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 3GHz

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 3GHz. For

single-ended signals, AC-couple INLO to ground. The

RF inputs are internally biased and need to be AC-cou-

pled using 680pF capacitors as shown in Figure 1 and

Figure 2. An internal 50Ω 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 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 MAX2015 requires power-supply bypass capacitors

connect a 0.1µF capacitor (C4, C6) and a 100pF capac-

itor (C3, C5) with the 100pF capacitor being closest to

the pin.

set R4 = 0Ω (see the typical applications circuits).

5.25V, set R4 = 75Ω ±1% (100ppm/°C max) and PWDN

must be connected to GND.

Power-Down Mode

The MAX2015 can be powered down by driving PWDN

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 = 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 MAX2015 can also be used as a detector/controller

within an AGC loop. Figure 3 depicts one scenario

where the MAX2015 is employed as the controller for a

variable-gain PA. As shown in the figure, the MAX2015

monitors the output of the PA through a directional cou-

pler. An internal integrator (Figure 2) compares the

0.1GHz to 3GHz, 75dB Logarithmic

Detector/Controller

8

_______________________________________________________________________________________

MAX2015

C6

C1

C5

1

2

OUT

SET

C4

C3

4

INLO

OUT

20kΩ

20kΩ

INHI

7

8

RFIN

C2

3

DETECTORS

R1

GND

6

PWDN

5

R4

Figure 1. Detector-Mode (RSSI) Typical Application Circuit

Table 1. Suggested Components of

Typical Applications Circuits

DESIGNATION

VALUE

TYPE

C1, C2

680pF

0603 ceramic capacitors

C3, C5

100pF

0603 ceramic capacitors

C4, C6

0.1µF

0603 ceramic capacitors

R1*

0

Ω

0603 resistor

R4**

0

Ω

0603 resistor

*RSSI mode only.