M51953A,B/M51954A,B
Notice for use
About the Power Supply Line
1. About bypass capacitor
Because the ripple and the spike of the high frequency noise and the low frequency are superimposed to the power
supply line, it is necessary to remove these.
Therefore, please install C
1
and C
2
for the low frequency and for the high frequency between the power supply line
and the GND line as shown in following figure 3.
V
CC
+
C
1
C
2
Power-supply
M51953
M51954
GND
Output
Example of ripple
noise measures
Delay capacitor
Cd
Figure 3 Example of Ripple Noise Measures
Setting of Delay Capacity
Please use capacitor Cd for the delay within the range of 10
µF
or less.
When a value that is bigger than this is set, the problem such as following (1), (2), and (3) becomes remarkable.
t
V
CC
Output
tpd
t
PHL
Figure 4 Time Chart at Momentary Voltage-Decrease
(1) The difference at delay time becomes remarkable.
A long delay setting of tens of seconds is fundamentally possible. However, when set delay time is lengthened, the
range of the difference relatively grows, too. When a set value is assumed to be ‘tpd’, the difference occurs in the
range from 0.47
×
tpd to 2.05
×
tpd. For instance, 34 seconds can be calculated at 100
µF.
However, it is likely to
vary within the ranges of 16-70 seconds.
(2) Difficulty to react to a momentary voltage decrease.
For example, the reaction time t
PHL
is 10
µs
when delay capacitor Cd = 0.1
µF.
The momentary voltage-decrease that is longer than such t
PHL
are occurs, the detection becomes possible. When the
delay capacitance is enlarged, t
PHL
also becomes long. For instance, it becomes about 100 to 200
µs
in case of
circuit constant C1 = 100
µF.
(Characteristic graph 1 is used and extrapolation in case of Cd = 100
µF.)
Therefore, it doesn't react to momentary voltage-decrease that is shorter than this.
(3) Original delay time is not obtained.
When the momentary voltage-decrease time ‘t’ is equivalent to t
PHL
, the discharge becomes insufficient and the
charge starts at that state. This phenomenon occurs at large capacitance. And, original delay time tpd is not
obtained.
Please refer to characteristic graph 2. (Delay time versus input pulse width)
REJ03D0776-0200 Rev.2.00 Aug 20, 2007
Page 7 of 10
RENESAS [ RENESAS TECHNOLOGY CORP ]
