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BU9833GUL-W_12 Datasheet, PDF (19/28 Pages) Rohm – WLCSP EEPROM | |||
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BU9833GUL-W (2Kbit)
Datasheet
âCautions on microcontroller connection
âRs
In I2C BUS, it is recommended that SDA port is of open drain input / output. However, when to use COMS input / output
of tri state to SDA port, insert a series resistance Rs between the pull up resistance RPU and the SDA terminal of
EEPROM. This controls over protection of SDA terminal against surge. Therefore, even when SDA port is open drain
input / output, Rs can be used.
ACK
RPU
RS
SCL
SDA
âHâ output of
microcontroller
âLâ output of EEPROM
Microcontroller
EEPROM
Figure 45. I/O circuit diagram
Over current flows to SDA line by âHâ output of
microcontroller and âLâ output of EEPROM.
Figure 46. Input / output collision timing
âMaximum 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 at the moment when EEPROM outputs âLâ to SDA bus
should sufficiently secure the input âLâ level (VIL) of microcontroller including recommended noise margin 0.1VCC.
VCC
RPU A
RS
VOL
IOL
Bus line
capacity CBUS
(VCC-VOL)ÃRS
RPU+RS
+ VOL+0.1VCC⦠VIL
â´ RS â¦
VIL-VOL-0.1VCC
1.1VCC-VIL
à RPU
Example) When VCC=3V, VIL=0.3VCC, VOL=0.4V, RPU=20kΩ,
VIL Microcontroller
EEPROM
Figure 47. I/O circuit diagram
From (2)
RS â¦
0.3Ã3-0.4-0.1Ã3
1.1Ã3-0.3Ã3
Ã20Ã103
⦠1.67[kΩ]
âMinimum 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.
RPU
RS
"L" output
"H" output
Over current I
Microcontroller
EEPROM
Figure 48. I/O Circuit diagram
VCC
â¦I
RS
RS ⧠VCC
I
Example) When Vcc =3V, I = 10mA,
3
RS ⧠10Ã10-3
⧠300[Ω]
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TSZ22111ã»15ã»001
19/24
TSZ02201-0R2R0G100450-1-2
04.SEP.2012 Rev.001
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