Datasheet

LTC6655
17
6655fa
IR Reflow Shift
The mechanical stress of soldering a part to a board can
cause the output voltage to shift. Moreover, the heat of
an IR reflow or convection soldering oven can also cause
the output voltage to shift. The materials that make up a
semiconductor device and its package have different rates
of expansion and contraction. After a part undergoes the
extreme heat of a lead-free IR reflow profile, like the one
applicaTions inForMaTion
Figure 19. Lead-Free Reflow Profile
Figure 20. Output Voltage Shift Due to IR Reflow
shown in Figure 19, the output voltage shifts. After the
device expands, due to the heat, and then contracts, the
stresses on the die have changed position. This shift is
similar, but more extreme than thermal hysteresis.
Experimental results of IR reflow shift are shown below
in Figure 20. These results show only shift due to reflow
and not mechanical stress.
MINUTES
0
TEMPERATURE (°C)
150
225
8
6655 F19
75
0
2
4
6
10
300
T = 150°C
T
S
= 190°C
T
L
= 217°C
T
P
= 260°C
380s
t
P
30s
t
L
130s
40s
120s
RAMP
DOWN
T
S(MAX)
= 200°C
RAMP TO
150°C
OUTPUT VOLTAGE SHIFT DUE TO IR REFLOW (%)
–0.029
0
NUMBER OF UNITS
2
4
6
–0.023 –0.017 –0.005–0.011
8
1
3
5
7
6655 F20
Figure 17. Low Frequency Noise Histogram of the LTC6655-2.5
Figure 18. LTC6655-2.5 Low Frequency Noise Spectrum
PEAK-TO-PEAK NOISE (nV)
450
0
NUMBER OF OBSERVATIONS
5
15
20
25
35
6655 F17
10
30
650
950
550
750 850
FREQUENCY (Hz)
0.1
0
NOISE VOLTAGE (nV/√Hz)
120
160
200
1 10 100
6655 F18
80
40