PCF8885TS [NXP]
IC SPECIALTY ANALOG CIRCUIT, Analog IC:Other;
| 型号： | PCF8885TS |
| 厂家： | 
NXP |
| 描述： | IC SPECIALTY ANALOG CIRCUIT, Analog IC:Other 光电二极管 |
| 文件： | 总45页 (文件大小：364K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
PCF8885
Capacitive 8-channel touch and proximity sensor with
auto-calibration and very low power consumption
Rev. 3 — 17 March 2014
Product data sheet
1. General description
The integrated circuit PCF8885 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
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)
Available in TSSOP28 and SOIC28 package
1. The definition of the abbreviations and acronyms used in this data sheet can be found in Section 22 on page 38.
PCF8885
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
Sliders and wheel-switches
Vandal proof switches
Switches in or under the upholstery, leather, handles, mats, carpets, tiles and glass
Switches for home automation
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
Name
Description
Version
PCF8885TS
TSSOP28
plastic small outline package; 28 leads;
body width 4.4 mm
PCF8885TS
4.1 Ordering options
Table 2.
Ordering options
Product type number Orderable part number Sales item
(12NC)
Delivery form
IC
revision
PCF8885TS/1
PCF8885TS/1,118
935296171118 tape and reel, 13 inch
1
5. Marking
Table 3.
Marking codes
Type number
PCF8885TS/1
Marking code
PCF8885TS
PCF8885
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© NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet
Rev. 3 — 17 March 2014
2 of 45
PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
6. Block diagram
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Fig 1. Block diagram of PCF8885
PCF8885
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Product data sheet
Rev. 3 — 17 March 2014
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PCF8885
NXP Semiconductors
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 35.
Fig 2. Pin configuration for TSSOP28 (PCF8885TS)
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
PCF8885TS
CLK_OUT
1
output
supply
clock output for chip cascading and
synchronization
[1]
VDD(INTREGD)
IN7 to IN0
2
internal regulated supply reference voltage
sensor input, channel 0 to 7[2]
3 to 10
analog
input/output
CPC7 to CPC0
11 to 18
analog
reservoir capacitor, channel 0 to 7[2]
input/output
VSS
19[3]
20
supply
input
ground supply voltage
serial clock line
SCL
SDA
TEST
21
input/output
input
serial data line
22
test pin;
must be connected to VSS
I2C subaddress LSB[4]
sleep mode;
A0
23
24
input
input
SLEEP
connect to VDD to force the circuit into
low-power sleep mode
INT
25
output
interrupt output
PCF8885
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© NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet
Rev. 3 — 17 March 2014
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
Table 4.
Pin description …continued
Input or input/output pins must always be at a defined level (VSS or VDD) unless otherwise specified.
Symbol
Pin
Type
Description
PCF8885TS
VDD
26
27
supply
input
supply voltage
INT_IN
interrupt input for chip cascading;
connect to VDD if not used
clock input;
CLK_IN
28
input
for the secondary chip when the primary
chip provides the clock signal
[1] The internal regulated supply voltage output must be decoupled with a decoupling capacitor to VSS
.
[2] If a channel is not used, the apropriate 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.
PCF8885
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© NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet
Rev. 3 — 17 March 2014
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PCF8885
NXP Semiconductors
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 PCF8885.
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.
PCF8885
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Product data sheet
Rev. 3 — 17 March 2014
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PCF8885
NXP Semiconductors
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.
PCF8885
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© NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet
Rev. 3 — 17 March 2014
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
9. Commands
The operation of the PCF8885 can be controlled by 12 commands and four configuration-
and 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 PCF8885
Command Operation Description
code
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 command Section 10.2.2.1
INT
sleep
00000101 enter sleep mode
00000110 enter active mode
command
command
Section 9.3
wake-up
write-config 00110000 write configuration register
read-config 00110011 read configuration register
write-clock 00110101 write clock setting register
write 1 byte Section 10.2
read 1 byte
write 1 byte Section 10.4
read 1 byte
read-clock 00110110
write-mask 00111001
read-mask 00111010
int-over-I2C 00111100
read-sensor -
read clock setting register
write the mask register
write 1 byte Section 10.5
read 1 byte
read the mask register
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
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.
PCF8885
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Product data sheet
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PCF8885
NXP Semiconductors
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 20) is set logic 1
the PCF8885 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 21.
PCF8885
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Product data sheet
Rev. 3 — 17 March 2014
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
10. Registers
The PCF8885 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
7
Default
value
6
5
4
3
2
1
0
CONFIG
SENS
OPM[1:0]
CH[7:0]
SWM
KM[1:0]
VROF INTM MSKMODE 00000000
00000000
CLKREG
MASK
CLO
CLI
x
FRQC[1:0]
FRQF[2:0]
00x01100
11111111
MSK[7:0]
10.2 Register: CONFIG
Table 7.
Bit
CONFIG - configuration register bit description
Symbol
Value
Description
Reference
7 to 6 OPM[1:0]
main operation mode
stand-alone device
Section 10.2.1.1
00[1]
01
secondary-chip in a
cascade
10
11
primary-chip in a cascade
unused
5
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
4 to 3 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
10
11
2-key mode:
only first two keys are
visible in the SENS register
1-key mode:
only first key-press is visible
in the SENS register
unused
PCF8885
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Product data sheet
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
Table 7.
CONFIG - configuration register bit description …continued
Bit
Symbol
Value
Description
Reference
2
VROF
voltage regulation
voltage regulation on
voltage regulation off
interrupt generation mode
Section 11
0[1]
1
1
INTM
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)
0
MSKMODE
channel masking mode
Section 10.5.1
0[1]
normal power:
masked out channels
remain operational
1
low power:
masked out channels are
powered down
[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 PCF8885 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
Conditions of
Main operating modes
Primary-chip
internal oscillator
enabled
Stand-alone[1]
internal oscillator
enabled
Secondary-chip
clock input
disabled
clock source
oscillator
clock output pin CLK_OUT
clock input pin CLK_IN
disabled
enabled
disabled
disabled
disabled
enabled
[1] Default operating mode after power-on.
The operating modes are implemented to support the application of two PCF8885 in the
system (see Section 13.8 on page 22).
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:
PCF8885
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Product data sheet
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PCF8885
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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 PCF8885 is set to direct switching mode.
10.2.1.3 Key-press modes
There are three key-press modes implemented in the PCF8885: 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 PCF8885, 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 PCF8885, 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 PCF8885 provides two mechanisms to inform the system controller that a sensor
activity has been detected.
10.2.2.1 Interrupt output INT
The PCF8885 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).
PCF8885
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Product data sheet
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PCF8885
NXP Semiconductors
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 PCF8885 provides the feature of interrupt over the I2C-bus. The PCF8885 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
SENS - sensor state register bit description
Symbol Value Description
00000000[1] to sensor state of the respective channels IN7 to
11111111 IN0
7 to 0 CH[7:0]
[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
Value
Description
7
CLO
CLK_OUT switch
0[1]
1
CLK_OUT disabled (unless IC is in
primary-chip mode)
CLK_OUT enabled
CLK_IN switch
6
CLI
0[1]
1
CLK_IN disabled (unless IC is in
secondary-chip mode)
CLK_IN enabled, internal oscillator is
powered down
[2]
5
-
-
unused
4 to 3 FRQC[1:0]
clock frequency, coarse setting
00
fclk = fosc 64
fclk = fosc 16
fclk = fosc 4
01[1]
10
11
fclk = fosc
2 to 0 FRQF[2:0]
oscillator tuning
fosc = 0.5 foscnom
000
001
010
011
100[1]
101
110
111
fosc = 0.625 foscnom
fosc = 0.75 foscnom
fosc = 0.875 foscnom
fosc = 1 foscnom
fosc = 1.25 foscnom
fosc = 1.5 foscnom
fosc = 1.75 foscnom
[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 PCF8885 contains an integrated oscillator as main clock source. With the values of
FRQF[2:0], the oscillator frequency can be tuned (see Equation 1).
fosc = m foscnom
(1)
PCF8885
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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:
fclk = fosc 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:
fs = fclk 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 PCF8885 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
0
1
sensor channel is disabled
sensor channel is enabled
[1] 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).
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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.
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Capacitive 8-channel touch and proximity sensor with auto-calibration
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.
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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 PCF8885. 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.
PCF8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
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 PCF8885 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 PCF8885 is Fast-mode
compatible and provides a robust addressing and command scheme.
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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Fig 9. 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).
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Capacitive 8-channel touch and proximity sensor with auto-calibration
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
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.
PCF8885
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PCF8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
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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 PCF8885 (see Table 12).
Table 12. I2C slave address byte
Bit
Slave address
7
6
5
4
3
2
1
0
MSB
LSB
Slave address
0
1
0
0
0
0
A0
R/W
The least significant bit of the slave address is bit R/W (see Table 13).
Table 13. R/W-bit description
R/W
0
Description
write data
read data
1
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 PCF8885 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
PCF8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
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. 15 “UM10204”.
13.7 Reading sensor data
The PCF8885 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 PCF8885 repeatedly sends the content of SENS again. This provides a facility to
observe the sensor activity continuously. This transaction is illustrated in Figure 15.
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Fig 15. Continuously reading sensor data
Using two PCF8885 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.
PCF8885
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PCF8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
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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 PCF8885 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 PCF8885 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 PCF8885 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.
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 PCF8885
circuits.
PCF8885
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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.
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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
Conditions
Min
0.5
0.5
0.5
50
30
10
-
Max
+8.0
+6.5
+6.5
+50
Unit
V
VDD
supply voltage
VDD(INTREGD) internal regulated supply voltage
V
VI
input voltage
on all input pins
V
ISS
ground supply current
current on pin SDA
mA
mA
mA
mW
V
ISDA
II/O(n)
Ptot
VESD
+30
input/output current on any other pin
total power dissipation
electrostatic discharge voltage
+10
100
[1]
[2]
[3]
[4]
HBM
CDM
-
2000
750
100
-
V
Ilu
latch-up current
-
mA
C
C
Tstg
Tamb
storage temperature
ambient temperature
60
40
+125
+85
operating device
[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. 17 “UM10569”) the devices have to be stored at a temperature of +8 C to
+45 C and a humidity of 25 % to 75 %.
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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
VDD
Parameter
Conditions
Min
2.5
2.5
Typ
Max
5.5
Unit
V
supply voltage
-
-
VDD(ext)
external supply voltage
VDD connected to
VDD(INTREGD); internal
regulator disabled
3.3
V
[1]
[2]
VDD(INTREGD) internal regulated supply
voltage
2.5
2.5
-
2.9
-
3.3
3.3
20
V
external supplied
V
IDD
supply current
idle state; fs = 1 kHz
10
100
A
nA
IDD(sleep)
sleep mode supply current
-
500
Digital inputs (CLK_IN, A0, INT_IN, TEST)
VIL
VIH
LOW-level input voltage
HIGH-level input voltage
VSS
-
-
0.3VDD
VDD
V
V
0.7VDD
Digital outputs (INT, CLK_OUT)
VOL
VOH
LOW-level output voltage
HIGH-level output voltage
IO = 0.5 mA
IO = 0.5 mA
VSS
-
-
0.2VDD
VDD
V
V
0.8VDD
Analog pins (IN0 to IN7 and CPC0 to CPC7)
VCPC
voltage on pin CPC
input capacitance
usable control range
VSS + 0.5 -
VDD(INTREGD) 0.5 V
Cin
sensing plate and parasitic
10
-
40
pF
I2C interface pins (SDA, SCL)
VIL
VIH
IOL
IL
LOW-level input voltage
0.5
-
0.3VDD
V
HIGH-level input voltage
LOW-level output current
leakage current
0.7VDD
-
5.5
-
V
VDD = 5.0 V; VOL = 0.4 V
20
-
-
mA
A
pF
[3]
[4]
0
-
-
Ci
capacitance for each I/O pin
-
10
External components
CCPC
Cdec
capacitance on pin CPC
decoupling capacitance
22
-
100
100
470
-
nF
nF
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.
PCF8885
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Product data sheet
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PCF8885
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Capacitive 8-channel touch and proximity sensor with auto-calibration
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fs = 1 kHz.
VDD = 2.5 V.
(1)
(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) DD = 3.3 V.
(3) VDD = 5.5 V.
V
Fig 19. IDD with respect to sampling frequency (internal clock)
PCF8885
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
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VDD = 5.5 V.
Fig 20. IDD with respect to sampling frequency (external clock)
PCF8885
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Product data sheet
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PCF8885
NXP Semiconductors
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
System timing
tstartup
start-up time
CCPC = 100 nF; fs = 1 kHz;
Cin = 40 pF
-
200
80
-
ms
kHz
ms
[1]
[2]
fosc
oscillator frequency
internal RC oscillator;
FRQF[2:0] = 100
58
-
112
-
tsw
switching time
fs = 1 kHz
64
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
s
s
s
s
ns
ns
ns
ns
s
s
tHD;STA hold time (repeated) START condition
0.26
0.26
0.5
0.26
0
-
tSU;STA
tLOW
set-up time for a repeated START condition
LOW period of the SCL clock
-
-
tHIGH
HIGH period of the SCL clock
-
tHD;DAT data hold time
tSU;DAT data set-up time
-
50
-
tr
tf
rise time of both SDA and SCL signals
fall time of both SDA and SCL signals
-
120
-
120
tSU;STO set-up time for STOP condition
0.26
0.5
-
-
tBUF
bus free time between a STOP and START
condition
Cb
capacitive load for each bus line
-
-
-
-
-
550
0.45
0.45
-
pF
s
s
s
tVD;DAT data valid time
-
tVD;ACK data valid acknowledge time
-
tw(int)
interrupt pulse width
interrupt over I2C
2
[1] Default value.
[2] For switching, 64 consecutive CUP pulses are needed.
PCF8885
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
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(2) VDD = 3.3 V; Ci = 41 pF.
(3)
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(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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PCF8885
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29 of 45
PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
19. Application information
19.1 Single device application
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Fig 23. Single device application diagram
PCF8885
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
19.2 28 sensor grid application in 2-key mode
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Fig 24. Application diagram for 28 sensors in 2-key mode
PCF8885
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Product data sheet
Rev. 3 — 17 March 2014
31 of 45
PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
Table 17. Input combinations for a 28 sensor grid in 2-key mode
Sensor
Inputs
IN7
0
0
0
0
0
0
1
0
0
0
0
0
1
0
0
0
0
1
0
0
0
1
0
0
1
0
1
1
IN6
0
0
0
0
0
1
0
0
0
0
0
1
0
0
0
0
1
0
0
0
1
0
0
1
0
1
0
1
IN5
0
0
0
0
1
0
0
0
0
0
1
0
0
0
0
1
0
0
0
1
0
0
1
0
0
1
1
0
IN4
0
0
0
1
0
0
0
0
0
1
0
0
0
0
1
0
0
0
1
0
0
0
1
1
1
0
0
0
IN3
0
0
1
0
0
0
0
0
1
0
0
0
0
1
0
0
0
0
1
1
1
1
0
0
0
0
0
0
IN2
0
1
0
0
0
0
0
1
0
0
0
0
0
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
IN1
1
0
0
0
0
0
0
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
IN0
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
PCF8885
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Product data sheet
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32 of 45
PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
19.3 Cascaded application
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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
PCF8885
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Product data sheet
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PCF8885
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
V
DD(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.
PCF8885
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Product data sheet
Rev. 3 — 17 March 2014
34 of 45
PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
20. Package outline
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PCF8885
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Product data sheet
Rev. 3 — 17 March 2014
35 of 45
PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
21. 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”.
21.1 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.
21.2 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:
• 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
21.3 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
PCF8885
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Product data sheet
Rev. 3 — 17 March 2014
36 of 45
PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
21.4 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 27) 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
235
350
220
< 2.5
2.5
220
220
Table 19. Lead-free process (from J-STD-020D)
Package thickness (mm) Package reflow temperature (C)
Volume (mm3)
< 350
260
350 to 2000
> 2000
260
< 1.6
260
250
245
1.6 to 2.5
> 2.5
260
245
250
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 27.
PCF8885
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Product data sheet
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PCF8885
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 27. Temperature profiles for large and small components
For further information on temperature profiles, refer to Application Note AN10365
“Surface mount reflow soldering description”.
22. Abbreviations
Table 20. Abbreviations
Acronym
CMOS
HBM
IC
Description
Complementary Metal Oxide Semiconductor
Human Body Model
Integrated Circuit
MM
Machine Model
MOS
MOSFET
MSL
Metal Oxide Semiconductor
Metal–Oxide–Semiconductor Field-Effect Transistor
Moisture Sensitivity Level
Printed-Circuit Board
PCB
RC
Resistance-Capacitance
Radio Frequency
RF
SMD
Surface Mount Device
PCF8885
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Product data sheet
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
23. 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] SNV-FA-01-02 — Marking Formats Integrated Circuits
[15] UM10204 — I2C-bus specification and user manual
[16] UM10505 — OM11057 quick start guide
[17] UM10569 — Store and transport requirements
[18] UM10664 — PCA8885 and PCF8885 evaluation board OM11056
[19] UM10720 — User manual for the TFT touch demo board OM11058
PCF8885
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Product data sheet
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
24. Revision history
Table 21. Revision history
Document ID
PCF8885 v.3
Modifications:
Release date
20140317
Data sheet status
Change notice
Supersedes
Product data sheet
-
PCF8885 v.2
• 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
• Changed product and ordering information Section 4
• Adjusted Figure 3, Figure 4, Figure 13, Figure 15
• Added Table 13
• Added Section 15
PCF8885 v.2
PCF8885 v.1
20121025
Product data sheet
-
-
PCF8885 v.1
-
20120221
Product data sheet
PCF8885
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Product data sheet
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
25. Legal information
25.1 Data sheet status
Document status[1][2]
Product status[3]
Development
Definition
Objective [short] data sheet
This document contains data from the objective specification for product development.
This document contains data from the preliminary specification.
This document contains the product specification.
Preliminary [short] data sheet Qualification
Product [short] data sheet Production
[1]
[2]
[3]
Please consult the most recently issued document before initiating or completing a design.
The term ‘short data sheet’ is explained in section “Definitions”.
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.
Suitability for use — NXP Semiconductors products are not designed,
25.2 Definitions
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.
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.
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.
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.
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.
25.3 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.
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.
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.
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.
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.
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.
PCF8885
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Product data sheet
Rev. 3 — 17 March 2014
41 of 45
PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
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.
whenever customer uses the product for automotive applications beyond
NXP Semiconductors’ specifications such use shall be solely at customer’s
own risk, and (c) customer fully indemnifies NXP Semiconductors for any
liability, damages or failed product claims resulting from customer design and
use of the product for automotive applications beyond NXP Semiconductors’
standard warranty and NXP Semiconductors’ product specifications.
Quick reference data — The Quick reference data is an extract of the
product data given in the Limiting values and Characteristics sections of this
document, and as such is not complete, exhaustive or legally binding.
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.
Non-automotive qualified products — Unless this data sheet expressly
states that this specific NXP Semiconductors product is automotive qualified,
the product is not suitable for automotive use. It is neither qualified nor tested
in accordance with automotive testing or application requirements. NXP
Semiconductors accepts no liability for inclusion and/or use of
25.4 Trademarks
non-automotive qualified products in automotive equipment or applications.
In the event that customer uses the product for design-in and use in
automotive applications to automotive specifications and standards, customer
(a) shall use the product without NXP Semiconductors’ warranty of the
product for such automotive applications, use and specifications, and (b)
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.
26. Contact information
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: salesaddresses@nxp.com
PCF8885
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Product data sheet
Rev. 3 — 17 March 2014
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
27. Tables
Table 1. Ordering information . . . . . . . . . . . . . . . . . . . . .2
Table 2. Ordering options. . . . . . . . . . . . . . . . . . . . . . . . .2
Table 3. Marking codes . . . . . . . . . . . . . . . . . . . . . . . . . .2
Table 4. Pin description . . . . . . . . . . . . . . . . . . . . . . . . . .4
Table 5. Commands of PCF8885. . . . . . . . . . . . . . . . . . .8
Table 6. Register overview . . . . . . . . . . . . . . . . . . . . . .10
Table 7. CONFIG - configuration register
bit description . . . . . . . . . . . . . . . . . . . . . . . . .10
Table 8. Main operating modes . . . . . . . . . . . . . . . . . .11
Table 9. SENS - sensor state register
bit description . . . . . . . . . . . . . . . . . . . . . . . . . .13
Table 10. CLKREG - clock setting register
bit description . . . . . . . . . . . . . . . . . . . . . . . . .14
Table 11. MASK - channel enable mask register
bit description . . . . . . . . . . . . . . . . . . . . . . . . .15
Table 12. I2C slave address byte . . . . . . . . . . . . . . . . . . .20
Table 13. R/W-bit description . . . . . . . . . . . . . . . . . . . . . .20
Table 14. Limiting values . . . . . . . . . . . . . . . . . . . . . . . . .24
Table 15. Static characteristics . . . . . . . . . . . . . . . . . . . .25
Table 16. Dynamic characteristics . . . . . . . . . . . . . . . . . .28
Table 17. Input combinations for a 28 sensor
grid in 2-key mode . . . . . . . . . . . . . . . . . . . . . .32
Table 18. SnPb eutectic process (from J-STD-020D) . . .37
Table 19. Lead-free process (from J-STD-020D) . . . . . .37
Table 20. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . .38
Table 21. Revision history . . . . . . . . . . . . . . . . . . . . . . . .40
PCF8885
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Product data sheet
Rev. 3 — 17 March 2014
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PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
28. Figures
Fig 1. Block diagram of PCF8885 . . . . . . . . . . . . . . . . . .3
Fig 2. Pin configuration for TSSOP28 (PCF8885TS). . . .4
Fig 3. Timing diagram of sensor sampling. . . . . . . . . . . .6
Fig 4. Functional diagram of sensor operation. . . . . . . . .7
Fig 5. Interrupt over the I2C-bus . . . . . . . . . . . . . . . . . .13
Fig 6. Oscillator block diagram. . . . . . . . . . . . . . . . . . . .15
Fig 7. Connection of VDD(ext) . . . . . . . . . . . . . . . . . . . . .17
Fig 8. Integrated voltage regulator behavior . . . . . . . . .17
Fig 9. Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Fig 10. Definition of START and STOP conditions. . . . . .19
Fig 11. System configuration . . . . . . . . . . . . . . . . . . . . . .19
Fig 12. Acknowledgement on the I2C-bus . . . . . . . . . . . .20
Fig 13. I2C-bus protocol write mode . . . . . . . . . . . . . . . .20
Fig 14. Reading sensor data . . . . . . . . . . . . . . . . . . . . . .21
Fig 15. Continuously reading sensor data . . . . . . . . . . . .21
Fig 16. Reading sensor data, alternately from
primary-chip and secondary-chip. . . . . . . . . . . . .22
Fig 17. Device protection diagram. . . . . . . . . . . . . . . . . .23
Fig 18. IDD with respect to temperature . . . . . . . . . . . . . .26
Fig 19. IDD with respect to sampling frequency
(internal clock) . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Fig 20. IDD with respect to sampling frequency
(external clock) . . . . . . . . . . . . . . . . . . . . . . . . . .27
Fig 21. Start-up time with respect to CCPC . . . . . . . . . . . .29
Fig 22. I2C interface timing . . . . . . . . . . . . . . . . . . . . . . .29
Fig 23. Single device application diagram . . . . . . . . . . . .30
Fig 24. Application diagram for 28 sensors
in 2-key mode . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Fig 25. Cascaded application diagram . . . . . . . . . . . . . .33
Fig 26. Package outline PCF8885TS (TSSOP28). . . . . .35
Fig 27. Temperature profiles for large and small
components . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
PCF8885
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Product data sheet
Rev. 3 — 17 March 2014
44 of 45
PCF8885
NXP Semiconductors
Capacitive 8-channel touch and proximity sensor with auto-calibration
29. Contents
1
General description. . . . . . . . . . . . . . . . . . . . . . 1
16
Limiting values . . . . . . . . . . . . . . . . . . . . . . . . 24
Static characteristics . . . . . . . . . . . . . . . . . . . 25
Dynamic characteristics. . . . . . . . . . . . . . . . . 28
I2C interface timing. . . . . . . . . . . . . . . . . . . . . 29
2
Features and benefits . . . . . . . . . . . . . . . . . . . . 1
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Ordering information. . . . . . . . . . . . . . . . . . . . . 2
Ordering options. . . . . . . . . . . . . . . . . . . . . . . . 2
Marking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 3
17
3
18
18.1
4
4.1
5
19
Application information . . . . . . . . . . . . . . . . . 30
Single device application . . . . . . . . . . . . . . . . 30
28 sensor grid application in 2-key mode . . . 31
Cascaded application. . . . . . . . . . . . . . . . . . . 33
19.1
19.2
19.3
6
7
7.1
7.2
Pinning information. . . . . . . . . . . . . . . . . . . . . . 4
Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 4
20
Package outline. . . . . . . . . . . . . . . . . . . . . . . . 35
21
Soldering of SMD packages. . . . . . . . . . . . . . 36
Introduction to soldering. . . . . . . . . . . . . . . . . 36
Wave and reflow soldering. . . . . . . . . . . . . . . 36
Wave soldering . . . . . . . . . . . . . . . . . . . . . . . 36
Reflow soldering . . . . . . . . . . . . . . . . . . . . . . 37
21.1
21.2
21.3
21.4
8
Functional description . . . . . . . . . . . . . . . . . . . 6
9
Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Command overview . . . . . . . . . . . . . . . . . . . . . 8
Command: soft-reset . . . . . . . . . . . . . . . . . . . . 8
Commands: Sleep and wake-up . . . . . . . . . . . 8
Command: read-sensor . . . . . . . . . . . . . . . . . . 9
9.1
9.2
9.3
9.4
22
23
24
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . 38
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Revision history . . . . . . . . . . . . . . . . . . . . . . . 40
10
Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Register overview. . . . . . . . . . . . . . . . . . . . . . 10
Register: CONFIG . . . . . . . . . . . . . . . . . . . . . 10
Operating modes . . . . . . . . . . . . . . . . . . . . . . 11
25
Legal information . . . . . . . . . . . . . . . . . . . . . . 41
Data sheet status . . . . . . . . . . . . . . . . . . . . . . 41
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . 42
10.1
10.2
10.2.1
25.1
25.2
25.3
25.4
10.2.1.1 Main operating modes . . . . . . . . . . . . . . . . . . 11
10.2.1.2 Switching modes . . . . . . . . . . . . . . . . . . . . . . 11
10.2.1.3 Key-press modes . . . . . . . . . . . . . . . . . . . . . . 12
26
27
28
29
Contact information . . . . . . . . . . . . . . . . . . . . 42
Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
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
10.4
10.4.1
10.5
Register: SENS . . . . . . . . . . . . . . . . . . . . . . . 13
Register: CLKREG . . . . . . . . . . . . . . . . . . . . . 14
Clock generation and frequency adjustment . 14
Register: MASK . . . . . . . . . . . . . . . . . . . . . . . 15
Channel masking . . . . . . . . . . . . . . . . . . . . . . 15
10.5.1
11
12
Power architecture . . . . . . . . . . . . . . . . . . . . . 17
Start-up procedure. . . . . . . . . . . . . . . . . . . . . . 18
13
Characteristics of the I2C-bus . . . . . . . . . . . . 18
Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
START and STOP conditions . . . . . . . . . . . . . 18
System configuration . . . . . . . . . . . . . . . . . . . 19
Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . 19
I2C-bus subaddress . . . . . . . . . . . . . . . . . . . . 20
I2C-bus protocol . . . . . . . . . . . . . . . . . . . . . . . 20
Fast-mode Plus (Fm+) support . . . . . . . . . . . 21
Reading sensor data. . . . . . . . . . . . . . . . . . . . 21
Device cascading . . . . . . . . . . . . . . . . . . . . . . 22
13.1
13.1.1
13.2
13.3
13.4
13.5
13.6
13.7
13.8
14
15
Internal circuitry. . . . . . . . . . . . . . . . . . . . . . . . 23
Safety notes . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
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: salesaddresses@nxp.com
Date of release: 17 March 2014
Document identifier: PCF8885
相关型号：
PCF8885TS/1,118
PCF8885 - Capacitive 8-channel touch and proximity sensor with auto-calibration and very low power consumption
NXP
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