CS209A Datasheet, PDF (5/8 Pages) Cherry Semiconductor Corporation – Proximity Detector

20 kΩ
CS209A
OSC
RF
CS209A
TANK
GND
4300 pF
DEMOD
C_DEMOD
2200 pF
V_CC
RL
1.0 kΩ
RL
1.0 kΩ
OUT₁
NORMALLY
HI
OUT₂
NORMALLY
LO
L: Core: Siemens B65531−D−R−33
52 Turns, 6 × 44 AWG, Litz Unserved
Single Polyurethane
L
Figure 5. Test and Application Diagram
V_OUT1
V_TANK
V_DEMOD
V_DEMOD
Figure 6. Capacitor Ripple
The feedback potentiometer connected between OSC and
RF is adjusted to achieve a certain detection distance range.
The larger the resistance the greater the trip−point distance.
(See Figure 4.) Note that this is a plot representative of one
particular set−up since detection distance is dependent on
the Q of the tank. Note also from the graph that the capacitor
voltage corresponding to the greatest detection distance has
a higher residual voltage when the metal object is well
outside the trip point. Higher values of feedback resistance
for the same inductor Q will therefore eventually result in a
latched−ON condition because the residual voltage will be
higher than the comparator’s thresholds.
As an example of how to set the detection range, place the
metal object at the maximum distance from the inductor the
Figure 7. Output Pulse for an 8 Tooth Gear
circuit is required to detect, assuming of course the Q of the
tank is high enough to allow the object to be within the IC’s
detection range. Then adjust the potentiometer to obtain a
lower resistance while observing one of the CS209A outputs
return to its normal state. (See Figure 5.) Readjust the
potentiometer slowly toward a higher resistance until the
outputs have switched to their tripped condition. Remove
the metal and confirm that the outputs switch back to their
normal state. Typically the maximum distance range the
circuit is capable of detecting is around 0.3 inch. The higher
the Q, the higher the detection distance.
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