Table 5-18 I2C Timing Requirements(1)
|
STANDARD MODE |
FAST MODE |
UNIT |
MIN |
MAX |
MIN |
MAX |
tc(SCL) |
Cycle time, SCL |
10 |
|
2.5 |
|
μs |
tsu(SCLH-SDAL) |
Setup time, SCL high before SDA low
(for a repeated START condition) |
4.7 |
|
0.6 |
|
μs |
th(SCLL-SDAL) |
Hold time, SCL low after SDA low
(for a START and a repeated START condition) |
4 |
|
0.6 |
|
μs |
tw(SCLL) |
Pulse duration, SCL low |
4.7 |
|
1.3 |
|
μs |
tw(SCLH) |
Pulse duration, SCL high |
4 |
|
0.6 |
|
μs |
tsu(SDA-SCLH) |
Setup time, SDA valid before SCL high |
250 |
|
100 |
|
μs |
th(SCLL-SDA) |
Hold time, SDA valid after SCL low |
0 |
3.45(1) |
0 |
0.9 |
μs |
tw(SDAH) |
Pulse duration, SDA high between STOP and START conditions |
4.7 |
|
1.3 |
|
μs |
tsu(SCLH-SDAH) |
Setup time, SCL high before SDA high
(for STOP condition) |
4 |
|
0.6 |
|
μs |
tw(SP) |
Pulse duration, spike (must be suppressed) |
|
|
0 |
50 |
ns |
Cb(2)(3) |
Capacitive load for each bus line |
|
400 |
|
400 |
pF |
(1) The I2C pins SDA and SCL do not feature fail-safe I/O buffers. These pins could potentially draw current when the device is powered down.
(2) The maximum th(SDA-SCLL) for I2C bus devices has only to be met if the device does not stretch the low period (tw(SCLL)) of the SCL signal.
(3) Cb = total capacitance of one bus line in pF. If mixed with fast-mode devices, faster fall-times are allowed.
NOTE
- A device must internally provide a hold time of at least 300 ns for the SDA signal (referred to the VIHmin of the SCL signal) to bridge the undefined region of the falling edge of SCL.
- The maximum th(SDA-SCLL) has only to be met if the device does not stretch the LOW period (tw(SCLL)) of the SCL signal. E.A Fast-mode I2C-bus device can be used in a Standard-mode I2C-bus system, but the requirement tsu(SDA-SCLH) ≥ 250 ns must then be met. This will automatically be the case if the device does not stretch the LOW period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must output the next data bit to the SDA line tr max + tsu(SDA-SCLH).