Data Sheet

PCA8885
Capacitive 8-channel touch and proximity sensor with
auto-calibration and very low power consumption
Rev. 4 — 13 March 2014
Product data sheet
1. General description
The integrated circuit PCA8885 is a capacitive 8-channel touch and proximity sensor that
uses a patented (EDISEN) method to detect a change in capacitance on remote sensing
plates. Changes in the static capacitances (as opposed to dynamic capacitance changes)
are automatically compensated using continuous auto-calibration. Remote sensing plates
(for example, conductive foils) can be connected to the IC1 using coaxial cable. The eight
input channels operate independently of each other. There is also a built-in option for a
matrix arrangement of the sensors: interrupt generation only when two channels are
activated simultaneously, suppression of additional channel outputs when two channels
are already active.
2. Features and benefits













1.
AEC-Q100 compliant for automotive applications
Dynamic touch and proximity sensor with 8 sensor channels
Support for matrix arrangement of sensors
Sensing plates can be connected remotely
Adjustable response time
Adjustable sensitivity
 Continuous auto-calibration
 Digital processing method
 Can cope with up to 6 mm of acrylic glass
Direct and latching switch modes
I2C Fast-mode Plus (Fm+) compatible interface
 Two I2C-bus addresses
 Cascading of two ICs possible
 Interrupt signaling over I2C-bus
Interrupt output
Large voltage operating range (VDD = 2.5 V to 5.5 V)
Sleep mode (IDD < 100 nA)
Low-power battery operation possible (IDD ~ 10 A)
Operating temperature range (Tamb = 40 C to +85 C)
The definition of the abbreviations and acronyms used in this data sheet can be found in Section 23 on page 39.
PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
3. Applications










Replacing mechanical switches
Hermetically sealed keys on a keyboard
Switches for medical applications
Switches for use in explosive environments
Audio control: on/off, channel, volume
Vandal proof switches
Switches in or under the upholstery, leather, handles, mats, carpets, tiles, and glass
Use of standard metal sanitary parts (for example a tap) as switch
Portable communication and entertainment units
White goods control panel
4. Ordering information
Table 1.
Ordering information
Type number
Package
PCA8885TS
Name
Description
Version
TSSOP28
plastic small outline package; 28 leads;
body width 4.4 mm
PCA8885TS
4.1 Ordering options
Table 2.
Ordering options
Product type number
Orderable part number Sales item
(12NC)
Delivery form
IC
revision
PCA8885TS/Q900/1
PCA8885TS/Q900/1,1
tape and reel, 13 inch
1
935297377118
5. Marking
Table 3.
PCA8885
Product data sheet
Marking codes
Product type number
Marking code
PCA8885TS/Q900/1
PCA8885TS
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
6. Block diagram
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Block diagram of PCA8885
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
7. Pinning information
7.1 Pinning
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Top view. For mechanical details, see Figure 26 on page 36.
Fig 2.
PCA8885
Product data sheet
Pin configuration for TSSOP28 (PCA8885TS)
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Rev. 4 — 13 March 2014
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
7.2 Pin description
Table 4.
Pin description
Input or input/output pins must always be at a defined level (VSS or VDD) unless otherwise specified.
Symbol
Pin
Type
Description
PCA8885TS
CLK_OUT
1
output
clock output for chip cascading and synchronization
VDD(INTREGD)[1] 2
supply
internal regulated supply reference voltage
IN7 to IN0
3 to 10
analog
input/output
sensor input, channel 0 to 7[2]
CPC7 to
CPC0
11 to 18
analog
input/output
reservoir capacitor, channel 0 to 7[2]
VSS
19[3]
supply
ground supply voltage
SCL
20
input
serial clock line
SDA
21
input/output
serial data line
TEST
22
input
test pin; must be connected to VSS
A0
23
input
I2C subaddress LSB[4]
SLEEP
24
input
sleep mode;
connect to VDD to force the circuit into low-power
sleep mode
INT
25
output
interrupt output
VDD
26
supply
supply voltage
INT_IN
27
input
interrupt input for chip cascading;
connect to VDD if not used
CLK_IN
28
input
clock input;
for the secondary chip when the primary chip
provides the clock signal
PCA8885
Product data sheet
[1]
The internal regulated supply voltage output must be decoupled with a decoupling capacitor to VSS.
[2]
If a channel is not used, the appropriate sensor input line has to be left open, the corresponding CPCn has
to be connected to VSS and the channel should be disabled in the MASK register (see Table 11 on
page 15).
[3]
The die paddle (exposed pad) is connected to VSS and should be electrically isolated.
[4]
Used to address two devices, for example: low address 3Ah, high address 3Bh.
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
8. Functional description
The sensing plates have to be connected to the sensor input pins IN0 to IN7. The
discharge times (tdch) on the sensor input pins, are compared to the discharge time
(tdch(ref)) of an internal RC timing element. The comparison is done sequentially for each
sensor input pin. The RC timing circuits are periodically charged from VDD(INTREGD) and
then discharged via a resistor to VSS. The charge-discharge cycle for each channel is
governed by the sampling rate (fs). The channels are sampled sequentially, while the
reference element is activated at the sampling point of each channel (see timing diagram
in Figure 3).
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For this example, the oscillator frequency and the clock division factor have been set to result in a 1 kHz sampling frequency.
Fig 3.
Timing diagram of sensor sampling
When the voltage of an RC combination falls below the level Vref, the appropriate
comparator output changes. The logic following the comparators determines which
comparator switched first. If the reference comparator switched first, then a pulse is given
on CUP. If the sensor comparator switched first, then a pulse is given on CDN. Figure 4
illustrates the functional principle of the PCA8885.
The pulses control the charge on the external capacitors CCPC on pins CPC0 to CPC7.
Every time a pulse is given on CUP, the capacitor CCPC is charged through a current
source (Isource) from VDD(INTREGD) for a fixed time causing the voltage on CCPC to rise by a
small increment. Likewise when a pulse occurs on CDN, capacitor CCPC is discharged
through a current sink (Isink) towards ground for a fixed time, causing the voltage on CCPC
to fall by a small decrement. The voltage on CCPC controls an additional current sink (ICPC)
that causes the capacitance attached to the input pins IN[0:7] to be discharged more
quickly. This arrangement constitutes a closed loop control system, that constantly tries to
equalize the discharge time (tdch) with the reference discharge time (tdch(ref)). In the
equilibrium state, the discharge times are nearly equal and the pulses alternate between
CUP and CDN.
PCA8885
Product data sheet
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
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Fig 4.
Functional diagram of sensor operation
The counter following this logic counts the pulses CUP or CDN respectively. The counter
is reset every time the pulse sequence changes from CUP to CDN or the other way round.
The outputs OUT0 to OUT7 are only activated when 64 consecutive pulses occurred on
CUP. Low-level interference or slow changes in the input capacitance do not cause the
output to switch.
Various measures, such as asymmetrical charge and discharge steps, are taken to
ensure that the output switches off correctly. A special start-up circuit ensures that the
device reaches equilibrium quickly when the supply is attached.
The sampling rate (fs) is derived from the internally generated oscillator frequency. The
oscillator frequency can be adjusted within a specified range by programming the
CLKREG register (see Table 10 on page 14).
The status of the output signals OUT0 to OUT7 is stored in the SENS register (see
Table 9 on page 13). An interrupt is generated on changes of the sensor states.
PCA8885
Product data sheet
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
9. Commands
The operation of the PCA8885 can be controlled by 12 commands and 4 configurationand status-registers (see Section 10 on page 10). Several configuration settings can be
programmed using single commands without associated data transfer. The configuration
register can however also be written using the write-config command. The clock and mask
registers can only be programmed using the write-clock and write-mask commands.
9.1 Command overview
Table 5.
Commands of PCA8885
Command
Operation
code
Description
Transfer
type
Reference
soft-reset
00000000
brings chip to reset state
command
Section 9.2,
Section 10.2.2.2
clear-INT
00000011
deactivates interrupt generation on pin
INT
command
Section 10.2.2.1
sleep
00000101
enter sleep mode
command
Section 9.3
wake-up
00000110
enter active mode
command
write-config 00110000
write configuration register
write 1 byte Section 10.2
read-config
read configuration register
read 1 byte
00110011
write-clock
00110101
write clock setting register
write 1 byte Section 10.4
read-clock
00110110
read clock setting register
read 1 byte
write-mask
00111001
write the mask register
write 1 byte Section 10.5
read-mask
00111010
read the mask register
read 1 byte
int-over-I2C
00111100
put the device in int-over-I2C mode
command
Section 10.2.2.1
read sensor state register and clears
the INT line
direct read
Section 9.4,
Section 10.2.2.1
read-sensor -
9.2 Command: soft-reset
Reset takes place during power-on of the circuit. There is no external hardware reset
input.
During operation, the device can be reset using the soft-reset command. The sensor
channels and all registers are reset to the default values and the int-over-I2C mode is
terminated. It does not affect the state of the analog section except for those functions that
are controlled by configuration bits.
9.3 Commands: Sleep and wake-up
Sleep mode is implemented to save power during periods where no sensor activity is
expected or supported.
In sleep mode, most of the circuit parts are put in power-down mode, in particular all
analog blocks consuming static and dynamic power. This includes the oscillator, thus no
internal activity remains. Also the voltage regulator is powered down, to reduce its
standalone power consumption.
PCA8885
Product data sheet
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
During sleep mode, the register configuration is maintained and the device remains
responsive to I2C commands. The charges in the CPC capacitors however cannot be
guaranteed, as there is no limitation on the duration of the sleep mode. Therefore the
analog part has to perform a normal start-up phase, including the fast start procedure for
the CPC capacitor charging.
Sleep mode is entered when the sleep command is received from the system controller or
when the SLEEP pin is set to HIGH. Resume is done by the wake-up command, or by
setting the SLEEP pin to LOW.
The hardware sleep mechanism using the SLEEP pin and the software sleep mechanism
using the sleep or wake-up commands are independent of each other:
• If the device was put to sleep using the sleep command, a wake-up command
resumes the operation. It cannot be resumed by activating the SLEEP pin.
• If the device was put to sleep by setting pin SLEEP to HIGH, then pin SLEEP must be
set to LOW to resume operation. It cannot be resumed with the wake-up command.
9.4 Command: read-sensor
The read-sensor command is the main transaction to read the actual state information of
the sensor state register SENS.
If the R/W bit (LSB of the I2C slave address byte, see Table 12 on page 19) is set logic 1
the PCA8885 regards the transaction as the read-sensor command. The read-sensor
command transaction supports a repeated reading of the SENS register (see Section 10.3
on page 13). When two circuits are used in a cascaded configuration, they alternately
return their SENS register content in a single transaction
The protocols for the repeated read mode and the alternating read mode are described in
Section 13.7 on page 20.
PCA8885
Product data sheet
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Capacitive 8-channel touch and proximity sensor with auto-calibration
10. Registers
The PCA8885 has four registers storing the configuration and the status information of the
device.
10.1 Register overview
Table 6.
Register overview
The bit position labeled as x is not relevant; if read, it can be either logic 0 or logic 1.
Register
name
Bit
CONFIG
OPM[1:0]
7
6
SENS
CH[7:0]
CLKREG
CLO
MASK
MSK[7:0]
5
4
SWM
3
KM[1:0]
2
1
VROF INTM
0
Default
value
MSKMODE
00000000
00000000
CLI
x
FRQC[1:0]
FRQF[2:0]
00x01100
11111111
10.2 Register: CONFIG
Table 7.
Bit
Symbol
7 to 6
OPM[1:0]
5
4 to 3
PCA8885
Product data sheet
CONFIG - configuration register bit description
Value
Description
Reference
main operation mode
Section 10.2.1.1
00[1]
stand-alone device
01
secondary-chip in a
cascade
10
primary-chip in a cascade
11
unused
SWM
switching mode
Section 10.2.1.2
0[1]
direct switching mode:
sensor release clears the
corresponding bit in the
SENS register
1
latching mode:
reading SENS register
clears bits in the SENS
register
KM[1:0]
key-press mode
Section 10.2.1.3
00[1]
N-key mode:
each sensor activity is
reflected in the SENS
register
01
2-key mode:
only first two keys are
visible in the SENS register
10
1-key mode:
only first key-press is visible
in the SENS register
11
unused
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Capacitive 8-channel touch and proximity sensor with auto-calibration
Table 7.
CONFIG - configuration register bit description …continued
Bit
Symbol
2
VROF
1
Description
Reference
voltage regulation
Section 11
0[1]
voltage regulation on
1
voltage regulation off
INTM
0
[1]
Value
interrupt generation mode
Section 10.2.2
0[1]
an interrupt is generated by
each bit changed in the
SENS register (press and
release)
1
an interrupt is generated by
each bit set in the SENS
register (press only)
MSKMODE
channel masking mode
0[1]
normal power:
masked out channels
remain operational
1
low power:
masked out channels are
powered down
Section 10.5.1
Default value.
All bits in this register can be written and read with the write-config and read-config
commands.
10.2.1 Operating modes
10.2.1.1
Main operating modes
The PCA8885 can operate in three operating modes: as a stand-alone device or in a
cascade as a primary-chip or a secondary-chip (see Table 8).
Table 8.
Main operating modes
Main operating modes
Conditions of
Stand-alone[1]
Primary-chip
Secondary-chip
clock source
internal oscillator
internal oscillator
clock input
oscillator
enabled
enabled
disabled
clock output pin CLK_OUT
disabled
enabled
disabled
clock input pin CLK_IN
disabled
disabled
enabled
[1]
Default operating mode after power-on.
The operating modes are implemented to support the application of two PCA8885 in the
system (see Section 13.8 on page 21).
10.2.1.2
Switching modes
There is a one to one relationship between the channels IN[0:7] and the bits in the SENS
register. The indication of the switching status of each channel is controlled by the two
switching modes supported:
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Capacitive 8-channel touch and proximity sensor with auto-calibration
Direct mode — In direct mode, the sensor state is directly reflected in the SENS register.
When the sensor is activated, the corresponding bit in the SENS register is immediately
set logic 1. When the sensor is released, the bit is cleared (set logic 0) again. The bits are
even cleared if the SENS register has not yet been read by the system controller.
Latching mode — In latching mode, every activated sensor sets the corresponding bit in
the SENS register logic 1. When the sensor is released, the SENS register is unaffected.
Reading the SENS register clears (set logic 0) those bits, whose sensor is not activated
anymore.
After reset, the PCA8885 is set to direct switching mode.
10.2.1.3
Key-press modes
There are three key-press modes implemented in the PCA8885: N-key, 1-key, and 2-key
mode.
N-key mode — In N-key mode, each sensor activity is reflected in register SENS
according to the configured switching mode. The N-key mode is the default key-press
mode after reset.
1-key mode — In 1-key mode, only the first sensor activation sets the corresponding bit
in register SENS. All further activations of the other sensors are suppressed at the SENS
register boundary. In this way, sensors in a keypad are masked out, which are activated
accidentally because they are arranged next to the activated sensor.
The 1-key mode supports sensor matrix arrangements with two PCA8885, where one chip
is attached to the columns and one to the rows (primary-chip and secondary-chip). Sensor
activation sets 1 bit for the column and 1 bit for the row in the SENS register of the
appropriate chip. Each activation of a sensor raises an interrupt. The system controller
must handle the situation where the INT is raised before the second sensor in the matrix
has been activated.
2-key mode — In 2-key mode, only the two first sensor activations set the corresponding
bits in register SENS. All further activations of the other sensors are suppressed at the
SENS register boundary. This mode supports in particular the matrix arrangement of
sensors using only one PCA8885, as illustrated in Figure 25 on page 33. In this way,
sensors in a matrix are masked out, which are activated accidentally because they are
arranged next to the intended sensors. This mode properly handles a delay in sensor
activation due to unequal sensor capacitance or area (non-centric sensor touching, and
so on) as long as the intended sensors react before sensors which are activated
accidentally. In 2-key mode, the INT output is only activated after 2 bits have been set in
the SENS register.
10.2.2 Interrupt generation
The PCA8885 provides two mechanisms to inform the system controller that a sensor
activity has been detected.
10.2.2.1
Interrupt output INT
The PCA8885 has an interrupt output, INT, to flag to the system controller that a
capacitive event has been detected. The controller can then fetch the sensor state by
reading the SENS register over the I2C-bus.
The interrupt generation is controlled by the INTM bit in the CONFIG register (see Table 7
on page 10).
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Capacitive 8-channel touch and proximity sensor with auto-calibration
• If INTM is logic 0 (default), then the change (set or clear) of each bit in register SENS
activates the INT output.
• If INTM is logic 1, then only sensor press events, resulting in bits being set logic 1 in
the SENS register, activate the INT output. Sensor release events, which cause the
corresponding bit in SENS to be cleared (set logic 0), do not activate the INT output.
In 2-key mode, the INT output is only activated after 2 bits have been set in the SENS
register.
The interrupt is automatically cleared when the system controller reads the SENS register.
Alternatively the INT can be cleared by using the clear-INT command, without reading the
actual sensor state.
10.2.2.2
Interrupt over the I2C-bus
In applications where the sensing plates are remote from the microcontroller, the interrupt
line can be saved by enabling the interrupt over I2C-bus.
The PCA8885 provides the feature of interrupt over the I2C-bus. The PCA8885 then
behaves like an I2C master with restricted functionality. The interrupt is signaled by setting
a START condition immediately followed by a STOP condition. It is illustrated in Figure 5.
No further I2C master capabilities are supported.
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Fig 5.
Interrupt over the I2C-bus
The system controller has to detect the START-STOP condition and react accordingly.
The interrupt over the I2C-bus can be enabled with the int-over-I2C command and
disabled with the soft-reset command.
In interrupt over the I2C-bus mode, the functionality of the INT output continues to work as
described in Section 10.2.2.1.
10.3 Register: SENS
Table 9.
Bit
7 to 0
SENS - sensor state register bit description
Symbol
Value
Description
CH[7:0]
00000000[1] to
sensor state of the respective channels IN7 to
IN0
11111111
[1]
Default value.
All bits in this register are read-only and can be read with the read-sensor command (see
Section 9.4).
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Capacitive 8-channel touch and proximity sensor with auto-calibration
10.4 Register: CLKREG
Table 10.
CLKREG - clock setting register bit description
Bit
Symbol
7
CLO
6
Value
CLK_OUT switch
0[1]
CLK_OUT disabled (unless IC is in
primary-chip mode)
1
CLK_OUT enabled
CLI
CLK_IN switch
0[1]
CLK_IN disabled (unless IC is in
secondary-chip mode)
1
CLK_IN enabled, internal oscillator is
powered down
-[2]
5
-
4 to 3
FRQC[1:0]
2 to 0
Description
unused
clock frequency, coarse setting
00
f clk = f osc  64
01[1]
f clk = f osc  16
10
f clk = f osc  4
11
f clk = f osc
FRQF[2:0]
oscillator tuning
000
f osc = 0.5  f osc  nom 
001
f osc = 0.625  f osc  nom 
010
f osc = 0.75  fosc  nom 
011
f osc = 0.875  f osc  nom 
100[1]
f osc = 1  f osc  nom 
101
f osc = 1.25  fosc  nom 
110
f osc = 1.5  f osc  nom 
111
f osc = 1.75  fosc  nom 
[1]
Default value.
[2]
Should always be written with logic 0 and if read, it can be either logic 0 or logic 1.
All bits in this register can be written and read with the write-clock and read-clock
commands.
10.4.1 Clock generation and frequency adjustment
The PCA8885 contains an integrated oscillator as main clock source. With the values of
FRQF[2:0], the oscillator frequency can be tuned (see Equation 1).
f osc = m  f osc  nom 
PCA8885
Product data sheet
(1)
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Capacitive 8-channel touch and proximity sensor with auto-calibration
The values of m can be varied in the range 0.5  m  1.75, where m = 1.0 corresponds to
the default value of FRQF[2:0] = 100.
The internal clock frequency (fclk) is derived from the oscillator frequency with Equation 2:
f clk = f osc  n
(2)
where the values for n are 1, 4, 16, or 64 and can be selected with FRQC[1:0]. The sensor
sampling frequency (fs) is derived from the internal clock frequency with Equation 3:
f s = f clk  8
(3)
The eight sensors are sampled sequentially, which results in a default sensor sampling
rate fs.
In secondary-chip mode, the internal clock generator is stopped, and the circuit is clocked
from the CLK_IN input pin.
The tuning of the oscillator frequency and the programmable clock divider (see Figure 6)
allows changing the sensor sampling rate, the adjustment of the reaction time and the
power consumption of the PCA8885 over a wide range.
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Fig 6.
Oscillator block diagram
10.5 Register: MASK
Table 11.
MASK - channel enable mask register bit description
Bit
Symbol
Value
Description
7 to 0
MSK[7:0]
00000000 to
11111111[1]
enable or disable the respective sensor
channels IN0 to IN7
[1]
0
sensor channel is disabled
1
sensor channel is enabled
Default value.
All bits in this register can be written and read with the write-mask and read-mask
commands.
10.5.1 Channel masking
The channel masking register MASK allows individual sensor channels to be enabled or
disabled for particular applications or certain modes (for example only the on/off sensor
should be active).
PCA8885
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
• When bit MSKMODE in register CONFIG (see Table 7) is set logic 0, then the
disabled channels are continuously sampled, but switching events are not reflected in
register SENS and do not cause interrupts.
• When bit MSKMODE in register CONFIG (see Table 7) is set logic 1, only channels
which are enabled are sampled. Reducing the number of sampled channels also
reduces the power consumption.
When a channel becomes newly enabled, the fast start-up method (see Section 12) is
used to reach the functional state quickly.
11. Power architecture
The circuit has an integrated voltage regulator, supplied by pin VDD. The regulator
provides an internal VDD(INTREGD) supply of nominally 2.8 V.
If a stable and noise free external supply voltage with 2.5 V < VDD(ext) < 3.3 V is available
in the system, VDD(INTREGD) can be provided from an external source (see Figure 7). In
this case VDD and VDD(INTREGD) must both be connected to VDD(ext). To reduce the current
consumption, the internal voltage regulator should be shut down by setting bit VROF
logic 1 (see Table 7 on page 10).
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Fig 7.
Connection of VDD(ext)
While the analog part of the circuit is powered from VDD(INTREGD), the I2C interface and the
registers are powered from VDD. Therefore the I2C interface remains accessible in sleep
mode, and the register values are maintained when VDD(INTREGD) is powered off.
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
16 of 46
PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
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Fig 8.
Integrated voltage regulator behavior
Figure 8 illustrates the behavior of the integrated voltage regulator. The gray area covers
the operational range of the PCA8885. The analog part of the circuit and the switch logic
is powered from VDD(INTREGD). The I2C interface and the registers are powered from VDD.
Therefore the I2C interface remains accessible in sleep mode, and the register values are
maintained when VDD(INTREGD) is powered off.
12. Start-up procedure
After power-on the registers in the VDD domain are reset, which includes the VROF bit
controlling the voltage regulator. The regulator is therefore enabled, and the VDD(INTREGD)
domain is powered on. As soon as a sufficient VDD(INTREGD) level is reached, the
Power-On Reset (POR) is released.
After release of the POR in the VDD(INTREGD) domain, the circuit starts with the sensor
sampling in the fast start mode (increased charge-pump currents quickly charge the CPC
capacitors close to their target value). As soon as the capacitor voltages are close to the
target value, the fast start phase is terminated, and the capacitors are charged in fine
steps to the final value. When this state is reached, the logic enables the up and down
counters, and the sensors are operational.
This start-up mechanism is executed independently for each channel.
13. Characteristics of the I2C-bus
The PCA8885 has an I2C serial interface which operates as a slave receiver or
transmitter. SDA and SCL are the data I/O and clock lines for the serial I2C Interface. SDA
is used as an input or as an open-drain output. SDA is actively pulled LOW and is
passively held HIGH by the external pull-up resistor on the I2C-bus.
In order to provide high link robustness, the I2C interface of the PCA8885 is Fast-mode
compatible and provides a robust addressing and command scheme.
PCA8885
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Rev. 4 — 13 March 2014
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
13.1 Bit transfer
One data bit is transferred during each clock pulse. The data on the SDA line must remain
stable during the HIGH period of the clock pulse as changes in the data line at this time
are interpreted as a control signal (see Figure 9).
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Bit transfer
13.1.1 START and STOP conditions
Both data and clock lines remain HIGH when the bus is not busy.
A HIGH-to-LOW change of the data line, while the clock is HIGH, is defined as the START
condition (S).
A LOW-to-HIGH change of the data line, while the clock is HIGH, is defined as the STOP
condition (P).
The START and STOP conditions are shown in Figure 10.
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Fig 10. Definition of START and STOP conditions
13.2 System configuration
A device generating a message is a transmitter; a device receiving a message is the
receiver. The device that controls the message is the master; and the devices which are
controlled by the master are the slaves. The system configuration is shown in Figure 11.
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Fig 11. System configuration
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
13.3 Acknowledge
The number of data bytes transferred between the START and STOP conditions from
transmitter to receiver is unlimited. Each byte of 8 bits is followed by an acknowledge
cycle.
• A slave receiver, which is addressed, must generate an acknowledge after the
reception of each byte.
• A master receiver must generate an acknowledge after the reception of each byte that
has been clocked out of the slave transmitter.
• The device that acknowledges must pull-down the SDA line during the acknowledge
clock pulse, so that the SDA line is stable LOW during the HIGH period of the
acknowledge related clock pulse (set-up and hold times must be considered).
• A master receiver must signal an end of data to the transmitter by not generating an
acknowledge on the last byte that has been clocked out of the slave. In this event, the
transmitter must leave the data line HIGH to enable the master to generate a STOP
condition.
Acknowledgement on the I2C-bus is shown in Figure 12.
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Fig 12. Acknowledgement on the I2C-bus
13.4 I2C-bus subaddress
Device selection depends on the I2C-bus slave address, on the transferred command
data, and on the hardware subaddress.
Two I2C-bus slave addresses are used to address the PCA8885 (see Table 12).
Table 12.
I2C slave address byte
Slave address
Bit
7
Slave address
0
6
5
4
3
2
1
0
1
0
0
0
0
A0
R/W
MSB
LSB
The least significant bit of the slave address is bit R/W (see Table 13).
PCA8885
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
Table 13.
R/W-bit description
R/W
Description
0
write data
1
read data
Bit 1 of the slave address is defined by connecting input A0 to either VSS (logic 0) or VDD
(logic 1). Therefore, two instances of PCA8885 can be distinguished on the same I2C-bus.
13.5 I2C-bus protocol
The I2C-bus protocol is shown in Figure 13. The sequence is initiated with a START
condition (S) from the I2C-bus master which is followed by the slave address.
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Fig 13. I2C-bus protocol write mode
After acknowledgement, a command is sent, and after a further acknowledge a data byte
is transmitted. After the last data byte, the I2C-bus master issues a STOP condition (P).
Alternatively a START may be asserted to RESTART an I2C-bus access.
13.6 Fast-mode Plus (Fm+) support
The Fast-mode Plus specification is supported. Besides providing a high transmission
speed, the main characteristic of Fast-mode Plus is the increased drive strength, allowing
lower impedance buses to be driven, and therefore less noise sensitive. Details on the
Fast-mode Plus specification are given in Ref. 14 “UM10204”.
13.7 Reading sensor data
The PCA8885 supports direct reading of the sensor state from the SENS register. If - after
sending the address - the R/W bit is immediately set to logic 1 without sending a
command, the circuit recognizes that it must immediately return the content of the SENS
register (see Figure 14)
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Fig 14. Reading sensor data
When the transaction, after reading the SENS register, is not terminated with a STOP bit,
the PCA8885 repeatedly sends the content of SENS again. This provides a facility to
observe the sensor activity continuously. This transaction is illustrated in Figure 15.
PCA8885
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Rev. 4 — 13 March 2014
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
5:
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Fig 15. Continuously reading sensor data
Using two PCA8885 in a cascade (see Section 13.8), one has to be the primary-chip and
the other the secondary-chip. When the direct read transaction is executed in a cascaded
configuration, the primary-chip transmits its SENS content register immediately after the
address byte, followed by the secondary-chip transmitting its SENS register content.
If the transaction - after reading the two SENS registers - is not terminated with a STOP
bit, the primary-chip and the secondary-chip continue sending the content of the SENS
registers alternately. Such a transaction is illustrated in Figure 16.
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Fig 16. Reading sensor data, alternately from primary-chip and secondary-chip
It must be noted, that for this alternate data transfer only one PCA8885 has to be
addressed. By definition the primary-chip must be addressed (A0 bit in the address set to
logic 0). In this particular case, the secondary-chip reacts on the address of the
primary-chip. For all other transactions targeting the secondary-chip, it must be properly
addressed with A0 set to logic 1.
13.8 Device cascading
Two PCA8885 devices can be connected to the same I2C-bus, which facilitates up to
8  8 keypads.
The device provides the following features to guarantee robust operation and to simplify
the system design using two devices:
• The 7-bit I2C address consists of 6 fixed bits and 1 selectable bit. The level externally
applied to pin A0 (VDD or VSS) defines the LSB of the I2C slave address. In this way,
two PCA8885 can be addressed on the same bus without the need for different hard
coded I2C addresses.
• The sensor activity can be synchronized, so that interference between the sensors of
the different chips is avoided. One chip is considered to be the primary-chip. It
provides the sample clock on pin CLK_OUT. The other chip is considered to be the
secondary-chip. It uses the clock provided by the primary-chip instead of the internal
clock. The primary-chip samples the sensors on the rising edge of the internal sample
clock. The CLK_IN signal is inverted to derive the sample clock in the secondary-chip.
Therefore the secondary-chip samples its sensors on the negative edge of the sample
clock of the primary-chip. In this way, no simultaneous sensor sampling occurs.
PCA8885
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
Primary-chip or secondary-chip modes are enabled by programming the configuration
register (see Table 7 on page 10).
• The interrupt signal can be cascaded. The INT output of the primary-chip can be
connected to the INT_IN input of the secondary-chip. The INT output of the
secondary-chip is then an OR’ed combination of the two interrupts.
• If two devices are cascaded and the int-over-I2C mode is desired, then it is sufficient
to put the secondary-chip in int-over-I2C mode. The primary-chip still signals an
interrupt over the INT output to the INT_IN input of the secondary-chip.
Figure 25 on page 33 illustrates a typical example of an application using two PCA8885
circuits.
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
14. Internal circuitry
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Fig 17. Device protection diagram
15. Safety notes
CAUTION
This device is sensitive to ElectroStatic Discharge (ESD). Observe precautions for handling
electrostatic sensitive devices.
Such precautions are described in the ANSI/ESD S20.20, IEC/ST 61340-5, JESD625-A or
equivalent standards.
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
16. Limiting values
Table 14. Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
Symbol
Parameter
VDD
Conditions
Min
Max
Unit
supply voltage
0.5
+8.0
V
VDD(INTREGD)
internal regulated supply
voltage
0.5
+6.5
V
VI
input voltage
0.5
+6.5
V
ISS
ground supply current
50
+50
mA
ISDA
current on pin SDA
30
+30
mA
II/O(n)
input/output current on any
other pin
10
+10
mA
Ptot
total power dissipation
mW
on all input pins
-
100
HBM
[1]
-
2000
V
CDM
[2]
-
750
V
latch-up current
[3]
-
100
mA
Tstg
storage temperature
[4]
60
+125
C
Tamb
ambient temperature
40
+85
C
VESD
Ilu
electrostatic discharge
voltage
[1]
Pass level; Human Body Model (HBM) according to Ref. 10 “JESD22-A114”.
[2]
Pass level; Charged-Device Model (CDM), according to Ref. 11 “JESD22-C101”.
[3]
Pass level; latch-up testing, according to Ref. 12 “JESD78” at maximum ambient temperature (Tamb(max)).
[4]
According to the store and transport requirements (see Ref. 16 “UM10569”) the devices have to be stored at a temperature of +8 C to
+45 C and a humidity of 25 % to 75 %.
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
17. Static characteristics
Table 15. Static characteristics
VDD = 2.5 V to 5.5 V, VSS = 0 V, Tamb = 40 C to +85 C; unless otherwise specified; min and max values are not production
tested, but verified on sampling basis.
Symbol
Parameter
VDD
supply voltage
VDD(ext)
external supply voltage
VDD(INTREGD)
internal regulated supply
voltage
Conditions
Min
Typ
Max
Unit
2.5
-
5.5
V
VDD connected to
VDD(INTREGD); internal
regulator disabled
2.5
-
3.3
V
2.5
2.9
3.3
V
2.5
-
3.3
V
-
10
20
A
-
100
500
nA
V
[1]
external supplied
IDD
supply current
idle state; fs = 1 kHz
IDD(sleep)
sleep mode supply current
[2]
Digital inputs (CLK_IN, A0, INT_IN, TEST)
VIL
LOW-level input voltage
VSS
-
0.3VDD
VIH
HIGH-level input voltage
0.7VDD
-
VDD
Digital outputs (INT, CLK_OUT)
VOL
LOW-level output voltage
IO = 0.5 mA
VSS
-
0.2VDD
V
VOH
HIGH-level output voltage
IO = 0.5 mA
0.8VDD
-
VDD
V
Analog pins (IN0 to IN7 and CPC0 to CPC7)
VCPC
voltage on pin CPC
usable control range
VSS + 0.5 -
VDD(INTREGD)  0.5 V
Cin
input capacitance
sensing plate and parasitic
10
-
40
pF
0.5
-
0.3VDD
V
I2C
interface pins (SDA, SCL)
VIL
LOW-level input voltage
VIH
HIGH-level input voltage
IOL
LOW-level output current
IL
leakage current
Ci
capacitance for each I/O pin
VDD = 5.0 V; VOL = 0.4 V
[3]
0.7VDD
-
5.5
V
20
-
-
mA
-
0
-
A
-
-
10
pF
22
100
470
nF
-
100
-
nF
External components
CCPC
capacitance on pin CPC
Cdec
decoupling capacitance
[4]
on pins VDD(INTREGD) and
VDD; ceramic chip capacitor
[1]
See Figure 8 for an illustration of the voltage regulation behavior and the related parameters.
[2]
Idle state is the steady state after completed power-on, without any mode change and without any activity on the sensor plates, and the
voltages on the reservoir capacitors CCPC are settled.
[3]
In case of an ESD event, the value may increase slightly.
[4]
The insulation resistance of the capacitor should be at least 5 G.
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
DDD
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fs = 1 kHz.
(1) VDD = 2.5 V.
(2) VDD = 3.3 V.
(3) VDD = 5.5 V.
Fig 18. IDD with respect to temperature
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(1) VDD = 2.5 V.
(2) VDD = 3.3 V.
(3) VDD = 5.5 V.
Fig 19. IDD with respect to sampling frequency (internal clock)
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
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26 of 46
PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
DDD
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(2) VDD = 3.3 V.
(3) VDD = 5.5 V.
Fig 20. IDD with respect to sampling frequency (external clock)
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
18. Dynamic characteristics
Table 16. Dynamic characteristics
VDD = 2.5 V to 5.5 V, VSS = 0 V, Tamb = 40 C to +85 C; unless otherwise specified; min and max values are not production
tested, but verified on sampling basis.
Symbol Parameter
Conditions
Min
Typ
Max
Unit
-
200
-
ms
System timing
tstartup
start-up time
CCPC = 100 nF; fs = 1 kHz;
Cin = 40 pF
fosc
oscillator frequency
internal RC oscillator;
FRQF[2:0] = 100
[1]
58
80
112
kHz
tsw
switching time
fs = 1 kHz
[2]
-
64
-
ms
I2C
interface characteristics (SDA, SCL)
tSP
pulse width of spikes that must be
suppressed by the input filter
0
-
50
ns
fSCL
SCL clock frequency
0
-
1000
kHz
tHD;STA
hold time (repeated) START condition
0.26
-
-
s
tSU;STA
set-up time for a repeated START condition
0.26
-
-
s
tLOW
LOW period of the SCL clock
0.5
-
-
s
tHIGH
HIGH period of the SCL clock
0.26
-
-
s
tHD;DAT
data hold time
0
-
-
ns
tSU;DAT
data set-up time
50
-
-
ns
tr
rise time of both SDA and SCL signals
-
-
120
ns
tf
fall time of both SDA and SCL signals
-
-
120
ns
tSU;STO
set-up time for STOP condition
0.26
-
-
s
tBUF
bus free time between a STOP and START
condition
0.5
-
-
s
Cb
capacitive load for each bus line
-
-
550
pF
tVD;DAT
data valid time
-
-
0.45
s
tVD;ACK
data valid acknowledge time
-
-
0.45
s
-
2
-
s
tw(int)
interrupt pulse width
interrupt over
[1]
Default value.
[2]
For switching, 64 consecutive CUP pulses are needed.
PCA8885
Product data sheet
I2C
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
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(1) VDD = 2.5 V; Ci = 41 pF.
(2) VDD = 3.3 V; Ci = 41 pF.
(3) VDD = 5.5 V; Ci = 41 pF.
(4) VDD = 3.3 V; Ci = 10 pF.
Fig 21. Start-up time with respect to CCPC
18.1 I2C interface timing
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PCA8885
Product data sheet
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PCA8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
19. Application information
19.1 Single device application
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(1) Pin CLK_IN can be tied to VSS or left open.
Fig 23. Single device application diagram
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
19.2 28 sensor grid application in 2-key mode
,1
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Fig 24. Application diagram for 28 sensors in 2-key mode
PCA8885
Product data sheet
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
Table 17.
Sensor
PCA8885
Product data sheet
Input combinations for a 28 sensor grid in 2-key mode
Inputs
IN7
IN6
IN5
IN4
IN3
IN2
IN1
IN0
1
0
0
0
0
0
0
1
1
2
0
0
0
0
0
1
0
1
3
0
0
0
0
1
0
0
1
4
0
0
0
1
0
0
0
1
5
0
0
1
0
0
0
0
1
6
0
1
0
0
0
0
0
1
7
1
0
0
0
0
0
0
1
8
0
0
0
0
0
1
1
0
9
0
0
0
0
1
0
1
0
10
0
0
0
1
0
0
1
0
11
0
0
1
0
0
0
1
0
12
0
1
0
0
0
0
1
0
13
1
0
0
0
0
0
1
0
14
0
0
0
0
1
1
0
0
15
0
0
0
1
0
1
0
0
16
0
0
1
0
0
1
0
0
17
0
1
0
0
0
1
0
0
18
1
0
0
0
0
1
0
0
19
0
0
0
1
1
0
0
0
20
0
0
1
0
1
0
0
0
21
0
1
0
0
1
0
0
0
22
1
0
0
0
1
0
0
0
23
0
0
1
1
0
0
0
0
24
0
1
0
1
0
0
0
0
25
1
0
0
1
0
0
0
0
26
0
1
1
0
0
0
0
0
27
1
0
1
0
0
0
0
0
28
1
1
0
0
0
0
0
0
All information provided in this document is subject to legal disclaimers.
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
19.3 Cascaded application
9''
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(1) If the SLEEP pin is not used, it must be connected to VSS.
(2) Pin CLK_IN can be tied to VSS or left open.
(3) Instead of the INT pin, interrupt over I2C-bus can be used. If the INT pin is not used, it must be left open.
Fig 25. Cascaded application diagram
PCA8885
Product data sheet
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
Figure 25 shows the typical connections for a general application using two chips. For
simplicity, the sensors attached to the secondary-chip are not shown in this diagram. The
sensors of the secondary-chip can be arranged independently of the sensors of the
primary-chip or combined in a common larger matrix.
Both chips use different I2C addresses programmed by the voltage level applied to pin A0.
The primary-chip has A0 connected to ground; the secondary-chip has A0 connected to
VDD(ext). In this way, each circuit is addressed individually.
In this case, the primary-chip is programmed to use the internal oscillator as clock
reference. The primary-chip is also programmed to enable the clock output. The
secondary-chip is programmed to use the clock output from the primary-chip as input
clock. The internal oscillator of the secondary-chip is shut down to save power in this
mode.
The interrupt output INT of the primary-chip is routed to the INT_IN input of the
secondary-chip, where it is OR’ed with the interrupt state of the secondary-chip.
The sensing plate capacitances may consist of a small metal area, for example behind an
isolating layer. Illustrated in Figure 25 is a 4  4 sensor arrangement. In this configuration,
a sensor touch always excites two sensor plates at the same time.
The sensing plates are connected to a coaxial cable (for remote sensors) or a shielded
connection, which in turn is connected to the input pin IN. The connection capacitance
contributes to the input capacitance and must not be neglected. An internal low pass filter
(not shown) is used to reduce RF interference. An additional low pass filter consisting of a
resistor RF and capacitor CF can be added to the input to improve RF immunity further
than required. For good performance, the total amount of capacitance on the input
(Cs + CCABLE + CF) should be in the proper range, the optimum point being around 30 pF.
Even if the external filtering is not required, placing CF can help to bring the input
capacitance to an optimal value. These conditions allow the control loop to adapt to the
static capacitance on CS and to compensate for slow changes in the sensing plate
capacitance. A higher capacitive input loading is possible, if an additional discharge
resistor RC is used. Resistor RC simply reduces the discharge time such that the internal
timing requirements can be fulfilled.
The sensitivity of the sensors can be influenced by the sensing plate area and capacitors
CCPC. The sensitivity is reduced when CCPC is reduced. When maximum sensitivity is
desired, CCPC can be increased, but it also increases sensitivity to interference. The
CPC[0:7] pins have high impedance and are sensitive to leakage currents.
Remark: CCPC should be a high-quality foil or ceramic capacitor, for example an
X7R type.
For the choice of proper component values for a given application, the component
specifications in Section 17 on page 25 must be followed.
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
20. Test information
20.1 Quality information
This product has been qualified in accordance with the Automotive Electronics Council
(AEC) standard Q100 - Failure mechanism based stress test qualification for integrated
circuits, and is suitable for use in automotive applications.
PCA8885
Product data sheet
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
21. Package outline
76623SODVWLFVPDOORXWOLQHSDFNDJHOHDGVERG\ZLGWKPP
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Fig 26. Package outline PCA8885TS (TSSOP28)
PCA8885
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 4 — 13 March 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
36 of 46
PCA8885
NXP Semiconductors
3&
$
7
6
Capacitive 8-channel touch and proximity sensor with auto-calibration
DDD
Fig 27. Three-dimensional package drawing of PCA8885
22. Soldering of SMD packages
This text provides a very brief insight into a complex technology. A more in-depth account
of soldering ICs can be found in Application Note AN10365 “Surface mount reflow
soldering description”.
22.1 Introduction to soldering
Soldering is one of the most common methods through which packages are attached to
Printed Circuit Boards (PCBs), to form electrical circuits. The soldered joint provides both
the mechanical and the electrical connection. There is no single soldering method that is
ideal for all IC packages. Wave soldering is often preferred when through-hole and
Surface Mount Devices (SMDs) are mixed on one printed wiring board; however, it is not
suitable for fine pitch SMDs. Reflow soldering is ideal for the small pitches and high
densities that come with increased miniaturization.
22.2 Wave and reflow soldering
Wave soldering is a joining technology in which the joints are made by solder coming from
a standing wave of liquid solder. The wave soldering process is suitable for the following:
• Through-hole components
• Leaded or leadless SMDs, which are glued to the surface of the printed circuit board
Not all SMDs can be wave soldered. Packages with solder balls, and some leadless
packages which have solder lands underneath the body, cannot be wave soldered. Also,
leaded SMDs with leads having a pitch smaller than ~0.6 mm cannot be wave soldered,
due to an increased probability of bridging.
The reflow soldering process involves applying solder paste to a board, followed by
component placement and exposure to a temperature profile. Leaded packages,
packages with solder balls, and leadless packages are all reflow solderable.
Key characteristics in both wave and reflow soldering are:
•
•
•
•
•
•
PCA8885
Product data sheet
Board specifications, including the board finish, solder masks and vias
Package footprints, including solder thieves and orientation
The moisture sensitivity level of the packages
Package placement
Inspection and repair
Lead-free soldering versus SnPb soldering
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
22.3 Wave soldering
Key characteristics in wave soldering are:
• Process issues, such as application of adhesive and flux, clinching of leads, board
transport, the solder wave parameters, and the time during which components are
exposed to the wave
• Solder bath specifications, including temperature and impurities
22.4 Reflow soldering
Key characteristics in reflow soldering are:
• Lead-free versus SnPb soldering; note that a lead-free reflow process usually leads to
higher minimum peak temperatures (see Figure 28) than a SnPb process, thus
reducing the process window
• Solder paste printing issues including smearing, release, and adjusting the process
window for a mix of large and small components on one board
• Reflow temperature profile; this profile includes preheat, reflow (in which the board is
heated to the peak temperature) and cooling down. It is imperative that the peak
temperature is high enough for the solder to make reliable solder joints (a solder paste
characteristic). In addition, the peak temperature must be low enough that the
packages and/or boards are not damaged. The peak temperature of the package
depends on package thickness and volume and is classified in accordance with
Table 18 and 19
Table 18.
SnPb eutectic process (from J-STD-020D)
Package thickness (mm)
Package reflow temperature (C)
Volume (mm3)
< 350
 350
< 2.5
235
220
 2.5
220
220
Table 19.
Lead-free process (from J-STD-020D)
Package thickness (mm)
Package reflow temperature (C)
Volume (mm3)
< 350
350 to 2000
> 2000
< 1.6
260
260
260
1.6 to 2.5
260
250
245
> 2.5
250
245
245
Moisture sensitivity precautions, as indicated on the packing, must be respected at all
times.
Studies have shown that small packages reach higher temperatures during reflow
soldering, see Figure 28.
PCA8885
Product data sheet
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
maximum peak temperature
= MSL limit, damage level
temperature
minimum peak temperature
= minimum soldering temperature
peak
temperature
time
001aac844
MSL: Moisture Sensitivity Level
Fig 28. Temperature profiles for large and small components
For further information on temperature profiles, refer to Application Note AN10365
“Surface mount reflow soldering description”.
23. Abbreviations
Table 20.
PCA8885
Product data sheet
Abbreviations
Acronym
Description
CMOS
Complementary Metal Oxide Semiconductor
HBM
Human Body Model
IC
Integrated Circuit
MM
Machine Model
MOS
Metal Oxide Semiconductor
MOSFET
Metal–Oxide–Semiconductor Field-Effect Transistor
MSL
Moisture Sensitivity Level
PCB
Printed-Circuit Board
RC
Resistance-Capacitance
RF
Radio Frequency
SMD
Surface Mount Device
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
24. References
[1]
AN10365 — Surface mount reflow soldering description
[2]
AN10832 — PCF8883 - capacitive proximity switch with auto-calibration
[3]
AN10853 — Handling precautions of ESD sensitive devices
[4]
AN11122 — Water and condensation safe touch sensing with the NXP capacitive
touch sensors
[5]
AN11157 — Capacitive touch sensing with high EMC performance, Application Note
[6]
AN11155 — General design guidelines for the NXP capacitive sensors
[7]
IEC 60134 — Rating systems for electronic tubes and valves and analogous
semiconductor devices
[8]
IEC 61340-5 — Protection of electronic devices from electrostatic phenomena
[9]
IPC/JEDEC J-STD-020D — Moisture/Reflow Sensitivity Classification for
Nonhermetic Solid State Surface Mount Devices
[10] JESD22-A114 — Electrostatic Discharge (ESD) Sensitivity Testing Human Body
Model (HBM)
[11] JESD22-C101 — Field-Induced Charged-Device Model Test Method for
Electrostatic-Discharge-Withstand Thresholds of Microelectronic Components
[12] JESD78 — IC Latch-Up Test
[13] JESD625-A — Requirements for Handling Electrostatic-Discharge-Sensitive
(ESDS) Devices
[14] UM10204 — I2C-bus specification and user manual
[15] UM10505 — OM11057 quick start guide
[16] UM10569 — Store and transport requirements
[17] UM10664 — PCA8885 and PCF8885 evaluation board OM11056
[18] UM10720 — User manual for the TFT touch demo board OM11058
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
25. Revision history
Table 21.
Revision history
Document ID
Release date
Data sheet status
Change notice
Supersedes
PCA8885 v.4
20140313
Product data sheet
-
PCA8885 v.3
Modifications:
•
The format of this data sheet has been redesigned to comply with the new identity
guidelines of NXP Semiconductors.
•
•
•
•
•
•
Legal texts have been adapted to the new company name where appropriate.
Emphasized the X7R statement (Section 19.3)
Adjusted Figure 7 and Figure 8
Adjusted Figure 3, Figure 4, Figure 13, Figure 15
Added Table 13
Added Section 15
PCA8885 v.3
20121002
Product data sheet
-
PCA8885 v.2
PCA8885 v.2
20120524
Product data sheet
-
PCA8885 v.1
PCA8885 v.1
20111124
Objective data sheet
-
-
PCA8885
Product data sheet
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PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
26. Legal information
26.1 Data sheet status
Document status[1][2]
Product status[3]
Definition
Objective [short] data sheet
Development
This document contains data from the objective specification for product development.
Preliminary [short] data sheet
Qualification
This document contains data from the preliminary specification.
Product [short] data sheet
Production
This document contains the product specification.
[1]
Please consult the most recently issued document before initiating or completing a design.
[2]
The term ‘short data sheet’ is explained in section “Definitions”.
[3]
The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status
information is available on the Internet at URL http://www.nxp.com.
26.2 Definitions
Draft — The document is a draft version only. The content is still under
internal review and subject to formal approval, which may result in
modifications or additions. NXP Semiconductors does not give any
representations or warranties as to the accuracy or completeness of
information included herein and shall have no liability for the consequences of
use of such information.
Short data sheet — A short data sheet is an extract from a full data sheet
with the same product type number(s) and title. A short data sheet is intended
for quick reference only and should not be relied upon to contain detailed and
full information. For detailed and full information see the relevant full data
sheet, which is available on request via the local NXP Semiconductors sales
office. In case of any inconsistency or conflict with the short data sheet, the
full data sheet shall prevail.
Product specification — The information and data provided in a Product
data sheet shall define the specification of the product as agreed between
NXP Semiconductors and its customer, unless NXP Semiconductors and
customer have explicitly agreed otherwise in writing. In no event however,
shall an agreement be valid in which the NXP Semiconductors product is
deemed to offer functions and qualities beyond those described in the
Product data sheet.
26.3 Disclaimers
Limited warranty and liability — Information in this document is believed to
be accurate and reliable. However, NXP Semiconductors does not give any
representations or warranties, expressed or implied, as to the accuracy or
completeness of such information and shall have no liability for the
consequences of use of such information. NXP Semiconductors takes no
responsibility for the content in this document if provided by an information
source outside of NXP Semiconductors.
In no event shall NXP Semiconductors be liable for any indirect, incidental,
punitive, special or consequential damages (including - without limitation - lost
profits, lost savings, business interruption, costs related to the removal or
replacement of any products or rework charges) whether or not such
damages are based on tort (including negligence), warranty, breach of
contract or any other legal theory.
Notwithstanding any damages that customer might incur for any reason
whatsoever, NXP Semiconductors’ aggregate and cumulative liability towards
customer for the products described herein shall be limited in accordance
with the Terms and conditions of commercial sale of NXP Semiconductors.
Right to make changes — NXP Semiconductors reserves the right to make
changes to information published in this document, including without
limitation specifications and product descriptions, at any time and without
notice. This document supersedes and replaces all information supplied prior
to the publication hereof.
PCA8885
Product data sheet
Suitability for use in automotive applications — This NXP
Semiconductors product has been qualified for use in automotive
applications. Unless otherwise agreed in writing, the product is not designed,
authorized or warranted to be suitable for use in life support, life-critical or
safety-critical systems or equipment, nor in applications where failure or
malfunction of an NXP Semiconductors product can reasonably be expected
to result in personal injury, death or severe property or environmental
damage. NXP Semiconductors and its suppliers accept no liability for
inclusion and/or use of NXP Semiconductors products in such equipment or
applications and therefore such inclusion and/or use is at the customer's own
risk.
Applications — Applications that are described herein for any of these
products are for illustrative purposes only. NXP Semiconductors makes no
representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
Customers are responsible for the design and operation of their applications
and products using NXP Semiconductors products, and NXP Semiconductors
accepts no liability for any assistance with applications or customer product
design. It is customer’s sole responsibility to determine whether the NXP
Semiconductors product is suitable and fit for the customer’s applications and
products planned, as well as for the planned application and use of
customer’s third party customer(s). Customers should provide appropriate
design and operating safeguards to minimize the risks associated with their
applications and products.
NXP Semiconductors does not accept any liability related to any default,
damage, costs or problem which is based on any weakness or default in the
customer’s applications or products, or the application or use by customer’s
third party customer(s). Customer is responsible for doing all necessary
testing for the customer’s applications and products using NXP
Semiconductors products in order to avoid a default of the applications and
the products or of the application or use by customer’s third party
customer(s). NXP does not accept any liability in this respect.
Limiting values — Stress above one or more limiting values (as defined in
the Absolute Maximum Ratings System of IEC 60134) will cause permanent
damage to the device. Limiting values are stress ratings only and (proper)
operation of the device at these or any other conditions above those given in
the Recommended operating conditions section (if present) or the
Characteristics sections of this document is not warranted. Constant or
repeated exposure to limiting values will permanently and irreversibly affect
the quality and reliability of the device.
Terms and conditions of commercial sale — NXP Semiconductors
products are sold subject to the general terms and conditions of commercial
sale, as published at http://www.nxp.com/profile/terms, unless otherwise
agreed in a valid written individual agreement. In case an individual
agreement is concluded only the terms and conditions of the respective
agreement shall apply. NXP Semiconductors hereby expressly objects to
applying the customer’s general terms and conditions with regard to the
purchase of NXP Semiconductors products by customer.
All information provided in this document is subject to legal disclaimers.
Rev. 4 — 13 March 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
42 of 46
PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
No offer to sell or license — Nothing in this document may be interpreted or
construed as an offer to sell products that is open for acceptance or the grant,
conveyance or implication of any license under any copyrights, patents or
other industrial or intellectual property rights.
26.4 Licenses
Export control — This document as well as the item(s) described herein
may be subject to export control regulations. Export might require a prior
authorization from competent authorities.
This NXP Semiconductors IC is made under license to European Patent
No. 0723339, owned by EDISEN - SENSOR SYSTEME GmbH & CO KG
and counterparts. Any license fee is included in the purchase price.
Translations — A non-English (translated) version of a document is for
reference only. The English version shall prevail in case of any discrepancy
between the translated and English versions.
26.5 Trademarks
ICs with capacitive sensing functionality
Notice: All referenced brands, product names, service names and trademarks
are the property of their respective owners.
I2C-bus — logo is a trademark of NXP Semiconductors N.V.
27. Contact information
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
PCA8885
Product data sheet
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Rev. 4 — 13 March 2014
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43 of 46
PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
28. Tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
Table 21.
Ordering information . . . . . . . . . . . . . . . . . . . . .2
Ordering options . . . . . . . . . . . . . . . . . . . . . . . . .2
Marking codes . . . . . . . . . . . . . . . . . . . . . . . . . .2
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . .5
Commands of PCA8885 . . . . . . . . . . . . . . . . . . .8
Register overview . . . . . . . . . . . . . . . . . . . . . .10
CONFIG - configuration register bit
description . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Main operating modes . . . . . . . . . . . . . . . . . . 11
SENS - sensor state register bit description . . .13
CLKREG - clock setting register bit
description . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
MASK - channel enable mask register bit
description . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
I2C slave address byte . . . . . . . . . . . . . . . . . . .19
R/W-bit description . . . . . . . . . . . . . . . . . . . . . .20
Limiting values . . . . . . . . . . . . . . . . . . . . . . . . .24
Static characteristics . . . . . . . . . . . . . . . . . . . .25
Dynamic characteristics . . . . . . . . . . . . . . . . . .28
Input combinations for a 28 sensor grid in
2-key mode . . . . . . . . . . . . . . . . . . . . . . . . . . .32
SnPb eutectic process (from J-STD-020D) . . .38
Lead-free process (from J-STD-020D) . . . . . .38
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . .39
Revision history . . . . . . . . . . . . . . . . . . . . . . . .41
PCA8885
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 4 — 13 March 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
44 of 46
PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
29. Figures
Fig 1.
Fig 2.
Fig 3.
Fig 4.
Fig 5.
Fig 6.
Fig 7.
Fig 8.
Fig 9.
Fig 10.
Fig 11.
Fig 12.
Fig 13.
Fig 14.
Fig 15.
Fig 16.
Fig 17.
Fig 18.
Fig 19.
Fig 20.
Fig 21.
Fig 22.
Fig 23.
Fig 24.
Fig 25.
Fig 26.
Fig 27.
Fig 28.
Block diagram of PCA8885 . . . . . . . . . . . . . . . . . .3
Pin configuration for TSSOP28 (PCA8885TS) . . .4
Timing diagram of sensor sampling . . . . . . . . . . . .6
Functional diagram of sensor operation. . . . . . . . .7
Interrupt over the I2C-bus . . . . . . . . . . . . . . . . . .13
Oscillator block diagram. . . . . . . . . . . . . . . . . . . .15
Connection of VDD(ext) . . . . . . . . . . . . . . . . . . . . .16
Integrated voltage regulator behavior . . . . . . . . .17
Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Definition of START and STOP conditions. . . . . .18
System configuration . . . . . . . . . . . . . . . . . . . . . .18
Acknowledgement on the I2C-bus . . . . . . . . . . . .19
I2C-bus protocol write mode . . . . . . . . . . . . . . . .20
Reading sensor data . . . . . . . . . . . . . . . . . . . . . .20
Continuously reading sensor data . . . . . . . . . . . .21
Reading sensor data, alternately from
primary-chip and secondary-chip. . . . . . . . . . . . .21
Device protection diagram . . . . . . . . . . . . . . . . . .23
IDD with respect to temperature . . . . . . . . . . . . . .26
IDD with respect to sampling frequency
(internal clock) . . . . . . . . . . . . . . . . . . . . . . . . . . .26
IDD with respect to sampling frequency
(external clock) . . . . . . . . . . . . . . . . . . . . . . . . . .27
Start-up time with respect to CCPC . . . . . . . . . . . .29
I2C interface timing . . . . . . . . . . . . . . . . . . . . . . .29
Single device application diagram . . . . . . . . . . . .30
Application diagram for 28 sensors in 2-key
mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Cascaded application diagram . . . . . . . . . . . . . .33
Package outline PCA8885TS (TSSOP28). . . . . .36
Three-dimensional package drawing of
PCA8885 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Temperature profiles for large and small
components . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
PCA8885
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 4 — 13 March 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
45 of 46
PCA8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
30. Contents
1
General description . . . . . . . . . . . . . . . . . . . . . . 1
2
Features and benefits . . . . . . . . . . . . . . . . . . . . 1
3
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4
Ordering information . . . . . . . . . . . . . . . . . . . . . 2
4.1
Ordering options . . . . . . . . . . . . . . . . . . . . . . . . 2
5
Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
6
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 3
7
Pinning information . . . . . . . . . . . . . . . . . . . . . . 4
7.1
Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.2
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 5
8
Functional description . . . . . . . . . . . . . . . . . . . 6
9
Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1
Command overview . . . . . . . . . . . . . . . . . . . . . 8
9.2
Command: soft-reset . . . . . . . . . . . . . . . . . . . . 8
9.3
Commands: Sleep and wake-up . . . . . . . . . . . 8
9.4
Command: read-sensor . . . . . . . . . . . . . . . . . . 9
10
Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1
Register overview . . . . . . . . . . . . . . . . . . . . . . 10
10.2
Register: CONFIG . . . . . . . . . . . . . . . . . . . . . 10
10.2.1
Operating modes . . . . . . . . . . . . . . . . . . . . . . 11
10.2.1.1 Main operating modes . . . . . . . . . . . . . . . . . . 11
10.2.1.2 Switching modes . . . . . . . . . . . . . . . . . . . . . . 11
10.2.1.3 Key-press modes . . . . . . . . . . . . . . . . . . . . . . 12
10.2.2
Interrupt generation . . . . . . . . . . . . . . . . . . . . 12
10.2.2.1 Interrupt output INT . . . . . . . . . . . . . . . . . . . . 12
10.2.2.2 Interrupt over the I2C-bus . . . . . . . . . . . . . . . . 13
10.3
Register: SENS . . . . . . . . . . . . . . . . . . . . . . . 13
10.4
Register: CLKREG . . . . . . . . . . . . . . . . . . . . . 14
10.4.1
Clock generation and frequency adjustment . 14
10.5
Register: MASK . . . . . . . . . . . . . . . . . . . . . . . 15
10.5.1
Channel masking . . . . . . . . . . . . . . . . . . . . . . 15
11
Power architecture . . . . . . . . . . . . . . . . . . . . . 16
12
Start-up procedure. . . . . . . . . . . . . . . . . . . . . . 17
13
Characteristics of the I2C-bus . . . . . . . . . . . . 17
13.1
Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
13.1.1
START and STOP conditions . . . . . . . . . . . . . 18
13.2
System configuration . . . . . . . . . . . . . . . . . . . 18
13.3
Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . 19
13.4
I2C-bus subaddress . . . . . . . . . . . . . . . . . . . . 19
13.5
I2C-bus protocol . . . . . . . . . . . . . . . . . . . . . . . 20
13.6
Fast-mode Plus (Fm+) support . . . . . . . . . . . 20
13.7
Reading sensor data. . . . . . . . . . . . . . . . . . . . 20
13.8
Device cascading . . . . . . . . . . . . . . . . . . . . . . 21
14
Internal circuitry. . . . . . . . . . . . . . . . . . . . . . . . 23
15
Safety notes . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
16
17
18
18.1
19
19.1
19.2
19.3
20
20.1
21
22
22.1
22.2
22.3
22.4
23
24
25
26
26.1
26.2
26.3
26.4
26.5
27
28
29
30
Limiting values . . . . . . . . . . . . . . . . . . . . . . . .
Static characteristics . . . . . . . . . . . . . . . . . . .
Dynamic characteristics. . . . . . . . . . . . . . . . .
I2C interface timing. . . . . . . . . . . . . . . . . . . . .
Application information . . . . . . . . . . . . . . . . .
Single device application . . . . . . . . . . . . . . . .
28 sensor grid application in 2-key mode . . .
Cascaded application. . . . . . . . . . . . . . . . . . .
Test information . . . . . . . . . . . . . . . . . . . . . . .
Quality information . . . . . . . . . . . . . . . . . . . . .
Package outline. . . . . . . . . . . . . . . . . . . . . . . .
Soldering of SMD packages . . . . . . . . . . . . . .
Introduction to soldering. . . . . . . . . . . . . . . . .
Wave and reflow soldering. . . . . . . . . . . . . . .
Wave soldering . . . . . . . . . . . . . . . . . . . . . . .
Reflow soldering . . . . . . . . . . . . . . . . . . . . . .
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . .
References. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Revision history . . . . . . . . . . . . . . . . . . . . . . .
Legal information . . . . . . . . . . . . . . . . . . . . . .
Data sheet status . . . . . . . . . . . . . . . . . . . . . .
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . .
Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . .
Licenses. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . .
Contact information . . . . . . . . . . . . . . . . . . . .
Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24
25
28
29
30
30
31
33
35
35
36
37
37
37
38
38
39
40
41
42
42
42
42
43
43
43
44
45
46
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
© NXP Semiconductors N.V. 2014.
All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
Date of release: 13 March 2014
Document identifier: PCA8885
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