TS4994

Application Information

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Figure 72. PSRR vs. frequency worst case condition

The two following graphs show typical application of TS4994 with four 0.1% tolerances and a random

choice for them.

Figure 73. PSRR vs. frequency with random

choice condition

Figure 74. PSRR vs. frequency with random

choice condition

CMRR performance

calculation of the CMRR.

We use the same kind of resistor (same tolerance) and

∆R is the tolerance value in %.

The following equation is valid for frequencies ranging from DC to about 1kHz. Above this frequency,

parasitic effects start to be significant and a literal equation is not possible to write.

The CMRR equation is (

∆R in %):

Example: With

∆R=1%, the minimum CMRR would be -34dB.

With a DC Vic=2.5V, the DC differential output (Voo) which results is 50mV maximum. As this Voo is

across the load, for an 8

Ω load the extra consumption would be 50mV/8=6.2mA.

100

1000

10000

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

Cb=0.1

µF

Cb=1

µF

Cb=0

20k

20

Cb=0.47

µF

Vcc = 2.5V, Vripple = 200mVpp

Av = 1, Cin = 4.7

µF

∆R/R = 0.1%, RL ≥ 8Ω

Tamb = 25

°C, Inputs = Grounded

Frequency (Hz)

100

1000

10000

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

Cb=0.1

µF

Cb=1

µF

Cb=0

20k

20

Cb=0.47

µF

Vcc = 5V, Vripple = 200mVpp

Av = 1, Cin = 4.7

µF

∆R/R ≤ 0.1%, RL ≥ 8Ω

Tamb = 25

°C, Inputs = Grounded

Frequency (Hz)

100

1000

10000

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

Cb=0.1

µF

Cb=1

µF

Cb=0

20k

20

Cb=0.47

µF

Vcc = 2.5V, Vripple = 200mVpp

Av = 1, Cin = 4.7

µF

∆R/R ≤ 0.1%, RL ≥ 8Ω

Tamb = 25

°C, Inputs = Grounded

Frequency (Hz)

)

dB

(

)

R

10000

(

200

R

Log

20

CMRR

⎦

⎤

⎢

⎣

⎡

∆

−

×

∆

×

≤