TS4994 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
TS4994
STMicroelectronics
'TS4994' PDF : 31 Pages View PDF
TS4994
Application Information
Figure 72. PSRR vs. frequency worst case condition
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
20
Vcc = 2.5V, Vripple = 200mVpp
Av = 1, Cin = 4.7µF
∆R/R = 0.1%, RL ≥ 8Ω
Tamb = 25°C, Inputs = Grounded
Cb=0.1µF
Cb=1µF Cb=0.47µF
100
1000
Frequency (Hz)
Cb=0
10000 20k
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
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
20
Vcc = 5V, Vripple = 200mVpp
Av = 1, Cin = 4.7µF
∆R/R ≤ 0.1%, RL ≥ 8Ω
Tamb = 25°C, Inputs = Grounded
Cb=0.1µF
Cb=0
Cb=1µF Cb=0.47µF
100
1000
Frequency (Hz)
10000 20k
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
20
Vcc = 2.5V, Vripple = 200mVpp
Av = 1, Cin = 4.7µF
∆R/R ≤ 0.1%, RL ≥ 8Ω
Tamb = 25°C, Inputs = Grounded
Cb=0.1µF
Cb=0
Cb=1µF Cb=0.47µF
100
1000
Frequency (Hz)
10000 20k
CMRR performance
For this calculation, we consider there to be no influence of Cin and Cfeed. Cb has no influence in the
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 %):
CMRR
≤
20
×
Log⎢⎣⎡(10∆0R00×
200
− ∆R2
)
⎤
⎥
⎦
(dB)
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 8Ω load the extra consumption would be 50mV/8=6.2mA.
22/31
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