MT88E46 Datasheet, PDF (13/23 Pages) Zarlink Semiconductor Inc – Bellcore Compliant Calling Number Identification Circuit

Advance Information MT88E46
1.00
1.000
PRELIMINARY
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.63095
0.60
3.0
3.5
4.0
4.5
5.0
Nominal Vdd (Volts)
Figure 9 - GS1 and GS2 Gain Ratios as a Function of Nominal Vdd
Gain Setting Resistor Calculation for Nominal Vdd between 3 and 5V
• For the desired nominal Vdd, use Figure 9 to calculate approximate Av.
• For the GS1 op-amp, start with the 0dB gain setting resistor values of R5_0dB, R6_0dB and R7_0dB. In
Figure 8 they are 53K6, 60K4 and 464K respectively. Keep R1, R2, R3, R4, C1, C2 as in Figure 8 to
keep the input highpass filter corner frequency constant for all gain settings.
• For the desired Av:
R7_Av = R7_0dB x Av
Scaled for desired gain. Choose the closest standard 1%
resistor value as R7_Av. Calculate Av_actual as R7_Av/R7_0dB.
R5_Av= R5_0dB x Av_actual
Scaled for good common mode range. Choose the closest
standard 1% resistor as R5_Av.
1/R6_Av= 1/R5_Av-1/R7_Av
Calculate R6_Av so that R5_Av = R6_Av || R7_Av. Choose the
closest standard 1% resistor as R6_Av.
• Repeat for R10, R11 and R12 for the GS2 op-amp.
Example:
• For the 3V gain of -4.0dB, Av = 0.63095.
• R7_-4dB = 0.63095 x 464K = 292.76K. The closest standard 1% resistor is 294K.
Av_actual is 294K/464K = 0.63362 or -3.96dB.
• R5_-4dB = 0.63362 x 53K6 = 33.96K. The closest standard 1% resistor is 34K0.
• 1/R6_-4dB = 1/34.0K - 1/294K = 1/38.45K. The closest standard 1% resistor is 38K3.
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