TS4972 datasheet(21/30 Pages) STMICROELECTRONICS

21 / 30 page

Application Information

TS4972

21/30

■ BTL Configuration Principle

The TS4972 is a monolithic power amplifier with a

BTL output type. BTL (Bridge Tied Load)

means that each end of the load is connected

to two single ended output amplifiers. Thus, we

have :

Single ended output 1 = Vout1 = Vout (V)

Single ended output 2 = Vout2 = -Vout (V)

And Vout1 - Vout2 = 2Vout (V)

The output power is:

For the same power supply voltage, the output

power in BTL configuration is four times higher

than

the

output

power

single

ended

configuration.

■ Gain In Typical Application Schematic

(cf. page 1)

In flat region (no effect of Cin), the output voltage

of the first stage is:

For the second stage : Vout2 = -Vout1 (V)

The differential output voltage is:

The differential gain named gain (Gv) for more

convenient usage is:

Remark : Vout2 is in phase with Vin and Vout1 is

180 phased with Vin. It means that the positive

terminal

the

loudspeaker

should

connected to Vout2 and the negative to Vout1.

■ Low and high frequency response

In low frequency region, the effect of Cin starts.

Cin with Rin forms a high pass filter with a -3dB

cut off frequency.

In high frequency region, you can limit the

bandwidth by adding a capacitor (Cfeed) in

parallel on Rfeed. Its form a low pass filter with

a -3dB cut off frequency.

■ Power dissipation and efficiency

Hypothesis :

• Voltage and current in the load are

sinusoidal (Vout and Iout)

• Supply voltage is a pure DC source (Vcc)

Figure 82: Flip-Chip 300µm Demoboard Top

Solder Layer

Figure 83: Flip-Chip 300µm Demoboard

Bottom Solder Layer

)

(

)

Vout

(

Pout

RMS

Vout1 = Vin

–

Rfeed

Rin

-------------------- (V)

Vout2

Vout1 = 2Vin

–

R feed

Rin

-------------------- (V)

Gv =

Vout2

Vout1

–

Vin

--------------------------------------- = 2

R feed

Rin

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

FCL =

π Rin Cin

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

H z

()

FCH =

π Rfeed Cfeed

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

()

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