TSH512 Hi-fi stereo/mono infrared transmitter and stereo sub-carrier generator Features ■ Supply voltage: 2.3 to 5.5 V ■ Carrier 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 TX2 standby for mono operation F TQFP44 10 x 10 mm Pin connections (top view) 44 43 42 41 40 39 38 33 PEA 2 32 + - ALC + 3 Infrared hi-fi stereo transmitters TX2 Infrared headsets ■ Stereo sub-carriers for video transmitters 6 ■ Voice-operated wireless webcams 7 31 Output buffer LNA 4 ■ ■ 34 - ■ 35 VCO 1 Applications 36 37 30 TSH512 5 29 VOX 28 - Monostable 27 + FM IF transmit systems 8 26 LNA 9 Description Output buffer TX1 + - ALC 25 + - 10 24 PEA 11 The TSH512 is a 0.4- to 11-MHz dual FM transmitter. Access pins to each section give high versatility and allow for several different applications: stereo headphone, multimedia headset, audio sub-carrier generator. The TSH512 integrates in a single chip low-noise audio preamplifiers with ALC (automatic level control), frequency-modulated oscillators, and linear output buffers to drive the external transistors. The sinusoidal carriers facilitate the filtering and allow high performance audio transmission. 23 VCO 12 13 14 15 16 17 18 19 20 21 22 The TSH512 forms a chipset with the dual receiver TSH511. The VOX (voice operated transmit) circuitry disables the output buffer when there is no audio signal to save battery power. For MONO applications, the STANDBY pin enables one transmitter only, reducing the supply current. May 2009 Doc ID 8120 Rev 7 1/31 www.st.com 31 Contents TSH512 Contents 1 Absolute maximum ratings and operating conditions . . . . . . . . . . . . . 3 2 Device diagrams and schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4 5 6 3.1 Supply section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2 Audio section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3 RF section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.1 Infrared stereo transmitter application (stereo headphones) . . . . . . . . . . 14 4.2 Sub-carrier generator application: voice-operated wireless camera . . . . 16 4.3 Multimedia application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.3.1 Headset side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.3.2 Computer side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.1 LNA section: low noise amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.2 Electret condenser microphone source . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.3 MIC-BIAS section: microphone bias voltage . . . . . . . . . . . . . . . . . . . . . . 20 5.4 ALC section: automatic level control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.5 VOX description: voice operated transmit . . . . . . . . . . . . . . . . . . . . . . . . 21 5.6 PEA section: pre-emphasis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 5.7 VCO section: voltage-controlled oscillator . . . . . . . . . . . . . . . . . . . . . . . . 25 5.8 Output buffer section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5.9 SBY pin: standby for mono operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 6.1 TQFP44 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7 Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2/31 Doc ID 8120 Rev 7 TSH512 1 Absolute maximum ratings and operating conditions Absolute maximum ratings and operating conditions Table 1. Absolute maximum ratings Symbol Parameter Value Unit 7 V VCC Supply voltage(1) Toper Operating free air temperature range -40 to +85 °C Tstg Storage temperature -65 to +150 °C Maximum junction temperature 150 °C Rthjc Thermal resistance junction to case 14 °C/W Rthja Thermal resistance junction to ambient area 45 °C/W Tj Latch-up Class (2) A ESD sensitive device: handling precautions required ESD HBM: human body model(3) except pins 20 and CDM: charged device model(4) MM: machine model(5) 36 2 1 0.2 kV 1. All voltage values, except differential voltage, are with respect to network ground terminal. 2. Corporate ST Microelectronics procedure number 0018695. 3. Human body model: a 100 pF capacitor is charged to the specified voltage, then discharged through a 1.5 kΩ resistor between two pins of the device. This is done for all couples of connected pin combinations while the other pins are floating. 4. Charged device model: all pins and the package are charged together to the specified voltage and then discharged directly to the ground through only one pin. This is done for all pins. 5. Machine model: a 200 pF capacitor is charged to the specified voltage, then discharged directly between two pins of the device with no external series resistor (internal resistor < 5 Ω). This is done for all couples of connected pin combinations while the other pins are floating. Table 2. Operating conditions Symbol Parameter Value Unit 2.3 to 5.5 V VCC Supply voltage faudio Audio frequency range 20 to 20,000 Hz fcarrier Carrier frequency range 0.4 to 11 MHz Doc ID 8120 Rev 7 3/31 Device diagrams and schematics 2 TSH512 Device diagrams and schematics This section contains a detailed block diagram of the TSH512 (Figure 1), with an accompanying pin description (Table 3 on page 5), as well as the schematics of a typical application (Figure 2 on page 6). DEC2 LNA-INN2 LNA-OUT2 ALC-INT2 PEA-INN2 PEA-OUT2 VCO-BIAS2 VCC VCO-A2 VCO-B2 VCO-OUT2 Block diagram LNA-INP2 Figure 1. 44 43 42 41 40 39 38 37 36 35 34 VCO 1 33 GND 32 BUF-IN2 31 BUF-OUT2 30 GND 29 VOX-TIMER 28 VOX-INTN 27 VOX-MUTE 26 VCC 25 BUF-OUT1 24 BUF-IN1 23 GND PEA - 2 - ALC + GND 3 + MIC-BIAS2 TX2 Output buffer LNA VCC 4 SBY 5 VOX-INTS 6 VOX-SENS 7 TSH512 VOX - Monostable + VCC 8 LNA GND MIC-BIAS1 9 Output buffer TX1 + - ALC + - 10 PEA 4/31 11 14 15 16 17 18 19 20 21 22 ALC-INT1 PEA-INN1 PEA-OUT1 VCO-BIAS1 VCC VCO-A1 VCO-B1 VCO-OUT1 13 LNA-OUT1 12 LNA-INN1 VCO LNA-INP1 DEC1 Doc ID 8120 Rev 7 TSH512 Device diagrams and schematics Table 3. Pin Pin descriptions Pin name Related to Direction(1) Pin description 1 DEC2 TX2 - Decoupling capacitor for internal voltage reference 2 MIC-BIAS2 TX2 O Microphone bias 3 GND - - Ground 4 VCC - - Supply voltage 5 SBY TX1 & TX2 I Standby control (input pin) 6 VOX-INTS TX1 & TX2 - Time constant terminal for audio signal integrator in VOX 7 VOX-SENS TX1 & TX2 - Gain adjustment for VOX input sensitivity 8 VCC - - Supply voltage 9 GND - - Ground 10 MIC-BIAS1 TX1 O Microphone bias 11 DEC1 TX1 - Decoupling capacitor for internal voltage reference 12 LNA-INP1 TX1 I LNA positive input 13 LNA-INN1 TX1 I LNA negative input 14 LNA-OUT1 TX1 O LNA output 15 ALC-INT1 TX1 - Time constant terminal for integrator in ALC 16 PEA-INN1 TX1 I Pre-emphasis amplifier negative input 17 PEA-OUT1 TX1 O Pre-emphasis amplifier output 18 VCO-BIAS1 TX1 O Bias for external VCO components 19 VCC - - Supply voltage 20 VCO-A1 TX1 - Oscillator component connection 21 VCO-B1 TX1 - Oscillator component connection 22 VCO-OUT1 TX1 O VCO output 23 GND - - Ground 24 BUF-IN1 TX1 I Input to the output buffer 25 BUF-OUT1 TX1 O Output of the output buffer 26 VCC - - Supply voltage 27 VOX-MUTE TX1 & TX2 O Mute control (output pin) in VOX 28 VOX-INTN TX1 & TX2 - Time constant terminal for noise integrator in VOX 29 VOX-TIMER TX1 & TX2 - Rise time for timer in VOX 30 GND - - Ground 31 BUF-OUT2 TX2 O Output of the output buffer 32 BUF-IN2 TX2 I Input to the output buffer 33 GND - - Ground 34 VCO-OUT2 TX2 O VCO output 35 VCO-B2 TX2 - Oscillator component connection Doc ID 8120 Rev 7 5/31 Device diagrams and schematics Table 3. Pin TSH512 Pin descriptions (continued) Pin name Related to Direction(1) TX2 - Oscillator component connection - - Supply voltage Pin description 36 VCO-A2 37 VCC 38 VCO-BIAS2 TX2 O Bias for external VCO components 39 PEA-OUT2 TX2 O Pre-emphasis amplifier output 40 PEA-INN2 TX2 I Pre-emphasis amplifier negative input 41 ALC-INT2 TX2 - Time constant terminal for internal peak detector in ALC 42 LNA-OUT2 TX2 O LNA output 43 LNA-INN2 TX2 I LNA negative input 44 LNA-INP2 TX2 I LNA positive input 1. Pin directions: I = input pin, O = output pin, - = pin to connect to supply or decoupling capacitors or external components. Figure 2. 6/31 Typical application schematics for stereo infrared transmitter Doc ID 8120 Rev 7 TSH512 Electrical characteristics 3 Electrical characteristics Table 4. Electrical characteristics for VCC = 2.7 V, Tamb = 25° C, faudio = 1 kHz, fcarrier = 2.8 MHz (unless otherwise specified) (1) Symbol Parameter Test conditions Min. Typ. Max. Unit 16 11 18.6 12.8 mA Overall circuit ICC_TOT Current consumption TX1 and TX2 are on TX1 on, TX2 on, MIC-BIAS1 and MIC-BIAS2 not used: VOX-MUTE=1 output buffers on VOX-MUTE=0, output buffers off -40° C < Tamb < +85° C VOX-MUTE=1 output buffers on VOX-MUTE=0, output buffers off ICC_SBY 19.6 13.8 TX1 on, TX2 off, MIC-BIAS1 and MIC-BIAS2 not used: VOX-MUTE=1,output buffers on Current consumption with VOX-MUTE=0, output buffers off TX2 in standby: SBY (pin5) active -40° C < T < +85° C 10 7 11.5 8 mA amb VOX-MUTE=1, output buffers on VOX-MUTE=0, output buffers off 12.1 8.6 LNA sections (for TX1 and TX2) GBPLNA Gain bandwidth product RinLNA Input resistance on positive input: (LNA-INP1 pin 12 or LNA-INP2 pin 44) THDLNA Total harmonic distortion En No external load GLNA = 0 dB, VoutLNA = 700 mVPP 7 MHz 30 kΩ 0.01 % -40° C < Tamb < +85° C Equivalent input noise voltage 0.05 0.05 GLNA = 40 dB, at f = 1 kHz RS = 390 Ω, Rfeedback = 39 kΩ 6 nV/√Hz 20 dB Automatic level control (ALC) section GALC VALC_OUT Voltage gain Regulated output level (at positive input of the PEA -40° C < Tamb < +85° C amplifier) 600 710 800 mVpp 597 803 Pre-emphasis amplifier (PEA) section GBPPEA Gain bandwidth product (PEA-OUT1 pin 17 or PEA-OUT2 pin 39) No load VOpp-PEA Output voltage RL = 22 kΩ Doc ID 8120 Rev 7 9 MHz 550 mVpp 7/31 Electrical characteristics Table 4. TSH512 Electrical characteristics for VCC = 2.7 V, Tamb = 25° C, faudio = 1 kHz, fcarrier = 2.8 MHz (unless otherwise specified) (continued) (1) Symbol Parameter Test conditions Min. Typ. Max. 0.05 0.15 Unit Audio LNA+ALC+PEA sections THDALC THDAGC ΦΜPEA GLNA = 0 dB, f = 1 kHz Total harmonic distortion in (V in)ALC < 25 mVrms (-30 dBu) linear region on PEA-OUT1 R = 22 kΩ tied to GND L pin17 or PEA-OUT2 pin 39 -40° C < Tamb < +85° C % 0.25 1.3 3 (Vin)ALC = 36 mVrms (-27 dBu) (Vin)ALC= 100 mVrms (-18 dBu) Total harmonic distortion in RL = 22 kΩ tied to GND compression region -40° C < Tamb < +85° C (Vin)ALC = 36 mVrms (-27 dBu) (Vin)ALC= 100 mVrms (-18 dBu) Phase margin at PEA-OUT1 pin 17 or PEA-OUT2 pin 39 1.7 4 % 2.5 5.3 RL = 22 kΩ LNA and PEA at unity gain Vin = 40 mV 70 ° Microphone biasing section VMIC-BIAS Microphone biasing voltage IMIC-BIAS = 2.5 mA (Section 5.3 on page 20) -40° C < Tamb < +85° C ΔVMIC-BIAS VMIC-BIAS temperature coefficient IMIC-BIAS PSRRMIC-BIAS enMIC-BIAS 2.15 2.35 V 2.14 Over temp. range: [0, 70° C] [-40, 85° C] IMIC-BIAS = 2.5 mA MIC-BIAS current capability Over VCC range [2.3 V–5.5 V] 2.25 2.36 260 460 ppm/°C 2.5 mA Power supply rejection ratio At 1 kHz and Vripple = 25 mVRMS of MIC-BIAS 50 dB Equivalent input noise of MIC-BIAS VCC = 2.7 V VCC = 5.0 V 22 42 nV/√Hz Monostable current source VCC = 2.7V (VOX-TIMER pin 29) 5 µA 1.4 V Vox operated switch (VOX) section IVOX-TIMER VTHVOX-TIMER Threshold voltage of the Monostable (time constant) VMUTE_L Low level output voltage (VOX-MUTE pin 27) VMUTE_H High level output voltage (VOX-MUTE pin 27) 8/31 RL = 2 kΩ 0.2 -40° C < Tamb < +85° C 0.2 RL = 2 kΩ -40° C < Tamb < +85° C Doc ID 8120 Rev 7 V VCC-0.3 VCC0.32 V TSH512 Electrical characteristics Table 4. Electrical characteristics for VCC = 2.7 V, Tamb = 25° C, faudio = 1 kHz, fcarrier = 2.8 MHz (unless otherwise specified) (continued) (1) Symbol Parameter Test conditions Min. Typ. Max. Unit Standby VSBY_IL maximum Maximum low level input voltage of standby input (SBY pin 5) 0.1xVCC V VSBY_IH minimum Minimum high level input voltage of standby input (SBY pin 5) 0.9xVCC V VCO section VCO-BIAS output voltage (VCO-BIAS1 pin 18 or VCO-BIAS2 pin 38) With no load 1.43 VVCO-BIAS -40° C < Tamb < +85° C 1.38 IVCO-BIAS VCO-BIAS output current capability VVCO-BIAS > 1.38 V VCO-BIAS voltage drift 2.3 V < VCC < 5.5 V [0, 70° C] VCC = 2.7 V [0, 70° C] VCC = 5.0 V [-40, 85° C] VCC = 2.7 V [-40, 85° C] VCC = 5.0 V Phase noise SVRVCO-BIAS Supply voltage rejection ratio of VCO-BIAS ZVCO-OUT VCO output impedance (VCO-OUT1 pin 22 or VCO-OUT2 pin 34) ZLVCO-OUT minimum Minimum load impedance δVVCO-BIAS PNLO VVCO-OUT VCO output level 1.47 1.51 1.56 VDC 40 µA 8 +265 +356 +265 +356 mV/V ppm/°C ppm/°C ppm/°C ppm/°C At 1 kHz, L = 120 µH (Q = 30) and RVCO not connected -80 dBc With no load 43 dB 400 Ω 1 kΩ L = 120 µH (Q = 30) VCO output connected to output buffer input RVCO = 100 kΩ 580 -40° C < Tamb < +85° C 569 620 660 mVpp 671 Output buffer ZBUF-IN GOB Input impedance (BUF-IN1 pin 24 or BUF-IN2 pin 32) 400 kΩ Linear voltage gain 10 dB Output AC voltage at 1dB compression point VBUF-OUT AC Output AC voltage (BUF-OUT1 pin 25 or BUF-OUT2 pin 31) ZL = 2 kΩ 1.3 ZL = 2 kΩ VBUF-IN = 0.60 Vpp 1.35 -40° C < Tamb < +85° C 1.33 Doc ID 8120 Rev 7 1.5 1.7 Vpp 1.72 9/31 Electrical characteristics TSH512 Electrical characteristics for VCC = 2.7 V, Tamb = 25° C, faudio = 1 kHz, fcarrier = 2.8 MHz (unless otherwise specified) (continued) (1) Table 4. Symbol Parameter Test conditions Min. Typ. Max. Unit VBUF-OUT DC Output DC voltage DC output current = 0.4 mA 1.25 VDC H2BUF-OUT 2nd harmonic level VBUF-OUT = 1.2 Vpp and ZL = 2 kΩ -40 dBc H3BUF-OUT 3rd harmonic level VBUF-OUT = 1.2 Vpp and ZL = 2 kΩ -30 dBc 1. Limits over -40° C < Tamb < +85° C range are guaranteed by statistical correlation. 3.1 Supply section Figure 3. Supply current vs. supply voltage 18 TX1+TX2+Buffers 16 TX1+TX2 14 TX1+Buffers ICC(mA) 12 TX1 10 8 6 4 2 0 0 1 2 3 4 5 6 VCC(V) 3.2 Audio section Figure 4. LNA distortion vs. frequency Figure 5. 100 1 GLNA = 0dB VCC = 2.7V GLNA = 0dB VOUT-LNA = 700mVpp 10 THDLNA+N (%) THDLNA+N (%) LNA distortion vs. LNA output voltage 0.1 VCC = 2.7V VCC = 2.3V 1 0.1 0.01 VCC = 5.5V 0.01 10 1E-3 100 1000 10000 10/31 0 200 400 600 800 1000 VOUT-LNA(mVpp) Frequency (Hz) Doc ID 8120 Rev 7 1200 1400 1600 TSH512 Electrical characteristics Figure 6. Supply current vs. temperature Figure 7. LNA distortion vs. frequency 10 16 VCC = 2.7V GLNA = 40dB VOUT-LNA = 700mVpp 14 TX1+TX2 TX1+TX2+Buffers THDLNA+N (%) ICC(mA) 12 10 8 TX1+Buffers 6 TX1 4 2 0 VCC = 2.7V 0 Figure 8. 20 40 TAMB(°C) 60 0.1 10 80 Figure 9. 0.8 800 0.7 700 1000 10000 PEA output voltage vs. temperature 600 VCC = 2.7V VOUT-PEA(VPP) VCC = 2.3V 0.5 VCC = 5.5V 0.4 0.3 0.1 0.05 0.10 0.15 0.20 0.25 0.30 0.35 VCC = 5V 400 300 100 0 -40 0.40 VCC = 2.7V 500 200 RL-PEA = 22KΩ GLNA = 0dB GPEA = 0dB 0.2 0.0 0.00 100 Frequency (Hz) PEA output voltage vs. LNA input voltage 0.6 VOUT-PEA(VPP) 1 RL-PEA=22KΩ GLNA = 0dB GPEA = 0dB -20 0 20 VIN-LNA(Vpp) 40 60 80 TAMB(°C) Figure 10. PEA output voltage vs. resistor load Figure 11. MIC-BIAS output voltage vs. supply voltage 600 VCC = 2.7V 4.5 IMIC-BIAS = 2.5mA 4.0 VMIC-BIAS(V) VOUT-PEA(mVPP) 500 400 3.5 3.0 2.5 300 2.0 200 100 1k 10k 100k 1M 1.5 2.0 RL-PEA(Ω ) 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 V CC (V) Doc ID 8120 Rev 7 11/31 Electrical characteristics TSH512 Figure 12. MIC-BIAS voltage vs. MC-BIAS current Figure 13. LNA+ALC+PEA distortion vs. input voltage 2.4 VMIC-BIAS(V) 2.2 THDLNA+ALC+PEA+N (%) 10 VCC = 2.3V 2.0 1.8 RL-PEA = 22KΩ GLNA = 0dB GPEA = 0dB VCC = 2.7V 1 VCC = 2.3V 0.1 1.6 VCC = 5.5V 0 1 2 3 0.01 4 0.02 0.04 0.06 0.08 0.10 VIN(Vpp) IMIC-BIAS(mA) Figure 14. MIC-BIAS output voltage vs. temperature Figure 15. MIC-BIAS voltage vs. MIC-BIAS current 2.4 2.40 VCC = 2.7V IMIC-BIAS = 2.5mA VCC=2.7V 2.35 VMIC-BIAS(V) VMIC-BIAS(V) 2.3 2.30 2.2 2.25 2.1 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 2.20 TAMB(°C) 12/31 0 1 2 IMIC-BIAS(mA) Doc ID 8120 Rev 7 3 TSH512 Electrical characteristics 3.3 RF section Figure 16. VCO output voltage vs. RVCO Figure 17. VCO-BIAS voltage vs. VCO-BIAS current 700 650 VCC = 2.7V Rfilter = 51Ω Cfilter = 470nF 1.40 550 VVCO-BIAS(V) VVCO-OUT(mVPP) 600 1.45 VCC = 2.7V L = 120µH (Q=30) FCARRIER = 2.8MHz 500 450 1.35 400 350 1.30 300 10k 100k 0 1M 10 20 RVCO(Ω ) Figure 18. VCO and output buffer spectrum 40 50 Figure 19. VCO-BIAS voltage vs. temperature 1.6 60 VCC = 2.7V No Load VCC = 2.7V RVCO = 22kΩ ZL = 2kΩ FCARRIER = 2.8MHz 40 30 1.5 VVCO-BIAS(V) 50 VBUF-OUT(dBmV) 30 IVCO-BIAS(mA) 20 10 1.4 0 -10 -20 1.3 -40 -30 -20 -10 -30 3 6 9 12 15 18 0 10 20 30 40 50 60 70 80 TAMB(°C) Frequency(MHz) Figure 20. VCO and output buffer spectrum 60 50 VCC = 2.7V L = 120µH (Q=30) RVCO = no connected ZL = 2kΩ BW = 200Hz FCARRIER = 2.8MHz 30 20 10 0 -10 -20 2.805 2.804 2.803 2.802 2.801 2.800 2.799 2.798 2.797 2.796 -30 2.795 VBUF-OUT(dBmV) 40 Frequency(MHz) Doc ID 8120 Rev 7 13/31 Application information 4 TSH512 Application information This section gives application information for some typical applications. 4.1 Infrared stereo transmitter application (stereo headphones) In this application, shown in Figure 21, the hi-fi 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 buffered to drive the LED. Figure 21. Hi-fi stereo headphone block diagram IR stereo HiFi transmitter Headphone side Vcc: 2.3 to 5.5V Current < 15 mA 2.3 MH z filter TSH512 LNA + ALC TSH511 buffer2 Audio amp2 photodiode Vcc RX2 SBY SQUELCH ²SQUELCH TX2 LNA Line inputs VOX LED buffer1 TX1 LNA + ALC s i er arr : c reo Hz ste .8 M i F Hi & 2 2.3 RX1 SBY1 Left channel Audio amp1 20 mW / 16 Ω 20 mW / 16 Ω SBY2 Right channel filter 2.8 MH z Power supply:: 2.3 to 5.5V Icc < 20 mA stereo The audio signals are transmitted on the left and the right channels using 2.8- and 2.3-MHz carriers. The VOX activates the TX1 transmitter when the audio signal is present (Figure 22). 14/31 Doc ID 8120 Rev 7 JACK3.5ST J2 2 3 1 8K2 R20 R21 33K C13 220nF 8K2 R10 R22 1K8 C28 470nF C29 470nF C14 470nF R11 1K8 1uF C30 +5V 3K9 R23 +5V 1uF 11 10 9 8 7 6 5 4 3 2 1 C15 44 100nF C31 DEC1 MIC-BIAS1 GND VCC VOX-SENS VOX-INTS SBY VCC C4 10uF LNA + - + - MIC-BIAS2 LNA + GND DEC2 100nF C16 43 LNA-INN2 LNA-INN1 13 LNA-OUT1 LNA-INP2 470K R12 C41 10uF 470k R24 LNA-INP1 12 LNA-OUT2 42 5K6 R2 5K6 PEA + PEA + - VOX ALC 470pF C6 10K R4 C5 2nF2 TSH512 IC2 ALC 15 ALC-INT1 C32 1uF 14 R30 47 R3 C17 1uF 41 ALC-INT2 40 PEA-INN2 39 PEA-OUT2 PEA-OUT1 R32 10K C42 2nF2 47 C8 100nF 470nF C18 +5V C7 470nF Monostable 470pF C33 17 PEA-INN1 16 R31 47 R13 R5 7K5 R6 3K 37 VCC VCC 38 VCO-BIAS2 VCO-BIAS1 18 47 R25 100nF C43 C35 470nF BUF-IN2 GND R14 47K C19 47K R37 C36 56pF R26 47K GND BUF-IN1 BUF-OUT1 VCC VOX-MUTE VOX-INTN VOX-TIMER GND 23 24 25 26 27 28 29 30 31 32 33 56pF C10 12pF C46 C37 56pF R27 24K R28 22nF 2K4 C40 +5V L2 120uH 1812LS (Coilcraft) TX1 = 2.8MHz D8 C38 56pF C39 470nF 22nF 2K4 R17 OFF 0 Ohm C24 ON NC 100nF R16 150K C23 10uF C22 See Note R15 VOX R15 L1 120uH 1812LS (Coilcraft) 56pF C21 56pF C20 C11 12pF +5V D3 390pF TX2 = 2.3MHz BUF-OUT2 C34 +5V 470nF +5V R9 47K +5V VCO-B1 36 VCO-A2 VCO-A1 20 39pF R7 270K R8 100K 35 VCO-B2 34 VCO-OUT2 VCO-OUT1 22 R35 100K R36 270K 19 R33 3K R34 7K5 C9 39pF C44 21 SMV1212 SMV1212 6-60pF C45 6-60pF C12 C47 Doc ID 8120 Rev 7 68pF 7 2K7 R29 2 4 IC3 TSH81 3 +5V 8 C48 22pF 6 100nF C25 C26 100uF Vcc 1K2 R38 47 R18 C27 100nF Q1 STZT2222A D7 HSDL4230 D6 HSDL4230 D5 HSDL4230 D4 HSDL4230 R19 10 100mW mini (1206) Vcc TSH512 Application information Figure 22. Application diagram 15/31 Application information 4.2 TSH512 Sub-carrier generator application: voice-operated wireless camera Thanks to its operating frequency, the TSH512 offers the possibility of generating usual audio sub-carriers for video applications (Figure 23). 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. Figure 23. Typical block diagram for audio sub-carrier generator Miniature camera Video S FM 2.4 GHz transmitter Sub-carrier Stand-By Stand-By 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 Audio sub-carrier 6 or 6.5 MHz 4.3 Multimedia application 4.3.1 Headset side filter The TSH512 is used in mono mode 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 save energy. The usual working frequency is 1.7 MHz for infrared mono operation. 16/31 Doc ID 8120 Rev 7 TSH512 Application information Figure 24. Headset-side block diagram TSH511 & 512 supply:: 2.3 to 5.5V, 25 mA HiFi stereo from the PC: 2 x 20 mW /16 Ω 1.7 MHz reject filter TSH511 buffer2 photodiode LNA Vcc SBY2 SBY Audio amp1 SBY1 RX1 Vcc MIC. BIAS RX2 SQUELCH TSH512 TX2 filter Audio amp2 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 -pass Stereo Rx: 2.3 & 2.8 MHz TX1 Microphone Tx: 1.7 MHz carrier LNA + ALC 1.7 MHz Band-pass - 4.3.2 filter Computer side In multimedia applications, the TSH512 transmits the hi-fi stereo from the PC to the headset. Figure 25. Computer-side block diagram TSH511 & 512 supply: 2.3 to 5.5V, 24 mA HiFi stereo Voice from the headset microphone mono Rx: 1.7 MHz TSH511 Audio amp2 RX2 TSH512 LNA LNA + ALC buffer2 TX2 RX1 SBY1 SBY LED Audio amp1 SBY2 HiFi stereo Tx: 2.3 & 2.8 MHz SQUELCH photodiode VOX filter LNA + ALC buffer1 TX1 Doc ID 8120 Rev 7 1.7 MHz Band-pass Vcc 17/31 General description 5 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 high versatility and therefore a lot of applications: mono infrared transmitter, stereo transmitter, mono/stereo sub-carrier generator for video transmissions (for example the popular 2.4 GHz video links). The block diagram for the TSH512 is shown in Figure 1 on page 4. 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 MIC BIAS voltage references provide bias for electret condenser microphones (ECM) with a high power supply rejection ratio. Each audio path also includes an automatic level control (ALC) to limit the overmodulation and the distortion on very high signal amplitudes. The following operational amplifier (PEA) allows a pre-emphasis transfer function before modulating the varicap diode. Built-in voltage references (VCO-BIAS) offer 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 linearly amplifies the FM carrier to provide a sinusoidal output. This sinusoidal signal reduces the inter-modulation products between the carriers, especially in two-way or in multi-carrier systems (see Section 4: Application information on page 14). The voice operated transmit function (VOX) automatically detects when an audio signal appears over the background noise. The standby of the second transmitter reduces consumption in mono operation. 5.1 LNA section: low noise amplifier For each transmitter, the audio source is connected to the LNA. The LNA stage is a low noise operational amplifier typically usable with a gain from 0 to 40 dB. 18/31 Doc ID 8120 Rev 7 TSH512 General description Figure 26. LNA schematics The LNA gain is given by: GLNA (dB) = 20.Log(1+RLNA2/RLNA1) The high-pass cut-off frequency is: fHPF = 1/(2.π.RLNA1.CLNA1) The lowpass filter cut-off frequency is: fLPF = 1/(2.π.RLNA2.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. Note: The capacitor C must be connected directly to input pin 12. 5.2 Electret condenser microphone source When an electret condenser microphone (ECM) is used, a high gain LNA is recommended, but low frequencies have to be attenuated. The ECM must be biased with a stable and clean reference voltage. The TSH512 provides the LNA and the MIC-BIAS sections to perform this function (see Section 5.3. MIC-BIAS section: microphone bias voltage). Doc ID 8120 Rev 7 19/31 General description TSH512 Figure 27. Electret condenser microphone source The capacitor C in series 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 automatic level control (ALC), the great variations of amplitude will not overmodulate the transmitter (refer to the Section 5.4: ALC section: automatic level control). The self-adaptive VOX (voice operated transmit) offers automatic transmitting with a good discrimination of the background noise (see Section 5.5: VOX description: voice operated transmit on page 21). 5.3 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 22 nV/√Hz). This allows more than 55 dB S/N considering a bandwidth of 7 kHz (Figure 27). The MIC-BIAS voltage is related to VCC as follows (with I MIC-BIAS= 2.5 mA): VMIC-BIAS = 0.844.Vcc-0.140 (volts) Moreover, the supply rejection ratio is guaranteed to be 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 depends linearly on the supply voltage VCC (refer to Figure 11 on page 11). 20/31 Doc ID 8120 Rev 7 TSH512 5.4 General description ALC section: automatic level control Both transmitters of the TSH512 include an automatic level control (ALC). When the level of the audio signal is too high, the ALC compresses the signal in order to avoid overmodulation of the FM VCO. In this way, the ALC reduces the distortion and maintains a reduced transmit spectrum with very high amplitude signals. Figure 28. Automatic level control schematics The ALC features a 20 dB 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 the capacitor value of CALC. A typical value of CALC is 1 µF with music as the audio signal (refer to Figure 22 on page 15). The decay time is the response time the ALC requires to recover to full gain amplifying mode after being in compression mode. The decay time depends mainly on the RALC resistor value. A typical value of RALC is 470 kΩ, with music as audio signal (Figure 22). 5.5 VOX description: voice operated transmit The voice operated transmit (VOX) section 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 the external LED drivers if needed. The audio signal of TX1 is amplified with a gain dependent on the values of Rsens and Csens. Rsens and Csens are connected to pin 7. The high-pass filtering has the following cut-off frequency: 1 f HPF = ------------------------------------------------2π ( R sens ⋅ C sens ) Doc ID 8120 Rev 7 21/31 General description TSH512 Figure 29. VOX delay and sensitivity schematics On pin 6, Rpeak and Cpeak integrate the rectified audio signal with a short time constant. This filtered signal follows the audio amplitude. Figure 30. VOX integrator and monostable schematics The self-adaptive VOX threshold is necessary because the ambient background noise variation is slow compared to the voice or the music. On pin 28, RCOMP and CCOMP integrate the amplitude to follow the background amplitude. Therefore, the comparator switches when an audio signal appears over the background noise. Referring to Figure 2, CCOMP will be typically a 100 nF capacitor and RCOMP will be determined depending on the audio signal. As soon as an audio signal is detected, the output of the monostable switches to "high" state and enables both output buffers. The monostable output is pin 27 and is called VOX-MUTE. 22/31 Doc ID 8120 Rev 7 TSH512 General description The monostable holds the TSH512 in transmit mode during a delay fixed by the value of CTRIG connected to pin 29. 1.4V VOX DELAY = ⎛ ------------⎞ ⋅ C trig ⎝ 5μA ⎠ Note that the VOX function is activated when the audio signal enters the first transmitter TX1. When the application needs a permanent transmission, it is possible to inhibit the VOX function, by removing the Ctrig capacitor and connecting 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 continues if an audio signal triggers the monostable. Figure 31. VOX state at power-on on POWER SUPPLY off high state if retriggered by audio 1 VOX -MUTE VOX Delay (Ctrig) 0 time Doc ID 8120 Rev 7 23/31 General description 5.6 TSH512 PEA section: pre-emphasis The amplitude-regulated audio coming from the ALC feeds the positive input of the operational amplifier called PEA (pre-emphasis). The pre-emphasis consists in a high-pass filter in order to compensate the behavior of the FM transmission. Figure 32. Pre-emphasis schematics RPEA1 and CPEA1 set the time constant of the pre-emphasis as: τ = RPEA1. CPEA1 50 µs or 75 µs time constants are generally used. Choosing the gain of the PEA stage also allows one to set the right modulation level to the varicap diode. The gain in the passband is: GPEA = 1+ (RPEA2/RPEA1) 24/31 Doc ID 8120 Rev 7 TSH512 5.7 General description VCO section: voltage-controlled oscillator Each TSH512 transmitter has its own oscillator to generate the carrier. The audio signal is applied to 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 power supply rejection ratio (PSRR) of the VCO-BIAS ensures good immunity with the noise of the power supply. Figure 33. VCO schematics The generated frequency can be set from 400 kHz to 11 MHz by external components. Refer to Table 1 for the usual frequencies in infrared audio. The working frequency is: 1 f VCO = -------------------------------2π ( L ⋅ Ct ) where Ct is the total capacity of CL, Cp, Cs and Cv: Ct = 1/(1/Cc+1/CL) with Cc = Cp+1/(1/Cv+1/Cs) It is possible to use varicap diodes SMV1212 (Alpha Ind.) or ZC833 (Zetex). Table 5. Usual infrared frequencies IR frequency in MHz Applications 1.6 AM mono 1.7 FM mono 2.3 FM right channel 2.8 FM left channel or mono The output level of the VCO can be reduced by adding the resistor RVCO between pin 19 and pin 20 or between pin 36 and pin 37 for TX1 and TX2 respectively. Doc ID 8120 Rev 7 25/31 General description 5.8 TSH512 Output buffer section The output buffers can deliver a sinusoidal signal with a 1.5 Vpp amplitude in a 1 kΩ 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 in Low state, the TSH512’s internal buffers are muted, and the external drivers can be switched off by controlling their bias. 5.9 SBY pin: standby for mono operation A high state on the Standby pin (SBY) sets the second transmitter TX2 to power-down. The SBY pin is typically used when the TSH512 is used as a mono transmitter (that is, infrared microphone transmitter). 26/31 Doc ID 8120 Rev 7 TSH512 6 Package information Package information In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark. Doc ID 8120 Rev 7 27/31 Package information 6.1 TSH512 TQFP44 package information Figure 34. TQFP44 package mechanical drawing Table 6. TQFP44 package mechanical data Dimensions Ref. Millimeters Min. Typ. A Max. Min. Typ. 1.6 A1 0.05 A2 1.35 b 0.30 c 0.09 D 11.80 D1 9.80 D3 Max. 0.063 0.15 0.002 1.40 1.45 0.053 0.055 0.057 0.37 0.45 0.012 0.015 0.018 0.20 0.004 12 12.20 0.465 0.472 0.480 10.00 10.20 0.386 0.394 0.402 8.00 0.006 0.008 0.315 E 11.80 12.00 12.20 0.465 0.472 0.480 E1 9.80 10.00 10.20 0.386 0.394 0.402 E3 8.00 0.315 e 0.80 0.031 L 0.45 L1 K ccc 28/31 Inches 0.60 0.75 0.018 1.00 0° 3.5° 0.024 0.030 0.039 7° 0.10 Doc ID 8120 Rev 7 0° 3.5° 7° 0.004 TSH512 7 Ordering information Ordering information Table 7. Order codes Part number Temperature range TSH512CF TSH512CFT TSH512CYFT(1) Package TQFP44 -40° C to +85°C TQFP44 (automotive grade level) Packing Tray Tape & reel Tape & reel Marking TSH512C TSH512CYF 1. Qualification and characterization according to AEC Q100 and Q003 or equivalent, advanced screening according to AEC Q001 & Q 002 or equivalent. Doc ID 8120 Rev 7 29/31 Revision history 8 TSH512 Revision history Table 8. Document revision history Date Revision Changes 08-Aug-2001 1 First release corresponding to preliminary data version of datasheet. 2 Datasheet updated for Maturity 30: – ESD sensitive device sentence added – 4 curves updated – Electrical parameters updated 3 Specific content changes as follows: – Application diagrams updated – Releases on curves – Application schematic diagram update – Electrical parameters updated 01-Apr-2005 4 Pin connection updated on Figure 1 on page 4. Rthja value added on Table 1 on page 3. Schematic updated on Figure 2 on page 6. Schematic updated on Figure 26 on page 19. 14-Oct- 2005 5 PPAP reference inserted in the datasheet, see order codes table. 13-Nov-2007 6 Document reformatted with minor text changes. Added footnote for automotive grade order codes to order codes table. 28-May-2009 7 Added data at -40° C < Tamb < +85° C in Table 4. Updated package mechanical drawing in Chapter 6: Package information. 09-Sep-2001 01-Dec-2003 30/31 Doc ID 8120 Rev 7 TSH512 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no liability whatsoever relating to the choice, selection or use of the ST products and services described herein. No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. 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