BU99022NUX-3 Datasheet, PDF (18/26 Pages) Rohm – I2C BUS 2kbit + 2kbit 2ports serial EEPROM

BU99022NUX-3
Datasheet
●I/O peripheral circuit
○Pull up resistance of SDA terminal
SDA is NMOS open drain, so requires pull up resistance. As for this resistance value (R_PU), select an appropriate value to this resistance
value from microcontroller V_IL, I_L, and V_OL-I_OL characteristics of this IC. If R_PU is large, action frequency is limited. The smaller the R_PU, the
larger the consumption current at action.
○Maximum value of R_PU
The maximum value of R_PU is determined by the following factors.
①SDA rise time to be determined by the capacitance (CBUS) of bus line of R_PU and SDA should be tR or below.
And AC timing should be satisfied even when SDA rise time is late.
②The bus electric potential A to be determined by input leak total (I_L) of device connected to bus at output of 'H' to SDA bus and R_PU
should sufficiently secure the input 'H' level (V_IH) of microcontroller and EEPROM including recommended noise margin 0.2Vcc.
VCC－ILRPU－0.2 VCC ≧ VIH
∴
RPU
≦
0.8VCC－VIH
IL
Ex.) VCC =3V IL=10μA VIH=0.7 VCC
from②
RPU
≦
0.8×3－0.7×3
10×10^-6
Microcontroller
IL
RPU
A
BU99022NUX-3
SDA terminal
IL
≦ 300 ［kΩ］
○ Minimum value of R_PU
The minimum value of R_PU is determined by the following factors.
When IC outputs LOW, it should be satisfied that V_OLMAX=0.4V and I_OLMAX=3mA.
Bus line
capacity
CBUS
Fig.52 I/O circuit diagram
VCC－VOL
RPU
≦
IOL
∴
RPU
≧
VCC－VOL
IOL
②VOLMAX= should secure the input 'L' level (V_IL) of microcontroller and EEPROM including recommended noise margin 0.1Vcc.
VOLMAX ≦ VIL－0.1 VCC
Ex.) VCC =3V、VOL=0.4V、IOL=3mA、microcontroller, EEPROM V_IL=0.3Vcc
from①
RPU
≧
3－0.4
3×10 ^-3
≧ 867 ［Ω］
And
VOL=0.4ï¼»Vï¼½
VIL=0.3×3
=0.9ï¼»Vï¼½
Therefore, the condition ② is satisfied.
○Pull up resistance of SCL terminal
When SCL control is made at CMOS output port, there is no need, but in the case there is timing where SCL becomes 'Hi-Z', add a pull
up resistance. As for the pull up resistance, one of several kΩ ~ several ten kΩ is recommended in consideration of drive performance
of output port of microcontroller.
www.rohm.com
© 2011 ROHM Co., Ltd. All rights reserved.
TSZ22111・14・001
18/23
TSZ02201-0R2R0G100010-1-2
2011.12.19 Rev.001