BR24G32-3A ROHM [Rohm], BR24G32-3A Datasheet - Page 21

• Manufacturer Part Number: BR24G32-3A
• Description: High Reliability Serial EEPROMs I2C BUS BR24xxxxfamily
• Manufacturer: ROHM [Rohm]

●Cautions on microcontroller connection
○RS
www.rohm.co
© 2012 ROHM Co., Ltd. All rights reserved.
BR24G32-3A
TSZ22111・15・001
○Maximum value of Rs
○Minimum 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.
①SDA rise time to be determined by the capacity (CBUS) of bus line of Rpu and SDA should be tR or below.
②The bus electric potential A to be determined by Rpu and Rs the moment when EEPROM outputs 'L' to SDA bus
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.
The maximum value of Rs is determined by the following relations.
sufficiently secure the input 'L' level (V
2
And AC timing should be satisfied even when SDA rise time is late.
C BUS, it is recommended that SDA port is of open drain input/output. However, when to use CMOS input / output of
V
'H' output
IL
Microcontroller
Micro controller
Fig.49 I/O circuit diagram
Microcontroller
Fig.46 I/O circuit diagram
Fig.48 I/O Circuit Diagram
V
Over current I
CC
Bus line
capacity
CBUS
R
R
PU
PU
R
R
R
I
PU
OL
S
S
R
A
S
EEPROM
'L'output
EEPROM
EEPROM
V
IL
OL
) of microcontroller including recommended noise margin 0.1Vcc.
'H' output of microcontroller
SCL
SDA
21/34
Ex.）V
CC
=3V V
∴
Fig.47 Input / output collision timing
(V
∴
CC－
Over current flows to SDA line by 'H'
output of microcontroller and 'L'
output of EEPROM.
IL
R
R
R
=0.3V
PU
Ex.) VCC=3V, I=10mA
S
S
V
R
R
V
CC
+R
S
S
OL
≦
≦
≦ 1.67［kΩ］
)×R
S
CC
≦
≧
'L' output of EEPROM
0.3×3－0.4－0.1×3
V
ACK
S
V
TSZ02201-0R2R0G100050 -1-2
V
IL－
R
1.1×3－0.3×3
OL
CC
I
I
1.1V
S
=0.4V R
V
+ V
OL－
≧
≧ 300［Ω］
CC
0.1V
-V
OL
15.May.2012 REV.001
10×10
IL
+0.1V
PU
CC
3
=20kΩ
-3
CC
× R
×
Datasheet
Datasheet
≦V
IL
20×10
PU
3