M54128L データシートの表示（PDF） - Renesas Electronics
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M54128L Datasheet PDF : 22 Pages
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M54128L/FP
Precaution for Use
Important information on use of the M54128L/FP is given below. Examples of improvements are no more than single
examples; improvement should be given adequate study.
1. Regarding the VS applied voltage
(1) The Is circuit current (clamping circuit characteristics of equivalent circuit) is as shown by the characteristic
diagram 1 on page 13. Sufficient care should be exercised when designing a power supply circuit.
Commercial power supply
Commercial
power supply
RS
VS
IC
VZ
(2) When rectifying a commercial power supply for use
a) As Vz, a 12 V or lower Zener diode should always be used
(the absolute maximum rating should not exceed 15 V).
b) At high temperatures, the clamping voltage is reduced and IS increases, but this is limited by RS.
(3) When using an ordinary DC power supply, VS should be from 7 to 12 V.
2. Regarding the IREF pin resistance (R = 130 kΩ)
This is the IC reference constant-current source. (Fluctuations in the power supply voltage and ambient temperature
characteristics are suppressed.)
This resistance determines the characteristics for various circuits, and so it is recommended that a high-precision
resistance (±2%) be used.
3. Regarding the printed circuit board layout
Due to the effect of external noise (or noise simulator etc.), erroneous operation is conceivable.
In order to improve noise resistance, the board layout should be such that wiring to external capacitors and resistors is
as short as possible.
Particular care should be taken in wiring to connect capacitors to the VS pin, the VCC pin, and the SCRT pin.
4. Care should be taken to ensure that the SCRT output pin does not fall to a voltage more negative than ground
level.
5. Regarding changes in sensitivity due to insulation degradation
When degradation of the insulation between the ZCT input pin and the high-voltage unit is imagined, by connecting a
resistance R = 100 kΩ or so between the VREF pin and ground, there may be improvement; this possibility should be
studied carefully.
However, the circuit current increases as I ≈ 2.7V/R, so caution should be exercised.
Rev.1.0, Sep.16.2003, page 10 of 21
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