BRCB008GWZ-3_13 Datasheet, PDF (17/29 Pages) Rohm – WLCSP EEPROM

BRCB008GWZ-3
Datasheet
I/O Peripheral Circuit
1. Pull-up Resistance of SDA terminal
SDA is NMOS open drain, so it requires a pull up resistor. As for this resistance value (R_PU), select an appropriate value
from microcontroller V_IL, I_L, and V_OL-I_OL characteristics of this IC. If R_PU is large, operating frequency is limited. The smaller
the R_PU, the larger is the supply current (Read).
2. Maximum Value of R_PU
The maximum value of R_PU is determined by the following factors.
(1) SDA rise time to be determined by the capacitance (C_BUS) of bus line and R_PU of SDA should be t_R or lower.
Furthermore, AC timing should be satisfied even when SDA rise time is slow.
(2)The bus electric potential _○A to be determined by the input current leak total (I_L) of the device connected to the bus
with output of 'H' to the SDA line and R_PU should sufficiently secure the input 'H' level (V_IH) of microcontroller and
EEPROM including recommended noise margin of 0.2Vcc.
VCC-I_LR_PU-0.2 VCC ≧ V_IH
∴ R_PU≦
0.8Vcc-V_IH
I_L
Ex.) Vcc =3V I_L=10µA V_IH=0.7 Vcc
From(2)
0.8×3-0.7×3
R_PU≦
10×10^-6
≦ 30 [kΩ]
Microcontroller
RPU
A
BRCB008GWZ-3
SDA terminal
IL
IL
Bus line
Capacity
C_BUS
Figure 36. I/O Circuit Diagram
3. Minimum Value of R_PU
The minimum value of R_PU is determined by the following factors:
(1)When IC outputs LOW, it should be satisfied that V_OLMAX=0.4V and I_OLMAX=3mA.
Vcc-V_OL
R_PU
≦I_OL
∴
RPU≧
Vcc-VOL
IOL
(2)VOLMAX=0.4V should secure the input 'L' level (V_IL) of microcontroller and EEPROM
including the recommended noise margin of 0.1Vcc.
VOLMAX ≦ VIL-0.1 VCC
Ex.) VCC =3V, VOL=0.4V, IOL=3mA, microcontroller, EEPROM V_IL=0.3Vcc
from(1)
3-0.4
R_PU≧ _3×10-3
≧ 867[Ω]
And V_OL=0.4ï¼»Vï¼½
VIL=0.3×3
=0.9ï¼»Vï¼½
Therefore, the condition (2) is satisfied.
4. Pull-up Resistance of SCL Terminal
When SCL control is made at the CMOS output port, there is no need for a pull up resistor. But when there is a time
where SCL becomes 'Hi-Z', add a pull up resistor. As for the pull up resistor value, one of several kΩ to several ten kΩ
is recommended in consideration of drive performance of output port of microcontroller.
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