M5451 datasheet(7/12 Pages) STMICROELECTRONICS

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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 Ptot 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 VOUT + VD is con-

stant. The total power dissipation of the IC de-

pends only on the number of segments activated.

Figure 13.

VOUT

+VC

DMAX

–

OMIN

–

MAX

----------------------------------------------------------------

+VC

VOUT +VD

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