AN-90 データシートの表示（PDF） - Fairchild Semiconductor
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AN-90 Datasheet PDF : 7 Pages
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TEMPERATURE CHARACTERISTICS
Figure 9 and Figure 10 give temperature variations in drain
characteristics for the N-channel and P-channel devices op-
erating at VCC = 5.0V and VCC = 10V respectively. As can be
seen from these curves the output sink and source current
decreases as temperature increases. The effect is almost
linear and can be closely approximated by a temperature co-
efficient of −0.3% per degree centigrade.
Since the tpd can be entirely attributed to rise and fall time,
the temperature dependence of tPD is a function of the rate
at which the output load capacitance can be charged and
discharged. This in turn is a function of the sink/source cur-
rent which was shown above to vary as −0.3% per degree
centigrade. Consequently we can say that tpd varies as
−0.3% per degree centigrade. Actual measurements of tpd
with temperature verifies this number.
AN006021-12
(A) Typical Output Drain Characteristic (N-Channel)
AN006021-13
(B) Typical Output Drain Characteristic (P-Channel)
FIGURE 9.
AN006021-14
(A) Typical Output Drain Characteristic (N-Channel)
AN006021-15
(B) Typical Output Drain Characteristic (P-Channel)
FIGURE 10.
AN006021-16
FIGURE 11. Typical Gate Transfer Characteristics
The drain characteristics of Figure 9 and Figure 10 show
considerable variation with temperature. Examination of the
transfer characteristics of Figure 11 indicates that they are
almost independent of temperature. The transfer character-
istic is not dependent on temperature because although both
the N-channel and P-channel device characteristics change
with temperature these changes track each other closely.
The proof of this tracking is the temperature independence
of the transfer characteristics. Noise margin and maximum/
minimum logic levels will then not be dependent on tempera-
ture.
As discussed previously power consumption is a function of
CPD, CL, VCC, f and ILEAKAGE. All of these terms are essen-
tially constant with temperature except ILEAKAGE. However,
the leakage current specified on each 54C/74C device ap-
plies across the entire temperature range and therefore rep-
resents a worst case limit.
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