IQ Switch® ProxSense™ REFERENCE DESIGN REGULATOR DESIGN NOTE AZD0001 Grant Harker 1 Introduction The IQS17 is a fully integrated capacitive sensor with differentiated touch and proximity sensitivity, user interface and load controller IC. A number of fully integrated onboard regulators and controllers enhances the IC’s performance and greatly reduces cost by eliminating any external regulators. The regulators help to ensure a stable operating voltage for reliable operation of the charge transfer circuit in both AC line and DC applications for excellent proximity sensitivity. The purpose of this document is to assist the designer using the IQS17 in designing the regulator needed for the circuit. A variety of regulator topologies are featured, briefly describing their functional working. The advantages and disadvantages of each of these circuits are also highlighted. These circuits also function as reference design examples. Refer to the IQS17 datasheet for any additional information required. For the latest documents please refer to the AZOTEQ website at www.azoteq.com. 2 General Regulator Overview The IQS17 has a digital filter that constantly adapts according to varying environmental factors. The filter will track slow changes like temperature drift, component aging and humidity and compensate for it. The filter is unable to suppress and adapt to any sudden shifts or sags in the supply voltage and will ultimately detect such variations as proximity conditions. For this reason it is important to design a stable regulator circuit for reliable and trouble-free operation of proximity and touch detections. The IQS17 regulators are specifically designed to input high voltage directly to the device pins by only limiting the input current to the IC. The regulators can also be configured to operate in two- or three-wire applications. Both these setups will be discussed individually. 2.1 Series Regulator The device has an internal series regulator to convert the input voltage VDDHI to a stable regulated output voltage of 3.3V (VDD). A bypass capacitor of about 100nF is required between the VDD and VSS pins. Care should be taken to limit these track lengths to the device pins. It is of utmost importance that the VDD voltage must be stable at all times for reliable proximity and touch detections. For this reason this regulator is not suited to power any other external circuitry. The VDDHI voltage should always be higher than the minimum specified value of 4.5V to ensure the series regulator is operating above the device’s drop-out voltage. Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved AZD0001 Reference Design Ver0.00 September 2006 1 IQ Switch® ProxSense™ REFERENCE DESIGN 2.2 Shunt Regulator D3 1 LIVE IQS17 Iin VDDHI RSERIES SHNT D4 Vin VDD Series Regulator C4 Shunt Regulator C3 GND Iled RLED LED NEUTRAL 2 VSS GND Figure 2-1 Figure 2-1 depicts a basic circuit to understand the functionality of the IQS17’s SHNT pin. A shunt regulator is formed by connecting the VDDHI and SHNT pins to each other. The input voltage will be regulated to a voltage VDDHI. A series resistor connected between the supply voltage and the VDDHI pin is required to limit the shunt current to within 10mA (ISHNT_MAX). If this value is exceeded, stable operation of the device is not guaranteed and false detections might occur. If a larger current needs to be shunted, the SHNT pin can be left unconnected and an external zener diode shown as D4 in Figure 2-1 can be used to replace the internal shunt regulator. The serial regulator will regulate VDDHI to a stable VDD. This will ensure a stable operating voltage for trouble free proximity and touch detections. This power supply circuit is not current efficient, but is a very cost-effective solution. This circuit is recommend for three-wire DC and AC applications. The neutral connection shown above must be connected to the negative terminal for a DC powered application. This simple but elegant design eliminates the need for any costly three-terminal regulators needed for many other capacitive sensing IC’s. Table 2-1 will assist the designer in selecting the right component values for the circuit shown above. All resistor values through out this document are chosen to comply with standard SMT 1206 device ratings. For this reason more than one resistor is needed at higher operating voltages to limit the component’s power consumption and maximum device voltage to an acceptable value. Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved AZD0001 Reference Design Ver0.00 September 2006 2 IQ Switch® ProxSense™ REFERENCE DESIGN Table 2-1 Design Constraints Voltage Type Design Variables Current Vin (V) Iin (mA) Iled (mA) D3 C4 (µF) RSERIES (Ω) RLED (Ω) DC 5 3 1 - 1 1k6 2k DC 12 3 1 - 1 2k 3k AC 12 3 1 BAT54 100 1k8 260 AC 110 3 1 1N4007 100 2x12k's 260 AC 220 3 1 1N4007 100 4x12k's 260 2.2.1 Series Shunt Regulator Q5 RSERIES R66 Vbe + VDDHI SHNT Vin D4 NEUTRAL 2 LIVE Iin 1 1 3 D3 C4 C5 VSS 2 Figure 2-2 Figure 2-2 illustrates how the shunt regulator can be connected to implement a series shunt regulator. An NPN transistor is connected between the currentlimiting resistor (RSERIES) and the VDDHI input pin of the IC, with the base of the transistor connected to the SHNT pin. VDDHI will be regulated to VDDHI -VBE, which is about 5.5V. This supply topology will be more power efficient, as less current will be wasted through the SHNT pin. It is very important to populate a bypass capacitor (C5) between the SHNT and VSS pins for stability reasons. A value in the region of 1uF will reduce the ripple voltage to less than 10mV. R66 should be in the order of about 100kΩ and any NPN transistor can be used as long as the device’s VCE and IC ratings are not exceeded. By using this setup a zener diode (D4) can be chosen to regulate at a higher voltage, thus achieving a two stage regulator. The higher this zener voltage the smaller the value of C4 can be. This can help reduce the size of the overall design. The advantage of this configuration is that VDD is basically regulated by three stages ensuring maximum stability against any voltage Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved AZD0001 Reference Design Ver0.00 September 2006 3 IQ Switch® ProxSense™ REFERENCE DESIGN drops or sudden current surges. Unfortunately the excess current will be dumped through D4, limiting the efficiency of the supply. The same values provided in Table 2-1 applies to the circuit of Figure 2-2. 2.3 Boost Regulator R69 RHIGH LOW CURRENT R72 D8 IQS17 Q5 RLOW VDDHI 2 Q3 3 1 2 LIVE 3 D5 R64 R66 C3 1 1 R60 VDD Series Regulator HIGH CURRENT SHNT Shunt Regulator GND HVSENSE R61 D6 VHVSENSE 3 1 Q4 R62 + C61 C60 C62 R65 2 R63 LOAD VSS 2 GND PWRCNTR Control Logic Figure 2-3 The IQS17 also contains a very power efficient regulator referred to as the boost regulator. Figure 2-3 indicates a conceptual circuit for this regulator which will be used to explain the basic functionality. This configuration is used in most two-wire applications. Refer to section 3 for an overview of the twowire topology. The basic idea of this circuit is to regulate the VBOOST voltage node at any adjustable level. A voltage is setup on this node and monitored by the HVSENSE input pin by means of a voltage divider circuit (formed by R64 and R65). If this voltage drops below 1.1V (VHVSENSE) the PWRCNTR pin will become active high, switching on transistor Q4 which in turn switches on transistor Q3. This transistor then provides a low impedance high current path, allowing the voltage on the storage capacitor (C60) to rise again to the selected VBOOST voltage level. The pulse on the PWRCNTR pin can be compared to a PWM signal adjusting the length of the ON time to the amount of current needed in the storage capacitor. If two-wire mode is selected by connecting a pull down resistor to the REOCNTR pin, the PWRCNTR pin is only activated during the TBOOST period, which is at the start of every half cycle. Once the voltage has risen higher than VHVSENSE, the PWRCNTR will become inactive, disabling the high current path. The majority of the total current needed to power the device is supplied through this path. The function of the high impedance low current path is to supply the device with current during the start-up phase of the device. Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved AZD0001 Reference Design Ver0.00 September 2006 4 IQ Switch® ProxSense™ REFERENCE DESIGN The function of D5 is to half-wave rectify the AC line supply while D8 protects Q3 against a high negative voltage. The purpose of D6 is to limit the maximum VBOOST voltage to an acceptable value, purely as a safety precaution for any over-voltages. If too much current is supplied through the low current path the voltage on this node may rise above the intended design value. D6 will shunt the excess current and limit the maximum voltage. The value of this zener diode should always be higher than the VBOOST voltage node. The VBOOST voltage is regulated down to a lower voltage by means of a series shunt regulator as explained earlier. The advantage of this supply configuration is that it conserves current, unlike the normal shunt regulator dumping any excess current. Current is only supplied when needed, minimizing the overall power consumption. It is advisable to use this regulator in most two-wire applications to ensure the device is provided with enough power when the load is on. This regulator circuit can also be used in any three-wire application if current conservation is important, but will be more costly than the normal shunt regulator circuit. 3 Two-wire Overview Lighting wall switches are most often connected between the LIVE and the LOAD terminals as there is no access to the NEUTRAL conductor, hence the name two-wire. Figure 3-1 below illustrates a normal two-wire wall switch found in most buildings. Figure 3-2 indicates how the IQS17 replaces a standard wall switch. The IQS17 module must be connected between the LIVE and the LOAD terminals as indicated in the figure below. Figure 3-1 Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved Figure 3-2 AZD0001 Reference Design Ver0.00 September 2006 5 IQ Switch® ProxSense™ REFERENCE DESIGN Due to this connection type the device is not powered when the load is ON and needs to be turned OFF at discrete intervals to keep the device powered at all times. By configuring the device in two-wire, the regulators control the timing by which the load is turned ON and OFF to keep the unit powered as shown in Figure 3-2. Figure 3-2 Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved AZD0001 Reference Design Ver0.00 September 2006 6 IQ Switch® ProxSense™ REFERENCE DESIGN Reference Two-wire Schematic R12 2 R 73 R 72 Q3 R 71 D5 L1 R69 R15 3 LIVE R68 R 70 R67 R13 R60 D8 1 Q5 R61 R64 D6 R31 R10 3 D1 A2 RV1 A1 1 Q4 G R1 U1 1 2 3 4 5 6 7 8 9 10 GND C60 R62 TEST ZC VSW TG LED VSS VDD HVSENSE SHNT VDDHI 18 OSC 17 REOCNTR 16 REOIN 15 SW SENSE_PLATE R2 14 CS 13 CX 12 TRPSEL 11 PWRCNTR IQS17 C62 2 C30 R66 C15 R16 1 3 R30 2 4 R25 C25 R63 C61 R11 C10 C3 C5 R8 R36 C1 R39 R65 LOAD(+) GND GND R5 LED GND Figure 4-1 Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved AZD0001 Reference Design Ver0.00 September 2006 7 GND GND IQ Switch® ProxSense™ REFERENCE DESIGN 5 Refdes R1 R2 R5 R8 R 10 R 11 R 12 R 13 R 15 R 16 R 25 R 30 R 31 R 36 R 39 R 60 R 61 R 62 R 63 R 64 R 65 R 66 R 67 R 68 R 69 R 70 R 71 R 72 R 73 C1 C3 C5 C10 C15 C25 Footprint RES-0603 RES-0603 RES-0603 RES-0603 RES-0603 RES-0603 RES-1206 RES-1206 RES-0603 RES-0603 RES-0603 RES-1206 RES-1206 RES-0603 RES-0603 RES-0603 RES-1206 RES-0603 RES-0603 RES-0603 RES-0603 RES-1206 RES-1206 RES-1206 RES-1206 RES-1206 RES-1206 RES-1206 RES-1206 CAP-0603 CAP-0603 CAP-0603 CAP-0603 CAP-0603 CAP-0603 C30* C60 C61 C62 Discrete Electrolytic CAP-0603 CAP-0603 D1 D5 D6 D8 Q3 Q4 Q5 RV1 L1* LED U1 TO220 MELF SOD123 MELF SOT23 SOT23 SOT23 Discrete Toroid 3mm SSOP Reference Two-wire Design Values 220V 50Hz Value Tollerance 18k 5% 2k 5% 1k 5% 100k 5% 1M 1% 1M 1% 510k 5% 510k 5% 1M 1% 1M 1% 10k 5% 2k7 5% 2k7 5% DNP 5% 10k 5% 30k 5% 6k2 5% 10k 5% 100k 5% 820k 5% 39k 5% 100k 5% 22k 5% 22k 5% 22k 5% 68 5% 68 5% 68 5% 68 5% 220nF 20% 100pF 20% 100nF 20% 1nF 20% 100pF 20% 100nF 20% 4.7uF 100nF 1uF BTA08800 1N4007 33V 1N4007 MMBTA94 MMBTA44 S9014 07D391k 20% 20% 20% IQS17 Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved Rating 50V X7R 16V X7R 50V X7R 50V X7R 16V X7R 50V X7R 275VAC Type X2 EXR 50V 16V X7R 50V X7R Refdes R1 R2 R5 R8 R 10 R 11 R 12 R 13 R 15 R 16 R 25 R 30 R 31 R 36 R 39 R 60 R 61 R 62 R 63 R 64 R 65 R 66 R 67 R 68 R 69 R 70 R 71 R 72 R 73 C1 C3 C5 C10 C15 C25 Footprint RES-0603 RES-0603 RES-0603 RES-0603 RES-0603 RES-0603 RES-1206 RES-1206 RES-0603 RES-0603 RES-0603 RES-1206 RES-1206 RES-0603 RES-0603 RES-0603 RES-1206 RES-0603 RES-0603 RES-0603 RES-0603 RES-1206 RES-1206 RES-1206 RES-1206 RES-1206 RES-1206 RES-1206 RES-1206 CAP-0603 CAP-0603 CAP-0603 CAP-0603 CAP-0603 CAP-0603 C30* C60 C61 C62 Discrete Electrolytic CAP-0603 CAP-0603 D1 TO220 D5 MELF D6 SOD123 D8 MELF Q3 SOT23 Q4 SOT23 Q5 SOT23 RV1 Discrete L1* Toroid LED 3mm U1 SSOP * Dependant on local EMC regulations AZD0001 Reference Design Ver0.00 115V 60Hz Value Tollerance 18k 5% 2k 5% 1k 5% 100k 5% 1M 1% 1M 1% 510k 5% 510k 5% 1M 1% 1M 1% 10k 5% 2k7 5% 2k7 5% DNP 5% 10k 5% 30k 5% 6k2 5% 10k 5% 100k 5% 820k 5% 39k 5% 100k 5% 11k 5% 11k 5% 11k 5% 15 5% 15 5% 15 5% 15 5% 220nF 20% 100pF 20% 100nF 20% 1nF 20% 100pF 20% 100nF 20% 4.7uF 100nF 1uF BTA08800 1N4007 33V 1N4007 MMBTA94 MMBTA44 S9014 07D391k 20% 20% 20% Rating 50V X7R 16V X7R 50V X7R 50V X7R 16V X7R 50V X7R 275VAC Type X2 EXR 50V 16V X7R 50V X7R IQS17 September 2006 8 IQ Switch® ProxSense™ REFERENCE DESIGN 6 Three-wire Overview If it is possible to access the LIVE and NEUTRAL conductors as shown in Figure 6-1 the device can be operated in three-wire mode. Figure 6-2 depicts how the IQS17 is connected in a standard three-wire setup. The IQS17 must be connected between the LIVE and NEUTRAL terminals. Unlike in the two-wire supply setup, the unit will constantly be powered in the three-wire configuration. This greatly reduces the supply complexity and cost. Figure 6-1 Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved Figure 6-2 AZD0001 Reference Design Ver0.00 September 2006 9 IQ Switch® ProxSense™ REFERENCE DESIGN 7 Reference Three-wire Schematic R46 R44 R43 R13 R42 D5 L1 R41 LIVE R40 R12 R15 R1 R84 R30 R16 R31 A2 R10 D1 U1 1 2 3 4 5 6 7 8 9 10 GND RV1 A1 R39 C15 G TEST ZC VSW TG LED VSS VDD HVSENSE SHNT VDDHI 18 OSC 17 REOCNTR 16 REOIN 15 SW SENSE_PLATE R2 14 CS 13 CX 12 TRPSEL 11 PWRCNTR IQS17 R25 C25 C41 C40 + R11 C10 C3 C5 R8 C30 R36 C1 NEUTRAL GND GND LOAD(+) R5 LED GND Figure 7-1 Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved AZD0001 Reference Design Ver0.00 September 2006 10 GND IQ Switch® ProxSense™ REFERENCE DESIGN 8 Reference Three-wire Design Values 220V 50Hz 115V 60Hz Refdes Footprint Value Tollerance R1 RES-0603 18k R2 RES-0603 2k R5 RES-0603 Rating Refdes Footprint Value Tollerance 5% R1 RES-0603 18k 5% 5% R2 RES-0603 2k 5% 260 5% R5 RES-0603 260 5% Rating R8 RES-0603 100k 5% R8 RES-0603 100k 5% R 10 RES-0603 1M 1% R 10 RES-0603 1M 1% R 11 RES-0603 1M 1% R 11 RES-0603 1M 1% R 12 RES-1206 510k 5% R 12 RES-1206 510k 5% R 13 RES-1206 510k 5% R 13 RES-1206 510k 5% R 15 RES-0603 1M 1% R 15 RES-0603 1M 1% R 16 RES-0603 1M 1% R 16 RES-0603 1M 1% R 25 RES-0603 10k 5% R 25 RES-0603 10 5% R 30 RES-1206 2k7 5% R 30 RES-1206 2k7 5% R 31 RES-1206 2k7 5% R 31 RES-1206 2k7 5% R 36 RES-0603 DNP 5% R 36 RES-0603 DNP 5% R 39 RES-0603 10k 5% R 39 RES-0603 10k 5% R 40 RES-1206 6k2 5% R 40 RES-1206 3k 5% R 41 RES-1206 6k2 5% R 41 RES-1206 3k 5% R 42 RES-1206 6k2 5% R 42 RES-1206 3k 5% R 43 RES-1206 6k2 5% R 43 RES-1206 3k 5% R 44 RES-1206 6k2 5% R 44 RES-1206 3k 5% R 46 RES-1206 6k2 5% R 46 RES-1206 3k 5% R 84 RES-0603 18k 5% R 84 RES-0603 18k 5% C1 CAP-0603 220nF 20% 50V X7R C1 CAP-0603 220nF 20% 50V X7R C3 CAP-0603 100pF 20% 16V X7R C3 CAP-0603 100pF 20% 16V X7R 50V X7R C5 CAP-0603 100nF 20% 50V X7R C5 CAP-0603 100nF 20% C10 CAP-0603 1nF 20% 50V X7R C10 CAP-0603 1nF 20% 50V X7R C15 CAP-0603 100pF 20% 16V X7R C15 CAP-0603 100pF 20% 16V X7R 100nF 20% 50V X7R C25 CAP-0603 C30* Discrete C40 Electrolytic C41 D1 50V X7R C25 CAP-0603 100nF 20% 275VAC Type X2 C30 Discrete 100nF 20% 275VAC 100uF 20% EXR 16V 20% 50V X7R 100uF 20% EXR 16V C40 Electrolytic CAP-0603 1nF 20% 50V X7R C41 CAP-0603 1nF TO220 BTA08-800 D1 TO220 BTA08-800 D5 MELF 1N4007 D5 MELF 1N4007 RV1 Discrete 07D391k RV1 Discrete 07D391k L1* Toroid L1 Toroid 1mH LED 3mm LED 3mm U1 SSOP U1 SSOP IQS17 IQS17 * Dependant on local EMC regulations Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved AZD0001 Reference Design Ver0.00 September 2006 11 IQ Switch® ProxSense™ REFERENCE DESIGN Design Note Revision History Version 0.00 This is a new document containing the production silicon parameters Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved AZD0001 Reference Design Ver0.00 September 2006 12 IQ Switch® ProxSense™ REFERENCE DESIGN PRETORIA OFFICE Physical Address 160 Witch Hazel Avenue st Hazel Court 1, 1 Floor Highveld Techno Park Centurion, Gauteng Republic of South Africa PAARL OFFICE Physical Address 109 Main Street Paarl 7646 Western Cape Republic of South Africa Tel: +27 12 665 2880 Fax: +27 12 665 2883 Email: [email protected] Tel: +27 21 863 0033 Fax: +27 21 863 1512 Email: [email protected] Postal Address PO Box 16767 Lyttelton 0140 Republic of South Africa Postal Address PO Box 3534 Paarl 7620 Republic of South Africa [email protected] www.azoteq.com This device is covered by the following patents; US6984900, US6952084, US6650066, US6621225, US6249089, EP1530178B1, EP1308913B1, EP1206168B1, EP1120018B1. More patents are pending. IQ Switch and ProxSense are trademarks of Azoteq. The information appearing in this Design Note is believed to be accurate at the time of publication. However, Azoteq assumes no responsibility arising from the use of the specifications described. The applications mentioned herein are used solely for the purpose of illustration and Azoteq makes no warranty or representation that such applications will be suitable without further modification, nor recommends the use of its products for application that may present a risk to human life due to malfunction or otherwise. Azoteq products are not authorized for use as critical components in life support devices or systems. No licenses to patents are granted, implicitly or otherwise, under any intellectual property rights. Azoteq reserves the right to alter its products without prior notification. For the most up-to-date information, please contact [email protected] or refer to the website. Copyright © AZOTEQ (PTY) LTD 2006 All Rights Reserved AZD0001 Reference Design Ver0.00 September 2006 13