Texas Instruments ADS9224REVM-PDK, User Manual, Page: 8 / 34

Power Supplies
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8 SBAU315A – July 2018 – Revised June 2019
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ADS9224REVM-PDK
4 Power Supplies
The PHI controller provides multiple power-supply options for the EVM, derived from the USB supply of
the computer.
The EEPROM on the ADS9224REVM use a 3.3-V power supply generated directly by the PHI. The ADC
and analog input drive circuits are powered by the
TPS7A4700 onboard the EVM. The TPS7A4700 is a
low-noise linear regulator that uses the 5.5-V supply out of a switching regulator on the PHI to generate a
much cleaner 5.0-V output. The 3.3-V supply to the digital section of the ADC is provided directly by an
LDO regulator on the PHI.
The power supply for each active component on the EVM is bypassed with a ceramic capacitor placed
close to that component. Additionally, the EVM layout uses thick traces or large copper fill areas, where
possible, between bypass capacitors and their loads in order to minimize inductance along the load
current path.
The LM7705 outputs a –230-mV option to drive the negative supply (VS–) of the fully-differential input
amplifiers. This option allows the amplifier outputs to swing all the way to ground and achieve a full-scale
differential signal at the ADC input. Configure JP8 in the [1-2] position to use the –230-mV supply for VS–.
If the entire full-scale range is not required, VS– can be connected to GND by configuring JP8 in the [2-3]
position. U8 can be disabled by uninstalling the jumper on JP7.
Table 4 lists the relevant power supply
test points on the EVM.
Table 4. Power-Supply Test Points
Designator Signal Description
TP17 GND EVM ground
TP18 LDO_IN_5V5 5.5-V supply from PHI EVM controller
TP19 VA 5-V analog supply
TP20 DVDD 3.3-V digital supply
TP21 VS– Negative supply for fully-differential input amplifiers