Rev 5

28

October 2005 1/28

TSH512Hi-fi Stereo/mono Infrared Transmitter

and Stereo Sub-carrier Generator

Supply voltage: 2.3V to 5.5V

Carrier frequency range: 0.4 to 11MHz

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

DescriptionThe TSH512 is a 0.4 to 11MHz dual FMtransmitter. Access pins to each section give highversatility and allow for several differentapplications: stereo headphone, multimediaheadset, audio sub-carrier generator.

The TSH512 integrates, in a single chip: low-noiseaudio preamplifiers with ALC (Automatic LevelControl), frequency-modulated oscillators, andlinear output buffers to drive external transistors.The sinusoidal carriers facilitate the filtering andallow high performance audio transmission.

The VOX (Voice Operated Transmit) circuitrydisables the output buffer when there is no audiosignal to save battery power. For MONOapplications, the STANDBY pin enables onetransmitter only, reducing the supply current.

The TSH512 forms a chipset with the dualreceiver TSH511.

Applications Infrared hi-fi stereo transmitters Infrared headsets Stereo sub-carrier for video transmitters Voice-operated wireless web cams FM IF transmit systems

Order Codes

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

3435363738394041424344

1

+- +

-

+- +

-

TSH512

Monostable

ALC

ALC

VCO

VCO

Outputbuffer

Outputbuffer

TX1

TX2LNA

LNA

VOX

-+

PEA

PEA2

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

3435363738394041424344

1

-- +-+-

+

TSH512

Monostable

ALC

ALC

VCO

VCO

Outputbuffer

Outputbuffer

TX1

TX2LNA

LNA

VOX

-+

PEA

PEA

Pin connections (top view)

FTQFP44

10 x 10 mm

Part NumberTemperature

RangePackage Packing Marking

TSH512CF

-40°C to +85°CTQFP44

TrayTSH512C

TSH512CFTTape & reel

TSH512CYFTTQFP44

(automotive grade level)TSH512CYF

www.st.com

Absolute Maximum Ratings TSH512

2/28

1 Absolute Maximum Ratings

Table 1. Key parameters and their absolute maximum ratings

Table 2. Operating conditions

Symbol Parameter Value Unit

Vcc Supply voltage(1)

1. All voltages values, except differential voltage, are with respect to network ground terminal

7 V

Toper Operating free air temperature range -40 to +85 °C

Tstg Storage temperature -65 to +150 °C

Tj Maximum junction temperature 150 °C

Rthjc Thermal resistance junction to case 14 °C/W

Rthja Thermal resistance junction to ambient area 45 °C/W

Latch-up Class(2)

2. Corporate ST Microelectronics procedure number 0018695

A

ESD sensitive device: handling precautions required

ESDexcept pin 20 & 36

HBM: Human Body Model(3)

CDM: Charged Device Model(4)

MM: Machine Model(5)

3. ElectroStatic Discharge pulse (ESD pulse) simulating a human body discharge of 100 pF through 1.5kΩ

4. Discharge to Ground of a device that has been previously charged.

5. ElectroStatic Discharge pulse (ESD pulse) approximating a pulse of a machine or mechanical equipment.

21

0.2kV

Symbol Parameter Value Unit

Vcc Supply voltage 2.3 to 5.5 V

faudio Audio frequency range 20 to 20,000 Hz

fcarrier Carrier frequency range 0.4 to 11 MHz

TSH512 Device diagrams and schematics

3/28

2 Device diagrams and schematics

This chapter contains a detailed block diagram of the TSH512 (Figure 1), with an accompanying pin description (Table 3 on page 4), as well as a typical application schematic (Figure 2 on page 6).

Figure 1. Block diagram

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

3435363738394041424344

1

+- +

-

+- +

-

TSH512

Monostable

ALC

ALC

VCO

VCO

Outputbuffer

Outputbuffer

TX1

TX2LNA

LNA

VOX

-+

PEA

PEA2

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

3435363738394041424344

1

-- +-+-

+

TSH512

Monostable

ALC

ALC

VCO

VCO

Outputbuffer

Outputbuffer

TX1

TX2LNA

LNA

VOX

-+

PEA

PEA

VC

O-B

IAS

2

VC

O-O

UT2

LNA

-INP

2

LNA

-INN

2

LNA

-OU

T2

ALC

-INT2

PE

A-IN

N2

PE

A-O

UT2

VC

C

VC

O-A

2

VC

O-B

2

VC

O-B

IAS

2

VC

O-O

UT2

LNA

-INP

2

LNA

-INN

2

LNA

-OU

T2

ALC

-INT2

PE

A-IN

N2

PE

A-O

UT2

VC

C

VC

O-A

2

VC

O-B

2

DEC2

MIC-BIAS2

GND

VCC

SBY

VOX-INTS

VOX-SENS

VCC

GND

MIC-BIAS1

DEC1

DEC2

MIC-BIAS2

GND

VCC

SBY

VOX-INTS

VOX-SENS

VCC

GND

MIC-BIAS1

DEC1

GND

BUF-IN2

BUF-OUT2

GND

VOX-TIMER

VOX-INTN

VOX-MUTE

VCC

BUF-OUT1

BUF-IN1

GND

GND

BUF-IN2

BUF-OUT2

GND

VOX-TIMER

VOX-INTN

VOX-MUTE

VCC

BUF-OUT1

BUF-IN1

GND

LNA

-INP

1

LNA

-INN

1

LNA

-OU

T1

ALC

-INT1

PE

A-IN

N1

PE

A-O

UT1

VC

O-B

IAS

1

VC

C

VC

O-A

1

VC

O-B

1

VC

O-O

UT1

LNA

-INP

1

LNA

-INN

1

LNA

-OU

T1

ALC

-INT1

PE

A-IN

N1

PE

A-O

UT1

VC

O-B

IAS

1

VC

C

VC

O-A

1

VC

O-B

1

VC

O-O

UT1

Device diagrams and schematics TSH512

4/28

Table 3. Pin descriptions

Pin 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

TSH512 Device diagrams and schematics

5/28

36 VCO-A2 TX2 - Oscillator component connection

37 VCC - - Supply Voltage

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

Table 3. Pin descriptions

Pin Pin name Related to Direction(1) Pin description

Device diagrams and schematics TSH512

6/28

Figure 2. Typical application schematic for stereo infrared transmitter

TSH512 Electrical Characteristics

7/28

3 Electrical Characteristics

Table 4. Electrical characteristics for VCC = 2.7V, Tamb = 25°C, faudio = 1kHz, fcarrier = 2.8MHz (unless otherwise specified)

Symbol Parameter Test condition Min. Typ. Max. Unit

Overall Circuit

ICC_TOTCurrent consumptionTX1 and TX2 are on

TX1 on, TX2 on, MIC-BIAS1 and MIC-BIAS2 not used:

VOX-MUTE=1 output buffers onVOX-MUTE=0, output buffers off

1611

18.612.8

mA

ICC_SBY

Current consumption with TX2 in stand-by: SBY (pin5) active

TX1 on, TX2 off, MIC-BIAS1 and MIC-BIAS2 not used:

VOX-MUTE=1,output buffers onVOX-MUTE=0, output buffers off

107

11.58

mA

LNA Sections (for TX1 and TX2)

GBPLNA Gain Band Product No external load 7 MHz

RinLNA

Input Resistance on positive input:

(LNA-INP1 pin 12 or LNA-INP2 pin 44)

30 kΩ

THDLNA Total Harmonic Distortion GLNA = 0dB VoutLNA = 700mVPP 0.01 0.05 %

EnEquivalent Input Noise Voltage

GLNA=40dB, at f=1kHzRs = 390Ω, Rfeedback = 39kΩ

6 nV/√Hz

Automatic Level Control (ALC) Section

GALC Voltage Gain 20 dB

VALC_OUT

Regulated Output Level(at positive input of the PEA amplifier)

600 710 800 mVpp

Pre-Emphasis Amplifier (PEA) Section

GBPPEA

Gain Band Product(PEA-OUT1 pin17 or PEA-OUT2 pin39)

No Load 9 MHz

VOpp-PEA Output voltage RL = 22kΩ 550 mVpp

Audio LNA+ALC+PEA sections

THDALC

Total Harmonic Distortion in linear region on PEA-OUT1 pin17 or PEA-OUT2 pin 39

GLNA = 0 dB, f = 1kHzVinALC < 25mVrms (-30dBu)RL = 22kΩ tied to GND

0.05 0.15 %

THDAGCTotal Harmonic Distortion incompression region

(Vin)ALC = 36mVrms (-27dBu)(Vin)ALC= 100mVrms (-18dBu)RL = 22 kΩ tied to GND

1.33

1.74 %

Electrical Characteristics TSH512

8/28

ΦΜPEA

Phase Margin at

PEA-OUT1 pin 17 orPEA-OUT2 pin 39

RL = 22kΩLNA and PEA at unity gainVin = 40mV

70 °

Microphone Biasing Section

VMIC-BIASMicrophone Biasing Voltage(Section 8.3 on page 21)

IMIC-BIAS = 2.5mA 2.15 2.25 2.35 V

∆VMIC-BIASVMIC-BIAS temperature coefficient

Over temp. range:

[0, 70°C][-40, 85°C]IMIC-BIAS = 2.5 mA

260460

ppm/°C

IMIC-BIAS MIC-BIAS current capability over VCC range [2.3V-5.5V] 2.5 mA

PSRRMIC-BIAS

Power Supply Rejection Ratio of MIC-BIAS

@ 1kHz and V ripple = 25mVRMS 50 dB

enMIC-BIASEquivalent input noise of MIC-BIAS

VCC = 2.7VVCC = 5.0V

2242

nV/√Hz

Vox Operated Switch (VOX) Section

IVOX-TIMERMonostable Current Source(VOX-TIMER pin 29)

VCC = 2.7V 5 µA

VTHVOX-TIMER

Threshold voltage of the Monostable (Time Constant)

1.4 V

VMUTE_LLow Level Output Voltage(VOX-MUTE Pin27)

RL = 2kΩ 0.2 V

VMUTE_HHigh Level Output Voltage(VOX-MUTE Pin27)

RL = 2kΩ Vcc-0.3 V

Standby

VSBY_ILmax.

Max. Low Level Input Voltage of Standby input (SBY Pin5)

0.1xVCC V

VSBY_IHmin.

Min. High Level Input Voltage of Standby input (SBY Pin5)

0.9xVCC V

VCO Section

VVCO-BIAS

VCO-BIAS output voltage(VCO-BIAS1 pin18 or VCO-BIAS2 pin 38)

With No Load 1.43 1.47 1.51 VDC

IVCO-BIASVCO-BIAS output current capability

VVCO-BIAS > 1.38V 40 µA

δVVCO-BIAS VCO-BIAS voltage drift

2.3V < Vcc < 5.5V[0, 70°C] Vcc = 2.7V[0, 70°C] Vcc = 5.0V[-40, 85°C] Vcc = 2.7V[-40, 85°C] Vcc = 5.0V

8+265+356+265+356

mV/Vppm/°Cppm/°Cppm/°Cppm/°C

Symbol Parameter Test condition Min. Typ. Max. Unit

TSH512 Electrical Characteristics

9/28

PNLO Phase Noise@ 1kHz, L = 120µH (Q=30) andRVCO not connected -80 dBc

SVRVCO-BIAS

Supply Voltage Rejection Ratio of VCO-BIAS

With No Load 43 dB

ZVCO-OUT

VCO Output Impedance(VCO-OUT1 pin22 or VCO-OUT2 pin34)

400 Ω

ZLVCO-OUT

min.Minimum Load Impedance 1 kΩ

VVCO-OUT VCO Output Level

L = 120µH (Q=30)VCO output connected to Output Buffer inputRVCO = 100kΩ

0.58 0.62 0.66 Vpp

Output Buffer

ZBUF-IN

Input Impedance(BUF-IN1 pin24 or BUF-IN2 pin32)

400 kΩ

GOB Linear Voltage Gain 10 dB

VBUF-OUTAC

Output AC voltage at 1dB compression point

ZL = 2kΩ 1.3

VppOutput AC voltage (BUF-OUT1 pin 25 or BUF-OUT2 pin 31)

ZL = 2kΩ VBUF-IN = 0.60Vpp 1.35 1.5 1.7

VBUF-OUTDC

Output DC voltage DC Output current = 0.4 mA 1.25 VDC

H2BUF-OUT 2nd Harmonic LevelVBUF-OUT = 1.2Vpp andZL = 2kΩ -40 dBc

H3BUF-OUT 3rd Harmonic LevelVBUF-OUT =1.2Vpp andZL = 2kΩ -30 dBc

Symbol Parameter Test condition Min. Typ. Max. Unit

Supply Section TSH512

10/28

4 Supply Section

Figure 3. Supply current vs. supply voltage

0 1 2 3 4 5 60

2

4

6

8

10

12

14

16

18

TX1

TX1+Buffers

TX1+TX2

TX1+TX2+Buffers

I CC(m

A)

VCC

(V)

TSH512 Audio section

11/28

5 Audio section

Figure 4. LNA distortion vs. frequency

Figure 5. LNA distortion vs. LNA output voltage

Figure 6. Supply current vs. temperature Figure 7. LNA distortion vs. frequency

Figure 8. PEA output voltage vs. LNA input voltage

Figure 9. PEA output voltage vs. temperature

10 100 1000 100000.01

0.1

1

VCC

= 2.7VG

LNA = 0dB

VOUT-LNA

= 700mVpp

TH

DL

NA+

N (

%)

Frequency (Hz)

0 200 400 600 800 1000 1200 1400 16001E-3

0.01

0.1

1

10

100

GLNA

= 0dB

VCC

= 5.5V

VCC

= 2.7V

VCC

= 2.3V

TH

DL

NA+

N (

%)

VOUT-LNA

(mVpp

)

-40 -20 0 20 40 60 800

2

4

6

8

10

12

14

16

18

20V

CC = 2.7V

TX1+TX2

TX1

TX1+Buffers

TX1+TX2+Buffers

I CC(m

A)

TAMB

(°C)

10 100 1000 100000.1

1

10

VCC

= 2.7VG

LNA = 40dB

VOUT-LNA

= 700mVpp

TH

DL

NA+

N (

%)

Frequency (Hz)

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.400.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

RL-PEA

= 22KΩG

LNA = 0dB

GPEA

= 0dB

VCC

= 5.5VVCC

= 2.7V

VCC

= 2.3V

VO

UT

-PE

A(V

PP)

VIN-LNA

(Vpp

)

-40 -20 0 20 40 60 800

100

200

300

400

500

600

700

800

RL-PEA

=22KΩG

LNA = 0dB

GPEA

= 0dB

VCC

= 2.7V

VCC

= 5V

VO

UT-

PE

A(V

PP)

TAMB

(°C)

Audio section TSH512

12/28

Figure 10. PEA output voltage vs. resistor load

Figure 11. MIC-BIAS output voltage vs. supply voltage

Figure 12. MIC-BIAS voltage vs. MC-BIAS current

Figure 13. LNA+ALC+PEA distortion vs. input voltage

Figure 14. MIC-BIAS output voltage vs. temperature

Figure 15. MIC-BIAS voltage vs. MIC-BIAS current

100 1k 10k 100k 1M200

300

400

500

600V

CC = 2.7V

VO

UT

-PE

A(m

VP

P)

RL-PEA

(Ω)

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.01.5

2.0

2.5

3.0

3.5

4.0

4.5IMIC-BIAS

= 2.5mA

VM

IC-B

IAS(V

)

VCC

(V)

0 1 2 3 4

1.6

1.8

2.0

2.2

2.4

VCC

= 2.3V

VM

IC-B

IAS(V

)

IMIC-BIAS

(mA)

0.02 0.04 0.06 0.08 0.100.01

0.1

1

10

RL-PEA

= 22KΩG

LNA = 0dB

GPEA

= 0dB

VCC

= 5.5V

VCC

= 2.7V

VCC

= 2.3V

TH

DL

NA

+AL

C+P

EA+

N (

%)

VIN

(Vpp

)

-40 -30 -20 -10 0 10 20 30 40 50 60 70 802.1

2.2

2.3

2.4

VCC

= 2.7VIMIC-BIAS

= 2.5mA

VM

IC-B

IAS(V

)

TAMB

(°C)0 1 2 3

2.20

2.25

2.30

2.35

2.40

VCC

=2.7V

VM

IC-B

IAS(V

)

IMIC-BIAS

(mA)

TSH512 Audio section

13/28

Figure 16. MIC-BIAS voltage vs. MIC-BIAS current

Figure 17. VOX delay vs. CTRIG capacitor

Figure 18. Monostable current source vs. temperature

0 1 2 3 4 5 63.8

4.0

4.2

4.4

4.6

4.8

VCC

= 5.5V

VM

IC-B

IAS(V

)

IMIC-BIAS

(mA)

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

35

VCC

= 2.7V

VO

XD

elay

(s)

CTRIG

(µF)

-40.0 -20.0 0.0 20.0 40.0 60.0 80.00

1

2

3

4

5

6

7V

CC = 2.7V

I VOX

-TIM

ER(µ

A)

TAMB

(°C)

RF Section TSH512

14/28

6 RF Section

Figure 19. VCO output voltage vs. RVCO Figure 20. VCO-BIAS voltage vs. VCO-BIAS current

Figure 21. VCO & output buffer spectrum Figure 22. VCO-BIAS voltage vs. temperature

Figure 23. VCO & output buffer spectrum

10k 100k 1M300

350

400

450

500

550

600

650

700V

CC = 2.7V

L = 120µH (Q=30)F

CARRIER = 2.8MHz

VV

CO

-OU

T(m

VP

P)

RVCO

(Ω)

0 10 20 30 40 501.30

1.35

1.40

1.45

VCC

= 2.7VR

filter = 51Ω

Cfilter

= 470nF

VV

CO

-BIA

S(V

)IVCO-BIAS

(mA)

3 6 9 12 15 18-30

-20

-10

0

10

20

30

40

50

60

VCC

= 2.7VR

VCO = 22kΩ

ZL = 2kΩ

FCARRIER

= 2.8MHz

VB

UF

-OU

T(d

Bm

V)

Frequency(MHz)

-40 -30 -20 -10 0 10 20 30 40 50 60 70 801.3

1.4

1.5

1.6V

CC = 2.7V

No Load

VV

CO

-BIA

S(V

)

TAMB

(°C)

2.79

5

2.79

6

2.79

7

2.79

8

2.79

9

2.80

0

2.80

1

2.80

2

2.80

3

2.80

4

2.80

5

-30

-20

-10

0

10

20

30

40

50

60

VCC

= 2.7VL = 120µH (Q=30)R

VCO = no connected

ZL = 2kΩ

BW = 200HzF

CARRIER = 2.8MHz

VB

UF

-OU

T(d

Bm

V)

Frequency(MHz)

TSH512 Application Information

15/28

7 Application Information

This chapter gives application information for some typical applications.

7.1 Infrared stereo transmitter application (stereo headphones)

In this application, shown in Figure 24, 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 attack the LED final stage.

The audio signals are transmitted on the left and the right channels using a 2.8 & 2.3MHz carriers. The VOX activates the transmitter TX1 when the audio signal is present (see Figure 25).

Figure 24. Hi-fi stereo headphone block diagram

Audio

amp1

Audioamp2

SB

Y1

SB

Y2

²SQ

UE

LC

H

LNA

LNA + ALC

LNA + ALC

SBY

buffer1

buffer2

RX2

RX1

Line inputs

Rightchannel

Leftchannel

Vcc

LED

photodiode

filter

f ilter

2.3 MHz

2.8 MHz

Vcc: 2.3 to 5.5V

Current < 15 mA

TSH512 TSH511

20 mW / 16 Ω

20 mW / 16 Ω

Power supply:

2.3 to 5.5VIcc < 20 mA stereo

IR stereo HiFi transmitter Headphone side

HiFi stereo:

2.3 & 2.8 MHz carrie

rs

VOX

TX1

TX2

²SQ

UE

LC

HS

QU

ELC

H

RX2

RX1

LED

filter

20 mW / 16 Ω

20 mW / 16 Ω

:

:

VOX

TX1

TX2

Application Information TSH512

16/28

Figure 25. Application diagram

DE

C2

1

MIC

-BIA

S2

2

GN

D3

VC

C4

SB

Y5

VO

X-I

NT

S6

VO

X-S

EN

S7

VC

C8

GN

D9

MIC

-BIA

S1

10

DE

C1

11

LNA-INP112

LNA-INN113

LNA-OUT114

ALC-INT115

PEA-INN116

PEA-OUT117

VCO-BIAS118

VCC19

VCO-A120

VCO-B121

VCO-OUT122

GN

D23

BU

F-I

N1

24

BU

F-O

UT

125

VC

C26

VO

X-M

UT

E27

VO

X-I

NT

N28

VO

X-T

IME

R29

GN

D30

BU

F-O

UT

231

BU

F-I

N2

32

GN

D33

VCO-OUT234

VCO-B235

VCO-A236

VCC37

VCO-BIAS238

PEA-OUT239

PEA-INN240

ALC-INT241

LNA-OUT242

LNA-INN243

LNA-INP244

LN

A

+ -+ -

AL

C

PE

A

LN

A+-

+-

AL

C

PE

A

VO

X

+ -

Monosta

ble

IC2

TS

H512

R23

3K

9

C29

470nF

R24

470k

R32

10K

R31 47

C33

470pF

C42

2nF

2

C43

100nF

R36

270K

R35

100K

C35

470nF

C34

470nF

+5V

R26

47K C

36

56pF

C37

56pF

C45

6-60pF

C46

12pF

L2 120uH

R37

47K

+5V

C47

68pF

C38

56pF

C13

220nF

R21

33K

C28

470nF

+5V

C39

470nF

C30

1uF

R12

470K

R4

10K

R3

47

C6

470pF

C5

2nF

2

C8

100nF

R7

270K

R8

100K

C7

470nF

C18

470nF

+5V

R14

47KC

19

56pF

C20

56pF

C10

6-60pF

C11

12pF

R9

47K

+5V

C12

390pF

C21

56pF

C15

1uF

C14

470nF

+5V

C40

22nF

C24

22nF

D4

HS

DL4230

D6

HS

DL4230

Vcc

1 2 3

J2

JA

CK

3.5

ST

C32 1uF

C17

1uF

+5V

L1

120uH

C26

100uFV

cc

C44

39pFC9

39pF

R22

1K

8

R20

8K

2

R10

8K

2

R11

1K

8

C31

100nF

R25

47

C16

100nF

R13

47

R30 5K

6

C41

10uF

R2

5K6

C4

10uF

NC

0 O

hm

VO

X

ON

OF

F

R15

TX

1 =

2.8

MH

z

TX

2 =

2.3

MH

z

C23

100nF

C27

100nF

C22

10uF

R16

150K

R333K

R347K5

R6

3K

R5

7K5

D5

HS

DL4230

D7

HS

DL4230

D8

SMV1212

D3

SMV1212

Q1

ST

ZT

2222A

R19

10

R18

47

R17

2K

4

R27

2K

4

R28

24K

R29

2K

7

IC3

TS

H81

+5V

+5V

C25

100nF

R15

See N

ote

1812LS

(C

oilc

raft)

1812LS

(C

oilc

raft)

100m

W m

ini

(1206)

3 2

6

7

84

R38

1K

2

C48

22pF

TSH512 Application Information

17/28

7.2 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 26). 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 26. Typical block diagram for audio sub-carrier generator

TSH512

LNA + ALC

LNA + ALC

MIC. BIAS

MIC. BIAS

TX2

VOX

SBY

buffer1

buffer2

Vcc

6 or 6.5 MHz filter

Electret CondenserMicrophone

Miniature camera

FM 2.4 GHztransmitter

6 or 6.5 MHzAudio sub-carrier

Video

VOX-MUTE

Stand-By

SSub-carrier

Stand-By

TX1

TSH512

LNA + ALC

LNA + ALC

MIC. BIAS

MIC. BIAS

TX2

VOX

SBY

buffer1

buffer2

Vcc

6 or 6.5 MHz filter

Electret CondenserMicrophone

Miniature camera

FM 2.4 GHztransmitter

6 or 6.5 MHzAudio sub-carrier

Video

VOX-MUTE

Stand-By

SSub-carrier

Stand-By

TX1

Application Information TSH512

18/28

7.3 Multimedia Application

7.3.1 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 1.7MHz for infrared mono operation.

7.3.2 Computer side

In multimedia applications, the TSH512 transmits the hi-fi stereo from the PC to the headset.

Figure 27. Headset side block diagram

Figure 28. Computer side block diagram

TSH512

LNA + ALC

LNA + ALC

MIC. BIAS

MIC. BIAS

TX2

TX1

VOX

SBY

buffer1

buffer2

photodiode

Vcc

LED

Vcc

Audioamp2

SB

Y1

SB

Y2

LNA

2.3 MHz

Band-pass

TSH511

HiFi stereo from the PC:2 x 20 mW /16 Ω

1.7 MHz

Band-pass

Voice transmitted to the PC

Microphone Tx:

1.7 MHz

carrier

Stereo Rx:

2.3 & 2.8 MHz

f ilter

1.7 MHz

reject

2.8 MHz

Band-pass

TSH511 & 512 supply:2.3 to 5.5V, 25 mA

Audio

amp1

filter

f ilter f ilter

RX2

RX1

SQ

UE

LC

H

1.7 MHz

reject

f ilter

Vcc

-

HiFi

-

Microphone Tx:

1.7 MHz

carrier

Stereo Rx:

2.3 & 2.8 MHz

f ilter

-pass

:

f ilter

f ilter f ilter

SQ

UE

LC

H

f ilter

LNA + ALC

LNA + ALC

SBY

buffer1

buffer2

LED

photodiode

TSH511 & 512 supply:

2.3 to 5.5V, 24 mA

TSH512Audioamp1

Audio

amp2

SB

Y1

SB

Y2

SQ

UE

LC

HS

QU

ELC

H

LNA

RX2

RX1

filter

TSH511

Vcc1.7 MHz

Band-pass

HiFi stereo Tx:

2.3 & 2.8 MHz

mono Rx:

1.7 MHz

Voice from the headset microphoneHiFi stereo

VOX

TX2

TX1

TSH512 General Description

19/28

8 General Description

The TSH512 is a 0.4 to 11MHz 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 (i.e.: popular 2.4GHz video links). The block diagram for the TSH512 is shown in Figure 1 on page 3.

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 over modulation 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) offers a regulated voltage to bias the varicap diodes. The Voltage Controlled Oscillator (VCO) is an integrated oscillator giving typically 600mV peak to peak at 2.8MHz.

The Output Buffer section linearly amplifies the FM carrier to provide a sinusoidal output. This sinusoidal signals reduce the inter-modulation products between the carriers, specially in two-way or in multi-carrier systems (see Application Information on page 15).

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.

8.1 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 0dB to 40dB.

Figure 29. LNA schematic

General Description TSH512

20/28

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 10mΩ and the capacitance lower than 50pF in order to keep a good stability.

8.2 Electret condenser microphone source

When a Electret Condenser Microphone (ECM) is used, a high gain LNA is recommended, 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 Section 8.3. MIC-BIAS section: microphone bias voltage).

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 ALC (Automatic Level control), the great variations of amplitude will not over-modulate the transmitter (refer to the chapter on ALC).

The self-adaptive VOX (Voice Operated Transmit) offers an automatic transmitting with a good discrimination of the background noise (see Section 8.5. VOX description: voice operated transmit).

Figure 30. Electret condenser microphone source

TSH512 General Description

21/28

8.3 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 22nV/√Hz). This allows more than 55dB S/N considering a bandwidth of 7kHz (see Figure 30).

The MIC-BIAS voltage is related with VCC as follow (with I MIC-BIAS= 2.5mA):

VMIC-BIAS = 0.844.Vcc-0.140 (Volts)

Moreover, the supply rejection ratio is guaranteed to be better than 50dB without any decoupling capacitor. To address biasing of most of the microphones, the current drive capability is 2.5mA. The MIC-BIAS voltage depends linearly on the supply voltage VCC (refer to Figure 11).

8.4 ALC section: automatic level control

Both transmitters of the TSH512 include Automatic Level Control (ALC). When the level of the audio signal is too high, the ALC compresses the signal in order to avoid over-modulation of the FM VCO. In this way, the ALC reduces the distortion and maintains a reduced transmit spectrum with very high-amplitude signals.

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 the audio signal (refer to Figure 25).

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 470kΩ, with music as audio signal (refer to Figure 25).

Figure 31. Automatic level control schematic

General Description TSH512

22/28

8.5 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 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:

On pin 6, Rpeak and Cpeak integrate the rectified audio signal with a short time constant. This filtered signal follows the audio amplitude.

Figure 32. VOX delay and sensitivity schematic

HPFf 1

2π Rsens Csens⋅( )-----------------------------------------------------=

TSH512 General Description

23/28

The self-adaptive VOX threshold is necessary because 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. Referring to Figure 2, CCOMP will be typically a 100nF 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 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.

Please 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. Just remove the 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 continues if an audio signal triggers the monostable.

Figure 33. VOX integrator and monostable schematic

VOXDELAY1.4V5µA------------⎝ ⎠⎛ ⎞ Ctrig⋅=

General Description TSH512

24/28

8.6 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.

RPEA1 and CPEA1 set the time constant of the pre-emphasis as:

τ = RPEA1. CPEA1

50 µs or 75µs 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 pass-band is:

GPEA = 1+ (RPEA2/RPEA1)

Figure 34. VOX state at power-on

Figure 35. Pre-emphasis schematic

time

VOX -MUTE

POWER SUPPLY

on

off

VOX Delay(Ctrig)

0

1high state if retriggered by audio

TSH512 General Description

25/28

8.7 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 PSRR (Power Supply Rejection ratio) of the VCO-BIAS ensures good immunity with the noise of the power supply.

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:

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’s possible to use varicap diodes SMV1212 (Alpha Ind.) or ZC833 (Zetex).

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.

Figure 36. VCO schematic

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

VCOf 1

2π L Ct⋅( )------------------------------=

General Description TSH512

26/28

8.8 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.

8.9 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 (i.e. infrared microphone transmitter).

TSH512 Package Mechanical Data

27/28

9 Package Mechanical Data

In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect. The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com.

TQFP44 Package

DIM.mm. inch

MIN. TYP MAX. MIN. TYP. MAX.

A 1.6 0.063

A1 0.05 0.15 0.002 0.006

A2 1.35 1.40 1.45 0.053 0.055 0.057

B 0.30 0.37 0.45 0.012 0.015 0.018

C 0.09 0.20 0.004 0.008

D 11.80 12.00 12.20 0.465 0.472 0.480

D1 9.80 10.00 10.20 0.386 0.394 0.402

D3 8.00 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 0.60 0.75 0.018 0.024 0.030

L1 1.00 0.039

K 0˚ 3.5˚ 7˚ 0˚ 3.5˚ 7˚

TQFP44 MECHANICAL DATA

0076922/D

Revision History TSH512

28/28

10 Revision History

Date Revision Changes

Aug. 2001 1 First release corresponding to Preliminary Data version of datasheet.

Sept. 2001 2

Datasheet updated for Maturity 30:

– ESD sensitive device sentence added

– 4 curves updated

– Electrical parameters updated

Dec. 2003 3

Specific content changes as follows:

– Application diagrams updated

– Releases on curves

– Application schematic diagram update

– Electrical parameters updated

Dec. 2003 3

Specific content changes as follows:

– Application diagrams updated

– Releases on curves

– Application schematic diagram update

– Electrical parameters updated

Oct. 2005 5– PPAP reference inserted in the datasheet see Table . Order Codes

on page 1.

Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequencesof use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license isgranted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication aresubject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics productsare 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.All other names are the property of their respective owners

© 2005 STMicroelectronics - All rights reserved

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