BR24A01AF-WME2 Datasheet, PDF (19/31 Pages) Rohm – Serial EEPROM Series Automotive EEPROM

BR24Axxx-WM (1K 2K 4K 8K 16K 32K 64K)
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, operating frequency is
limited. The smaller the R_PU, the larger the consumption current at operation.
○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 (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.
(2)The 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 RPU should sufficiently secure the input 'H' level (VIH) of microcontroller and EEPROM including recommended
noise margin 0.2 V_CC.
Vcc - I_LR_PU - 0.2Vcc ≧ V_IH
0.8Vcc - V_IH
∴ R_PU =
I_L
Microcontroller
Ex. ) When V_CC =3V, I_L=10μA, V_IH=0.7 V_CC,
from (2)
R_PU
≦
0.8×3- 0.7×3
10×10^-6
IL
≦ 300 [kΩ]
○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.
V_CC-V_OL
R_PU
≦ I_OL
V_C-V_OL
∴ R_PU ≦
I_OL
R_PU
A
BR24AXX
SDA terminal
IL
Bus line
バス_caラ_pイ_acン_ity容量
C^CB^BU^US^S
Figure 50. I/O circuit diagram
(2)V_OLMAX=0.4V should secure the input 'L' level (V_IL) of microcontroller and EEPROM including recommended noise
margin 0.1 V_CC.
VOLMAX ≦ VIL-0.1 V_CC
Ex. ) When V_CC =3V, VOL=0.4V, IOL=3mA, microcontroller, EEPROM VIL=0.3 V_CC
from (1)
R_PU ≧
3－0.4
3×10 ^-3
≧ 867 [Ω]
And
V_OL = 0.4 [V]
V_IL = 0.3×3
= 0.9 [V]
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 to several ten kΩ is recommended in
consideration of drive performance of output port of microcontroller.
●A0, A1, A2, WP process
○Process of device address terminals (A0,A1,A2)
Check whether the set device address coincides with device address input sent from the master side or not, and select
one among plural devices connected to a same bus. Connect this terminal to pull up or pull down, or VCC or GND. And,
pins (N, C, PIN) not used as device address may be set to any of ‘H’, 'L', and 'Hi-Z'.
Types with N.C.PIN
BR24A16/F/FJ -WM
A0, A1, A2
BR24A08/F/FJ-WM
A0, A1
BR24A04/F/FJ -WM
A0
○Process of WP terminal
WP terminal is the terminal that prohibits and permits write in hardware manner. In 'H' status, only READ is available and
WRITE of all address is prohibited. In the case of 'L', both are available. In the case of use it as an ROM, it is
recommended to connect it to pull up or V_CC. In the case to use both READ and WRITE, control WP terminal or connect it
to pull down or GND.
www.rohm.com
© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
19/28
TSZ02201-0R1R0G100140-1-2
31.Aug.2012 Rev.001