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BR24G1MNUX-3AE2
(Rev.:2013)

Serial EEPROM Series Standard EEPROM I2C BUS EEPROM (2-Wire)

ROHM Semiconductor 

BR24Gxxx-3A (128K 256K 1M)

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 resistor value (RPU), select an appropriate value

from microcontroller VIL, IL, and VOL-IOL characteristics of this IC. If RPU is large, operating frequency is limited. The

smaller the RPU, the larger is the supply current (Read).

2. Maximum Value of RPU

The maximum value of RPU is determined by the following factors.

(1)SDA rise time to be determined by the capacitance (CBUS) of bus line of RPU and SDA should be tR or lower.

Furthermore, 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 (IL) 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 of 0.2VCC.

VCC-ILRPU-0.2 VCC ≧ VIH

∴

RPU

≦

0.8VCC－VIH

IL

Ex.) VCC =3V IL=10μA VIH=0.7 VCC

From (2)

RPU

≦

0.8×3－0.7×3

10×10-6

Microcontroller

IL

RPU

A

BR24GXX

SDA terminal

IL

≦ 300 [kΩ]

Bus line

capacity

CBUS

3. Minimum Value of RPU

Figure 49. I/O Circuit Diagram

The minimum value of RPU is determined by the following factors.

(1) When IC outputs LOW, it should be satisfied that VOLMAX=0.4V and IOLMAX=3mA.

VCC－VOL

RPU

≦

IOL

∴

RPU

≧

VCC－VOL

IOL

(2) VOLMAX=0.4V should secure the input 'L' level (VIL) 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 VIL=0.3VCC

from (1)

RPU

≧

3－0.4

3×10 -3

≧ 867 [Ω]

And

VOL=0.4 [V]

VIL=0.3×3

=0.9 [V]

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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© 2013 ROHM Co., Ltd. All rights reserved.

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