BU9888FV-W Datasheet, PDF (9/17 Pages) Rohm – High Reliability Serial EEPROMs

BU9888FV-W
3) Equivalent circuit
Output circuit
DO
OEint.
Fig.33 Output circuit (DO)
Input circuit
SK
DI
CS int.
Technical Note
Input circuit
CS
RESET int.
CSint.
Fig.34 Input circuit (CS)
Input circuit
VDD
TEST1
Fig.35 Input circuit (SK,DI)
Fig.36 Input circuit (TEST1)
4) I/O peripheral circuit
4-1) Pull down CS.
By making CS=“L” at power ON/OFF, mistake in operation and mistake write are prevented.
○Pull down resistance Rpd of CS pin
To prevent mistake in operation and mistake write at power ON/OFF, CS pull down resistance is necessary.
Select an appropriate value to this resistance value from microcontroller VOH, IOH, and VIL characteristics of this IC.
Microcontroller
VOHM
EEPROM
VIHE
“H” output _IOHM
Rpd
“L” input
Fig.37 CS pull down resistance
Rpd ≧
VOHM ≧
VOHM
IOHM
VIHE
・・・①
・・・②
Example) When V_CC =5V, VIHE=2V, VOHM=2.4V, IOHM=2mA,
from the equation ①,
Rpd ≧
2.4
2×10^-3
∴ Rpd ≧ 1.2 [kΩ]
With the value of Rpd to satisfy the above equation, VOHM becomes
2.4V or higher, and VIHE (=2.0V), the equation ② is also satisfied.
・VIHE : EEPROM VIH specifications
・VOHM : Microcontroller VOH specifications
・IOHM : Microcontroller IOH specifications
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9/16
2011.01 - Rev.A