Datasheet

LT6656
14
6656fc
For more information www.linear.com/LT6656
APPLICATIONS INFORMATION
Figure 12. Lead Free Reflow Profile Due to IR Reflow
Figure 9. LT6656 S6, DC –40°C to 85°C Hysteresis
Figure 11. LT6656 LS8 –40°C to 85°C Hysteresis
Figure 10. LT6656 LS8 0°C to 70°C Hysteresis
HYSTERESIS (ppm)
–160 –120 –40–80
NUMBER OF UNITS
20
18
14
12
8
4
16
10
6
2
0
6656 F09
160
12040 800
–40°C TO 25°C
85°C TO 25°C
2.5V OPTION
V
IN
= 3V
C
L
= 1µF
I
L
= 0
Figure 8. LT6656 S6, DC 0°C to 70°C Hysteresis
HYSTERESIS (ppm)
–60 –40 –20
NUMBER OF UNITS
30
25
15
5
20
10
0
6656 F08
6040200
2.5V OPTION
V
IN
= 3V
C
L
= 1µF
I
L
= 0
0°C TO 25°C
70°C TO 25°C
IR reflow. Common lead free IR reflow profiles reach over
250°C, considerably more than lead solder profiles. The
higher reflow temperature of the lead free parts exacerbates
the issue of thermal expansion and contraction causing
the output shift to generally be greater than with a leaded
reflow process.
The lead free IR reflow profile used to experimentally
measure the output voltage shift in the LT6656-2.5 is
shown in Figure 12. Similar results can be expected us
-
ing a convection reflow oven. Figures 13 and 14 show the
change in output voltage that was measured for parts that
were run through the reflow process for 1 cycle and also 3
cycles. Additional drift of the LT6656 after IR reflow does
not vary significantly.
HYSTERESIS (ppm)
–60 –40 –20
NUMBER OF UNITS
20
15
5
10
0
6656 F10
6040200
1.25V OPTION
V
IN
= 2V
C
L
= 1µF
I
L
= 0
0°C TO 25°C
70°C TO 25°C
HYSTERESIS (ppm)
–160 –120 –40–80
NUMBER OF UNITS
20
15
10
5
0
6656 F11
16012040 800
–40°C TO 25°C
85°C TO 25°C
1.25V OPTION
V
IN
= 2V
C
L
= 1µF
I
L
= 0
0 2 4 6
MINUTES
8
0
75
150
225
300
6656 F12
10
120s
40s
t
P
30s
T
P
= 260°C
RAMP
DOWN
RAMP TO
150°C
T
S
= 190°C
T = 150°C
t
L
130s
T
L
= 217°C
T
S(MAX)
= 200°C
380s