Intelligent ultrasonic ranging ASIC SB5227 peripheral circuit design
Posted on Nov 10, 2015 8481
SB5227 ultrasonic signal output is very weak, it must be sent to the drive via the power amplifier. A typical transmission
circuit as shown in FIG. SB5227 ultrasonic signal from the output pin 10, and a buffer amplifier F (VT1, VT2) drive transmitter. Using low-power transistors VT1, VT2 optional power FET. The receiver circuit includes the following six parts: input protection circuit (C1, R1, VD1 and VD2); impedance matching and current amplifier (VT1); two voltage amplifier (VT2, IC1); band-pass filter (L1, C6) ; output-stage amplifier (VT3); a voltage comparator (IC2). C1 is a DC blocking capacitor, R1 is a current limiting resistor. VD1 and VD2 constitute bidirectional overvoltage limiter circuit. VT1 requires the use of J-FET, VT2 and VT3 selection of low-power transistors. IC1 is TL061 single op amp, IC2 is Quad voltage comparator LM339 (now only the way in which). Bandpass filter center frequency should be the same as the center frequency of the receiver. Adjustment potentiometer RP can change the receiver sensitivity, improve anti-jamming capability. Under normal IC2 output high, when receiving the first rising edge of the ultrasonic burst on output low, the SB5227 to the 8 feet, so that the internal timer is stopped counting. The technical conditions require a higher reception circuit, but also increase automatic gain control (AGC), automatic search window circuit.