DESCRITION
The CS209A is a bipolar monolithic integrated circuit for use in metal detection/proximity sensing applications. The IC (see Figure 1) 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 dependent on the Q of the LC tank. During low Q conditions, a variable low−level feedback circuit provides drive to maintain oscillation. The peak
demodulator senses the negative portion of the oscillator envelope 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
•6.0 mA Supply Current Consumption at VCC= 12 V
•Output Current Sink Capability
−20 mA at 4.0 VCC
−100 mA at 24 VCC