analog&RFmodels
Well-known member
spacing in final post not what i had after pasting text in - not sure how to prevent that
maybe i should attach a text file next time
FYI - here are some results for T4 in a small sealed plastic box.
Results are good even down to 4 cubic inches.
tamb = 26-27 c, 1 hour soak, ir thermometer w 0.1 inch target dia
all below: t4 running at 816 mhz fed w 5.0 volts
situation iq top center cpu tempmon
horizontal with small air flow ceiling fan 133 ma 48 c 61 c
horizontal still air 139 ma 61 c 75 c
inside sealed plastic box 4 cubic inch 143 ma 72 c 87 c
top center box outside surf at 39 c
816 is not usable but 720 is
4 cubic inch box was 0.66 x 2.10 x 2.90 inch medium hardness
plastic with 0.050 inch wall thickness.
Although the tempco of iq is positive, there is not enough gain
for a runaway (gain seems to be about 0.2).
The variance with volume/surface area was small - 5 deg c
improvement when vol increased to 11 cubic inch plastic.
The variance with material was small - 7 deg c improvement
when box matl 0.032 aluminum.
Versus clock in 4 cubic inch plastic box, amb = 26-27 c, still
air, box horizontal on plastic spacers, all numbers from
tempmon (limit is 90 c):
Outdoor:
Direct sunlight on the box will subtract 10-30 deg f from the
allow amb numbers. Here where I am, in the summer, 396 would
be borderline so for outdoor use it would be best to provide
a decent, short conduction path between the chip top surface
and the inside wall of an aluminum box.
Variance was +- 0.7 deg c from run to run and about +- 2 T4 to
T4 giving an rss of +- 2.1 deg c.
defragster edit: { added # / CODE block around table - that preserves some spacing elements }
maybe i should attach a text file next time
FYI - here are some results for T4 in a small sealed plastic box.
Results are good even down to 4 cubic inches.
tamb = 26-27 c, 1 hour soak, ir thermometer w 0.1 inch target dia
all below: t4 running at 816 mhz fed w 5.0 volts
situation iq top center cpu tempmon
horizontal with small air flow ceiling fan 133 ma 48 c 61 c
horizontal still air 139 ma 61 c 75 c
inside sealed plastic box 4 cubic inch 143 ma 72 c 87 c
top center box outside surf at 39 c
816 is not usable but 720 is
4 cubic inch box was 0.66 x 2.10 x 2.90 inch medium hardness
plastic with 0.050 inch wall thickness.
Although the tempco of iq is positive, there is not enough gain
for a runaway (gain seems to be about 0.2).
The variance with volume/surface area was small - 5 deg c
improvement when vol increased to 11 cubic inch plastic.
The variance with material was small - 7 deg c improvement
when box matl 0.032 aluminum.
Versus clock in 4 cubic inch plastic box, amb = 26-27 c, still
air, box horizontal on plastic spacers, all numbers from
tempmon (limit is 90 c):
Code:
clock no box with box allow amb c allow amb f
396 50 c 58 c 58 136
528 54 c 61 c 55 131
600 60 c 67 c 49 120
720 67 c 78 c 38 100
816 76 c 87 c 29 84 nil margin
Outdoor:
Direct sunlight on the box will subtract 10-30 deg f from the
allow amb numbers. Here where I am, in the summer, 396 would
be borderline so for outdoor use it would be best to provide
a decent, short conduction path between the chip top surface
and the inside wall of an aluminum box.
Variance was +- 0.7 deg c from run to run and about +- 2 T4 to
T4 giving an rss of +- 2.1 deg c.
defragster edit: { added # / CODE block around table - that preserves some spacing elements }
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