AN431 datasheet(3/15 Pages) STMICROELECTRONICS

部件名	AN431

功能描述	Using ST6 analog inputs for multiple key decoding

PDF	15 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

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3 / 15 page

ANALOG KEYBOARD

3/15

Key Nr

Valid Code

Range

Distance to

next key

18-1A

30-33

49-4E

63-68

7C-81

97-9B

B0-B4

CA-CD

E5-E6

Table 1. Key code ranges

Resistor

Value ( )

-2% ( )

10000

9800

1100

1078

1300

1274

1800

1764

2400

2352

3300

3234

5100

4998

8200

8036

16000

15680

Active Key

R Error Range (LSB)

Distance to next Key

Table 2. Used resistors and Tolerance

4th - 3xVDD/n and for the nth - (n-1)xVDD/n. Re-

sistor values from the tolerance set used

must be selected to meet this requirement.

The recommended resistor values for a

10-key keyboard with 2% resistors from the

E24 series, used with a 10k

Ω pull-up resistor,

are shown in table 2. If more current can be al-

lowed, then a 1k

Ω resistor can be used in

which case the serial resistor values should

be divided by 10.

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