TCA8418 Datasheet, PDF (19/37 Pages) Texas Instruments – I2C CONTROLLED KEYPAD SCAN IC WITH INTEGRATED ESD PROTECTION

TCA8418
www.ti.com ......................................................................................................................................................................................... SCPS215 – SEPTEMBER 2009
ADDRESS REGISTER NAME⁽¹⁾
REGISTER DESCRIPTION
0×2B
DEBOUNCE_DIS 3
Debounce disable
0: enabled
1: disabled
(1) Only KEY_EVENT_A register is shown
7
6
5
debounce time bits
BIT
4
3
N/A N/A
0
0
2
1
0
N/A
0
C9DD
0
C8D
D
0
DEBOUNCE ENABLED
GPI with INTE
INT
50 ms
VALID HIGH TRIGGER INTERRUPT
50 ms
VALID LOW TRIGGER INTERRUPT
DEBOUNCE ENABLED
GPI with INTE
INT
VALID HIGH TRIGGER INTERRUPT
VALID LOW TRIGGER INTERRUPT
Debounce disable will have the same effect for GPI mode or for rows in keypad scanning mode. The reset line
always has a 50-µs debounce time.
The debounce time for inputs is the time required for the input to be stable to be noticed. This time is 50 µs.
The debounce time for the keypad is for the columns only. The minimum time is 20 ms. All columns are scanned
once every 20 ms to detect any key presses. Two full scans are required to see if any keys were pressed. If the
first scan is done just after a key press, it will take 20 ms to detect the key press. If the first scan is down much
later than the key press, it will take 40 ms to detect a key press.
GPIO Pull Disable Register, GPIO_PULL1–3 (Address 0×2C–0×2E)
This register enables or disables pullup registers from inputs.
Typical Application
Figure 8 shows an application in which the TCA8418E can be used.
placeholder
Figure 8. Typical Application
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): TCA8418
Submit Documentation Feedback
19