ADL5519-EVALZ Analog Devices Inc, ADL5519-EVALZ Datasheet - Page 28

• Manufacturer Part Number: ADL5519-EVALZ
• Description: EVALUATION BOARD FOR ADL5519
• Manufacturer: Analog Devices Inc
• Series: -r
• Type: Controllerr

Specifications of ADL5519-EVALZ

• Frequency: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: *
• Other names: Q4463053

ADL5519
APPLICATIONS INFORMATION
MEASUREMENT MODE
The ADL5519 is placed in measurement mode by connecting
OUTA, OUTB to VSTA, VSTB, respectively. The part has an offset
voltage, a negative slope, and a V
cept at the high end of its input signal range.
The output voltage vs. input signal voltage of the ADL5519 is
linear-in-dB over a multidecade range. The equation for this
function is of the following form:
where:
x is the feedback factor in V
V
V
the V
V
An offset voltage, V
the detector signal so that the minimum value for V
x × V
The slope is very stable vs. process and temperature variation.
When Base-10 logarithms are used, V
volts/decade. A decade corresponds to 20 dB; V
V
As noted in Equation 13 and Equation 14, the V
a negative slope. This is also the correct slope polarity to control
the gain of many VGAs in a negative feedback configuration.
Because both the slope and intercept vary slightly with frequency,
see the Specifications section for application-specific values for
slope and intercept.
Although demodulating log amps respond to input signal
voltage and not input signal power, it is customary to discuss
the amplitude of high frequency signals in terms of power. In
this case, the characteristic impedance of the system, Z
be known to convert voltages to their corresponding power levels.
The following equations are used to perform this conversion:
For example, P
in terms of dBm (decibels referred to 1 mW), in a 50 Ω system is
SLOPE/DEC
INTERCEPT
INTERCEPT
SLOPE/dB
V
x × V
P (dBm) = 10 × log
P (dBV) = 20 × log
P (dBm) = P (dBV) − 10 × log
P
P
2 dBV − 10 × log
OUT
OFFSET
INTERCEPT
INTERCEPT
OUT
represents the slope in V/dB.
vs. V
is nominally −440 mV/decade or −22 mV/dB.
is the x-axis intercept of the linear-in-dB portion of
is 2 dBV for a sinusoidal input signal.
= x × V
SLOPE/dB
. If x = 1, the minimum V
IN
(dBm) =
(dBV) − 10 × log
INTERCEPT
curve.
× 20 × log
SLOPE/DEC
OFFSET
10
, for a sinusoidal input signal expressed
(50 × 10
10
10
, of 0.45 V is internally added to
(V
× log
(V
10
rms
SET
rms
(V
/1 V
2
10
= V
/(Z
IN
10
−3
(V
/V
(Z
OUTA,
) = 15 dBm
0
rms
IN
OUT
10
0
INTERCEPT
× 1 mW))
/V
OUT
× 1 mW/1 V
)
(Z
/x.
V
SLOPE/DEC
INTERCEPT
0
OUTB
value is 0.45 V.
× 1 mW/1 V
)
measurement inter-
represents the
) =
SLOPE/DEC
OUT
rms
2
voltage has
) =
OUT
rms
0
2
/20 =
, must
)
is
(13)
(14)
(15)
(16)
(17)
Rev. A | Page 28 of 40
For a square wave input signal in a 200 Ω system
More information about the intercept variation dependence upon
waveform can be found in the
As the input signals to Channel A and Channel B are swept over
their nominal input dynamic range of −5 dBm to −55 dBm, the
output swings from 0.5 V to 1.6 V. The voltages of OUTA, OUTB
are also internally applied to a difference amplifier with a gain
of 1. When the input power is swept, OUTP swings from approxi-
mately 0.5 V to 1.75 V, and OUTN swings from 1.75 V to 0.5 V.
The VLVL pin sets the common-mode voltage for OUTP, OUTN.
An output common-mode voltage of ≤1.15 V can be set using
a resistor divider between the VREF and VLVL pins. Measurement
of large differences between INHA, INHB can be affected by
on-chip signal leakage.
CONTROLLER MODE
In addition to being a measurement device, the ADL5519 can
also be configured to set and control signal levels. Each of the two
log detectors can be separately configured to set and control the
output power level of a VGA or variable voltage attenuator (VVA).
See the Controller Mode section of the
information on running a single channel in controller mode.
Alternatively, the two log detectors can be configured to measure
and control the gain of an amplifier or signal chain. The channel
difference outputs can be used to control a feedback loop to the
ADL5519 RF inputs. A capacitor connected between FBKA and
OUTP forms an integrator, keeping in mind that the on-chip 1 kΩ
feedback resistor forms a 0. (The value of the on-chip resistors can
vary as much as ±20% with manufacturing process variation.)
If Channel A is driven and Channel B has a feedback loop from
OUTP through a VGA, OUTP integrates to a voltage value
such that
The output value from OUTN may or may not be useful. It is
given by
for VLVL < OUTA/3.
Otherwise,
P
−1 dBV − 10 × log
OUTB = (OUTA + VLVL)/2
OUTN = 0 V
OUTN = (3 × VLVL − OUTA)/2
INTERCEPT
(dBm) =
10
[(200 Ω × 1 mW/1V
AD8313
AD8317
and
AD8307
rms
datasheet for more
2
)] = +6 dBm
data sheets.
(18)
(19)
(20)