参数资料
| 型号： | BR24T08F-WE2 |
| 厂商： | Rohm Semiconductor |
| 文件页数： | 14/22页 |
| 文件大小： | 0K |
| 描述： | IC EEPROM I2C 8K 400KHZ 8-SOP |
| 标准包装： | 1 |
| 格式 - 存储器： | EEPROMs - 串行 |
| 存储器类型： | EEPROM |
| 存储容量： | 8K (1K x 8) |
| 速度： | 400kHz |
| 接口： | I²C，2 线串口 |
| 电源电压： | 1.7 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 8-SOIC（0.173"，4.40mm 宽） |
| 供应商设备封装： | 8-SOP |
| 包装： | 标准包装 |
| 其它名称： | BR24T08F-WE2DKR |
BR24T □□□□ Series
Technical Note
● I/O peripheral circuit
○ Pull up resistance of SDA terminal
SDA is NMOS open drain, so requires pull up resistance. As for this resistance value (R PU ), select an appropriate value to
this resistance value from microcontroller V IL , I L , and V OL -I OL characteristics of this IC. If R PU is large, action frequency is
limited. The smaller the R PU , the larger the consumption current at action.
○ Maximum value of R PU
The maximum value of R PU is determined by the following factors.
① SDA rise time to be determined by the capacitance (CBUS) of bus line of R PU and SDA should be tR or below.
And AC timing should be satisfied even when SDA rise time is late.
② The bus electric potential A to be determined by input leak total (I L ) of device connected to bus at output of 'H' to
SDA bus and R PU should sufficiently secure the input 'H' level (V IH ) of microcontroller and EEPROM including
recommended noise margin 0.2Vcc.
V CC － I L R PU － 0.2 V CC ≧ V IH
? R PU ?
0 . 8 V CC ? V IH
I L
Microcontroller
BR24TXX
R PU ?
Ex.) VCC =3V IL=10μA VIH=0.7 VCC
from ②
0 . 8 ? 3 ? 0 . 7 ? 3
10 ? 10 ? 6
I L
R PU
A
I L
SDA terminal
? 300 [k Ω ]
Bus line
capacity
CBUS
Fig.52 I/O circuit diagram
○ Minimum value of R PU
The minimum value of R PU is determined by the following factors.
When IC outputs LOW, it should be satisfied that V OLMAX =0.4V and I OLMAX =3mA.
V CC ? V OL
R PU
? I OL
? R PU ?
V CC ? V OL
I OL
② V OLMAX = should secure the input 'L' level (V IL ) of microcontroller and EEPROM
including recommended noise margin 0.1Vcc.
V OLMAX ≦ V IL － 0.1 V CC
Ex.) V CC =3V, V OL =0.4V, I OL =3mA, microcontroller, EEPROM V IL =0.3Vcc
from ① R PU ?
3 ? 0 . 4
3 ? 10 ? 3
And
?
867[ Ω ]
V OL =0.4 ［ V ］
V IL =0.3 × 3
=0.9 ［ V ］
Therefore, the condition ② is satisfied.
○ Pull up resistance of SCL terminal
When SCL control is made at CMOS output port, there is no need, but in the case there is timing where SCL becomes
'Hi-Z', add a pull up resistance. As for the pull up resistance, one of several k Ω ~ several ten k Ω is recommended in
consideration of drive performance of output port of microcontroller.
www.rohm.com
? 2011 ROHM Co., Ltd. All rights reserved.
14/21
2011.03 - Rev.A
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