TCA8418E_15 Datasheet, PDF (7/50 Pages) Texas Instruments – I2C Controlled Keypad Scan IC With Integrated ESD Protection

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TCA8418E
SCPS222C – MAY 2010 – REVISED OCTOBER 2015
6.7 Reset Timing Requirements for Standard Mode, Fast Mode, Fast Mode Plus (FM+) I²C Bus
over recommended operating free-air temperature range (unless otherwise noted) (see Figure 19)
t_W
t_REC
t_RESET
Reset pulse duration
Reset recovery time
Time to reset
MIN
120 ⁽¹⁾
120 ⁽¹⁾
120 ⁽¹⁾
MAX
UNIT
μs
μs
μs
(1) The GPIO debounce circuit uses each GPIO input which passes through a two-stage register circuit. Both registers are clocked by the
same clock signal, presumably free-running, with a nominal period of 50 μs. When an input changes state, the new state is clocked into
the first stage on one clock transition. On the next same-direction transition, if the input state is still the same as the previously clocked
state, the signal is clocked into the second stage, and then on to the remaining circuits. Since the inputs are asynchronous to the clock,
it will take anywhere from zero to 50 μs after the input transition to clock the signal into the first stage. Therefore, the total debounce
time may be as long as 100 μs. Finally, to account for a slow clock, the spec further guard-banded at 120 μs.
6.8 Switching Characteristics for Standard Mode, Fast Mode, Fast Mode Plus (FM+) I²C Bus
PARAMETER
Key event or Key
unlock or Overflow
t_IV
Interrupt valid time
GPI_INT with
Debounce_DIS_Low
GPI_INT with
Debounce_DIS_High
CAD_INT
t_IR
Interrupt reset delay time
t_PV
Output data valid
t_PS
Input data setup time
t_PH
Input data hold time
FROM
TO
ROW0–7,
INT
COL0–9
SCL
SCL
SCL
P port
P port
INT, CAD_INT
INT
CAD_INT
ROW0–7,
COL0–9
SCL
SCL
MIN
MAX UNIT
20
60
40
120
μs
10
30
20
60
200 ns
400 ns
0
ns
300
ns
6.9 Keypad Switching Characteristics for Standard Mode, Fast Mode, Fast Mode Plus (FM+) I²C
Bus
PARAMETER
Key press to detection delay
Key release to detection delay
Keypad unlock timer
Keypad interrupt mask timer
Debounce
MIN
MAX
UNIT
25
μs
25
μs
7
s
31
s
60
ms
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