BU9891GUL-W Rohm, BU9891GUL-W Datasheet - Page 11

• Manufacturer Part Number: BU9891GUL-W
• Description: WL-CSP EEPROM family Microwire Bus
• Manufacturer: Rohm

© 2010 ROHM Co., Ltd. All rights reserved.
BU9891GUL-W
www.rohm.com
3) Equivalent circuit
4) I/O peripheral circuit
4-1) Pull down CS.
○Pull down resistance Rpd of CS pin
4-2) DO is available in both pull up and pull down.
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.
By making CS=“L” at power ON/OFF, mistake in operation and mistake write are prevented.
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.
Microcontroller
“H” output
Output circuit
Input circuit
DI
VOHM
Fig.44 CS pull down resistance
IOHM
Fig.40 Output circuit (DO)
Fig.42 Input circuit (DI)
CS
SK
DI
DO
High-Z
D0
OEint.
Rpd
CS int.
VIHE
Fig.45 READY output timing at DO=OPEN
“L” input
EEPROM
BUSY
READY
Enlarged
11/17
DO
Example) When V
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
・VOHM
・IOHM
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DO
CS
SK
DI
DO
∴ Rpd ≧ 1.2 [kΩ]
from the equation ①,
Input citcuit
CS
Input circuit
VOHM ≧ VIHE
SK
BUSY
BUSY
“H”
: EEPROM VIH specifications
: Microcontroller VOH specifications
: Microcontroller IOH specifications
Rpd ≧
Rpd ≧
CC
Improvement by DO pull up
=5V, VIHE=2V, VOHM=2.4V, IOHM=2mA,
Fig.41 Input circuit (CS)
Fig.43 Input circuit (SK)
READY
VOHM
IOHM
2×10
High-Z
2.4
-3
RESET int.
When DO=pull up
When DO=OPEN
CS=SK=DI=”H”
CS=SK=DI=”H”
・・・②
・・・①
CS int.
Technical Note
2010.07 - Rev.A
CSint.
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