CHERRY CS209AYN8

CS209A
CS209A
Proximity Detector
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 dependent on the Q of the LC tank. During
low Q conditions, a variable low-level
Features
feedback circuit provides drive to maintain 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.
■ Separate Current
Regulator for Oscillator
A transient suppression circuit is
included to absorb negative transients
at the tank circuit terminal.
■ 6mA Supply Current
Consumption at
VCC = 12V
Absolute Maximum Ratings
Supply Voltage ................................................................................................24V
Power Dissipation (TA = 125¡C).............................................................200mW
Storage Temperature Range ....................................................Ð55¡C to +165¡C
Junction Temperature...............................................................Ð40¡C to +150¡C
Electrostatic Discharge (except TANK pin) ................................................2kV
Lead Temperature Soldering
Wave Solder(through hole styles only) ...........10 sec. max, 260¡C peak
Reflow (SMD styles only) ...........60 sec. max above 183¡C, 230¡C peak
Block Diagram
■ Negative Transient
Suppression
■ Variable Low-Level
Feedback
■ Improved Performance
over Temperature
■ Output Current Sink
Capability
20mA at 4VCC
100mA at 24VCC
Package Options
14L SO
OSC 1
14
N.C.
TANK 2
13
RF
Gnd 3
12
VCC
OUT1 4
11
N.C.
N.C. 5
10
DEMOD
OUT2
DVBE/R Current
Regulator
VBE/R Current
Regulator
300mA
VCC
6
9
N.C.
N.C. 7
8
N.C.
Oscillator
OSC
4.8kW
23.6kW
8L PDIP & SO
OSC
Feedback
OUT1
RF
OSC 1
VCC
Neg Transient
Suppression
2
VCC
Gnd 3
6
DEMOD
OUT1 4
5
OUT2
TANK
DEMOD
GND
RF
7
OUT2
+
COMP
TANK
8
-
DEMOD
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
Rev. 3/11/99
1
A
¨
Company
CS209A
Electrical Characteristics: -40¡C ² TA ² 125¡C unless otherwise specified
PARAMETER
TEST CONDITIONS
Supply Current ICC
VCC = 4V
VCC = 12V
VCC = 24V
Tank Current
VCC = 20V
MIN
Demodulator Charge Current VCC = 20V
TYP
MAX
UNIT
3.5
6.0
11.0
6.0
11.6
20.0
mA
mA
mA
-550
-300
-100
µA
-60
-30
-10
µA
Output Leakage Current
VCC = 24V
0.01
10.00
µA
Output VSAT
VCC = 4V, IS =20mA
VCC = 24V, IS =100mA
60
200
200
500
mV
mv
Oscillator Bias
VCC = 20V
1.1
1.9
2.5
V
Feedback Bias
VCC = 20V
1.1
1.9
2.5
V
Osc - Rf Bias
VCC = 20V
-250
100
550
mV
Protect Voltage
ITANK = -10mA
-10.0
-8.9
-7.0
V
Detect Threshold
720
1440
1950
mV
Release Threshold
550
1200
1700
mV
Package Pin Description
PACKAGE PIN#
PIN SYMBOL
FUNCTION
8L PDIP & SO
14L SO
1
1
OSC
2
2
TANK
Connects to parallel tank circuit.
3
3
Gnd
Ground connection.
4
4
OUT1
Complementary open collector output; When OUT1 =
LOW, metal is present.
5
6
OUT2
Complementary open collector output; When OUT2 =
HIGH, metal is present.
6
10
DEMOD
Input to comparator controlling OUT1 and OUT 2.
7
12
VCC
Supply voltage.
8
13
RF
Adjustable feedback resistor connected between OSC and
RF set detection range.
5,7,8,9,11,14
NC
No Connection.
Adjustable feedback resistor connected between OSC and
RF sets detection range.
Typical Performance Characteristics
Output Switching Delay vs. Output Load
Output Switching Delay vs. Temperature
6.5
8
(VCC = 12V, Rload = 1kW)
Switching Delay (ms)
Switching Delay (ms)
(T = 22°C, VCC= 12V)
6
4
5.5
4.5
3.5
2.5
2
100
4
8
12
16
-40
20
Output Load (kW)
-20
0
20
40
Temperature (°C)
2
60
80
100
120
CS209A
Typical Performance Characteristics: continued
Demodulator Voltage vs. Distance for Different RF
Object
Detected
DEMOD (V)
1.75
(T = 21°C, VCC = 12V)
1.5
2.5kW
5kW
7.5kW
12.5kW
15kW
17.5kW
Object Not
Detected,
L Unloaded.
1.25
1.0
0.75
0.0
0.100
0.200
0.300
0.400
Distance To Object (in.)
Principle of Operation
The CS209A is a metal detector circuit which operates on
the principle of detecting a reduction in Q of an inductor
when it is brought into close proximity of metal. The
CS209A contains an oscillator set up by an external parallel
resonant tank and a feedback resistor connected between
OSC and RF. (See Test and Applications Diagram) The
impedance of a parallel resonant tank is highest when the
frequency of the source driving it is equal to the tankÕs resonant frequency. In the CS209A the internal oscillator
operates close to the resonant frequency of the tank circuit
selected. As a metal object is brought close to the inductor,
the amplitude of the voltage across the tank gradually
begins to drop. When the envelope of the oscillation reaches a certain level, the IC causes the output stages to switch
states.
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 comparatorÕs thresholds.
As an example of how to set the detection range, place the
metal object at the maximum distance from the inductor
the circuit is required to detect, assuming of course the Q
of the tank is high enough to allow the object to be within
the ICÕs detection range. Then adjust the potentiometer to
obtain a lower resistance while observing one of the
CS209A outputs return to its normal state (see Test and
Applications Diagram). 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.
The detection is performed as follows: A capacitor connected to DEMOD is charged via an internal 30µA current
source. This current, however, is diverted away from the
capacitor in proportion to the negative bias generated by
the tank at TANK. Charge is therefore removed from the
capacitor tied to DEMOD on every negative half cycle of
the resonant voltage. (See Figure 1) The voltage on the
capacitor at DEMOD, a DC voltage with ripple, is then
directly compared to an internal 1.44V reference. When the
internal comparator trips it turns on a transistor which
places a 23.6k½ resistor in parallel to the 4.8k½. The resulting reference then becomes approximately 1.2V. This hysteresis is necessary for preventing false triggering.
For this application it is recommended to use a core
which concentrates the magnetic field in only one direction. This is accomplished very well with a pot core half.
The next step is to select a core material with low loss factor (inverse of Q). The loss factor can be represented by a
resistance in series with the inductor which arises from
core losses and is a function of frequency.
The final step in obtaining a high Q inductor is the selection of wire size. The higher the frequency the faster the
decrease in current density towards the center of the wire.
Thus most of the current flow is concentrated on the surface of the wire resulting in a high AC resistance. LITZ
wire is recommended for this application. Considering
the many factors involved, it is also recommended to
operate at a resonant frequency between 200 and 700kHz.
The formula commonly used to determine the Q for parallel resonant circuits is:
R
QP @
2¹fRL
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 graph Demodulator Voltage vs Distance for
Different RF). 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
3
CS209A
Principle of Operation: continued
where R is the effective resistance of the tank. The resistance component of the inductor consists primarily of core
losses and Òskin effectÓ or AC resistance.
Note that the above is only a comparison among different
metals and no attempt was made to achieve the greatest
detection distance.
The resonant capacitor should be selected to resonate with
the inductor within the frequency range recommended in
order to yield the highest Q. The capacitor type should be
selected to have low ESR: multilayer ceramic for example.
A different type of application involves, for example,
detecting the teeth of a rotating gear. For these applications the capacitor on DEMOD should not be selected too
small (not below 1000pF) where the ripple becomes too
large and not too large (not greater than 0.01µF) that the
response time is too slow. Figure 1 for example shows the
capacitor ripple only and Figure 2 shows the entire capacitor voltage and the output pulses for an 8-tooth gear rotating at about 2400 rpm using a 2200pF capacitor on the
DEMOD pin.
Detection distances vary for different metals. Following
are different detection distances for some selected metals
and metal objects relative to one particular circuit set-up:
Commonly encountered metals:
¥
¥
¥
¥
¥
Stainless steel
Carbon steel
Copper
Aluminum
Brass
0.101"
0.125"
0.044"
0.053"
0.052"
Because the output stages go into hard saturation, a time
interval is required to remove the stored base charge
resulting in both outputs being low for approximately 3µs
(see Output Switching Delay vs. Temperature graph). If
more information is required about output switching
characteristics please consult the factory.
Coins:
¥ US Quarter
¥ Canadian Quarter
¥ 1 German Mark
¥ 1 Pound Sterling
¥ 100 Japanese Yen
¥ 100 Italian Lira
12 oz. soda can:
0.055"
0.113"
0.090"
0.080"
0.093"
0.133"
0.087"
VOUT1
VTANK
VDEMOD
VDEMOD
Figure 1. Capacitor ripple.
Figure 2. Output pulse for an 8 tooth gear.
4
CS209A
Test and Application Diagram
VCC
RL
1kW
RL
1kW
OSC
20kW
CS209A
OUT1
RF
OUT2
TANK
NORMALLY
HI
NORMALLY
LO
DEMOD
Gnd
4300pF
CDEMOD
2200 pF
L
5
L: Core: Siemens B65531-D-R-33
52 Turns, 6x44 AWG, Litz Unserved
Single Polyurethane
CS209A
Package Specification
PACKAGE THERMAL DATA
PACKAGE DIMENSIONS IN mm (INCHES)
Thermal Data
RQJC
typ
RQJA
typ
D
Lead Count
8L PDIP
8L SO
14L SO
Metric
Max
Min
10.16 9.02
5.00
4.80
8.75
8.55
English
Max
Min
.400
.355
.197
.189
.344
.337
8L PDIP
52
100
8L SO
45
165
14L SO
30
125
¡C/W
¡C/W
Plastic DIP (N); 300 mil wide
7.11 (.280)
6.10 (.240)
8.26 (.325)
7.62 (.300)
1.77 (.070)
1.14 (.045)
2.54 (.100) BSC
3.68 (.145)
2.92 (.115)
.356 (.014)
.203 (.008)
0.39 (.015)
MIN.
.558 (.022)
.356 (.014)
REF: JEDEC MS-001
Some 8 and 16 lead
packages may have
1/2 lead at the end
of the package.
All specs are the same.
D
Surface Mount Narrow Body (D); 150 mil wide
4.00 (.157)
3.80 (.150)
6.20 (.244)
5.80 (.228)
0.51 (.020)
0.33 (.013)
1.27 (.050) BSC
1.75 (.069) MAX
1.57 (.062)
1.37 (.054)
1.27 (.050)
0.40 (.016)
0.25 (.010)
0.19 (.008)
D
0.25 (0.10)
0.10 (.004)
REF: JEDEC MS-012
Ordering Information
Part Number
CS209AYN8
CS209AYD8
CS209AYDR8
CS209AYD14
CS209AYDR14
Rev. 3/11/99
Description
8 L PDIP
8L SO Narrow
8L SO Narrow (tape & reel)
14L SO Narrow
14L SO Narrow (tape & reel)
Cherry Semiconductor Corporation reserves the
right to make changes to the specifications without
notice. Please contact Cherry Semiconductor
Corporation for the latest available information.
6
© 1999 Cherry Semiconductor Corporation