Analog Functionality

Table 1. Internal Op Amp Parameters
Op Amp #	Analog Function	Passive Components	Design Equations
2	Low-pass filter	R2, R3, R5, R6, C13, C14, C17	R2=R3=R5=R6=R C13=C17=C R1=R7 Common⁢−mode f−3 dB⁡≅12πRC Differential⁢−mode⁡ f−3 dB⁡≅12π(2R)(C2+C14) Differential⁢ amplifier⁢ gain⁡≅R72R
	Reference voltage bias	R1, R7
	Differential amplifier input	R2, R3, R5, R6
	Differential amplifier feedback	R1

Figure 1. Internal Op Amp Configuration

Differential⁢ amplifier⁢⁢ gain⁡=30kΩ2*1kΩ=15

Differential⁢ mode f−3 dB⁡≅12π(2*1kΩ)(56 pF2+56 pF)≅948 KHz

Common⁢ − mode f−3 dB⁡≅12π(1kΩ)(56 pF)≅2.8 MHz

Figure 2. Voltage Divider and Low-Pass Filter for Phase Back-EMF

Cutoff⁡ frequency−3⁢ dB=12π(30k∥2k+300) 10 nF≅7321 Hz

30 degree phase shift⁢ frequency⁡=tan⁡ (30)2π(30k∥2k+300) 10 nF=4226 Hz

Thus, the theoretical maximum speed of the motor will be:

4226 Hz *60⁡≅253560 eRPM

Mechanical⁢ RPM⁢=eRPM/Pole⁢ pairs