AD8363ACPZ-R7 datasheet(20/36 Pages) AD

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AD8363

Rev. 0 | Page 20 of 36

VTGT INTERFACE

The target voltage can be set with an external source or by

connecting the VREF pin (nominally 2.3 V) to the VTGT pin

through a resistive voltage divider. With 1.4 V on the VTGT pin,

the rms voltage that must be provided by the VGA to balance the

AGC feedback loop is 1.4 V × 0.05 = 70 mV rms. Most of the

characterization information in this data sheet was collected at

VTGT = 1.4 V. Voltages higher and lower than this can be used;

however, doing so increases or decreases the gain at the internal

squaring cell, which results in a corresponding increase or

decrease in intercept. This in turn affects the sensitivity and the

usable measurement range. Because the gain of the squaring

cell varies with temperature, oscillations or a loss in measurement

range can result. For these reasons, do not reduce VTGT below 1.3 V.

VTGT

50k

Ω

50k

Ω

10k

Ω

ESD

VPOS

COMM

g × X2

ITGT

Figure 52. VTGT Interface Simplified Schematic

OPERATION TO 125°C

Most of the information in this data sheet describes operation up

to, but not exceeding, 85°C. Operation up to 125°C is possible;

however, the performance of the AD8363 above 85°C can be

degraded. Figure 53 shows the typical operation at 125°C as

compared to other temperatures using the TCM1 and TCM2

values in Table 4. Temperature compensation can be optimized

for operation above 85°C by modifying the voltages on the TCM1

and TCM2 pins from those shown in Table 4.

–3

–1

–2

–60

–50

–40

–30

–20

–10

PIN (dBm)

INHI INPUT

VTCM1 = 0.52V, VTCM2 = 0.6V

–40°C

+25°C

+85°C

+125°C

Figure 53. VOUT and Log Conformance Error vs.

Input Amplitude at 2.14 GHz, −40°C to +125°C

BASIS FOR ERROR CALCULATIONS

The slope and intercept used in the error plots are calculated

using the coefficients of a linear regression performed on data

collected in its central operating range. The error plots in the

Typical Performance Characteristics section are shown in two

formats: error from the ideal line and error with respect to 25°C.

The error from the ideal line is the decibel difference in VOUT

from the ideal straight-line fit of VOUT calculated by the linear-

regression fit over the linear range of the detector, typically at

25°C. The error in decibels is calculated by

Error (dB) = (VOUT − Slope × (PIN − PZ))/Slope

(12)

where PZ is the x-axis intercept expressed in dBm (the input

amplitude that produces a 0 V output, if such an output is possible).

The linear range of the detector was assumed to be −20 dBm to

−40 dBm. The error from the ideal line is not a measure of absolute

accuracy because it is calculated using the slope and intercept of

each device. However, it verifies the linearity and the effect of

temperature and modulation on the response of the device.

Examples of this type of plot are Figure 3 and Figure 4. The slope

and intercept that form the ideal line are those at 25°C with CW

modulation. Figure 27, Figure 28, Figure 30, and Figure 31 show

the error with various popular forms of modulation with respect to

the ideal CW line. This method for calculating error is accurate

assuming each device is calibrated at room temperature and/or

CW modulation, as appropriate.

In the second plot format, the VOUT voltage at a given input

amplitude and temperature is subtracted from the corresponding

VOUT at 25°C and then divided by the 25°C slope to obtain an error

in decibels. This type of plot does not provide any information on

the linear-in-dB performance of the device; it merely shows the

decibel equivalent of the deviation of VOUT over temperature,

given a calibration at 25°C. When calculating error from any

one particular calibration point, this error format is accurate. It is

accurate over the full range shown on the plot assuming enough

calibration points are used. Figure 5 shows this plot type.

The error calculation for Figure 32 is in the same method as the

first type previously mentioned, except that instead of varying

the operating temperature of the device, the operating voltage

was varied and the error is expressed with the nominal (5 V)

response as the base response.

The error calculations for Figure 26 are similar to that for the

VOUT plots. The slope and intercept of the VTEMP function vs.

temperature were determined and applied as follows:

Error (°C) = (VTEMP − Slope × (Temp − TZ))/Slope

(13)

where:

TZ is the x-axis intercept expressed in degrees Celsius (the

temperature that would result in a VTEMP of 0 V (an

extrapolation because this is not possible).

Temp is the temperature of the AD8363 in degrees Celsius.

Slope is expressed in V/°C.

VTEMP is the voltage at the TEMP pin at that temperature.

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