AC Characteristics
Applicable over recommended operating range from TA = -40°C to +85°C, VCC = +1.8V to +5.5V, CL = 100 pF (unless oth-
erwise noted). Test conditions are listed in Note 2.
1.8-volt
2.7-volt
5.0-volt
Symbol
fSCL
Parameter
Min
Max
Min
Max
Min
Max
Units
kHz
µs
Clock Frequency, SCL
Clock Pulse Width Low
Clock Pulse Width High
Clock Low to Data Out Valid
100
400
1000
tLOW
4.7
4.0
0.1
1.3
1.0
0.6
0.4
tHIGH
tAA
µs
4.5
0.05
0.9
0.05
0.55
µs
Time the bus must be free before a new
transmission can start(1)
tBUF
4.7
1.3
0.5
µs
tHD.STA
tSU.STA
tHD.DAT
tSU.DAT
tR
Start Hold Time
4.0
4.7
0
0.6
0.6
0
0.25
0.25
0
µs
µs
µs
ns
µs
ns
µs
ns
ms
Start Set-up Time
Data In Hold Time
Data In Set-up Time
Inputs Rise Time(1)
Inputs Fall Time(1)
Stop Set-up Time
Data Out Hold Time
Write Cycle Time
200
100
100
1.0
0.3
0.3
tF
300
300
100
tSU.STO
tDH
4.7
0.6
50
0.25
50
100
tWR
20
10
10
Write
Cycles
Endurance(1)
5.0V, 25°C, Page Mode
100K
100K
100K
Notes: 1. This parameter is characterized and is not 100% tested.
2. AC measurement conditions:
RL (connects to VCC): 1.3KΩ (2.7V, 5V), 10KΩ (1.8V)
Input pulse voltages: 0.3VCC to 0.7VCC
Input rise and fall times: ≤50ns
Input and output timing reference voltages: 0.5VCC
Device Operation
CLOCK and DATA TRANSITIONS: The SDA pin is nor-
mally pulled high with an external device. Data on the SDA
pin may change only during SCL low time periods (refer to
Data Validity timing diagram). Data changes during SCL
high periods will indicate a start or stop condition as defined
below.
ACKNOWLEDGE: All addresses and data words are seri-
ally transmitted to and from the EEPROM in 8-bit words.
The EEPROM sends a zero during the ninth clock cycle to
acknowledge that it has received each word.
STANDBY MODE: The AT24C128/256 features a low
power standby mode which is enabled: a) upon power-up
and b) after the receipt of the STOP bit and the completion
of any internal operations.
START CONDITION: A high-to-low transition of SDA with
SCL high is a start condition which must precede any other
command (refer to Start and Stop Definition timing dia-
gram).
MEMORY RESET: After an interruption in protocol, power
loss or system reset, any 2-wire part can be reset by follow-
ing these steps: (a) Clock up to 9 cycles, (b) look for SDA
high in each cycle while SCL is high and then (c) create a
start condition as SDA is high.
STOP CONDITION: A low-to-high transition of SDA with
SCL high is a stop condition. After a read sequence, the
stop command will place the EEPROM in a standby power
mode (refer to Start and Stop Definition timing diagram).
AT24C128/256
4
ATMEL [ ATMEL ]
