BU9891GUL-W Datasheet, PDF (12/18 Pages) Rohm – WL-CSP EEPROM family Microwire Bus

BU9891GUL-W
Technical Note
○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.
Microcontroller
Rpu
VILM
“L” input
EEPROM
IOLE
VOLE
“L” output
Fig.46 DO pull up resistance
Microcontroller
VIHM
“H” input Rpd
EEPROM
VOHE
IOHE _{“H” output}
Fig.47 DO pull down resistance
Rpu
Vcc－VOLE
≧
IOLE
VOLE ≦ VILM
・・・③
・・・④
Example) When V_CC =5V, VOLE=0.4V, IOLE=2.1mA, VILM=0.8V,
from the equation ③,
5－0.4
Rpu ≧ _2.1×10-3
∴
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 : EEPROM VOL specifications
・IOLE : EEPROM IOL specifications
・VILM : Microcontroller VIL specifications
VOHE
Rpd ≧ _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
5) READY / BUSY status display (DO terminal)
This display outputs the internal status signal. When CS is started after tCS (Min.200ns)
from CS fall after write command input, “H” or “L” is output.
R/B display＝“L” (BUSY) = write under execution
(DO status) After the timer circuit in the IC works and creates the period of tE/W, this time circuit completes automatically.
And write to the memory cell is made in the period of tE/W, and during this period, other command is not
accepted.
R/B display = “H” (READY) = command wait status
(DO status) Even after tE/W (max.5ms) from write of the memory cell, the following command is accepted.
Therefore, CS=“H” in the period of tE/W, and when input is in SK, DI, malfunction may occur, therefore, DI=“L”
in the area
CS=“H”. (Especially, in the case of shared input port, attention is required.)
*Do not input any command while status signal is output. Command input in BUSY area is cancelled, but command input in READY area is accepted.
Therefore, status READY output is cancelled, and malfunction and mistake write may be made.
CS
STATUS
SK
CLOCK
DI
WRITE
INSTRUCTION
DO ^High-Z
tSV
READY
BUSY
Fig.48 R/B status output timing chart
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© 2010 ROHM Co., Ltd. All rights reserved.
12/17
2010.07 - Rev.A