参数资料
| 型号： | BR24T08F-WE2 |
| 厂商： | Rohm Semiconductor |
| 文件页数： | 15/22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
In I C BUS, it is recommended that SDA port is of open drain input/output. However, when to use CMOS input / output of
● Cautions on microcontroller connection
R S
2
tri state to SDA port, insert a series resistance Rs between the pull up resistance Rpu and the SDA terminal of EEPROM.
This is controls over current that occurs when PMOS of the microcontroller and NMOS of EEPROM are turned ON
simultaneously. Rs also plays the role of protection of SDA terminal against surge. Therefore, even when SDA port is
open drain input/output, Rs can be used.
ACK
SCL
R PU
R S
SDA
'H' output of microcontroller
'L' output of EEPROM
Microcontroller
EEPROM
Over current flows to SDA line by 'H'
output of microcontroller and 'L'
output of EEPROM.
Fig.53 I/O circuit diagram
Fig.54 Input / output collision timing
○ Maximum value of Rs
The maximum value of Rs is determined by the following relations.
① SDA rise time to be determined by the capacity (CBUS) of bus line of Rpu 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 Rpu and Rs the moment when EEPROM outputs 'L' to SDA bus
sufficiently secure the input 'L' level (V IL ) of microcontroller including recommended noise margin 0.1Vcc.
V CC
? V CC ? V OL ? ? V OL ? 0 . 1 V CC ? V IL
R PU ? R S
R PU
R S
A
V OL
? R S ?
? V CC ? V OL ? ? R PU
1 . 1 V CC ? V IL
I OL
Bus line
Ex) V CC =3V
V IL =0.3V CC V OL =0.4V R PU =20k Ω
V IL
capacity
CBUS
Micro controller
EEPROM
R S ?
0 . 3 ? 3 ? 0 . 4 ? 0 . 1 ? 3
1 . 1 ? 3 ? 0 . 3 ? 3
? 20 ? 10 3
Fig.55 I/O Circuit Diagram
? 1 . 67 [ k Ω ]
○ Minimum value of Rs
The minimum value of Rs is determined by over current at bus collision. When over current flows, noises in power source
line, and instantaneous power failure of power source may occur. When allowable over current is defined as I, the
following relation must be satisfied. Determine the allowable current in consideration of impedance of power source line
in set and so forth. Set the over current to EEPROM 10mA or below.
R PU
R S
'L'output
V CC
R S
? R S ?
? I
V CC
I
Over current I
EX) V CC =3V I=1mA
'H' output
R S ?
3
10 ? 10 ? 3
Microcontroller
EEPROM
Fig.56 I/O circuit diagram
? 300 [ Ω ]
www.rohm.com
? 2011 ROHM Co., Ltd. All rights reserved.
15/21
2011.03 - Rev.A
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