AD8311

Rev. A | Page 19 of 24

10

–60

0

1.6

VSET (V)

0

–10

–20

–30

–40

–50

4

–3

2

1

0

–1

–2

3

0.2

0.4

0.6

0.8

1.0

1.2

1.4

–40°C

+25°C

+85°C

–40°C

+25°C

DOES NOT TAKE INTO ACCOUNT TRANSFER

FUNCTIONS’ NONLINEARITIES AT +25°C

+85°C

Another way of presenting the error function of a log amp

detector is shown in Figure 40. In this case, the dB error at hot

and cold temperatures is calculated with respect to the transfer

function at ambient. This is a key difference in comparison to

the previous plots. Up to now, all errors have been calculated

with respect to the ideal transfer function at ambient.

When we use this alternative technique, the error at ambient

becomes by definition equal to 0 (see Figure 40).

This would be valid if the device transfer function perfectly

followed the ideal PIN = VSET / SLOPE + INTERCEPT equation.

However since a log amp in practice never perfectly follows this

equation (especially outside of its linear operating range), this

plot tends to artificially improve linearity and extend the

dynamic range. This plot is a useful tool for estimating

temperature drift at a particular power level with respect to the

(nonideal) response at ambient. However, achieving this level of

accuracy in an end application requires calibration at multiple

points in the device’s operating range.

Figure 40. Error vs. Temperature with respect to Output Voltage at 25 °C

DEVICE HANDLING

The wafer-level chip scale package consists of solder bumps

connected to the active side of the die. The part is lead-free with

95.5% tin, 4.0% silver, and 0.5% copper solder bump

composition. The WLCSP package can be mounted on printed

circuit boards using standard surface-mount assembly

techniques; however, caution should be taken to avoid

damaging the die. See the AN-617 application note for

additional information. WLCSP devices are bumped die, and

exposed die can be sensitive to light condition, which can

influence specified limits.