ADL5902ACPZ-R2 datasheet(19/28 Pages) AD

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ADL5902

Rev. 0 | Page 19 of 28

calculated by the linear-regression fit over the linear range of

the detector, typically at 25°C. The error in decibels is calculated

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

(15)

where PZ is the x-axis intercept expressed in decibels relative to

1 milliwatt (the input amplitude that would produce a 0 V output

if such an output were possible).

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. An

example of this type of plot is Figure 3. The slope and intercept

that form the ideal line are those at 25°C with CW modulation.

Figure 21 and Figure 24 show the error with various popular

forms of modulation with respect to the ideal CW line. This

method for calculating error is accurate, assuming that each

device is calibrated at room temperature.

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 that enough calibration points are used.

Figure 6 shows this plot type.

The error calculations for Figure 30 are similar to those for the

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

temperature are determined and applied as follows:

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

(16)

where:

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

temperature that would result in a VTEMP of 0 V if this were

possible).

Temp is the ambient temperature of the ADL5902 in degrees

Celsius.

Slope is, typically, 4.9 mV/°C.

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

MEASUREMENT MODE BASIC CONNECTIONS

The ADL5902 requires a single supply of nominally 5 V. The

supply is connected to the two VPOS supply pins. These pins

should each be decoupled using the two capacitors with values

equal or similar to those shown in Figure 45. These capacitors

should be placed as close as possible to the VPOS pins.

An external 60.4 Ω resistor combines with the relatively high RF

input impedance of the ADL5902 to provide a broadband 50 Ω

match. An ac coupling capacitor should be placed between this

resistor and INHI. The INLO input should be ac-coupled to

ground using the same value capacitor. Because the ADL5902

has a minimum input operating frequency of 50 MHz, 100 pF

ac coupling capacitors can be used.

The ADL5902 is placed in measurement mode by connecting

VOUT to VSET. In measurement mode, the output voltage is

proportional to the log of the rms input signal level.

BIAS AND POWER-

DOWN CONTROL

LINEAR-IN-dB VGA

(NEGATIVE SLOPE)

IDET

26pF

ADL5902

VREF

2.3V

TEMPERATURE

SENSOR

INLO

INHI

VPOS

POS

TEMP

VSET

VOUT

CLPF

COMM

VTGT

VREF

TADJ/PWDN

G = 5

ITGT

60.4

Ω

C10

100pF

C12

100pF

0.1µF

100pF

0.1µF

R11

Ω

R10

3.74k

Ω

R12

(SEE TABLE 4)

(SEE

TABLE 4)

10µF

(SEE THE

CHOOSING A

VALUE FOR

CLPF SECTION.)

RFIN

Figure 45. Basic Connections for Operation in Measurement Mode

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