Obsolete Product(s) - Obsolete Product(s)
7/12
M5450, M5451
POWER DISSIPATION OF THE IC
The power dissipation of the IC can be limited us-
ing different configurations.
Figure 11- In the application R must be chosen
taking into account the worst operating conditions.
Figure 11.
R is determined by the maximum number of seg-
ments activated
The worst case condition for the device is when
roughly half of the maximum number of segments
are activated.
It must be checked that the total power dissipation
does not exceed the absolute maximum ratings of
the device.
In critical cases more resistors can be used in con-
junction with groups of segments.
In this case the current variation in the single resis-
tor is reduced and P
tot
limited.
Figure 12 - In this configuration the drop on the se-
rial connected diodes is quite stable if the diodes
are properly chosen.
The total power dissipation of the IC depends, in a
first approximation, only on the number of seg-
ments activated.
Figure 12.
Figure 13 - In this configuration V
OUT
+ V
D
is con-
stant. The total power dissipation of the IC de-
pends only on the number of segments activated.
Figure 13.
V
D
V
OUT
R
I
D
+V
C
R
V
C
V
DMAX
– V
OMIN
–
N
MAX
L
D
----------------------------------------------------------------=
+V
C
+V
C
V
OUT
+V
D
