Datasheet

(625mA instead of 500mA).
- All electrical parameters of the device, con-
cerning the calculation, are at maximum val-
ues.
- Thermal shutdown threshold is at minimum
value.
- No heat sink nor air circulation (R
th
equal to
R
thj-amb
).
Therefore:
V
s
= 30V, R
DSON0
= 0.6
Ω
, I
q
= 6mA, I
os
= 4mA @
V
os
= 2.5V,
Θ
Lim = 135°C
R
thj-amb
= 100°C/W (Minidip); 90°C/W (SO20);
70°C/W (SIP9)
It follows:
I
outx
= 0.625mA, R
DSONx
= 1.006
Ω
, P
q
= 180mW,
P
os
= 110mW
From equation 4, we can find:
T
ambx
= 66.7°C (Minidip);
73.5°C (SO20);
87.2°C (SIP9).
Therefore, the IPS TDE1897/1898, although
guaranteed to operate up to 85°C ambient tem-
perature, if used in the worst conditions, can meet
some limitations.
SIP9 package, which has the lowest R
thj-amb
, can
work at maximum operative current over the en-
tire ambient temperature range in the worst condi-
tions too. For other packages, it is necessary to
consider some reductions.
With the aid of equation 3, we can draw a derat-
ing curve giving the maximum current allowable
versus ambient temperature. The diagrams, com-
puted using parameter values above given, are
depicted in figg. 6 to 8.
If an increase of the operating area is needed,
heat dissipation must be improved (R
th
reduced)
e.g. by means of air cooling.
+
-
+IN
-IN
D1
D2
CONTROL
LOGIC
Ios
LOAD
OUTPUT
OUTPUT STATUSGND
µP POLLING
+Vs
DC BUS 24V +/-25%
D93IN014
Figure 5:
Application Circuit.
TDE1897R - TDE1898R
7/12