LT1460 LINER [Linear Technology], LT1460 Datasheet - Page 19

• Manufacturer Part Number: LT1460
• Description: Micropower Precision Series Reference Family
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
deform the board a fi xed amount as shown in Figure 15.
The fl exure #1 represents no displacement, fl exure #2 is
concave movement, fl exure #3 is relaxation to no displace-
ment and fi nally, fl exure #4 is a convex movement. This
motion is repeated for a number of cycles and the relative
output deviation is noted. The result shown in Figure 16a
is for two LT1460S8-2.5s mounted vertically and Figure
16b is for two LT1460S8-2.5s mounted horizontally. The
parts oriented in Figure 16a impart less stress into the
package because stress is absorbed in the leads. Figures
16a and 16b show the deviation to be between 125µV and
–1
–1
2
1
0
2
1
0
0
0
Figure 17a. Same Two LT1460S8-2.5s in Figure 16a,
but with Slots
Figure 16a. Two Typical LT1460S8-2.5s, Vertical
Orientation Without Slots
1
2
3
4
Figure 15. Flexure Numbers
10
10
U
FLEXURE NUMBER
FLEXURE NUMBER
U
LONG DIMENSION
20
20
W
SLOT
30
30
1460 F15
U
1460 F16a
1460 F17a
40
40
250µV and implies a 50ppm and 100ppm change respec-
tively. This corresponds to a 13- to 14-bit system and is
not a problem for most 10- to 12-bit systems unless the
system has a calibration. In this case, as with temperature
hysteresis, this low level can be important and even more
careful techniques are required.
The most effective technique to improve PC board stress
is to cut slots in the board around the reference to serve
as a strain relief. These slots can be cut on three sides of
the reference and the leads can exit on the fourth side. This
“tongue” of PC board material can be oriented in the long
direction of the board to further reduce stress transferred
to the reference.
The results of slotting the PC boards of Figures 16a and
16b are shown in Figures 17a and 17b. In this example
the slots can improve the output shift from about 100ppm
to nearly zero.
–1
–1
1
0
2
1
0
2
0
0
Figure 16b. Two Typical LT1460S8-2.5s, Horizontal
Orientation Without Slots
Figure 17b. Same Two LT1460S8-2.5s in Figure 16b,
but with Slots
10
10
FLEXURE NUMBER
FLEXURE NUMBER
LONG DIMENSION
20
20
SLOT
30
30
LT1460
19
1460 F17b
1460 F16b
1460f
40
40