BR93G66-3 Datasheet, PDF (22/40 Pages) Rohm – MicroWire BUS EEPROM (3-Wire)

BR93G66-3
Datasheet
Selection of Resistance Value R
The resistance R becomes a short-circuit current limiting resistance during signal conflicts and it does not affect the
basic operations of the device. When short-circuit current flows, glitches in the power source lines may be produced.
Determine the maximum transient current in the power lines wherein glitches are not produced. Select the value of
resistance R that will satisfy the EEPROM input level VIH/VIL, even under the influence of voltage fluctuations resulting
from short-circuit current and so forth. Assuming the allowable short-circuit current defined as I, the following relation
should be satisfied.
(3) Address Data A0 = “1” input, dummy bit “0” Output Timing
(When microcontroller DI/O output is high, EEPROM DO outputs low, and high is input to DI)
(a) Make the through current to EEPROM 10mA or below.
(b) See to it that the level VIH of EEPROM should satisfy the following.
Microcontroller
EEPROM
DI/O PORT
High output
VOHM
IOHM
DI
R
DO
VOLE
Low outpu
Conditions
VIHE ≦ IOHM×R + VOLE
At this moment, if VOLE=0V,
VIHE ≦ IOHM×R
∴
R≧
VIHE
IOHM
・・・⑦
・VIHE
・VOLE
・IOHM
: EEPROM VIH specifications
: EEPROM VOL specifications
: Microcontroller IOH specifications
Figure 53. Circuit at DI, DO Direct Connection (Microcontroller DI/O high output, EEPROM low output)
(4) DO STATUS READY Output Timing
(When the microcontroller DI/O is low, EEPROM DO output high, and low is input to DI)
(a) Set the EEPROM input level VIL so as to satisfy the following.
Microcontroller
Low output ^{DI/O PORT}
VOLM
IOLM
EEPROM
DI
R
DO
VOHE
High output
Conditions
VILE ≧ VOHE – IOLM×R
As this moment, VOHE=Vcc
VILE ≧ Vcc – IOLM×R
∴
R≧
Vcc – V_ILE
I_OLM
・・・⑧
・VILE
・VOHE
・IOLM
: EEPROM VIL specifications
: EEPROM VOH specifications
: Microcontroller IOL specifications
Example) When VCC=5V, VOHM=5V, IOHM=0.4mA, VOLM=5V, IOLM=0.4mA,
From the equation ⑦,
From the equation⑧,
R≧
VIHE
IOHM
R ≧ ^3.5
0.4×10^-3
R ≧ ^{Vcc – VILE}
IOLM
5 – 1.5
R≧
2.1×10^-3
∴
R ≧ 8.75 [kΩ] ・・・⑨
∴
R ≧ 1.67 [kΩ] ・・・⑩
Therefore, from the equations ⑨ and ⑩,
∴
R ≧ 8.75 [kΩ]
Figure 54. Circuit at DI, DO Direct Connection (Microcontroller DI/O low output, EEPROM high output)
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