Description:

The PW-0268 ultrasonic sonar ranging IC is ideally suited for echo ranging systems. This chip has many designfeatures to enhance its performance and ease of use in this application.The externally tunable RC Oscillator automatically tracks and compensates for the shift of the resonate frequency ofthe transducer due to temperature changes.The Fix Gain Preamplifier can be tailored to compensate for varying transducer sensitivities. The 32-step TimeControlled Variable Gain Amplifier slope can be modified by adjusting the frequency of the system clock.An onboard Comparator converts the analog signal of the returning echo to a TTL level digital signal for use with anexternal microprocessor.The integrated Band Pass Filters can be adjusted for custom applications by changing a few external components. Thefrequency of the System Clock can be adjusted to control other operating parameters of the chip including the transmitpulse width and sample rate.The I_O pin, (pin 1) is a bi-direction pin and is designed as an open collector connection with an internal pull highresistor. When the I_O pin is being pulled low by an external transistor, the RC oscillator generates a tone burst signalat DRIVER_0 (pin 11), the output driver stage for the transducer. After the transmit pulse, the I_O pin, (pin 1) willagain go low if a valid echo signal is detected.The reflected echo signal is presented to the first stage pre-amplifier through ECHO (pin 10). The gain of preamplifier can be adjusted to accommodate transducers with varying sensitivities by changing an external resistorbetween ECHO (pin 10) and GR_I (pin 9).The 32 steps time controlled variable gain amplifier input TCG_I (pin7) and output TCG_O (pin 6) is synchronized tostart incrementing at the end of control pulse signal I-O, (pin 1) and is reset at the beginning of the next control pulse.Only a few passive components are needed for the active band pass filter. There are two stages, a low pass, LP_I (pin5) and LP_O (pin 4) and upper band pass, HP_I (pin 3) to HP_O (pin 2). The center frequency and bandwidth of thefilter are chosen based on the type of ultrasonic transducer being used and the specific application. The amplified echosignal after being filtered is routed to a comparator, which shapes and coverts the analog echo signal into digital signaloutputted at I_O (pin 1) for further µP handling.The unique temperature compensating Ultrasonic R/C Oscillator circuitry tracks the resonant frequency drift of thetransducer that is causes by environment temperature changes. Simply adding dual diodes and one resistor betweenDRIVER_O (pin 11) and Ftrace (pin 12) is all that is needed to complete this function.

Features:

 Operating Voltage: 6 – 12Vdc single source

 Operating Frequency: broadband output ranging up to 200KHz

 Variable R/C Oscillator: compensates for transducer resonate frequency drift due to temperature.

 High Gain Amplifier: varies with time over 32 steps

 Integrated Band Pass Filter: reduces external component count

 Bi-direction I/O Pin: simplifies the control function for transmitting a pulse and receiving an echo

 An adjustable System Clock: enables the control of, the number of pulses transmitted, the slope of the variable

gain amplifier, and the pulse repetition rate.

 The PW0268 IC is suitable for use in car reversing aids, electronic tape measures and other sonar ranging applications.