimensions Min. A A1 A2 B C D D1 D3 e E E1 E3 L L1 K 0.05 1.35 0.30 0.09 Millimeters Typ. Max. 1.60 0.15 1.45 0.40 0.20 Min. 0.002 0.053 0.012 0.004 Inches Typ. Max. 0.063 0.006 0.057 0.016 0.008 1.40 0.37 12.00 10.00 8.00 0.80 12.00 10.00 8.00 0.60 1.00 0.055 0.015 0.472 0.394 0.315 0.031 0.472 0.394 0.315 0.024 0.039 0.45 0.75 0.018 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 19/19