ADL5906SCPZN-R7 datasheet(19/30 Pages) AD

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Data Sheet

ADL5906

THEORY OF OPERATION

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Rev. B | 19 of 30

wake-up response varies depending on the input coupling and the

value of CRMS.

Figure 46. TADJ/PWDN Interface Simplified Schematic

VSET INTERFACE

The VSET interface has a high input impedance of 72 kΩ. The

voltage at VSET is converted to an internal current used to set the

internal VGA gain. The VGA attenuation control is approximately 18

dB/V.

Figure 47. VSET Interface Simplified Schematic

OUTPUT INTERFACE

The ADL5906 incorporates rail-to-rail output drivers with pull-up and

pull-down capabilities. The level shift circuitry and the output ampli-

fier are very fast compared to the typical rms response required by

a complex waveform. In essence, the output stage from the CRMS

pin to the VRMS output is only a dc signal because by definition

VRMS is supposed to be a single rms value. The VRMS pin can

source and sink up to 10 mA.

Figure 48. VRMS Interface Simplified Schematic

VTGT INTERFACE

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

necting the VREF pin (nominally 2.3 V) to the VTGT pin through

a resistive voltage divider. With 0.8 V on the VTGT pin, the rms

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

feedback loop is 0.8 V × 0.05 = 40 mV rms. Most of the characteri-

zation information in this data sheet was collected at VTGT = 0.8 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, in addition to the sensitivity to different carrier modulation

schemes. As VTGT decreases, the squaring circuits produce more

noise; this becomes noticeable in the output response at low input

signal amplitudes. As VTGT increases, measurement error due to

modulation increases, and temperature drift tends to decrease. The

chosen VTGT value of 0.8 V represents a compromise between

these characteristics.

Figure 49. VTGT Interface

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 Perform-

ance Characteristics section are shown in two formats: error from

the ideal line and error with respect to the 25°C output voltage. The

error from the ideal line is the decibel difference in VRMS from the

ideal straight-line fit of VRMS 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) = (VRMS − Slope × (PIN − PZ))/Slope

(9)

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

1 mW (the input amplitude that produces 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 tempera-

ture and modulation on the response of the device. An example

of this type of plot is Figure 9. The slope and intercept that form

the ideal line are those at 25°C with CW modulation. Figure 4,

Figure 5, Figure 7, and Figure 8 show the error with various popular

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