LT1236LS8 datasheet(9/16 Pages) LINER

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LT1236LS8

1236ls8f

applicaTions inForMaTion

Figure 2b. Hysteresis Plot –40°C to 85°C

Figure 2a. Hysteresis Plot 0°C to 70°C

DISTRIBUTION (ppm)

–120

–80

–40

120

1236ls8 F02b

25°C TO –40°C TO 25°C

25°C TO 85°C TO 25°C

DISTRIBUTION (ppm)

–50

–10

–30

1236ls8 F02a

25°C TO 0°C TO 25°C

25°C TO 70°C TO 25°C

Hysteresis

Thermal hysteresis is a measure of change of output volt-

age as a result of temperature cycling. Figure 2a and 2b

illustrate the typical hysteresis based on data taken from

the LT1236LS8. A proprietary design technique minimizes

thermal hysteresis.

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

shown in Figure 3, the output voltage shifts. After the

device expands, due to the heat, and then contracts, the

Humidity Sensitivity

Plastic mold compounds absorb moisture. With changes

in relative humidity, plastic packaging materials change

the amount of pressure they apply to the die inside, which

can cause slight changes in the output of a voltage refer-

ence, usually on the order of 100ppm. The LS8 package is

hermetic, so it is not affected by humidity, and is therefore

more stable in environments where humidity may be a

concern.However,PCBoardmaterialmayabsorbmoisture

and apply mechanical stress to the LT1236LS8. Proper

board materials and layout are essential.

Figure 3. Lead-Free Reflow Profile

Figure 4. Output Voltage Shift Due to IR Reflow

MINUTES

150

225

1236ls8 F03

300

T = 150°C

TS = 190°C

TL = 217°C

TP = 260°C

380s

30s

130s

40s

120s

RAMP

DOWN

TS(MAX) = 200°C

RAMP TO

150°C

REFLOW SHIFT (%)

–0.05

–0.03

–0.01

–0.04

–0.02

0.01

1236ls8 F04

× REFLOW

24Hr REST

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 4. These results show only shift due to reflow

and not mechanical stress.

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