TCA8418E Datasheet, PDF (19/35 Pages) Texas Instruments – I2C CONTROLLED KEYPAD SCAN IC WITH INTEGRATED ESD PROTECTION

TCA8418E
www.ti.com
SCPS222B – MAY 2010 – REVISED SEPTEMBER 2010
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-ms debounce time.
The debounce time for inputs is the time required for the input to be stable to be noticed. This time is 50 ms.
The debounce time for the keypad is for the columns only. The minimum time is 25 ms. All columns are scanned
once every 25 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 25 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.
COL COL COL COL COL COL COL COL COL COL
ROW
X0 X0 X0 X0 X0 X0 X0 X0 X0 X0
ROW
X1 X1 X1 X1 X1 X1 X1 X1 X1 X1
ROW
X2 X2 X2 X2 X2 X2 X2 X2 X2 X2
ROW
X3 X3 X3 X3 X3 X3 X3 X3 X3 X3
ROW
X4 X4 X4 X4 X4 X4 X4 X4 X4 X4
ROW
X5 X5 X5 X5 X5 X5 X5 X5 X5 X5
ROW
X6 X6 X6 X6 X6 X6 X6 X6 X6 X6
ROW
X7 X7 X7 X7 X7 X7 X7 X7 X7 X7
Copyright © 2010, Texas Instruments Incorporated
Product Folder Link(s): TCA8418E
Submit Documentation Feedback
19