2 Internal Amplifier

Operational amplifiers internal to the dsPIC33AK256MPS306 can be configured and enabled for amplifying motor currents (internal Op Amp configuration). The amplifier circuits are shown in the Figure   1 and Figure 4-2. The detailed schematics of the block, “Filter, Feedback and Bias Circuit” used in Figure   1, are shown in Figure 2-2.

Figure 2-1. dsPIC® DSC Internal Amplifiers
Figure 2-2. Filter, Feedback and Bias Circuit

Equation 2-1 provides the amplifier gain calculations. Equation 2-2 and Equation 2-3 provide the equations to calculate cutoff frequencies of the Differential-mode and Common-mode filters.

Equation 2-1. Amplifier Gain
Equation 2-2. Cutoff Frequency Differential-Mode Filter
Equation 2-3. Cutoff Frequency Common-Mode Filter

Table 2-1 summarizes the amplifier gain and filter cutoff frequencies for the amplifier circuit used in the DIM. The customer can select different values based on the application requirements, ensuring peak current is within the operating range of the motor control development board in which the DIM is inserted.

Table 2-1. Amplifier Gain and Cutoff Frequencies
Component ValuesAmplifier GainDifferential-Mode Filter Cutoff FrequencyCommon-Mode Filter Cutoff Frequency
RIN1RIN2RFC1C2
100Ω100Ω4.99 kΩ1000 pFNot Populated24.95796 kHz—