1461C3 Ver la hoja de datos (PDF) - Linear Technology
Número de pieza
componentes Descripción
Fabricante
1461C3 Datasheet PDF : 16 Pages
| |||
LT1461
APPLICATIO S I FOR ATIO
parts alone. What is more interesting are parts IR soldered
onto a PC board. If the PC board is then temperature cycled
several times from – 40°C to 85°C, the resulting hysteresis
curve is shown in Figure 8. This graph shows the influence
of the PC board stress on the reference.
When the LT1461 is soldered onto a PC board, the output
shifts due to thermal hysteresis. Figure 9 shows the effect
of soldering 40 pieces onto a PC board using standard IR
reflow techniques. The average output voltage shift is
–110ppm. Remeasurement of these parts after 12 days
shows the outputs typically shift back 45ppm toward their
initial value. This second shift is due to the relaxation of
stress incurred during soldering.
The LT1461 is capable of dissipating high power, i.e., for
the LT1461-2.5, 17.5V • 50mA = 875mW. The SO-8
package has a thermal resistance of 190°C/W and this
dissipation causes a 166°C internal rise producing a
junction temperature of TJ = 25°C + 166°C = 191°C. What
will actually occur is the thermal shutdown will limit the
junction temperature to around 150°C. This high tempera-
ture excursion will cause the output to shift due to thermal
hysteresis. Under these conditions, a typical output shift
is –135ppm, although this number can be higher. This
high dissipation can cause the 25°C output accuracy to
exceed its specified limit. For best accuracy and preci-
sion, the LT1461 junction temperature should not ex-
ceed 125°C.
12
11
WORST-CASE HYSTERESIS
ON 35 UNITS
10
9
85°C TO 25°C
8
7
6
5
4
3
2
1
0
– 200 –160 –120 – 80 – 40
0
40
HYSTERESIS (ppm)
– 40°C TO 25°C
80 120 160 200
1461 F08
Figure 8. – 40°C to 85°C Hysteresis of 35 Parts Soldered Onto a PC Board
12
10
8
6
4
2
0
–300 –200 –100 0 100 200 300
OUTPUT VOLTAGE SHIFT (ppm)
1461 F09
Figure 9. Typical Distribution of Output Voltage Shift After Soldering Onto PC Board
13
Share Link: 