CBM7
C
7021
Capa ve Tou S
acitiv
uch Senso Controller
or o
Datasheet
D
Chipsbank Microe
electronic Co., L
cs
Ltd.
No 701 7/F, Building No. 12,
o.
1
Ke Central Ro 2, Softwa Park
eji
oad
are
Hig Tech Indu
gh
ustrial Park, Shenzhen, P
P.R.China, 518057
(07
755)8616969
90
Em
mail:
info@ch
hipsbank.com
m
UR
http://ww
RL:
ww.chipsbank
k.com
Specification Revision History：
Doc.Version
V0.1
V0.2
V0.3
V0.4
V0.5
V0.6
Date
2011-11-02
2011-11-08
2011-12-6
2012-2-13
2012-3-5
2012-3-8
Revision Description
Preliminary version
Updated product application
Updated package type
Updated package type
Updated package type
Updated register list
Updated Package outline
Author
Touch Sensor Group
Touch Sensor Group
Touch Sensor Group
Touch Sensor Group
Touch Sensor Group
Touch Sensor Group
Contents
1.
2.
Introduction ............................................................................. 3
fundamental............................................................................. 3
2.1.1. Self Capacitance ................................................................................................ 4
2.1.2. Mutual Capacitance ........................................................................................... 4
2.1.
Capacitive Sensing Methods ..................................................................... 3
2.2.
Self-Capacitance Equivalent Model ......................................................... 4
2.3.
Capacitance Conversion............................................................................ 5
3.
4.
Features ................................................................................... 6
Packaging ................................................................................ 7
4.1.
Package type ............................................................................................. 7
4.2.
PIN Description ........................................................................................ 7
5.
6.
Communication Interface ........................................................ 8
Timing Description ............................................................... 12
5.1.
I2C Slave Interface ................................................................................... 9
6.1.
Power-on Reset ....................................................................................... 12
6.2.
IDLE MODE Timing .............................................................................. 12
7.
8.
Register List .......................................................................... 13
Electrical Characteristics ....................................................... 14
8.1.
Absolute Maximum Ratings ................................................................... 14
8.2.
DC Electrical Characteristics .................................................................. 14
8.3.
AC Electrical Characteristics .................................................................. 14
8.4.
Timing Specification ............................................................................... 14
8.5.
EMI/EMC Specification ......................................................................... 15
9.
Package Outline .................................................................... 16
2
CBM7021 Datasheet
2
1. Introduction
CBM7021 is low-cost single chip solution for capacitive touch sensor controller. The chip is mainly
used for mechanical buttons replacement in home appliances, consumer electronics, industrial areas.
With robust sensing technology, it has high performance across a variety materials and thickness, high
noise immunity, waterproof and dustproof.
CBM7021 is 8-bit RISC architecture microcontroller devices with I2C Host/Slave, UART interface.
For function application, CBM7021 support Button information for customers. In operation mode, it
can support protocol and I/O mode for customer. Developer can use I/O mode to get a valid button
message and develop their system very easily, and no longer need to decode the communication
package.
The capacitive touch sensor can be designed by placing a copper pad on the PCB directly, covered
with a plastic or glass case. It provides auto-calibrate the parameter for a wide range of capacitance on
the touch sensor(1pF ~ 40pF). The system controller converts finger data to button presses, depending
on finger location and human interface context.
CBM7021 robust sense solutions leverage our flexible programmable system-on-chip architecture,
which accelerate time-to-market, integrates critical system functions and reduced BOM costs.
CBM7021 supports multi-package for various application.
2. fundamental
Chipsbank Sensor Controller use changes in capacitance to detect the presence of a finger or near a
touch surface, as shown in Figure 2-1. This capacitive sensor example illustrates a touch sensor
replacement for a mechanical button.
Figure 2-1. Illustration of a Capacitance Sensor Application
2.1. Capacitive Sensing Methods
Capacitance can be measured between two points using either self capacitance or mutual
capacitance.
3
CBM7021 Datasheet
3
Self Capacitance
Mutual Capacitance
Figure 2-1-1. Self-Capacitance and Mutual-Capacitance Methods
2.1.1. Self Capacitance
Self capacitance uses a single pin and measures the capacitance between that pin and ground. A
self-capacitance sensing system operates by driving current on a pin connected to a sensor and
measuring the voltage. When a finger is placed on the sensor it increases the measured capacitance.
The self-capacitance effect is best suited for single-touch sensors, such as buttons and sliders.
Chipsbank Sensor solutions use self-capacitance sensing.
2.1.2. Mutual Capacitance
Mutual capacitance uses a pair of pins and measures the capacitance between those pins. A
mutual-capacitance system operates by driving a current on a transmit pin and measuring the charge
on a receive pin. When a finger is placed between the transmit and receive pins it decreases the
measured capacitance. The mutual-capacitance effect is best suited to multitouch systems, such as
touch screens.
2.2. Self-Capacitance Equivalent Model
In CBM7021 self-capacitance system, the sensor capacitance measured by the controller is named C
X
.
Figure 2-2-1 shows field lines only around the sensor pad, the actual electric field is more complicated.
When a finger is not on the sensor, C
X
equals the parasitic capacitance of the system. This parasitic
capacitance, C
P
, is a simplification of the distributed capacitance that includes the effects of the sensor
pad, the overlay, the trace between the Sensor Controller pin and the sensor pad, the vias through the
circuit board, and the pin capacitance of the Sensor Controller. C
P
is related to the electric field around
the sensor pad. Although Figure 2-2-1 shows field lines only around the sensor pad, the actual electric
field is more complicated.
Figure. 2-2-1. C
P
and Electric Field
4
CBM7021 Datasheet
4
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