TS4872(2002) View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

TS4872
(Rev.:2002)

RAIL TO RAIL INPUT/OUTPUT 1W AUDIO POWER AMPLIFIER WITH STANDBY MODE

STMicroelectronics 

TS4872

Fig. 84 : PSRR changes with Cb

Fig. 85 : PSRR measurement schematic

-30

Cin=100nF

-40 Cb=1µF

Vcc = 5 & 2.6V

Rfeed = 22k, Rin = 22k

Rg = 100Ω, RL = 8Ω

Tamb = 25°C

-50

-60

-70

10

Cin=100nF

Cb=100µF

100

1000

10000

Frequency (Hz)

100000

s Note on PSRR measurement

What is the PSRR ?

The PSRR is the Power Supply Rejection Ratio.

It’s a kind of SVR in a determined frequency

range. The PSRR of a device, is the ratio between

a power supply disturbance and the result on the

output.

We can say that the PSRR is the ability of a device

to minimize the impact of power supply

disturbances to the output.

How we measure the PSRR ?

For PSRR measurement schematic see figure 85

Vripple

Vcc

Rin

Cin

Rfeed

6

1 Vin- -

7 Vin+ +

Rg

100 Ohms

3 Bypass

5 Standby

Bias

Cb

2

Vout1 8

-

Av=-1

+

Vout2 4

Vs-

RL

Vs+

TS4872

s Principle of operation

• We fixed the DC voltage supply (Vcc)

• We fixed the AC sinusoidal ripple voltage

(Vripple)

• No bypass capacitor Cs is used

The PSRR value for each frequency is :

PSRR(d B) = 20 x Log 10

-----R-----m-----s----(--V-----r--i-p---p---l-e---)-----

Rms(Vs + - Vs-)

Remark : The measure of the Rms voltage is not a

Rms selective measure but a full range (2 Hz to

125 kHz) Rms measure. It means that we

measure the effective Rms signal + the noise.

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