TSH512CYFT - STMicroelectronics - Datasheet.Directory

May 2009 Doc ID 8120 Rev 7 1/31

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

Applications

■Infrared hi-fi stereo transmitters

■Infrared headsets

■Stereo sub-carriers for video transmitters

■Voice-operated wireless webcams

■FM IF transmit systems

Description

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.

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.

The TSH512 forms a chipset with the dual

receiver TSH511.

12 13 14 15 16 17 18 19 20 21 22

3435

3738394041

424344

TSH512

Monostable

ALC

VCO

Output

buffer

Output

buffer

TX1

TX2

LNA

VOX

PEA

12 13 14 15 16 17 18 19 20 21 22

3435

3738394041

424344

--+

TSH512

Monostable

ALC

VCO

Output

buffer

Output

buffer

TX1

TX2

LNA

VOX

PEA

Pin connections (top view)

TQFP44

10 x 10 mm

www.st.com

         
Contents TSH512
2/31  Doc ID 8120 Rev 7
Contents
Absolute maximum ratings and operating conditions   . . . . . . . . . . . . . 3
Device diagrams and schematics  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3Electrical characteristics   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1 Supply section  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10
2 Audio section  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10
3 RF section   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  13
Application information   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1 Infrared stereo transmitter application (stereo headphones)  . . . . . . . . . .  14
2 Sub-carrier generator application: voice-operated wireless camera   . . . .  16
3 Multimedia application  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  16
3.1 Headset side  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2 Computer side  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1 LNA section: low noise amplifier   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  18
2 Electret condenser microphone source  . . . . . . . . . . . . . . . . . . . . . . . . . .  19
3 MIC-BIAS section: microphone bias voltage   . . . . . . . . . . . . . . . . . . . . . .  20
4 ALC section: automatic level control   . . . . . . . . . . . . . . . . . . . . . . . . . . . .  21
5 VOX description: voice operated transmit   . . . . . . . . . . . . . . . . . . . . . . . .  21
6 PEA section: pre-emphasis  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  24
7 VCO section: voltage-controlled oscillator  . . . . . . . . . . . . . . . . . . . . . . . .  25
8 Output buffer section   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  26
9 SBY pin: standby for mono operation . . . . . . . . . . . . . . . . . . . . . . . . . . . .  26
Package information  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
1 TQFP44 package information   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  28
Ordering information   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
8Revision history   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

TSH512 Absolute maximum ratings and operating conditions

Doc ID 8120 Rev 7 3/31

1 Absolute maximum ratings and operating conditions

Table 1. Absolute maximum ratings

Symbol Parameter Value Unit

VCC Supply voltage(1)

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

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

Tstg Storage temperature -65 to +150 °C

TjMaximum 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.

ESD sensitive device: handling precautions required

ESD

except pins 20 and

HBM: human body model(3)

CDM: charged device model(4)

MM: machine model(5)

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.

0.2

Table 2. Operating conditions

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

Device diagrams and schematics TSH512

4/31 Doc ID 8120 Rev 7

2 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).

Figure 1. Block diagram

12 13 14 15 16 17 18 19 20 21 22

3435

3738394041

424344

TSH512

Monostable

ALC

VCO

Output

buffer

Output

buffer

TX1

TX2

LNA

VOX

PEA

12 13 14 15 16 17 18 19 20 21 22

3435

3738394041

424344

--+

TSH512

Monostable

ALC

VCO

Output

buffer

Output

buffer

TX1

TX2

LNA

VOX

PEA

VCO-BIAS2

VCO-OUT2

LNA-INP2

LNA-INN2

LNA-OUT2

ALC-INT2

PEA-INN2

PEA-OUT2

VCC

VCO-A2

VCO-B2

VCO-BIAS2

VCO-OUT2

LNA-INP2

LNA-INN2

LNA-OUT2

ALC-INT2

PEA-INN2

PEA-OUT2

VCC

VCO-A2

VCO-B2

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

BUF-IN2

BUF-OUT2

GND

VOX-TIMER

VOX-INTN

VOX-MUTE

VCC

BUF-OUT1

BUF-IN1

GND

LNA-INP1

LNA-INN1

LNA-OUT1

ALC-INT1

PEA-INN1

PEA-OUT1

VCO-BIAS1

VCC

VCO-A1

VCO-B1

VCO-OUT1

LNA-INP1

LNA-INN1

LNA-OUT1

ALC-INT1

PEA-INN1

PEA-OUT1

VCO-BIAS1

VCC

VCO-A1

VCO-B1

VCO-OUT1

TSH512 Device diagrams and schematics

Doc ID 8120 Rev 7 5/31

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

Device diagrams and schematics TSH512

6/31 Doc ID 8120 Rev 7

Figure 2. Typical application schematics for stereo infrared transmitter

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 (continued)

Pin Pin name Related to Direction(1) Pin description

TSH512 Electrical characteristics

Doc ID 8120 Rev 7 7/31

3 Electrical characteristics

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

(unless otherwise specified) (1)

Symbol Parameter Test conditions Min. Typ. Max. Unit

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

18.6

12.8 mA

-40° C < Tamb <+85°C

VOX-MUTE=1 output buffers on

VOX-MUTE=0, output buffers off

19.6

13.8

ICC_SBY

Current consumption with

TX2 in standby: SBY (pin5)

active

TX1 on, TX2 off, MIC-BIAS1 and

MIC-BIAS2 not used:

VOX-MUTE=1,output buffers on

VOX-MUTE=0, output buffers off

11.5

8mA

-40° C < Tamb <+85°C

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 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, Vout

LNA = 700 mVPP 0.01 0.05 %

-40° C < Tamb < +85° C 0.05

En Equivalent input noise

voltage

GLNA =40dB, at f=1kHz

RS=390Ω, Rfeedback =39kΩ6nV/√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

-40° C < Tamb < +85° C 597 803

Pre-emphasis amplifier (PEA) section

GBPPEA

Gain bandwidth product

(PEA-OUT1 pin 17 or

PEA-OUT2 pin 39)

No load 9 MHz

VOpp-PEA Output voltage RL = 22 kΩ550 mVpp

Electrical characteristics TSH512

8/31 Doc ID 8120 Rev 7

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 = 1 kHz

(Vin)ALC < 25 mVrms (-30 dBu)

RL = 22 kΩ tied to GND

0.05 0.15 %

-40° C < Tamb < +85° C 0.25

THDAGC

Total harmonic distortion in

compression region

(Vin)ALC = 36 mVrms (-27 dBu)

(Vin)ALC= 100 mVrms (-18 dBu)

RL = 22 kΩ tied to GND

1.3

1.7

-40° C < Tamb <+85°C

(Vin)ALC = 36 mVrms (-27 dBu)

(Vin)ALC= 100 mVrms (-18 dBu)

2.5

5.3

ΦΜPEA

Phase margin at

PEA-OUT1 pin 17 or

PEA-OUT2 pin 39

RL=22kΩ

LNA and PEA at unity gain

Vin = 40 mV

70 °

Microphone biasing section

VMIC-BIAS

Microphone biasing voltage

(Section 5.3 on page 20)

IMIC-BIAS = 2.5 mA 2.15 2.25 2.35 V

-40° C < Tamb < +85° C 2.14 2.36

ΔVMIC-BIAS

VMIC-BIAS temperature

coefficient

Over temp. range:

[0, 70° C]

[-40, 85° C]

IMIC-BIAS = 2.5 mA

260

460 ppm/°C

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

PSRRMIC-BIAS

Power supply rejection ratio

of MIC-BIAS At 1 kHz and Vripple = 25 mVRMS 50 dB

enMIC-BIAS

Equivalent input noise of

MIC-BIAS

VCC =2.7V

VCC =5.0V

42 nV/√Hz

Vox operated switch (VOX) section

IVOX-TIMER

Monostable current source

(VOX-TIMER pin 29) VCC = 2.7V 5 µA

VTHVOX-TIMER

Threshold voltage of the

Monostable (time constant) 1.4 V

VMUTE_L

Low level output voltage

(VOX-MUTE pin 27)

RL = 2 kΩ0.2 V

-40° C < Tamb <+85°C 0.2

VMUTE_H

High level output voltage

(VOX-MUTE pin 27)

RL = 2 kΩVCC-0.3

-40° C < Tamb <+85°C VCC-

0.32

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

(unless otherwise specified) (continued) (1)

Symbol Parameter Test conditions Min. Typ. Max. Unit

TSH512 Electrical characteristics

Doc ID 8120 Rev 7 9/31

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

VVCO-BIAS

VCO-BIAS output voltage

(VCO-BIAS1 pin 18 or

VCO-BIAS2 pin 38)

With no load 1.43 1.47 1.51

VDC

-40° C < Tamb < +85° C 1.38 1.56

IVCO-BIAS

VCO-BIAS output current

capability VVCO-BIAS > 1.38 V 40 µA

δVVCO-BIAS VCO-BIAS voltage drift

2.3 V < VCC < 5.5 V

[0, 70° C] VCC =2.7V

[0, 70° C] VCC =5.0V

[-40, 85° C] VCC =2.7V

[-40, 85° C] VCC =5.0V

+265

+356

+265

+356

mV/V

ppm/°C

PNLO Phase noise At 1 kHz, L = 120 µH (Q = 30) and

RVCO 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 pin 22 or

VCO-OUT2 pin 34)

400 Ω

ZLVCO-OUT

minimum Minimum load impedance 1 kΩ

VVCO-OUT VCO output level

L= 120µH (Q=30)

VCO output connected to output

buffer input RVCO = 100 kΩ

580 620 660 mVpp

-40° C < Tamb < +85° C 569 671

Output buffer

ZBUF-IN

Input impedance

(BUF-IN1 pin 24 or BUF-IN2

pin 32)

400 kΩ

GOB Linear voltage gain 10 dB

VBUF-OUT

Output AC voltage at 1dB

compression point ZL=2kΩ1.3

Vpp

Output AC voltage

(BUF-OUT1 pin 25 or

BUF-OUT2 pin 31)

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

-40° C < Tamb < +85° C 1.33 1.72

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

(unless otherwise specified) (continued) (1)

Symbol Parameter Test conditions Min. Typ. Max. Unit

Electrical characteristics TSH512

10/31 Doc ID 8120 Rev 7

3.1 Supply section

3.2 Audio section

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=2kΩ-40 dBc

H3BUF-OUT 3rd harmonic level VBUF-OUT =1.2V

pp and ZL=2kΩ-30 dBc

1. Limits over -40° C < Tamb < +85° C range are guaranteed by statistical correlation.

Figure 3. Supply current vs. supply voltage

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

(unless otherwise specified) (continued) (1)

Symbol Parameter Test conditions Min. Typ. Max. Unit

0123456

TX1

TX1+Buffers

TX1+TX2

TX1+TX2+Buffers

ICC(mA)

VCC(V)

Figure 4. LNA distortion vs. frequency Figure 5. LNA distortion vs. LNA output

voltage

10 100 1000 10000

0.01

0.1

VCC = 2.7V

GLNA = 0dB

VOUT-LNA = 700mVpp

THDLNA+N (%)

Frequency (Hz)

0 200 400 600 800 1000 1200 1400 1600

1E-3

0.01

0.1

100

GLNA = 0dB

VCC = 5.5V

VCC = 2.7V

VCC = 2.3V

THDLNA+N (%)

VOUT-LNA(mVpp)

TSH512 Electrical characteristics

Doc ID 8120 Rev 7 11/31

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

020406080

VCC = 2.7V

TX1+TX2

TX1

TX1+Buffers

TX1+TX2+Buffers

ICC(mA)

TAMB(°C)

10 100 1000 10000

0.1

VCC = 2.7V

GLNA = 40dB

VOUT-LNA = 700mVpp

THDLNA+N (%)

Frequency (Hz)

Figure 8. PEA output voltage vs. LNA input

voltage

Figure 9. PEA output voltage vs. temperature

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

RL-PEA = 22KΩ

GLNA = 0dB

GPEA = 0dB

VCC = 5.5V

VCC = 2.7V

VCC = 2.3V

VOUT-PEA(VPP)

VIN-LNA(Vpp)

-40 -20 0 20 40 60 80

100

200

300

400

500

600

700

800

RL-PEA=22KΩ

GLNA = 0dB

GPEA = 0dB

VCC = 2.7V

VCC = 5V

VOUT-PEA(VPP)

TAMB(°C)

Figure 10. PEA output voltage vs. resistor

load

Figure 11. MIC-BIAS output voltage vs. supply

voltage

100 1k 10k 100k 1M

200

300

400

500

600

VCC = 2.7V

VOUT-PEA(mVPP)

RL-PEA(Ω)

2.02.53.03.54.04.55.05.56.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

IMIC-BIAS = 2.5mA

VMIC-BIAS(V)

VCC(V)

Electrical characteristics TSH512

12/31 Doc ID 8120 Rev 7

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

current

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

voltage

01234

1.6

1.8

2.0

2.2

2.4

VCC = 2.3V

VMIC-BIAS(V)

IMIC-BIAS(mA)

0.02 0.04 0.06 0.08 0.10

0.01

0.1

RL-PEA = 22KΩ

GLNA = 0dB

GPEA = 0dB

VCC = 5.5V

VCC = 2.7V

VCC = 2.3V

THDLNA+ALC+PEA+N (%)

VIN(Vpp)

Figure 14. MIC-BIAS output voltage vs.

temperature

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

current

-40-30-20-10 0 1020304050607080

2.1

2.2

2.3

2.4

VCC = 2.7V

IMIC-BIAS = 2.5mA

VMIC-BIAS(V)

TAMB(°C)

0123

2.20

2.25

2.30

2.35

2.40

VCC=2.7V

VMIC-BIAS(V)

IMIC-BIAS(mA)

TSH512 Electrical characteristics

Doc ID 8120 Rev 7 13/31

3.3 RF section

Figure 16. VCO output voltage vs. RVCO Figure 17. VCO-BIAS voltage vs. VCO-BIAS

current

10k 100k 1M

300

350

400

450

500

550

600

650

700

VCC = 2.7V

L = 120µH (Q=30)

FCARRIER = 2.8MHz

VVCO-OUT(mVPP)

RVCO(Ω)

0 1020304050

1.30

1.35

1.40

1.45

VCC = 2.7V

Rfilter = 51Ω

Cfilter = 470nF

VVCO-BIAS(V)

IVCO-BIAS(mA)

Figure 18. VCO and output buffer spectrum Figure 19. VCO-BIAS voltage vs. temperature

Figure 20. VCO and output buffer spectrum

369121518

-30

-20

-10

VCC = 2.7V

RVCO = 22kΩ

ZL = 2kΩ

FCARRIER = 2.8MHz

VBUF-OUT(dBmV)

Frequency(MHz)

-40-30-20-100 1020304050607080

1.3

1.4

1.5

1.6

VCC = 2.7V

No Load

VVCO-BIAS(V)

TAMB(°C)

2.795

2.796

2.797

2.798

2.799

2.800

2.801

2.802

2.803

2.804

2.805

-30

-20

-10

VCC = 2.7V

L = 120µH (Q=30)

RVCO = no connected

ZL = 2kΩ

BW = 200Hz

FCARRIER = 2.8MHz

VBUF-OUT(dBmV)

Frequency(MHz)

Application information TSH512

14/31 Doc ID 8120 Rev 7

4 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

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).

Audio

amp1

Audi o

amp2

SBY1

SBY2

²SQUELCH

LNA

LNA + ALC

SBY

buffer1

buffer2

RX2

RX1

Line inputs

Right

channel

Left

channel

Vcc

LED

photodiode

filter

2.3 MHz

2.8 MHz

Vcc: 2.3 to 5.5V

Current < 15 mA

TSH512 TSH511

20 mW / 16 Ω

Power supply:

2.3 to 5.5V

Icc < 20 mA stereo

IR stereo HiFi transmitter Headphone side

HiFi stereo:

2.3 & 2.8 MHz carriers

VOX

TX1

TX2

²SQUELCHSQUELCH

RX2

RX1

LED

filter

20 mW / 16 Ω

VOX

TX1

TX2

TSH512 Application information

Doc ID 8120 Rev 7 15/31

Figure 22. Application diagram

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 23

BUF-IN1 24

BUF-OUT1 25

VCC 26

VOX-MUTE 27

VOX-INTN 28

VOX-TIMER 29

GND 30

BUF-OUT2 31

BUF-IN2 32

GND 33

VCO-OUT2 34

VCO-B2 35

VCO-A2 36

VCC 37

VCO-BIAS2 38

PEA-OUT2 39

PEA-INN2 40

ALC-INT2 41

LNA-OUT2 42

LNA-INN2 43

LNA-INP2 44

LNA

ALC

PEA

LNA +

ALC

PEA

VOX

Monostable

IC2

TSH512

R23

3K9

C29

470nF

R24

470k

R32

10K

R31

C33

470pF

C42

2nF2

C43

100nF

R36

270K

R35

100K

C35

470nF

C34

470nF

+5V

R26

47K

C36

56pF

C37

56pF

C45

6-60pF

C46

12pF

120uH

R37

47K

+5V

C47

68pF

C38

56pF

C13

220nF

R21

33K

C28

470nF

+5V

C39

470nF

C30

1uF

R12

470K

10K

470pF

2nF2

100nF

270K

100K

470nF

C18

470nF

+5V

R14

47K

C19

56pF

C20

56pF

C10

6-60pF

C11

12pF

47K

+5V

C12

390pF

C21

56pF

C151uF

C14

470nF

+5V

C40

22nF

C24

22nF

HSDL4230

Vcc

JACK3.5ST

C321uF

C17

1uF

+5V

120uH

C26

100uF

Vcc

C44

39pF C9

39pF

R22

1K8

R20

8K2

R10

8K2

R11

1K8

C31

100nF

R25

C16

100nF

R13

R30

5K6

C41

10uF

5K6

10uF

0 Ohm

VOX

OFF

R15

TX1 = 2.8MHz

TX2 = 2.3MHz

C23

100nF

C27

100nF

C22

10uF

R16

150K

R33

R34

7K5

HSDL4230

SMV1212

STZT2222A

R19

R18

R17

2K4

R27

2K4

R28

24K

R29

2K7

IC3 TSH81

+5V

C25

100nF

R15

See Note

1812LS (Coilcraft)

100mW mini

(1206)

R38

1K2

C48

22pF

Application information TSH512

16/31 Doc ID 8120 Rev 7

4.2 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 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

4.3 Multimedia application

4.3.1 Headset side

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.

TSH512

LNA + ALC

MIC. BIAS

TX2

VOX

SBY

buffer1

buffer2

Vcc

6 or 6.5 MHz

filter

Electret Condenser

Microphone

Miniature camera

FM 2.4 GHz

transmitter

6 or 6.5 MHz

Audio sub-carrier

Video

VOX-MUTE

Stand-By

Sub-carrier

Stand-By

TX1

TSH512

LNA + ALC

MIC. BIAS

TX2

VOX

SBY

buffer1

buffer2

Vcc

6 or 6.5 MHz

filter

Electret Condenser

Microphone

Miniature camera

FM 2.4 GHz

transmitter

6 or 6.5 MHz

Audio sub-carrier

Video

VOX-MUTE

Stand-By

Sub-carrier

Stand-By

TX1

TSH512 Application information

Doc ID 8120 Rev 7 17/31

Figure 24. Headset-side block diagram

4.3.2 Computer side

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

headset.

Figure 25. Computer-side block diagram

TSH512

LNA + ALC

MIC. BIAS

TX2

TX1

VOX

SBY

buffer1

buffer2

photodiode

Vcc

LED

Vcc

Audi o

amp2

SBY1

SBY2

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

filter

1.7 MHz

reject

2.8 MHz

Band-pass

TSH511 & 512 supply:

2.3 to 5.5V, 25 mA

Audi o

amp1

filter

filter filter

RX2

RX1

SQUELCH

1.7 MHz

reject

f ilter

Vcc

HiFi

Microphone Tx:

1.7 MHz

carrier

Stereo Rx:

2.3 & 2.8 MHz

filter

-pass

filter

filter filter

SQUELCH

f ilter

LNA + ALC

SBY

buffer1

buffer2

LED

photodiode

TSH511 & 512 supply:

2.3 to 5.5V, 24 mA

TSH512 Audio

amp1

Audio

amp2

SBY1

SBY2

SQUELCHSQUELCH

LNA

RX2

RX1

filter

TSH511

Vcc

1.7 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

General description TSH512

18/31 Doc ID 8120 Rev 7

5 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 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) 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.

TSH512 General description

Doc ID 8120 Rev 7 19/31

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).

General description TSH512

20/31 Doc ID 8120 Rev 7

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 over-

modulate 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).

TSH512 General description

Doc ID 8120 Rev 7 21/31

5.4 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 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.

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:

fHPF

2πRsens Csens

⋅()

--------------------------------------------------=

General description TSH512

22/31 Doc ID 8120 Rev 7

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.

TSH512 General description

Doc ID 8120 Rev 7 23/31

The monostable holds the TSH512 in transmit mode during a delay fixed by the value of

CTRIG connected to pin 29.

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

VOXDELAY

1.4V

5μA

------------

⎝⎠

⎛⎞

Ctrig

⋅=

time

VOX -MUTE

POWER SUPPLY

off

VOX Delay

(Ctrig)

high state if retriggered by audio

General description TSH512

24/31 Doc ID 8120 Rev 7

5.6 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.

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)

TSH512 General description

Doc ID 8120 Rev 7 25/31

5.7 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 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 Ta b l e 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 is 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.

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

fVCO

2πLC

⋅()

---------------------------------=

General description TSH512

26/31 Doc ID 8120 Rev 7

5.8 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).

TSH512 Package information

Doc ID 8120 Rev 7 27/31

6 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.

Package information TSH512

28/31 Doc ID 8120 Rev 7

6.1 TQFP44 package information

Figure 34. TQFP44 package mechanical drawing

Table 6. TQFP44 package mechanical data

Ref.

Dimensions

Millimeters Inches

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 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°

ccc 0.10 0.004

TSH512 Ordering information

Doc ID 8120 Rev 7 29/31

7 Ordering information

Table 7. Order codes

Part number Temperature

range Package Packing Marking

TSH512CF

-40° C to +85°C

TQFP44 Tray TSH512C

TSH512CFT Tape & reel

TSH512CYFT(1)

1. Qualification and characterization according to AEC Q100 and Q003 or equivalent, advanced screening

according to AEC Q001 & Q 002 or equivalent.

TQFP44

(automotive grade level) Tape & reel TSH512CYF

Revision history TSH512

30/31 Doc ID 8120 Rev 7

8 Revision history

Table 8. Document revision history

Date Revision Changes

08-Aug-2001 1 First release corresponding to preliminary data version of datasheet.

09-Sep-2001 2

Datasheet updated for Maturity 30:

– ESD sensitive device sentence added

– 4 curves updated

– Electrical parameters updated

01-Dec-2003 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 Ta b l e 4 .

Updated package mechanical drawing in Chapter 6: Package

information.

TSH512

Doc ID 8120 Rev 7 31/31

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