BU9888FV-W Datasheet, PDF (10/17 Pages) Rohm – High Reliability Serial EEPROMs

BU9888FV-W
Technical Note
4-2) DO is available in both pull up and pull down.
Do output become “High-Z” in other READY / BUSY output timing than after data output at read command and write
command. When malfunction occurs at “High-Z” input of the microcontroller port connected to DO, it is necessary to
pull down and pull up DO. When there is no influence upon the microcontroller actions, DO may be OPEN.
If DO is OPEN, and at timing to output status READY, at timing of CS=“H”, SK=“H”, DI=“H”, EEPROM recognizes this
as a start bit, resets READY output, and DO=”High-Z”, therefore, READY signal cannot be detected. To avoid such
output, pull up DO pin for improvement.
CS
CS _{“H”}
SK
DI
D0
High-Z
DO
SK
Enlarged
DI
READY
BUSY
DO _BUSY
DO _BUSY
High-Z
CS=SK=DI=”H”
When DO=OPEN
Improvement by DO pull up
READY
CS=SK=DI=”H”
When DO=pull up
Fig.38 READY output timing at DO=OPEN
○Pull up resistance Rpu and pull down resistance Rpd of DO pin
As for pull up and pull down resistance value, select an appropriate value to this resistance value from microcontroller
VIH, VIL, and VOH, IOH, VOL, IOL characteristics of this IC.
Rpu ≧
・・・③
Microcontroller
Rpu
VILM
EEPROM
IOLE
VOLE
VOLE ≦ VILM
・・・④
Example) When V_CC =5V, VOLE=0.4V, IOLE=2.1mA, VILM=0.8V,
from the equation ③,
“L” input
Rpu ≧
“L” output
Fig.39 DO pull up resistance
Microcontroller
VIHM
“H” input Rpd
EEPROM
VOHE
IOHE _{“H” output}
Fig.40 DO pull down resistance
∴
Rpu ≧ 2.2 [kΩ]
With the value of Rpu to satisfy the above equation, VOLE becomes 0.4V
or below, and with VILM(=0.8V), the equation ④ is also satisfied.
・VOLE
・IOLE
・VILM
: EEPROM VOL specifications
: EEPROM IOL specifications
: Microcontroller VIL specifications
Rpd ≧ ^VOHE
IOHE
・・・⑤
VOHE ≧ VIHM
・・・⑥
Example) When V_CC =5V, VOHE=Vcc－0.2V, IOHE=0.1mA,
VIHM=Vcc×0.7V from the equation ⑤,
Rpd ≧
5－0.2
0.1×10^-3
∴
Rpd ≧ 48 [kΩ]
With the value of Rpd to satisfy the above equation, VOHE becomes 2.4V
or below, and with VIHM (=3.5V), the equation ⑥ is also satisfied.
・VOHE
・IOHE
・VIHM
: EEPROM VOH specifications
: EEPROM IOH specifications
: Microcontroller VIH specifications
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© 2011 ROHM Co., Ltd. All rights reserved.
10/16
2011.01 - Rev.A