ADS8699IPWR datasheet(28/74 Pages) TI2

28 / 74 page

The device internal reference is factory-trimmed to ensure the initial accuracy specification. The histogram in

Figure 7-8 shows the distribution of the internal voltage reference output taken from more than 3420 production

devices.

REFIO Voltage (V)

100

200

300

400

500

600

700

800

900

1000

4.094 4.0945 4.095 4.0955 4.096 4.0965 4.097 4.0975 4.098

D060

Figure 7-8. Internal Reference Accuracy Histogram at Room Temperature

The initial accuracy specification for the internal reference can be degraded if the die is exposed to any

mechanical or thermal stress. Heating the device when being soldered to a printed circuit board (PCB) and any

subsequent solder reﬂow is a primary cause for shifts in the VREF value. The main cause of thermal hysteresis is

a change in die stress and is therefore a function of the package, die-attach material, and molding compound, as

well as the layout of the device itself.

In order to illustrate this effect, 30 devices were soldered using lead-free solder paste with the manufacturer

suggested reflow profile, as explained in the AN-2029 Handling & Process Recommendations application report.

The internal voltage reference output is measured before and after the reflow process and the typical shift in

value is shown in Figure 7-9. Although all tested units exhibit a positive shift in their output voltages, negative

shifts are also possible. The histogram in Figure 7-9 shows the typical shift for exposure to a single reflow profile.

Exposure to multiple reflows, which is common on PCBs with surface-mount components on both sides, causes

additional shifts in the output voltage. If the PCB is to be exposed to multiple reflows, solder the ADS869x in the

second pass to minimize device exposure to thermal stress.

Error in REFIO Voltage (mV)

0.5

1.5

2.5

3.5

4.5

5.5

6.5

-7

-6

-5

-4

-3

-2

-1

D070

Figure 7-9. Solder Heat Shift Distribution Histogram

ADS8691, ADS8695, ADS8699

SBAS777B – DECEMBER 2016 – REVISED MARCH 2021

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ADS8699IPWR Datasheet(PDF) 28 Page - Texas Instruments

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