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BU9891GUL-W Datasheet, PDF (14/18 Pages) Rohm – WL-CSP EEPROM family Microwire Bus | |||
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BU9891GUL-W
Technical Note
âSelection of resistance value R
The resistance R becomes through current limit resistance at data collision. When through current flows, noises of
power source line and instantaneous stop of power source may occur. When allowable through current is defined as I,
the following relation should be satisfied. Determine allowable current amount in consideration of impedance and so
forth of power source line in set. And insert resistance R, and set the value R to satisfy EEPROM input level VIH/VIL
even under influence of voltage decline owing to leak current and so forth. Insertion of R will not cause any influence
upon basic operations.
(1) Address data A0 = â1â input, dummy bit â0â output timing
(When microcontroller DI/O output is âHâ, EEPROM DO outputs âLâ, and âHâ is input to DI)
ã»Make the through current to EEPROM 10mA or below.
ã»See to it that the level VIH of EEPROM should satisfy the following.
Conditions
Microcontroller
EEPROM
DI/O PORT
DI
âHâ output
VOHM
IOHM
R
DO
VOLE
âLâ output
VOHM ⦠VIHE
VOHM ⦠IOHMÃR + VOLE
At this moment, if VOLE=0V,
VOHM ⦠IOHMÃR
â´
Râ§
VOHM
IOHM
ã»ã»ã»â¦
ã»VIHE : EEPROM VIH specifications
ã»VOLE : EEPROM VOL specifications
ã»VOHM : Microcontroller VOH specifications
ã»IOHM : Microcontroller IOH specifications
Fig.53 Circuit at DI, DO direct connection (Microcontroller DI/O âHâ output, EEPROM âLâ output)
(2) DO status READY output timing
(When the microcontroller DI/O is âLâ, EEPROM DO output âHâ, and âLâ is input to DI)
ã»Set the EEPROM input level VIL so as to satisfy the following.
Microcontroller
âLâ output DI/O PORT
VOLM
EEPROM
DI
IOHM
R
DO
VOHE
âHâ output
Conditions
VOLM ⧠VILE
VOLM ⧠VOHE â IOLMÃR
As this moment, VOHE=Vcc
VOLM ⧠Vcc â IOLMÃR
Vcc â VOLM
â´
IOLM
ã»ã»ã»â§
ã»VILE
ã»VOHE
ã»VOLM
ã»IOLM
: EEPROM VIL specifications
: EEPROM VOH specifications
: Microcontroller VOL specifications
: Microcontroller IOL specifications
Example) When Vcc=5V, VOHM=5V, IOHM=0.4mA, VOLM=5V, IOLM=0.4mA,
From the equation â¦,
R ⧠VOHM
IOHM
Râ§
5
0.4Ã10-3
From the equationâ§,
R ⧠Vcc â VOLM
IOLM
R ⧠5 â 0.4
2.1Ã10-3
â´
R ⧠12.5 [kâ¦] ã»ã»ã»â¨
â´
R ⧠2.2 [kâ¦] ã»ã»ã»â©
Therefore, from the equations ⨠and â©,
â´
R ⧠12.5 [kâ¦]
Fig.54 Circuit at DI, DO direct connection (Microcontroller DI/O âLâ output, EEPROM âHâ output)
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14/17
2010.07 - Rev.A
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