TCA955 schematic block diagram and application examples

TCA955 internally includes input amplifier
, double circuit, monostable trigger circuit, triangle wave generator, comparator, precharge
circuit and voltage indication circuit. Frequency generator (FG) installed coaxially with the motor
. Its output signal frequency reflects the motor speed. It is differentially input from pins 2 and 3 of TCA
955 , or it can be single-ended input from pin 2 (the other end is grounded) as shown in the picture. The input
amplifier has a high voltage gain of 80dB. Even if the input signal is small, a
square wave pulse signal of sufficient amplitude can still be sent to the double frequency circuit. Corresponding to the leading edge and trailing edge of the square wave signal, a double frequency sharp pulse signal
can be obtained. . The purpose of doubling the signal is to reduce the ripple of the DC speed signal after F/V conversion. The signal after doubling the frequency (with a period of D) is used to trigger the monostable trigger circuit. The trigger delay to is determined by the external resistor V and capacitor C.