BR93G76-3A_1 Datasheet, PDF (19/40 Pages) Rohm – MicroWire BUS EEPROM (3-Wire)

BR93G76-3A
Datasheet
2) At standby
When CS is low , even if SK,DI,DO are low,high or with middle electric potential, current does not over I_SB1 Max.
3) I/O peripheral circuit
3-1) Pull down CS.
By making CS=low at power ON/OFF, mistake in operation and mistake write are prevented.
○Pull down resistance Rcs 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 V_OH, I_OH, and V_IL characteristics of this IC.
Microcontroller
VOHM
high output _IOHM
EEPROM
VIHE
Rcs
low input
Figure 44. CS pull down resistance
Rcs ≧
V_OHM
I_OHM
V_OHM ≧ V_IHE
・・・①
・・・②
Example) When VCC =5V, V_IHE=2V, V_OHM=2.4V, I_OHM=2mA,
from the equation ①,
2.4
Rcs ≧ _2×10-3
∴ Rcs ≧ 1.2 [kΩ]
With the value of Rpd to satisfy the above equation, V_OHM becomes
2.4V or higher, and V_IHE (=2.0V), the equation ② is also satisfied.
・V_IHE : EEPROM VIH specifications
・V_OHM : Microcontroller V_OH specifications
・I_OHM : Microcontroller I_OH specifications
3-2) DO is available in both pull up and pull down.
Do output always is High-Z except in READY / BUSY STATUS and data output in read command.
Malfunction may occur when High-Z is input to the microcontroller port connected to DO, it is necessary to pull down
and pull up DO. When there is no influence upon the microcontroller operations, DO may be OPEN.
If DO is OPEN, and at timing to output STATUS READY, at timing of CS=high, SK=high, DI=high, 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 high
SK
DI
D0
High-Z
DO
SK
Enlarged
DI
READY
BUSY
DO _BUSY
DO
BUSY
High-Z
CS=SK=DI=high
When DO=OPEN
Improvement by DO pull up
READY
CS=SK=DI=high
When DO=pull up
Figure 45. READY output timing at DO=OPEN
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TSZ22111・15・001
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TSZ02201-09190G100080-1-2
07.JAN.2013 REV.001