MAX2014
50MHz to 1000MHz, 75dB Logarithmic
Detector/Controller
9
Detailed Description
The MAX2014 is a successive detection logarithmic
amplifier designed for use in RF power measurement
and AGC applications with a 50MHz to 1000MHz
frequency range from a single 2.7V to 3.6V power
supply. It is pin compatible with other leading logarith-
mic amplifiers.
The MAX2014 provides for improved performance with
a high 75dB dynamic range at 100MHz, and exception-
al accuracy over the extended temperature range and
supply voltage range.
RF Input
The MAX2014 differential RF input (INHI, INLO) allows
for broadband signals between 50MHz and 1000MHz.
For single-ended signals, AC-couple INLO to ground.
The RF inputs are internally biased and need to be AC-
coupled using 680pF capacitors as shown in Figures 1
and 2. An internal 50Ω resistor between INHI and INLO
provides a good 50MHz to 1000MHz match.
SET Input
The SET input is used for loop control when in controller
mode or to set the slope of the output signal (mV/dB)
when in detector mode. The internal input structure of
SET is two series 20kΩ resistors connected to ground.
The center node of the resistors is fed to the negative
input of the internal output op amp.
Power-Supply Connections
The MAX2014 requires power-supply bypass capacitors
connected close to each V
CC
pin. At each V
CC
pin,
connect a 0.1µF capacitor (C4, C6) and a 100pF capac-
itor (C3, C5), with the 100pF capacitor being closest to
the pin.
For power-supply voltages (V
S
) between 2.7V and 3.6V,
set R4 = 0Ω (see the typical application circuits, Figures
1 and 2 ).
For power-supply voltages (V
S
) between 4.75V and
5.25V, set R4 = 75Ω ±1% (100ppm/°C max) and PWDN
must be connected to GND.
Power-Down Mode
The MAX2014 can be powered down by driving PWDN
with logic-high (logic-high = V
CC
). In power-down
mode, the supply current is reduced to a typical value
of 1µA. For normal operation, drive PWDN with a logic-
low. It is recommended when using power-down that
an RF signal not be applied before the power-down
signal is low.
Applications Information
Detector (RSSI) Mode
In detector mode, the MAX2014 acts like an RSSI,
which provides an output voltage proportional to the
input power. This is accomplished by providing a feed-
back path from OUT to SET (R1 = 0Ω; see Figure 1).
By connecting SET directly to OUT, the op amp gain is
set to 2V/V due to two internal 20kΩ feedback resistors.
This provides a detector slope of approximately
18mV/dB with a 0.5V to 1.8V output range.
Controller Mode
The MAX2014 can also be used as a detector/controller
within an AGC loop. Figure 3 depicts one scenario
where the MAX2014 is employed as the controller for a
