BU9889GUL-W Rohm, BU9889GUL-W Datasheet - Page 14

• Manufacturer Part Number: BU9889GUL-W
• Description: WL-CSP EEPROM family I2C BUS
• Manufacturer: Rohm

●Cautions on microcontroller connection
© 2010 ROHM Co., Ltd. All rights reserved.
BU9889GUL-W
www.rohm.com
○ Rs
○ Maximum value of Rs
(1)SDA rise time to be determined by the capacity (CBUS) of bus line of Rpu and SDA shoulder be tR or below.
(2)The bus electric potential ○
○ Maximum value of Rs
In I
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.
The maximum value of Rs is determined by following relations.
And AC timing should be satisfied even when SDA rise time is late.
should sufficiently secure the input 'L' level (V
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.
2
C BUS, it is recommended that SDA port is of open drain input/output. However, when to use CMOS input / output of
V
IL
Microcontroller
Microcontroller
'H' output
Fig.43 I/O circuit diagram
Microcontroller
Fig.46 I/O circuit diagram
Fig.45 I/O circuit diagram
V
R
CC
PU
Bus line
capacity CBUS
R
R
Over currentⅠ
A
PU
S
R
I
to be determined by Rpu and Rs the moment when EEPROM outputs 'L' to SDA bus
OL
S
R
EEPROM
A
PU
R
S
EEPROM
EEPROM
'L' output
V
OL
IL
) of microcontroller including recommended noise margin 0.1Vcc.
14/17
Example）
from(2),
SCL
SDA
'H' output of microcontroller
When V
(V
∴
∴
CC
Over current flows to SDA line by 'H' output of microcontroller
and 'L' output of EEPROM.
R
R
R
－V
Example）When V
V
R
R
PU
S
S
CC
S
S
CC
+R
OL
Fig.44 Input/output collision timing
≦
≦
≦
=3V, V
≦
≧
)×R
S
0.3×3－0.4－0.1×3
1.67［kΩ］
V
S
V
R
IL
CC
1.1×3－0.3×3
I
I
－V
S
1.1V
IL
+ V
=0.3V
≧
≧ 300［Ω］
OL
CC
－0.1V
CC
OL
－V
'L' output of EEPROM
10×10
ACK
CC,
=3V, I=10mA
+0.1V
IL
3
V
CC
-3
www.DataSheet4U.com
OL
CC
2010.01 - Rev.A
Technical Note
=0.4V, R
≦V
×
×
IL
R
20×10
PU
PU
=20kΩ,
3