BS801C データシートの表示（PDF） - Holtek Semiconductor

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BS801C

(BS801C - BS808C) Touch Key

Holtek Semiconductor 

A.C. Characteristics

Symbol

Parameter

fSCD

SCD Clock

fKRT

Key Response Time

tKH

Maximum Key Hold Time

tCAL

Auto-Calibration Period

BS801C/02C/04C/06C/08C

Test Conditions

VDD

Conditions

3V

¾

3V

¾

3V

¾

3V

¾

Ta=25°C

Min. Typ. Max. Unit

10.4

13.0

15.6

kHz

75

100

125

ms

30

40

50

s

1.8

2.5

3.2

s

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

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