参数资料
型号: BR24L01A-W
厂商: Rohm Semiconductor
文件页数: 17/41页
文件大小: 0K
描述: IC EEPROM 1KBIT 400KHZ 8DIP
标准包装: 2,000
格式 - 存储器: EEPROMs - 串行
存储器类型: EEPROM
存储容量: 1K (128 x 8)
速度: 400kHz
接口: I²C,2 线串口
电源电压: 1.8 V ~ 5.5 V
工作温度: -40°C ~ 85°C
封装/外壳: 8-DIP(0.300",7.62mm)
供应商设备封装: 8-DIP
包装: 管件
产品目录页面: 1378 (CN2011-ZH PDF)
BR24L □□ -W Series,BR24S □□□ -W 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
Rs
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
should sufficiently secure the input 'L' level (V IL ) of microcontroller including recommended noise margin 0.1Vcc.
V CC
R PU
A
(V CC - V OL )×R S
R PU +R S
+
V OL +0.1V CC ≦ V IL
R S
I OL
V OL
R S
V IL - V OL - 0.1V CC
1.1V CC - V IL
×
R PU
Bus line
capacity CBUS
Example) When V CC =3V, VIL=0.3V CC , V OL =0.4V, R PU =20k ?
V IL
Microcontroller
EEPROM
from(2),
R S
0.3×3 - 0.4 - 0.1×3
1.1×3 - 0.3×3
1.67 [ k ? ]
×
20×10 3
Fig.55 I/O circuit diagram
○ 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
Example)When V CC =3V, I=10mA
10×10
'H' output
Microcontroller
EEPROM
R S
3
-3
300 [ ? ]
Fig.56 I/O circuit diagram
www.rohm.com
? 2009 ROHM Co., Ltd. All rights reserved.
17/40
2009.09 - Rev.D
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