Datasheet
SLRS028A − SEPTEMBER 1988 − REVISED NOVEMBER 2004
8
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
THERMAL INFORMATION
power-dissipation precautions
Significant power may be dissipated in the SN75374 driver when charging and discharging high-capacitance
loads over a wide voltage range at high frequencies. Figure 12 shows the power dissipated in a typical SN75374
as a function of frequency and load capacitance. Average power dissipated by this driver is derived from the
equation:
P
T(AV)
= P
DC(AV)
+ P
C(AV)
+ P
S(AV)
where P
DC(AV)
is the steady-state power dissipation with the output high or low, P
C(AV)
is the power level during
charging or discharging of the load capacitance, and P
S(AV)
is the power dissipation during switching between
the low and high levels. None of these include energy transferred to the load, and all are averaged over a full
cycle.
The power components per driver channel are:
P
DC(AV)
+
(
P
H
t
H
) P
L
t
L
)
T
P
C(AV)
[ CV
2
f
c
P
S(AV)
+
(
P
LH
t
LH
) P
HL
t
HL
)
T
where the times are as defined in Figure 15.
t
L
t
H
T = 1/f
t
LH
t
HL
Figure 13. Output-Voltage Waveform