Datasheet

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
OS
) 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
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Figure 2. MAX9939 Interface Diagnostic Window