MAX9939EVKIT+ Datasheet MAX9939EVKIT+ | P4-P6

Evaluates: MAX9939

Programming Gain and Input

Offset Voltage

The Gain/Offset Setting group box of the MAX9939 EV

kit software controls the data written to the two internal

registers of the MAX9939 IC. The Gain Selection drop-

down list writes to the gain register to set the gain of the

amplifier. The Input Offset(mV) drop-down list writes to

the input offset voltage (V

) register to cancel the

inherent offset voltage of the amplifier. Refer to Tables

3 and 4 in the MAX9939 IC data sheet for gain and

input offset voltage settings.

Shutdown

The Shutdown checkbox of the MAX9939 EV kit GUI

allows the user to place the device in a low-power shut-

down mode with only the digital part of the chip staying

active. Leave the Shutdown checkbox unchecked for

normal circuit operation.

General-Purpose 3-Wire (SPI)

Interface Utility

The general-purpose 3-wire interface utility (Figure 2)

can also be used to communicate with the MAX9939

using low-level SPI commands. Select the Options |

Interface menu item and select the 3-wire interface

tab to access the utility. The utility configures the 3-wire

serial-interface parameters, such as MSB position,

CPOL, CPHA, MOSI/MISO inverted logic, CS active

state (high or low), SPI clock (SCLK) speed, and cus-

tom selection of SPI signal pins. The data to be sent is

MAX9939 Evaluation Kit

4 _______________________________________________________________________________________

Figure 2. MAX9939 Interface Diagnostic Window

8-bit data represented by a two-digit hexadecimal

code. The code is entered in the Data bytes to be writ-

ten edit box and transmitted by pressing the Send

Now button.

Detailed Description of Hardware

Power Input

The MAX9939 EV kit operates from a single supply

VCC between 2.9V to 5.5V. Using 3-pin jumper JU1,

the EV kit can be powered through the host PC’s USB

port or by an external power supply. By default, a shunt

is installed across pins 2-3 and the USB provides 5V

(+5VUSB) to power the EV kit. Install a shunt across

pins 1-2 to use an external power supply applied at the

VCC pad. Table 1 lists the selectable jumper options.

Default Configuration as an Active Filter

The MAX9939 EV kit comes standard with the

MAX9939 configured as an anti-aliasing filter to provide

a cutoff frequency to maximize the Nyquist bandwidth

of an ADC. The external resistors and capacitors are

chosen to create a 1.3kHz lowpass, 3rd-order, 0.1dB

Chebyshev multiple-feedback active filter. Refer to the

Applications Information

section in the MAX9939 IC

data sheet for a more detailed description of using the

MAX9939 IC as an active filter.

Evaluating the EV Kit as a Differential-

Input, Differential-Output PGA

The MAX9939 EV kit can also be evaluated as a differ-

ential-input, differential-output programmable gain

amplifier by configuring the output stage as follows:

1) Remove R24, R25, C20, and C21.

2) Replace R20 with a 0Ω resistor.

3) Replace R18 and R19 with 10kΩ resistors.

4) If an anti-aliasing filter is required, replace C2, C22

and R21, R22 capacitor/resistor values as required.

If an anti-aliasing filter is not required, replace R21

and R22 with 0Ω resistors while leaving C2 and C22

open.

5) Utilize the OUT_DIFF BNC connector to analyze the

differential output. Caution: Ensure that pin 2 of

the IN_DIFF BNC connector and pin 2 of the

OUT_DIFF BNC connector are isolated from each

other (i.e., not shorted together).

Evaluates: MAX9939

MAX9939 Evaluation Kit

_______________________________________________________________________________________ 5

SHUNT

POSITION

VCC DESCRIPTION

1-2

EV kit requires an external power supply

applied at the VCC pad

2-3*

EV kit is powered through the host PC’s

USB port (+5VUSB)

Table 1. Jumper JU1 Functions (VCC)

Default position.

Evaluates: MAX9939

MAX9939 Evaluation Kit

6 _______________________________________________________________________________________

Figure 3a. MAX9939 EV Kit Schematic (Sheet 1 of 3)

P1-P3 P4-P6 P7-P9 P10-P11

MAX9939EVKIT+

Mfr. #:

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Manufacturer:

Maxim Integrated

Description:

KIT EVAL FOR MAX9939

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