BS801C/02C/04C/06C/08C
A.C. Characteristics
Test Conditions
Symbol
f
SCD
f
KRT
t
KH
t
CAL
Parameter
V
DD
SCD Clock
Key Response Time
Maximum Key Hold Time
Auto-Calibration Period
3V
3V
3V
3V
Conditions
¾
¾
¾
¾
10.4
75
30
1.8
13.0
100
40
2.5
15.6
125
50
3.2
kHz
ms
s
s
Min.
Typ.
Max.
Unit
Ta=25°C
Functional Description
Introduction
This range of BS80xC touch key devices offer an easy
and reliable means of implementing touch switch func-
tions in a range of applications. A single external capaci-
tor is the only external component required for most
applications while a single line serial bus offers conve-
nient communication with an external MCU.
Device Operation State
There are two operating states known as the One-key
State and the Any-key State. Devices with an OKW pin,
namely the BS804C, BS806C and BS808C, can oper-
ate in either the One-key State or the Any-key State.
When these devices are powered up, the condition of
the OKW pin will be automatically read. If the OKW pin is
low then the device will enter the Any-key State and if
the pin is floating the device will enter the One-key
State. As the BS801C and BS802C devices do not have
an OKW pin they will always operate in the Any-key
State.
In the Any-key State, as the name suggests all of the
Keyn touch inputs will be active, however in the One-key
State only Key0 will be active. After power up if the
BS804C, BS806C and BS808C device enters the
One-key State then touching any Key other than Key0
will have no effect. If a touch action is however detected
on Key0, then the device will enter the Any-key State
and operate normally with all keys active. However,
within a timer period of around 20 seconds, if no touch
actions are detected on any Key input, then the device
will revert to the One-key State.
The advantage of choosing the One-key State over the
Any-key State is that it will result in lower power con-
sumption as only one key remains active. The logic sta-
tus of the OKW pin is only read when the device powers
up and will determine the operating state of the device
after power-on. For the BS804C and BS808C devices,
this power-on state can be overridden later by sending
the appropriate command to the device on its SCD pin.
The logic level on the OKW pin must not be changed af-
ter power on. Internal circuitry ensures that the internal
pull-high resistor on the OKW pin will not consume cur-
rent after power-on.
Part No.
BS804C
BS806C
BS808C
OKW Open
One-key
State
OKW Low
Any-key
State
The logic status of the OKW pin is read when the device
powers up. The logic level on this pin must not be
changed after power on. Internal circuitry ensures that
the internal pull-high resistor on the OKW pin will not
consume current.
Part No.
BS804C
BS806C
BS808C
Any-key On Time in
One-key State
Approx 20 secs
Rev. 1.00
5
December 2, 2009
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
