Detector Mode

The MAX2016 EV kit is assembled with a 0Ω resistor for

R3. This sets the slope of the difference output signal,

VOUTD, to approximately -25mV/dB (RF = 100MHz). To

increase the slope of the difference output signal,

increase the value of R3. For example, if a 20kΩ resis-

tor is used for R3, the slope for the difference signal

increases to -50mV/dB.

The bandwidth and response time of the difference out-

put amplifier can be controlled with an external capaci-

tor, C15. With no external capacitor, the bandwidth is

greater than 20MHz. Refer to the Applications

Information section in the MAX2016 data sheet for the

equation to calculate the required capacitance.

Gain-Controller Mode

The MAX2016 can be used as a gain controller within

an automatic gain-control (AGC) loop. In the gain-con-

and RFINB monitor the VGA’s input and output power

levels, respectively. The MAX2016 produces a DC volt-

age at VOUTD that is proportional to the difference in

these two RF input power levels. An internal op amp

compares the DC voltage with a reference voltage at

SETD. The op amp increases or decreases the voltage

at VOUTD until VOUTD equals to SETD. Thus, the

MAX2016 adjusts the gain of the VGA to a level deter-

mined by the voltage applied to SETD. Operate SETD

between 0.5V and 1.5V for the best dynamic range.

Frequency-Response Modifications

The MAX2016 EV kit has been optimized to support a

minimum operating frequency of 100MHz. However, if

desired, the kit can be modified to operate at a lower

frequency. The EV kit design includes external capaci-

tors (C5 and C12) to lower the frequency operation

below 100MHz. These capacitors should be loaded in

conjunction with changes in the values of C1, C2, C8,

and C9 to lower the input frequency range below

100MHz. Refer to the Applications Information section

in the MAX2016 data sheet for the equation to calculate

the required capacitance.

Power-Supply Connection

The MAX2016 is designed to operate from a single

+2.7V to +3.6V supply. To operate under a higher sup-

ply voltage range, a resistor must be connected in

voltage delivered to the chip. For a +4.75V to +5.25V

supply, change R6 to a 37.4Ω (±1%) resistor.

Layout Considerations

The MAX2016 evaluation board can be a guide for

board layout. Pay close attention to the thermal design

and close placement of the parts to the IC. The

MAX2016 package exposed paddle (EP) conducts heat

from the part and provides a low-impedance electrical

connection. The EP must be attached to the PCB

ground plane with a low thermal and electrical contact.

Ideally, this can be achieved by soldering the backside

package contact directly to a top metal ground plane on

the PCB. Alternatively, the EP can be connected to a

ground plane using an array of plated vias directly

below the EP. The MAX2016 EV kit uses nine equally

spaced, 0.012in-diameter, plated through holes to con-

nect the EP to the lower ground planes.

Keep the input traces carrying RF signals as short as

possible to minimize radiation and insertion loss due to

the PCB. The isolation of the RF inputs is dependent

upon the layout of these traces, which must be physical-

ly isolated from one another for optimum performance.

Each power-supply node on the PCB should have its

own decoupling capacitor. This minimizes supply cou-

pling from one section of the PCB to another. Using a

star topology for the supply layout, in which each power-

supply node in the circuit has a separate connection to

the central node, can further minimize coupling between

sections of the PCB.

MAX2016 Evaluation Kit

4

_______________________________________________________________________________________

MAX2016

LOGARITHMIC

DETECTOR

LOGARITHMIC

DETECTOR

20kΩ

VGA

GAIN-CONTROL INPUT

RFINA

RFINB

OUTD

SETD

VGA INPUT

VGA OUTPUT

SET-POINT

DAC

COUPLER

COUPLER

Figure 3. In the Gain-Controller Mode, the VOUTD Maintains

the Gain of the VGA