Description
The CS209A is a bipolar monolithic integrated circuit for use in metal detection/proximity sensing applications. The IC (see block diagram) contains two on-chip current regulators, oscillator and low-level feedback circuitry, peak detection/demodulation circuit, a comparator and two complementary output stages.
The oscillator, along with an external LC network, provides controlled oscillations where amplitude is highly depen dent on the Q of the LC tank. During low Q conditions, a variable low-level
feedback circuit provides drive to main tain oscillation. The peak demodulator senses the negative portion of the oscillator envelop and provides a demodulated waveform as input to the comparator. The comparator sets the states of the complementary outputs by comparing the input from the demodulator to an internal reference. External loads are required for the output pins.
A transient suppression circuit is included to absorb negative transients at the tank circuit  terminal.

FEATUREs
■ Separate Current Regulator for Oscillator
■ Negative Transient Suppression
■ Variable Low-Level Feedback
■ Improved Performance over Temperature
■ 6mA Supply Current Consumption at VCC= 12V
■ Output Current Sink Capability 20mA at 4VCC 100mA at 24VCC