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: [email protected] 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