BR24G04-3A(2013) データシートの表示（PDF） - ROHM Semiconductor

部品番号

コンポーネント説明

メーカー

BR24G04-3A
(Rev.:2013)

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

ROHM Semiconductor 

BR24G04-3A

Datasheet

●Cautions on Microcontroller Connection

○RS

In I2C BUS, it is recommended that SDA port is of open drain input/output. However, when to use CMOS input / output of

tri state to SDA port, insert a series resistance Rs between the pull up resistance Rpu and the SDA terminal of EEPROM.

This is controls over current that occurs when PMOS of the microcontroller and NMOS of EEPROM are turned ON

simultaneously. Rs also plays the role of protection of SDA terminal against surge. Therefore, even when SDA port is

open drain input/output, Rs can be used.

RPU

RS

SCL

SDA

'H' output of microcontroller

ACK

'L' output of EEPROM

Microcontroller

EEPROM

Figure 46. I/O circuit diagram

Over current flows to SDA line by 'H'

output of microcontroller and 'L'

output of EEPROM.

Figure 47. Input / output collision timing

○Maximum value of Rs

The maximum value of Rs is determined by the following relations.

①SDA rise time to be determined by the capacity (CBUS) of bus line of Rpu 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 Rpu and Rs the moment when EEPROM outputs 'L' to SDA bus

sufficiently secure the input 'L' level (VIL) of microcontroller including recommended noise margin 0.1Vcc.

VCC

RPU A

RS

IOL

Bus line

capacity

CBUS

VIL Micro controller

VOL

EEPROM

Figure 48. I/O Circuit Diagram

(VCC－VOL)×RS

RPU+RS

+ VOL+0.1VCC≦VIL

VIL－VOL－0.1VCC

∴ RS ≦

× RPU

1.1VCC-VIL

Ex.）VCC=3V　VIL=0.3VCC　VOL=0.4V　RPU=20kΩ

RS

≦

0.3×3－0.4－0.1×3

1.1×3－0.3×3

×

20×103

≦ 1.67［kΩ］

○Minimum value of Rs

The minimum value of Rs is determined by over current at bus collision. When over current flows, noises in power source

line, and instantaneous power failure of power source may occur. When allowable over current is defined as I, the

following relation must be satisfied. Determine the allowable current in consideration of impedance of power source line

in set and so forth. Set the over current to EEPROM 10mA or below.

VCC ≦

RS

I

RPU

RS

'L'output

∴ RS

≧ VCC

I

Over current I

Ex.) VCC=3V, I=10mA

'H' output

Microcontroller

EEPROM

Figure 49. I/O circuit diagram

RS

≧

3

10×10-3

≧ 300［Ω］

www.rohm.co

© 2014 ROHM Co., Ltd. All rights reserved.

TSZ22111・15・001

21/33

TSZ02201-0R2R0G100560-1-2

27.Aug.2014 REV.003

Share Link: