Datasheet

4−8
4.4.6 Characteristics of the SDA and SCL I/O Stages for F/S-Mode I
2
C-Bus Devices,
(1)
PARAMETER
STANDARD MODE FAST MODE
UNITS
PARAMETER
MIN MAX MIN MAX
UNITS
f
SCL
SCL clock frequency 0 100 0 400 kHz
t
HD-STA
Hold time (repeated) START condition. After this period, the
first clock pulse is generated.
4 0.6 µs
t
LOW
LOW period of the SCL clock 4.7 1.3 µs
t
HIGH
HIGH period of the SCL clock 4 0.6 µs
t
SU-STA
Setup time for repeated START 4.7 0.6 µs
t
SU-DAT
Data setup time 250 100 µs
t
HD-DAT
Data hold time
(2)(3)
0 3.45 0 0.9 µs
t
r
Rise time of both SDA and SCL signals 1000 20 + 0.1 C
b
(4)
300 ns
t
f
Fall time of both SDA and SCL signals 300 20 + 0.1 C
b
(4)
300 ns
t
SU-STO
Setup time for STOP condition 4 0.6 µs
t
BUF
Bus free time between a STOP and START condition 4.7 1.3 µs
C
B
Capacitive load for each bus line 400 400 pF
V
nL
Noise margin at the LOW level for each connected device
(including hysteresis)
0.1 V
DD
0.1 V
DD
V
V
nH
Noise margin at the HIGH level for each connected device
(including hysteresis)
0.2 V
DD
0.2 V
DD
V
NOTES: 1. All values referred to V
IHmin
and V
ILmax
levels (see Section 4.4.5).
NOTES: 2. Note that SDA does not have the standard I
2
C specification 300-ns internal hold time. SDA must be valid by the rising and falling
edges of SCL. TI recommends that a minimum 2-kΩ pullup resistor be used to avoid potential timing issues.
NOTES: 3. A fast-mode I
2
C-bus device can be used in a standard-mode I
2
C-bus system, but the requirement t
SU-DAT
≥ 250 ns must then be
met. This is automatically 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 t
r max
+ t
SU-DAT
= 1000 + 250 = 1250 ns (according
to the standard-mode I
2
C-bus specification) before the SCL line is released.
NOTES: 4. C
b
= total capacitance of one bus line in pF.
SDA
SCL
t
f
t
SU-DAT
t
HD-STA
t
r
t
BUF
t
SU-STO
P
S
t
SP
t
SU-STA
Sr
t
HIGH
t
HD-DAT
t
LOW
t
r
t
HD-STA
S
t
f
Figure 4−5. I
2
C Start and Stop Conditions Timing Waveforms