BR24T32-WG_ データシートの表示（PDF） - ROHM Semiconductor

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BR24T32-WG_

High Reliability Serial EEPROMs I2C BUS BR24□□□□ family

ROHM Semiconductor 

BR24T□□□□Series

Technical Note

●Notes on power ON

At power on, in IC internal circuit and set, Vcc rises through unstable low voltage area, and IC inside is not completely reset,

and malfunction may occur. To prevent this, functions of POR circuit and LVCC circuit are equipped. To assure the action,

observe the following conditions at power on.

1. Set SDA = 'H' and SCL ='L' or 'H’

2. Start power source so as to satisfy the recommended conditions of tR, tOFF, and Vbot for operating POR circuit.

VCC

tR

Recommended conditions of tR, tOFF,Vbot

tR

tOFF

Vbot

0

Fig.59

tOFF

Vbot

Rise waveform diagram

10ms or below

100msor below

10ms or larger

10msor larger

0.3V or below

0.2V or below

3. Set SDA and SCL so as not to become 'Hi-Z'.

When the above conditions 1 and 2 cannot be observed, take the following countermeasures.

a) In the case when the above condition 1 cannot be observed. When SDA becomes 'L' at power on .

→Control SCL and SDA as shown below, to make SCL and SDA, 'H' and 'H'.

VCC

SCL

tLOW

SDA

After Vcc becomes stable

tDH tSU:DAT

Fig.60 When SCL= 'H' and SDA= 'L'

After Vcc becomes stable

tSU:DAT

Fig.61 When SCL='L' and SDA='L'

b) In the case when the above condition 2 cannot be observed.

→After power source becomes stable, execute software reset(P12).

c) In the case when the above conditions 1 and 2 cannot be observed.

→Carry out a), and then carry out b).

●Low voltage malfunction prevention function

LVCC circuit prevents data rewrite action at low power, and prevents wrong write. At LVCC voltage (Typ. =1.2V) or below, it

prevent data rewrite.

●Vcc noise countermeasures

○Bypass capacitor

When noise or surge gets in the power source line, malfunction may occur, therefore, for removing these, it is

recommended to attach a bypass capacitor (0.1µF) between IC Vcc and GND. At that moment, attach it as close to IC as

possible. And, it is also recommended to attach a bypass capacitor between board Vcc and GND.

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