QProx™ ™ QT113 / QT113H CHARGE-TRANSFER TOUCH SENSOR Projects a proximity field through air Less expensive than many mechanical switches Sensitivity easily adjusted via capacitor value Turns small objects into intrinsic touch sensors 100% autocal for life - no adjustments required ! ! ! ! ! ! ! 2.5 to 5V, 600µ µA single supply operation Toggle mode for on/off control (strap option) 10s, 60s, infinite auto-recal timeout (strap options) Gain settings in 2 discrete levels HeartBeat™ health indicator on output Active-low (QT113) or active-high outputs (QT113H) Only one external part required - a 1¢ capacitor Vdd 1 O ut 2 O pt1 3 O pt2 4 Q T113 ! ! ! ! ! 8 Vss 7 Sn s2 6 Sn s1 5 Gain APPLICATIONS ! ! Light switches Prox sensors ! ! Appliance control Security systems ! ! Access systems Pointing devices ! ! Elevator buttons Toys & games The QT113 charge-transfer (“QT’”) touch sensor is a self-contained digital IC capable of detecting near-proximity or touch. It will project a proximity sense field through air, via almost any dielectric, like glass, plastic, stone, ceramic, and most kinds of wood. It can also turn small metal-bearing objects into intrinsic sensors, making them responsive to proximity or touch. This capability coupled with its ability to self calibrate continuously can lead to entirely new product concepts. It is designed specifically for human interfaces, like control panels, appliances, toys, lighting controls, or anywhere a mechanical switch or button may be found; it may also be used for some material sensing and control applications provided that the presence duration of objects does not exceed the recalibration timeout interval. The QT113 requires only a common inexpensive capacitor in order to function. Power consumption is only 600µA in most applications. In most cases the power supply need only be minimally regulated, for example by Zener diodes or an inexpensive 3-terminal regulator. The QT113’s RISC core employs signal processing techniques pioneered by Quantum; these are specifically designed to make the device survive real-world challenges, such as ‘stuck sensor’ conditions and signal drift. Even sensitivity is digitally determined and remains constant in the face of large variations in sample capacitor CS and electrode CX. No external switches, opamps, or other analog components aside from CS are usually required. The option-selectable toggle mode permits on/off touch control, for example for light switch replacement. The Quantum-pioneered HeartBeat™ signal is also included, allowing a host microcontroller to monitor the health of the QT113 continuously if desired. By using the charge transfer principle, the IC delivers a level of performance clearly superior to older technologies in a highly cost-effective package. TA 00C to +700C 00C to +700C -400C to +850C -400C to +850C Quantum Research Group Ltd AVAILABLE OPTIONS SOIC QT113-S QT113H-S QT113-IS QT113H-IS 8-PIN DIP QT113-D QT113H-D Copyright Quantum Research Group Ltd R1.10/0104 Figure 1-1 Standard mode options 1 - OVERVIEW +2.5 to 5 The QT113 is a digital burst mode charge-transfer (QT) sensor designed specifically for touch controls; it includes all hardware and signal processing functions necessary to provide stable sensing under a wide variety of changing conditions. Only a single low cost, non-critical capacitor is required for operation. SENSING ELECTRODE 1 2 Figure 1-1 shows the basic QT113 circuit using the device, with a conventional output drive and power supply connections. 3 Vdd OUT OPT1 1.1 BASIC OPERATION SNS2 GAIN 7 5 Cs 10nF Cx 4 6 The QT113 employs bursts of charge-transfer cycles to OPT2 SNS1 acquire its signal. Burst mode permits power consumption in OUTPUT=DC Vss the microamp range, dramatically reduces RF emissions, TIMEOUT=10 Secs 8 lowers susceptibility to EMI, and yet permits excellent TOGGLE=OFF GAIN=HIGH response time. Internally the signals are digitally processed to reject impulse noise, using a 'consensus' filter which requires three consecutive confirmations of a detection 1.2 ELECTRODE DRIVE The internal ADC treats Cs as a floating transfer capacitor; as before the output is activated. a direct result, the sense electrode can be connected to The QT switches and charge measurement hardware either SNS1 or SNS2 with no performance difference. In both functions are all internal to the QT113 (Figure 1-2). A 14-bit cases the rule Cs >> Cx must be observed for proper single-slope switched capacitor ADC includes both the operation. The polarity of the charge buildup across Cs required QT charge and transfer switches in a configuration during a burst is the same in either case. that provides direct ADC conversion. The ADC is designed to dynamically optimize the QT burst length according to the It is possible to connect separate Cx and Cx’ loads to SNS1 rate of charge buildup on Cs, which in turn depends on the and SNS2 simultaneously, although the result is no different values of Cs, Cx, and Vdd. Vdd is used as the charge than if the loads were connected together at SNS1 (or reference voltage. Larger values of Cx cause the charge SNS2). It is important to limit the amount of stray capacitance transferred into Cs to rise more rapidly, reducing available on both terminals, especially if the load Cx is already large, resolution; as a minimum resolution is required for proper for example by minimizing trace lengths and widths so as not operation, this can result in dramatically reduced apparent to exceed the Cx load specification and to allow for a larger gain. Conversely, larger values of Cs reduce the rise of sensing electrode size if so desired. differential voltage across it, increasing available resolution The PCB traces, wiring, and any components associated with by permitting longer QT bursts. The value of Cs can thus be or in contact with SNS1 and SNS2 will become touch increased to allow larger values of Cx to be tolerated (Figures sensitive and should be treated with caution to limit the touch 4-1, 4-2, 4-3 in Specifications, rear). area to the desired location. Multiple touch electrodes can be The IC is responsive to both Cx and Cs, and changes in Cs used, for example to create a control button on both sides of an object, however it is impossible for the sensor to can result in substantial changes in sensor gain. distinguish between the two touch areas. Option pins allow the selection or alteration of several special features and sensitivity. 1.3 ELECTRODE DESIGN Figure 1-2 Internal Switching & Timing 1.3.1 ELECTRODE GEOMETRY AND SIZE ELE C TRO DE R esult Do ne Single -Slo pe 14-bit Switched Cap acito r AD C Bu rst Controller Start SNS2 Cs Cx SNS1 There is no restriction on the shape of the electrode; in most cases common sense and a little experimentation can result in a good electrode design. The QT113 will operate equally well with long, thin electrodes as with round or square ones; even random shapes are acceptable. The electrode can also be a 3-dimensional surface or object. Sensitivity is related to electrode surface area, orientation with respect to the object being sensed, object composition, and the ground coupling quality of both the sensor circuit and the sensed object. If a relatively large electrode surface is desired, and if tests show that the electrode has more capacitance than the QT113 can tolerate, the electrode C ha rg e Am p -2- can be made into a sparse mesh (Figure 1-3) having lower crumpled into a ball. Virtual ground planes are more effective Cx than a solid plane. Sensitivity may even remain the same, and can be made smaller if they are physically bonded to as the sensor will be operating in a lower region of the gain other surfaces, for example a wall or floor. curves. 1.3.4 FIELD SHAPING 1.3.2 KIRCHOFF’S CURRENT LAW Like all capacitance sensors, the QT113 relies on Kirchoff’s Current Law (Figure 1-4) to detect the change in capacitance of the electrode. This law as applied to capacitive sensing requires that the sensor’s field current must complete a loop, returning back to its source in order for capacitance to be sensed. Although most designers relate to Kirchoff’s law with regard to hardwired circuits, it applies equally to capacitive field flows. By implication it requires that the signal ground and the target object must both be coupled together in some manner for a capacitive sensor to operate properly. Note that there is no need to provide actual hardwired ground connections; capacitive coupling to ground (Cx1) is always sufficient, even if the coupling might seem very tenuous. For example, powering the sensor via an isolated transformer will provide ample ground coupling, since there is capacitance between the windings and/or the transformer core, and from the power wiring itself directly to 'local earth'. Even when battery powered, just the physical size of the PCB and the object into which the electronics is embedded will generally be enough to couple a few picofarads back to local earth. 1.3.3 VIRTUAL CAPACITIVE GROUNDS When detecting human contact (e.g. a fingertip), grounding Figure 1-3 Mesh Electrode Geometry The electrode can be prevented from sensing in undesired directions with the assistance of metal shielding connected to circuit ground (Figure 1-5). For example, on flat surfaces, the field can spread laterally and create a larger touch area than desired. To stop field spreading, it is only necessary to surround the touch electrode on all sides with a ring of metal connected to circuit ground; the ring can be on the same or opposite side from the electrode. The ring will kill field spreading from that point outwards. If one side of the panel to which the electrode is fixed has moving traffic near it, these objects can cause inadvertent detections. This is called ‘walk-by’ and is caused by the fact that the fields radiate from either surface of the electrode equally well. Again, shielding in the form of a metal sheet or foil connected to circuit ground will prevent walk-by; putting a small air gap between the grounded shield and the electrode will keep the value of Cx lower and is encouraged. In the case of the QT113, sensitivity can be high enough (depending on Cx and Cs) that 'walk-by' signals are a concern; if this is a problem, then some form of rear shielding may be required. 1.3.5 SENSITIVITY The QT113 can be set for one of 2 gain levels using option pin 5 (Table 1-1). This sensitivity change is made by altering the internal numerical threshold level required for a detection. Note that sensitivity is also a function of other things: like the value of Cs, electrode size, shape, and orientation, the composition and aspect of the object to be sensed, the thickness and composition of any overlaying panel material, and the degree of ground coupling of both sensor and object. 18.104.22.168 Increasing Sensitivity In some cases it may be desirable to increase sensitivity further, for example when using the sensor with very thick panels having a low dielectric constant. Sensitivity can often be increased by using a bigger electrode, reducing panel thickness, or altering panel composition. Increasing electrode size can have diminishing of the person is never required. The human body naturally returns, as high values of Cx will reduce sensor gain (Figures has several hundred picofarads of ‘free space’ capacitance to the local environment (Cx3 in Figure 1-4), which is more than two orders of magnitude greater than that required to create Figure 1-4 Kirchoff's Current Law a return path to the QT113 via earth. The QT113's PCB however can be physically quite small, so there may be little ‘free space’ coupling (Cx1 in Figure 1-4) between it and the environment to complete the return path. If the QT113 circuit CX2 ground cannot be earth grounded by wire, for example via the supply connections, then a ‘virtual capacitive ground’ may be required to increase return coupling. A ‘virtual capacitive ground’ can be created by connecting the QT113’s own circuit ground to: (1) A nearby piece of metal or metallized housing; (2) A floating conductive ground plane; (3) A nail driven into a wall; (4) A larger electronic device (to which its output might be connected anyway). Free-floating ground planes such as metal foils should maximize exposed surface area in a flat plane if possible. A square of metal foil will have little effect if it is rolled up or -3- S e n se E le ctro de S EN SO R CX1 Su rro und in g e nv iro nm e n t C X3 Drift compensation (Figure 2-1) is performed by making the reference level track the raw signal at a slow rate, but only while there is no detection in effect. The rate of adjustment must be performed slowly, otherwise legitimate detections could be ignored. The QT113 drift compensates using a slew-rate limited change to the reference level; the threshold and hysteresis values are slaved to this reference. Figure 1-5 Shielding Against Fringe Fields Once an object is sensed, the drift compensation mechanism ceases since the signal is legitimately high, and therefore should not cause the reference level to change. Sen se wire The QT113's drift compensation is 'asymmetric': the reference level drift-compensates in one direction faster than it does in the other. Specifically, it compensates faster for decreasing signals than for increasing signals. Increasing signals should not be compensated for quickly, since an approaching finger could be compensated for partially or entirely before even approaching the sense electrode. However, an obstruction over the sense pad, for which the sensor has already made full allowance for, could suddenly be removed leaving the sensor with an artificially elevated reference level and thus become insensitive to touch. In this latter case, the sensor will compensate for the object's removal very quickly, usually in only a few seconds. Sense wire U nshielded Electrode S hielded E lec trode 4-1 to 4-3). The value of Cs also has a dramatic effect on sensitivity, and this can be increased in value (up to a limit). Also, increasing the electrode's surface area will not substantially increase touch sensitivity if its diameter is already much larger in surface area than the object being detected. The panel or other intervening material can be made thinner, but again there are diminishing rewards for doing so. Panel material can also be changed to one having a higher dielectric constant, which will help propagate the field through to the front. Locally adding some conductive material to the panel (conductive materials essentially have an infinite dielectric constant) will also help; for example, adding carbon or metal fibers to a plastic panel will greatly increase frontal field strength, even if the fiber density is too low to make the plastic bulk-conductive. 22.214.171.124 Decreasing Sensitivity In some cases the QT113 may be too sensitive, even on low gain. In this case gain can be lowered further by a number of strategies: making the electrode smaller, making the electrode into a sparse mesh using a high space-to-conductor ratio (Figure 1-3), or by decreasing Cs. With large values of Cs and small values of Cx, drift compensation will appear to operate more slowly than with Table 1-1 Gain Setting Strap Options Tie Pin 5 to: Vdd Vss (Gnd) the converse. Note that the positive and negative drift compensation rates are different. 2.1.2 THRESHOLD CALCULATION Unlike the QT110 device, the internal threshold level is fixed at one of two setting as determined by Table 1-1. These setting are fixed with respect to the internal reference level, which in turn can move in accordance with the drift compensation mechanism.. The QT113 employs a hysteresis dropout below the threshold level of 17% of the delta between the reference and threshold levels. 2.1.3 MAX ON-DURATION If an object or material obstructs the sense pad the signal may rise enough to create a detection, preventing further 2 - QT113 SPECIFICS 2.1 SIGNAL PROCESSING The QT113 processes all signals using 16 bit math, using a number of algorithms pioneered by Quantum. The algorithms are specifically designed to provide for high 'survivability' in the face of numerous adverse environmental changes. Gain High - 6 counts Low - 12 counts Figure 2-1 Drift Compensation S ign a l H yste resis T hr es ho ld R e fe re nce 2.1.1 DRIFT COMPENSATION ALGORITHM Signal drift can occur because of changes in Cx and Cs over time. It is crucial that drift be compensated for, otherwise false detections, non-detections, and sensitivity shifts will follow. O u tpu t -4- operation. To prevent this, the sensor includes a timer which increasing levels of Cs reduce response time. Figure 4-3 monitors detections. If a detection exceeds the timer setting, shows the typical effects of Cs and Cx on response time. the timer causes the sensor to perform a full recalibration (when not set to infinite). This is known as the Max 2.2 OUTPUT FEATURES On-Duration feature. The QT113 is designed for maximum flexibility and can After the Max On-Duration interval, the sensor will once again accommodate most popular sensing requirements. These function normally, even if partially or fully obstructed, to the are selectable using strap options on pins OPT1 and OPT2. best of its ability given electrode conditions. There are two All options are shown in Table 2-1. finite timeout durations available via strap option: 10 and 60 2.2.1 DC MODE OUTPUT seconds (Table 2-1). The output of the QT113 can respond in a DC mode, where the output is active-low upon detection. The output will 2.1.4 DETECTION INTEGRATOR It is desirable to suppress detections generated by electrical remain active-low for the duration of the detection, or until the noise or from quick brushes with an object. To accomplish Max On-Duration expires (if not infinite), whichever occurs this, the QT113 incorporates a detect integration counter that first. If a max on-duration timeout occurs first, the sensor increments with each detection until a limit is reached, after performs a full recalibration and the output becomes inactive which the output is activated. If no detection is sensed prior until the next detection. to the final count, the counter is reset immediately to zero. In In this mode, three Max On-Duration timeouts are available: the QT113, the required count is 3. 10 seconds, 60 seconds, and infinite. The Detection Integrator can also be viewed as a 'consensus' filter, that requires three detections in three successive bursts Table 2-1 Output Mode Strap Options to create an output. Tie Pin 3 to: Tie Pin 4 to: Max OnDuration DC Out Vdd Vdd 10s DC Out Vdd Gnd 60s Toggle Gnd Gnd 10s DC Out Gnd Vdd infinite 2.1.5 FORCED SENSOR RECALIBRATION The QT113 has no recalibration pin; a forced recalibration is accomplished only when the device is powered up. However, supply drain is low so it is a simple matter to treat the entire IC as a controllable load; simply driving the QT113's Vdd pin directly from another logic gate or a microcontroller port (Figure 2-2) will serve as both power and 'forced recal'. The source resistance of most CMOS gates and microcontrollers are low enough to provide direct power without problem. Note that most 8051-based micros have only a weak pullup drive capability and will require CMOS buffering. 74HC or 74AC series gates can directly power the QT113, as can most other microcontrollers. Infinite timeout is useful in applications where a prolonged detection can occur and where the output must reflect the detection no matter how long. In infinite timeout mode, the designer should take care to be sure that drift in Cs, Cx, and Vdd do not cause the device to ‘stick on’ inadvertently even Option strap configurations are read by the QT113 only on when the target object is removed from the sense field. powerup. Configurations can only be changed by powering 2.2.2 TOGGLE MODE OUTPUT the QT113 down and back up again; again, a microcontroller This makes the sensor respond in an on/off mode like a flip can directly alter most of the configurations and cycle power flop. It is most useful for controlling power loads, for example to put them in effect. in kitchen appliances, power tools, light switches, etc. 2.1.6 RESPONSE TIME Max On-Duration in Toggle mode is fixed at 10 seconds. The QT113's response time is highly dependent on burst When a timeout occurs, the sensor recalibrates but leaves length, which in turn is dependent on Cs and Cx (see Figures the output state unchanged. 4-1, 4-2). With increasing Cs, response time slows, while 2.2.3 HEARTBEAT™ OUTPUT Figure 2-2 Powering From a CMOS Port Pin P O RT X .m 0.01µF C MO S m icro controller V dd P O RT X .n O UT Q T11 0 V ss The QT113 output has a full-time HeartBeat™ ‘health’ indicator superimposed on it. This operates by taking 'Out' into a 3-state mode for 300µs once after every QT burst. This output state can be used to determine that the sensor is operating properly, or, it can be ignored using one of several simple methods. The HeartBeat indicator can be sampled by using a pulldown resistor on Out, and feeding the resulting negative-going pulse into a counter, flip flop, one-shot, or other circuit. Since Out is normally high, a pulldown resistor will create negative HeartBeat pulses (Figure 2-3) when the sensor is not detecting an object; when detecting an object, the output will remain low for the duration of the detection, and no HeartBeat pulse will be evident. If the sensor is wired to a microcontroller as shown in Figure 2-4, the microcontroller can reconfigure the load resistor to either ground or Vcc depending on the output state of the QT113, so that the pulses are evident in either state. -5- Figure 2-3 Figure 2-4 Getting HearBeat pulses with a pull-down resistor Using a micro to obtain HB pulses in either output state +2 .5 to 5 H eartBeat™ P ulses 1 2 2 PORT_M.x V dd O UT S NS 2 7 Ro 3 Microcontroller 3 4 O PT 1 GAIN O PT 2 S NS 1 OUT SNS2 OPT1 GAIN OPT2 SNS1 7 Ro 5 PORT_M.y 6 4 5 6 V ss 8 Electromechanical devices like relays will usually ignore this short pulse. The pulse also has too low a duty cycle to visibly affect LED’s. It can be filtered completely if desired, by adding an RC timeconstant to filter the output, or if interfacing directly and only to a high-impedance CMOS input, by doing nothing or at most adding a small non-critical capacitor from Out to ground (Figure 2-5). ‘stiction’, the opposite effect, can occur if a load is shed when Out is active. The output of the QT113 can directly drive a resistively limited LED. The LED should be connected with its cathode to the output and its anode towards Vcc, so that it lights when the sensor is active. If desired the LED can be connected from Out to ground, and driven on when the sensor is The QT113H variant has an active-high output; the heartbeat inactive. signal of the QT113H works in exactly the same manner. The QT113H variant has an active-high output. 2.2.4 OUTPUT DRIVE The QT113’s `output is active low and can sink up to 5mA of non-inductive current. If an inductive load is used, such as a small relay, the load should be diode clamped to prevent damage. When set to operate in a proximity mode (at high gain) the current should be limited to 1mA to prevent gain shifting side effects from occurring, which happens when the load current creates voltage drops on the die and bonding wires; these small shifts can materially influence the signal level to cause detection instability as described below. Care should be taken when the QT113 and the load are both powered from the same supply, and the supply is minimally regulated. The QT113 derives its internal references from the power supply, and sensitivity shifts can occur with changes in Vdd, as happens when loads are switched on. This can induce detection ‘cycling’, whereby an object is detected, the load is turned on, the supply sags, the detection is no longer sensed, the load is turned off, the supply rises and the object is reacquired, ad infinitum. To prevent this occurrence, the output should only be lightly loaded if the device is operated from an unregulated supply, e.g. batteries. Detection Figure 2-5 Eliminating HB Pulses G ATE OR MIC RO INPU T 2 C MO S O UT SN S 2 O PT1 GA IN O PT2 SN S 1 7 Co 100p F 3 4 5 6 3 - CIRCUIT GUIDELINES 3.1 SAMPLE CAPACITOR Charge sampler Cs can be virtually any plastic film or medium-K ceramic capacitor. The acceptable Cs range is from 10nF to 500nF depending on the sensitivity required; larger values of Cs demand higher stability to ensure reliable sensing. Acceptable capacitor types include polycarbonate, PPS film, or NPO/C0G ceramic. 3.2 OPTION STRAPPING The option pins Opt1 and Opt2 should never be left floating. If they are floated, the device will draw excess power and the options will not be properly read on powerup. Intentionally, there are no pullup resistors on these lines, since pullup resistors add to power drain if tied low. The Gain input should be connected to either Vdd or Gnd. Tables 1-1 and 2-1 show the option strap configurations available. 3.4 POWER SUPPLY, PCB LAYOUT The power supply can range from 2.5 to 5.0 volts. At 3 volts current drain averages less than 600µA in most cases, but can be higher if Cs is large. Increasing Cx values will actually decrease power drain. Operation can be from batteries, but be cautious about loads causing supply droop (see Output Drive, previous section). As battery voltage sags with use or fluctuates slowly with temperature, the QT113 will track and compensate for these changes automatically with only minor changes in sensitivity. If the power supply is shared with another electronic system, care should be taken to assure that the supply is free of -6- Figure 3-1 ESD Suppression Circuit + 2 .5 to 5 + R e2 1 2 D1 V dd OUT S NS 2 7 R e3 S E NS IN G ELE C TRO DE R e1 3 D2 5 O PT1 C1 10µF G AIN 4 Cs 6 O PT2 S NS 1 V ss Because the charge and transfer times of the QT113 are relatively long, the circuit can tolerate very large values of Re, even to 100k ohms in most cases where electrode Cx is small. The added diodes shown (1N4150 or equivalent low-C diodes, or a single BAV99 dual-diode) will shunt the ESD transients away from the part, and Re1 will current limit the rest into the QT113's own internal clamp diodes. C1 should be around 10µF if it is to absorb positive transients from a human body model standpoint without rising in value by more than 1 volt. If desired C1 can be replaced with an appropriate Zener diode. Directly placing semiconductor transient protection devices, Zeners, or MOV's on the sense lead is not advised; these devices have extremely large amounts of unstable parasitic C which will swamp the QT113 and render it useless. 8 Re1 should be as large as possible given the load value of Cx and the diode capacitances of D1 and D2, digital spikes, sags, and surges which can adversely affect but Re1 should be low enough to permit at least 6 the QT113. The QT113 will track slow changes in Vdd, but it timeconstants of RC to occur during the charge and transfer can be affected by rapid voltage steps. phases. if desired, the supply can be regulated using a conventional Re2 functions to isolate the transient from the QT113's Vdd low current regulator, for example CMOS regulators that have pin; values of around 1K ohms are reasonable. low quiescent currents. As with all ESD protection networks, it is crucial that the transients be led away from the circuit. PCB ground layout is 3.5 ESD PROTECTION crucial; the ground connections to D1, D2, and C1 should all In cases where the electrode is placed behind a dielectric go back to the power supply ground or preferably, if panel, the QT113 will usually be adequately protected from available, a chassis ground connected to earth. The currents direct static discharge. However, even with a plastic or glass should not be allowed to traverse the area directly under the panel, transients can still flow into the electrode via induction, QT113. or in extreme cases, via dielectric breakdown. Porous materials may allow a spark to tunnel right through the If the QT113 is connected to an external circuit via a cable or material; partially conducting materials like 'pink poly' will long twisted pair, it is possible for ground-bounce to cause conduct the ESD right to the electrode. Testing is required to damage to the Out pin; even though the transients are led reveal any problems. The QT113 does have diode protection away from the QT113 itself, the connected signal or power on its terminals which can absorb and protect the device from ground line will act as an inductor, causing a high differential most induced discharges, up to 20mA; the usefulness of the voltage to build up on the Out wire with respect to ground. If internal clamping will depending on the dielectric properties, this is a possibility, the Out pin should have a resistance Re3 in series with it to limit current; this resistor should be as panel thickness, and rise time of the ESD transients. large as can be tolerated by the load. ESD dissipation can be aided further with an added diode protection network as shown in Figure 3-1, in extreme cases. -7- 4.1 ABSOLUTE MAXIMUM SPECIFICATIONS Operating temp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . as designated by suffix Storage temp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55OC to +125OC VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5 to +6.5V Max continuous pin current, any control or drive pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±20mA Short circuit duration to ground, any pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . infinite Short circuit duration to VDD, any pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . infinite Voltage forced onto any pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.6V to (Vdd + 0.6) Volts 4.2 RECOMMENDED OPERATING CONDITIONS VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +2.5 to 5.5V Short-term supply ripple+noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±5mV Long-term supply stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±100mV Cs value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10nF to 500nF Cx value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 to 100pF 4.3 AC SPECIFICATIONS Parameter Vdd = 3.0, Ta = recommended operating range, Cs=100nF unless noted Description TRC Recalibration time TPC Charge duration Min Typ Max Units 550 ms 2 µs TPT Transfer duration TBS Burst spacing interval 2.1 80 ms Cs = 10nF to 500nF; Cx = 0 TBL Burst length 0.5 75 ms Cs = 10nF to 500nF; Cx = 0 30 ms Cx = 10pF; See Figure 4-3 300 µs TR Response time THB Heartbeat pulse width 2 Notes µs 4.4 SIGNAL PROCESSING Description Min Typ Threshold differential 6 or 12 Max Units counts Hysteresis 17 % Consensus filter length 3 samples Positive drift compensation rate 1,000 ms/level Negative drift compensation rate 100 ms/level 10, 60, infinite secs Post-detection recalibration timer duration Note 1: Percentage of signal threshold -8- Notes Option pin selected Note 1 Option pin selected 4.5 DC SPECIFICATIONS Vdd = 3.0V, Cs = 10nF, Cx = 5pF, TA = recommended range, unless otherwise noted Parameter Description VDD Min Supply voltage IDD Typ 2.45 Supply current 600 VDDS Supply turn-on slope VIL Low input logic level VHL High input logic level VOL Low output voltage VOH High output voltage IIL Input leakage current CX Load capacitance range IX Min shunt resistance AR Acquisition resolution Units 5.25 V 1,500 Notes µA 100 V/s 0.8 OPT1, OPT2 V OPT1, OPT2 V OUT, 4mA sink V OUT, 1mA source ±1 µA OPT1, OPT2 100 pF 0.6 Vdd-0.7 0 Required for proper startup V 2.2 ✡ 1M S Sensitivity range 1,000 Note 2: Sensitivity depends on value of Cx and Cs. Refer to Figures 4-1, 4-2. 14 bits 28 fF Resistance from SNS1 to SNS2 Note 2 Figure 4-2 - Typical Threshold Sensitivity vs. Cx, Low Gain, at Selected Values of Cs; Vdd = 3.0 Figure 4-1 - Typical Threshold Sensitivity vs. Cx, High Gain, at Selected Values of Cs; Vdd = 3.0 10.00 Detection Threshold, pF 10.00 Detection Threshold, pF Max 1.00 10nF 20nF 50nF 100nF 200nF 500nF 0.10 0.01 0 10 20 30 1.00 10nF 20nF 50nF 100nF 200nF 500nF 0.10 0.01 40 0 Cx Load, pF 10 20 Cx Load, pF -9- 30 40 Chart 4-3 - Typical Response Time vs. Cx; Vdd = 3.0 Response Time, ms 1000.00 10nF 100.00 20nF 50nF 100nF 200nF 10.00 500nF 1.00 0 10 20 30 40 Cx Load 5 ORDERING INFORMATION PART TEMP RANGE PACKAGE MARKING QT113-D QT113-S QT113-IS QT113H-D QT113H-S QT113H-IS 0 - 70C 0 - 70C -40 - 85C 0 - 70C 0 - 70C -40 - 85C PDIP SOIC-8 SOIC-8 PDIP SOIC-8 SOIC-8 QT1 + 13 QT1 + 3 QT1 + F QT1 + 13H QT1 + E QT1 + K - 10 - Package type: 8-pin Dual-In-Line SYMBOL a A M m Q P L L1 F R r S S1 Aa x Y Min Millimeters Max 6.096 7.62 9.017 7.62 0.889 0.254 0.355 1.397 2.489 3.048 0.381 3.048 7.62 8.128 0.203 7.112 8.255 10.922 7.62 0.559 1.651 2.591 3.81 3.556 4.064 7.062 9.906 0.381 Notes Typical BSC Typical BSC Min Inches Max 0.24 0.3 0.355 0.3 0.035 0.01 0.014 0.055 0.098 0.12 0.015 0.12 0.3 0.32 0.008 0.28 0.325 0.43 0.3 0.022 0.065 0.102 0.15 0.14 0.16 0.3 0.39 0.015 Notes Typical BSC Typical BSC Package type: 8-pin SOIC SYMBOL Min Millimeters Max M W Aa H h D L E e ß Ø 4.800 5.816 3.81 1.371 0.101 1.27 0.355 0.508 0.19 0.381 0º 4.979 6.198 3.988 1.728 0.762 1.27 0.483 1.016 0.249 0.762 8º Notes Min Inches Max BSC 0.189 0.229 0.15 0.054 0.004 0.050 0.014 0.02 0.007 0.229 0º 0.196 0.244 0.157 0.068 0.01 0.05 0.019 0.04 0.01 0.03 8º - 11 - Notes BSC Quantum Research Group Ltd ©2001QRG Ltd. Patented and patents pending 651 Holiday Drive Bldg. 5 / 300 Pittsburgh, PA 15220 USA Tel: 412-391-7367 Fax: 412-291-1015 [email protected] http://www.qprox.com In the United Kingdom Enterprise House, Southampton, Hants SO14 3XB Tel: +44 (0)23 8045 3934 Fax: +44 (0)23 8045 3939 This device expressly not for use in any medical or human safety related application without the express written consent of an officer of the company.