Datasheet

PGA400 EVM User Guide
TI CONFIDENTIAL – NDA Restrictions
Page 16 of 50
Figure 11. VOUT1/VOUT2 Output Filtering
4.2 ADC Measurement of VOUT1/VOUT2 DAC Outputs
The EVM comes equipped with two ADCs that are used to monitor and report the voltage at the
VOUT1/VOUT2 outputs back to the GUI. The EVM uses two ADS1100, 16-bit ADCs, to monitor
the two outputs. The ADCs are enabled by configuring the PGA400-Q1 DAC Output MUX to
route the VOUT1/VOUT2 outputs into the ADCs. The PGA400-Q1 DAC Output MUX and the
ADCs are all configurable with the GUI.
4.3 OWI Activation Circuitry – VOUT1
The VOUT1 pin on the PGA400-Q1 is shared between the DAC output and the OWI transceiver.
When the PGA400-Q1 is running in MCU mode, the only way to signal to the IC that it needs to
enter OWI mode is to use a pull-up to bring the VOUT1 pin of the device to 7.5V for at least
10ms before it is released back to its previous value. The OWI activation circuitry is comprised
of a simple PMOS pull-up to 7.5V that is activated with a GPIO from the TI-GER USB
Communication Board. The GUI ensures that the PGA400-Q1 DAC Output MUX is open while
the OWI activation pulse occurs so that the 5V tolerant circuitry for the ADCs and the OWI
transceiver are not damaged with the 7.5V pulse. The figure below shows the OWI Activation
Circuit.