Datasheet

275
ATmega48PA/88PA/168PA [DATASHEET]
9223F–AVR–04/14
29.7 Two-wire Serial Interface Characteristics
Table 29-8 describes the requirements for devices connected to the 2-wire serial bus. The Atmel
®
ATmega48PA/88PA/168PA 2-wire serial interface meets or exceeds these requirements under the noted conditions. Timing
symbols refer to Figure 29-5.
Table 29-8. Two-wire Serial Bus Requirements
Parameter Condition Symbol Min. Max Unit
Input low-voltage V
IL
-0.3 0.3 V
CC
V
Input high-voltage V
IH
0.7 V
CC
V
CC
+ 0.5 V
Hysteresis of Schmitt trigger inputs V
hys
(1)
0.05 V
CC
(2)
– V
Output low-voltage 3mA sink current V
OL
(1)
0 0.4 V
Rise time for both SDA and SCL t
r
(1)
20 + 0.1C
b
(3)(2)
300 ns
Output fall time from V
IHmin
to V
ILmax
10pF < C
b
< 400pF
(3)
t
of
(1)
20 + 0.1C
b
(3)(2)
250 ns
Spikes suppressed by input filter t
SP
(1)
0 50
(2)
ns
Input current each I/O pin 0.1V
CC
< V
i
< 0.9V
CC
I
i
-10 10 µA
Capacitance for each I/O pin C
i
(1)
– 10 pF
SCL clock frequency f
CK
(4)
> max(16f
SCL
, 250kHz)
(5)
f
SCL
0 400 kHz
Value of pull-up resistor
f
SCL
≤ 100kHz Rp
f
SCL
> 100kHz Rp
Hold time (repeated) START condition
f
SCL
≤ 100kHz t
HD;STA
4.0 – µs
f
SCL
> 100kHz t
HD;STA
0.6 – µs
Low period of the SCL clock
f
SCL
≤ 100kHz t
LOW
4.7 – µs
f
SCL
> 100kHz t
LOW
1.3 – µs
High period of the SCL clock
f
SCL
≤ 100kHz t
HIGH
4.0 – µs
f
SCL
> 100kHz t
HIGH
0.6 – µs
Set-up time for a repeated START
condition
f
SCL
≤ 100kHz t
SU;STA
4.7 – µs
f
SCL
> 100kHz t
SU;STA
0.6 – µs
Data hold time
f
SCL
≤ 100kHz t
HD;DAT
0 3.45 µs
f
SCL
> 100kHz t
HD;DAT
0 0.9 µs
Data setup time
f
SCL
≤ 100kHz t
SU;DAT
250 – ns
f
SCL
> 100kHz t
SU;DAT
100 – ns
Setup time for STOP condition
f
SCL
≤ 100kHz t
SU;STO
4.0 – µs
f
SCL
> 100kHz t
SU;STO
0.6 – µs
Bus free time between a STOP and START
condition
f
SCL
≤ 100kHz t
BUF
4.7 – µs
f
SCL
> 100kHz t
BUF
1.3 – µs
Notes: 1. In the Atmel ATmega48PA/88PA/168PA, this parameter is characterized and not 100% tested.
2. Required only for f
SCL
> 100kHz.
3. C
b
= capacitance of one bus line in pF.
4. f
CK
= CPU clock frequency
5. This requirement applies to all Atmel ATmega48PA/88PA/168PA 2-wire serial interface operation. Other devices con-
nected to the 2-wire serial bus need only obey the general f
SCL
requirement.
V
CC
0,4V–
3mA
----------------------------
1000ns
C
b
-----------------

V
CC
0,4V–
3mA
----------------------------
300ns
C
b
--------------
