Philips Semiconductors
Product specification
4-digit LED-driver with I2C-Bus interface
SAA1064
POWER DISSIPATION
The total maximum power dissipation of the SAA1064 is made up by the following parts:
1. Maximum dissipation when none of the outputs are programmed (continuous line in Fig.7).
2. Maximum dissipation of each programmed output. The dashed line in Fig.7 visualises the dissipation when all the
segments are programmed (max. 16 in the static, and max. 32 in the dynamic mode). When less segments are
programmed one should take a proportional part of the maximum value.
3. Maximum dissipation of the programmed segment drivers which can be expressed as:
Padd = VO × IO × N.
Where:
Padd = The additional power dissipation of the segment drivers
VO
IO
N
= The low state segment driver output voltage
= The programmed segment output current
= The number of programmed segments in the static mode, or half the number of
programmed segment drivers in the dynamic mode.
Under no conditions the total maximum dissipation (500 mW for the SO and 1000 mW for the DIL package) should be
exceeded.
Example: VCC = 5 V
VO
IO
= 0.25 V
= 12 mA
24 programmed segments in dynamic mode
Ptot = P1 + P2 + P3
= 75 mW + (50 * 24/32) mW + (0.25 * 12.10−3 * 12) mW
= 148.5 mW
February 1991
14
NXP [ NXP ]
