Specifications
26 CY3280-SmartSense CapSense Auto-Tuning Kit Guide, Doc. # 001-64672 Rev. *A
A.1.2 Power Supply
In the schematic:
■ CapSense controller CY8C20246A is used to detect finger touch on sensors BTN0-BTN3. It
drives active low LEDs (LED0-LED3) based on detected touch on sensors.
■ CY8C20246A controller can be powered either from on-board AAA batteries or from external
sources (VDD_EXT / VDD_DEV).
■ Supply from battery and VDD_EXT are gated by the Power button, but VDD_DEV is not.
■ CapSense controller CY8CMBR2044 is used to detect finger touch on the Power button. It turns
on/off series pass switch based on detected status. CY8CMBR2044 is configured to operate for a
period of 1 year on battery power.
■ Power LED turns on when any of the three power sources are activated.
■ Connectors J1 and J2 are expansion connectors. Unused I/Os of controller CY8C20246A are
routed to these connectors.
■ Connector J5 is used for ISSP programming of CY8C20246A. ISSP pins P1[0] and P1[1] are
routed to this connector.
■ If required, connector J5 can be reused as an I
2
C header. For this, configure P1[0] and P1[1] as
I
2
C pins in the PSoC Designer project. However, CapSense buttons, BTN1 and BTN2, cannot be
used. An alternative option is to configure P1[5] and P1[7] as I2C pins; both are mapped to J5.
■ It is not recommended to configure ISSP pins P1[0] and P1[1] as CapSense sensors. However
these pins are used as sensors in this kit only to demonstrate SmartSense self tuning capability.
■ SmartSense requires an external modulation capacitor Cmod, connected from VSS to one of two
dedicated PSoC pins P0[1] or P0[3]. The CY3280-SmartSense kit uses P0[3] as the Cmod (C4)
pin. The recommended value for the external modulation capacitor is 2.2 nF. A ceramic capacitor
must be used. The temperature capacitance coefficient is not important.
■ Cypress strongly recommends using a 560-Ω series resistor on all CapSense sensor traces to
suppress RF interference. This resistor must be placed as close to the CapSense controller as
possible.
1206R
D1
LED Red
21
Power Section
VDD_Dev
VDD_Dev
VDD_SW
TWO AAA 1.5V 1125mAh Battery
VI N
VIN
PW R _BT N
C2
0.1 uF d
Series Pass Switch
Power Button
VOU T
GN D
NC
EN
GND1
VIN
U4
MI C94090 SC -70-6
5
1
2
6 3
4
R6
ZERO
12
D8 DIODE SC HOTTKY
21
Shield
Sensor
B4
CapSen se But to n 13mm R ound
1
VIN
VIN
R3
5. 1K
12
U1
CY8 CMBR 2044
SCANRATE/ SLEEP
12
VSS
7
ARST
9
XR E S
11
GP O0
2
TOG GL E/ F S S
3
GPO3
14
GP O1
1
CS0
5
CS3
10
CS1
6
CS2
8
VDD
13
GP O 2
16
CMO D
15
DELAY
4
Capsense Based Power Button (CY8CMBR2044)
PW R _B T N
CMOD1
C1
2200 pFd
R4
560E
PW R _ ON_ I NV
VDD_Bat
Test Points
C6
10 uFd 16 v
CMOD2
Place CMOD p ad nea r U1.
CMOD1
CMOD
U2
SN74L VC1GU 04
NC
1
A
2
GND
3
VCC
5
Y
4
PW R _ ON
VIN
C9
0.1 uFd
VIN
R7
ZERO
12
DN P
PWR _ ON _I NV
R1
5. 1K
12
VIN
D3
DIOD E SCHO TTKY
2 1
VDD_Bat
VDD_SW
R5
3 30 ohm
1 2
D2
DIOD E SCHO TTKY
2 1
PWR _O N
R2
5. 1K
1 2
VIN
VIN
J4
Batt ery Clip AAA
1
2
3
4
VD D _ E x t
J3
Batt ery Clip AAA
1
2
3
4
VDD_Dev
VD D _ S W
-
+
-
+
C7
10 uFd 16v
VDD_SW
COMN
C8
0.1 uFd
VDD_ BAT