BR24T32-W(2015) Просмотр технического описания (PDF) - ROHM Semiconductor

Номер в каталоге

Компоненты Описание

Список матч

BR24T32-W
(Rev.:2015)

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

ROHM Semiconductor 

BR24T32-W

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 (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 and RPU of SDA should be tR 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 (IL) of device connected to bus at

output of 'H' to the SDA line 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

≦ 30 [kΩ]

Microcontroller

RPU

A

BR24TXX

SDA terminal

IL

IL

Bus line

capacity

CBUS

Figure 44. I/O Circuit Diagram

3. Minimum Value of RPU

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.

www.rohm.com

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

TSZ22111･15･001

18/33

TSZ02201-0R2R0G100060-1-2

03.Feb.2015 Rev.004

Share Link: