BR25H160F-2LB_14 Datasheet, PDF (24/32 Pages) Rohm – Operation SPI BUS EEPROM

BR25H160F-2LB
Datasheet
Power-Up/Down conditions
○At power ON/OFF, set CSB “H” (=VCC).
When CSB is “L”, this IC gets in input accept status (active). If power is turned on in this status, noises and the likes may
cause malfunction, mistake write or so. To prevent these, at power ON, set CSB “H”. (When CSB is in “H” status, all inputs
are canceled.)
Vcc
Vcc
GND
Vcc
CSB
GND
Good
example
Bad
example
Figure 60. CSB timing at power ON/OFF
(Good example) CSB terminal is pulled up to VCC.
At power OFF, take 10ms or higher before supply. If power is turned on without observing this condition, the IC internal
circuit may not be reset, which please note.
(Bad example) CSB terminal is “L” at power ON/OFF.
In this case, CSB always becomes “L” (active status), and EEPROM may have malfunction, mistake write owing to noises
and the likes.
Even when CSB input is High-Z, the status becomes like this case, which please note.
○LVCC circuit
LVCC (VCC-Lockout) circuit prevents data rewrite action at low power, and prevents wrong write.
At LVCC voltage (Typ. =1.9V) or below, it prevent data rewrite.
○P.O.R. circuit
This IC has a POR (Power On Reset) circuit as mistake write countermeasure. After POR action, it gets in write disable
status. The POR circuit is valid only when power is ON, and does not work when power is OFF. When power is ON, if the
recommended conditions of the following tR, tOFF, and Vbot are not satisfied, it may become write enable status owing to
noises and the likes.
Vcc
tR
Recommended conditions of tR, tOFF, Vbot
tR
tOFF
Vbot
tOFF
Vbot
0
Figure 61. Rise waveform
10ms or below
100ms or below
10ms or higher
10ms or higher
0.3V or below
0.2V or below
Noise countermeasures
○VCC noise (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.
○SCK noise
When the rise time (tR) of SCK is long, and a certain degree or more of noise exists, malfunction may occur owing to clock
bit displacement. To avoid this, a Schmitt trigger circuit is built in SCK input. The hysteresis width of this circuit is set about
0.2V, if noises exist at SCK input, set the noise amplitude 0.2Vp-p or below. And it is recommended to set the rise time
(tR) of SCK 100ns or below. In the case when the rise time is 100ns or higher, take sufficient noise countermeasures.
Make the clock rise, fall time as small as possible.
○WPB noise
During execution of write status register command, if there exist noises on WPB pin, mistake in recognition may occur and
forcible cancellation may result, which please note. To avoid this, a Schmitt trigger circuit is built in WPB input. In the same
manner, a Schmitt trigger circuit is built in CSB input, SI input and HOLDB input too.
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27.Feb.2014 Rev.002