Technical Note

11/16

BR35H□□□-WC Series

www.rohm.com

2011.03 - Rev.C

© 2011 ROHM Co., Ltd. All rights reserved.

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High speed operations

In order to realize stable high speed operations, pay attention to the following input / output pin conditions.

○

Input pin pull up, pull down resistance

When attaching pull up, pull down resistance to the EEPROM input pin, select an appropriate value for the

microcontroller VOL, IOL from the VIL characteristics of this IC.

○

Pull up resistance

Also, in order to prevent malfunction or erroneous write at power ON/OFF, be sure to make CSB pull up.

○

Pull down resistance

The operations speed changes according to the amplitude VIHE, VILE of the signals input to the EEPROM. More stable

high speed operations can be realized by inputting signals with Vcc / GND levels of amplitude. On the contrary, when

signals with an amplitude of 0.8Vcc / 0.2Vcc are input, operation speed slows down.

*1

and to have the amplitude of the signals input to the EEPROM close to the Vcc / GND amplitude level.

(

○

SO load capacitance condition

The load capacitance of the SO output pin affects the SO output delay characteristic. (Data output delay time, time from

HOLDB to High-Z, output rise time, output fall time.). Make the SO load capacitance small to improve the output delay

characteristic.

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Other cautions

Make all wires from the microcontroller to EEPROM input pin the same length. This in order to prevent setup / hold

violation to the EEPROM.

“L” output

“L” input

Microcontroll

EEPROM

Fig.44 Pull up resistance

5－0.4

2×10

-3

∴

2.3[kΩ]

from the equation ①,

Microcontroll

EEPROM

“H” output

“H” input

Fig.45 Pull down resistance

･･･③

･･･④

5－0.5

0.4×10

-3

∴

11.3[kΩ]

EEPROM

SO

CL

Fig.46 SO load dependency of data output delay time tPD

･･･①

･･･②

also satisfied.

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