PCF88831 NXP [NXP Semiconductors], PCF88831 Datasheet - Page 16

• Manufacturer Part Number: PCF88831
• Description: Capacitive proximity switch with auto-calibration, large voltage operating
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
13. Application information
3.
PCF8883
Product data sheet
Fig 15. Typical application
For further information see
“UM10370”.
C
The coaxial cable is optional.
SENS
SENSING PLATE
C
= sensing plate capacitance.
SENS
Figure 15
connected to pin V
both V
The sampling rate is determined by the capacitance C
rate reduces the reaction time and increases the current consumption.
The sensing plate capacitance C
behind an isolating layer. The sensing plate can be connected to a coaxial cable (C
which in turn is connected to the input pin IN. Alternatively, the sensing plate can be
directly connected to the input pin IN. An internal low pass filter is used to reduce RF
interference. An additional low pass filter consisting of a resistor R
be added to the input to further improve RF immunity as required. For good performance,
the total amount of capacitance on the input (C
proper range, the optimum point being around 30 pF. These conditions allow the control
loop to adapt to the static capacitance on C
the sensing plate capacitance. A higher capacitive input loading is possible provided that
an additional discharge resistor R
reduces the discharge time such that the internal timing requirements are fulfilled.
The sensitivity of the sensor can be influenced by the sensing plate area and capacitor
C
sensitivity is desired C
COAXIAL CABLE
CPC
Ref. 2
. The sensitivity is significantly reduced when C
DD
“AN10832”. Information about the appropriate evaluation board can be found in
and V
shows the typical connections for a general application
DD(INTREGD)
All information provided in this document is subject to legal disclaimers.
Pulse
DD
R
F
. It is recommended to connect smoothing capacitors to ground to
Toggle
CPC
Rev. 2 — 8 March 2011
can be increased, but this also increases sensitivity to
(values for C
R
V
C
Push-
button
DD(INTREGD)
SENS
C
C
F
is placed as shown in
Capacitive proximity switch with auto-calibration
may consist of a small metal area, for example
dec
TYPE
CPC
V
IN
SS
, see
SENS
PCF8883
SENS
V
Table
and to compensate for slow changes in
DD(INTREGD)
013aaa079
+ C
CPC
CLIN
CLIN
5).
OUT
V
CABLE
DD
is reduced. When maximum
Figure
on pin CLIN. A higher sampling
+ C
15. Resistor R
3
F
. The positive supply is
F
) should be in the
and capacitor C
PCF8883
© NXP B.V. 2011. All rights reserved.
Ref. 11
C
simply
CABLE
16 of 25
F
can
)