Detailed Description
The MAX2015 is a successive detection logarithmic
amplifier designed for use in RF power measurement
and AGC applications with a 0.1GHz to 2.5GHz
frequency range from a single 2.7V to 3.6V power
supply. It is pin compatible with other leading logarith-
mic amplifiers.
The MAX2015 provides for improved performance with a
high 75dB dynamic range at 100MHz, and exceptional
accuracy over the extended temperature range and sup-
ply voltage range.
RF Input
The MAX2015 differential RF input (INHI, INLO) allows
for broadband signals between 100MHz and 2.5GHz.
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 Figure 1
and Figure 2. An internal 50
resistor between INHI
and INLO provides a good 50MHz to 3.0GHz 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 20k
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 MAX2015 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 = 0
(see
Typical Apllications Circuits
).
For power-supply voltages (V
S
) between 4.75V and
5.25V, set R4 = 75
±1% (100ppm/
°
C max) and PWDN
must be connected to GND.
Power-Down Mode
The MAX2015 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 MAX2015 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 = 0
; see Figure 1).
By connecting SET directly to OUT, the op amp gain is
set to 2V/V due to two internal 20k
feedback resistors.
This provides a detector slope of approximately
18mV/dB with a 0.5V to 1.8V output range.
M
0.1GHz to 2.5GHz, 75dB Logarithmic
Detector/Controller
8
_______________________________________________________________________________________
MAX2015
C6
C1
C5
1
2
OUT
SET
C4
C3
4
V
CC
V
CC
INLO
OUT
20k
20k
INHI
7
8
RFIN
C2
3
DETECTORS
R1
GND
6
PWDN
5
R4
V
S
Figure 1. Detector-Mode (RSSI) Typical Application Circuit
Table 1. Suggested Components of
Typical Applications Circuits
DESIGNATION
C1, C2
C3, C5
C4, C6
R1*
R4**
VALUE
680pF
100pF
0.1μF
0
0
TYPE
0603 ceramic capacitors
0603 ceramic capacitors
0603 ceramic capacitors
0603 resistor
0603 resistor
*
RSSI mode only.
**
V
S
= 2.7V to 3.6V.