max2016etit Maxim Integrated Products, Inc., max2016etit Datasheet - Page 11

• Manufacturer Part Number: max2016etit
• Description: Max2016 Lf-to-2.5ghz Dual Logarithmic Detector/controller For Power, Gain, And Vswr Measurements
• Manufacturer: Maxim Integrated Products, Inc.

Controller for Power, Gain, and VSWR Measurements
The differential RF inputs allow for the measurement of
broadband signals ranging from low frequency to
2.5GHz. For single-ended signals, RFINA- and RFINB-
are AC-coupled to ground. The RF inputs are internally
biased and need to be AC-coupled. Using 680pF
capacitors, as shown in the Typical Application Circuit,
results in a 10MHz highpass corner frequency. An
internal 50Ω resistor between RFINA+ and RFINA- (as
well as RFINB+ and RFINB-) produces a good low-fre-
quency to 3.0GHz match.
The SET_ inputs are used for loop control when the
device is in controller mode. Likewise, these same
SET_ inputs are used to set the slope of the output sig-
nal (mV/dB) when the MAX2016 is in detector mode.
The center node of the internal resistor-divider is fed to
the negative input of the power detector’s internal out-
put op amp.
The MAX2016 has an on-chip 2V voltage reference.
The internal reference output is connected to REF. The
output can be used as a reference voltage source for
the comparators or other components and can source
up to 2mA.
Each OUT_ is a DC voltage proportional to the RF input
power level. The change of OUT_ with respect to the
power input is approximately 18mV/dB (R
Figure 1. VSWR Monitoring Configuation
TRANSMITTER
SETA, SETB, and SETD Inputs
______________________________________________________________________________________
LF-to-2.5GHz Dual Logarithmic Detector/
COUPLER
OUTA and OUTB
CIRCULATOR
1
Reference
ATTENUATOR
= R
2
= 0Ω).
RFINA
RFINB
LOGARITHMIC
LOGARITHMIC
DETECTOR
DETECTOR
The input power level can be determined by the following
equation:
where P
the output voltage intersects the horizontal axis.
OUTD is a DC voltage proportional to the difference of
the input RF power levels. The change of the OUTD
with respect to the power difference is -25mV/dB (R3 =
0Ω). The difference of the input power levels (gain) can
be determined by the following equation:
where V
P
The MAX2016 can be used to measure the VSWR of an
RF signal, which is useful for detecting the presence or
absence of a properly loaded termination, such as an
antenna (see Figure 1). The transmitted wave from the
power amplifier is coupled to RFINA and to the anten-
na. The reflected wave from the antenna is connected
to RFINB through a circulator. When the antenna is
missing or damaged, a mismatch in the nominal load
MAX2016
RFINA
= P
CENTER
INT
P
RFINA
RFINB
Monitoring VSWR and Return Loss
is the extrapolated intercept point of where
20kΩ
V
REF
Applications Information
.
P
is the output voltage, typically 1V, when
−
RFIN
P
RFINB
_
=
COUTL
CSETL
SLOPE
=
V
OUTD
SETD
GND
OUT
(
V
OUTD
_
+
SLOPE
P
−
INT
V
COUTL
OUTD
CENTER
)
OUTD
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