ETC IQS17

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.
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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
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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.
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AZD0001
Reference Design Ver0.00
September 2006
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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
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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
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AZD0001
Reference Design Ver0.00
September 2006
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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
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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
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Figure 6-2
AZD0001
Reference Design Ver0.00
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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
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