BU9847GUL-W Datasheet, PDF (3/5 Pages) Rohm – Silicon Monolithic Integrated Circuit

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◇ NOTES FOR POWER SUPPLY
Vcc rises through the low voltage region in which internal circuit of IC and the controller are unstable, so that device
may not work properly due to an incomplete reset of internal circuit. To prevent this, the device has the feature of
P.O.R. and LVCC. In the case of power up, keep the following conditions to ensure functions of P.O.R. and LVCC.
1. It is necessary to be "SDA='H'" and "SCL='L' or 'H'".
2. Follow the recommended conditions of tR, tOFF, Vbot for the function of P.O.R. during power up.
tR
Vcc
tOFF
Vbot
0
Fig.-2 Vcc RISING WAVEFORM
◇RECOMMENDED CONDITIONS OF tR, tOFF, Vbot
tR
tOFF
Vbot
Below 10ms Above 10ms Below 0.3V
Below 100ms Above 10ms Below 0.2V
3. Prevent SDA and SCL from being "High-Z".
In case that condition 1. and/or 2. cannot be met,
take following actions.
A） Unable to keep condition 1.
( SDA is "LOW" during power up.)
Vcc
tLOW
SCL
→ Control SDA ,SCL to be "HIGH" as Fig.-3(a),
3(b).
B） Unable to keep condition 2.
→ After power becomes stable, execute
software reset.
SDA
After Vcc becomes stable
tDH tSU:DAT
Fig.-3（a） SCL='H' and SDA='L'
C） Unable to keep both conditions 1 and 2.
→ Follow the instruction A first, then the instruction B.
After Vcc becomes stable
tSU:DAT
Fig.-3（b） SCL='L' and SDA='L'
◇CAUTIONS ON USE
(1) Absolute maximum ratings
If the absolute maximum ratings such as impressed voltage and action temperature range and so forth are
exceeded, LSI may be destructed. Do not impress voltage and temperature exceeding the absolute maximum
ratings. In the case of fear exceeding the absolute maximum ratings, take physical safety countermeasures such
as fuses, and see to it that conditions exceeding the absolute maximum ratings should not be impressed to LSI.
(2) GND electric potential
Set the voltage of GND terminal lowest at any action condition. Make sure that each terminal voltage is lower
than that of GND terminal.
(3) Thermal design
In consideration of permissible loss in actual use condition, carry out heat design with sufficient margin.
(4) Terminal to terminal shortcircuit and wrong packaging
When to package LSI onto a board, pay sufficient attention to LSI direction and displacement. Wrong packaging
may destruct LSI. And in the case of shortcircuit between LSI terminals and terminals and power source,
terminal and GND owing to foreign matter, LSI may be destructed.
(5) Use in a strong electromagnetic field may cause malfunction, therefore, evaluated design sufficiently.
REV. A