Datasheet

PGA400 EVM User Guide
TI CONFIDENTIAL – NDA Restrictions
Page 10 of 50
Figure 5. Simplified Block Diagram of PGA400-Q1 Input
Circuitry
3.1 Resistive Bridge Sensors
There are two main ways to simulate a resistive bridge sensor on the PGA400-Q1 EVM. The
first is a simple resistive bridge with two variable legs that can be used to adjust the voltage to
the VIN1P/VIN1N and VIN2P/VIN2N inputs. The second uses 16-bit DACs and ADCs to set and
measure the voltage at the inputs. Either one of these simulators can be fed through an input
filter and then into the PGA400-Q1 inputs.
3.1.1 Variable Resistive Bridge
The EVM is equipped with a variable resistive bridge that can be used to adjust the voltage at
the inputs of the PGA400-Q1. The bridge is biased with the VBRG regulator from the PGA400-
Q1. The resistance of each leg of the bridge varies from 17.5k to 22.k. The figure below shows
the channel 1 resistive bridge that is used to vary the voltage to the VIN1P/VIN1N inputs. The
channel 2 resistive bridge is identical.