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

detected signal with a reference voltage determined by

es or decreases the voltage at OUT, according to how

erence. The MAX2015 adjusts the power of the PA to a

level determined by the voltage applied to SET. With R1 =

0

Ω, the controller mode slope is approximately

19mV/dB (RF = 100MHz).

Layout Considerations

As with any RF circuit, the layout of the MAX2015 circuit

affects the device’s performance. Use an abundant num-

ber of ground vias to minimize RF coupling. Place the

input capacitors (C1, C2) and the bypass capacitors

(C3–C6) as close to the IC as possible. Connect the

bypass capacitors to the ground plane with multiple vias.

0.1GHz to 2.5GHz, 75dB Logarithmic

Detector/Controller

_______________________________________________________________________________________

9

MAX2015

C6

R4

C1

C5

1

2

OUT

SET

C4

C3

4

INLO

20k

Ω

20k

Ω

INHI

7

8

RFIN

C2

3

DETECTORS

GND

6

PWDN

5

Figure 2. Controller-Mode Typical Application Circuit

MAX2015

OUT

SET

20k

Ω

20k

Ω

IN

COUPLER

LOGARITHMIC

DETECTOR

TRANSMITTER

POWER AMPLIFIER

GAIN-CONTROL INPUT

SET-POINT

DAC

Figure 3. System Diagram for Automatic Gain-Control Loop

1

2

3

4

8

7

6

5

OUT

SET

GND

PWDN

INLO

INHI

MAX2015

µMAX

TOP VIEW

Pin Configuration

Chip Information

TRANSISTOR COUNT: 3157

PROCESS: BiCMOS