Hardware Description
9
SPRUII7 – June 2018
Copyright © 2018, Texas Instruments Incorporated
C2000™ Piccolo™ F28004x Series LaunchPad™ Development Kit
2.1.9.3
Alternate Power
Additional jumpers are provided outside of the BoosterPack connector for additional external power
connections for 3.3 V or 5 V. These can be used to supply an external board or for powering the
LaunchPad with an external supply. When using these connection points, ensure that no other power
supplies are connected.
JP4 and JP6 are provided as extra connection points for a 3.3 V supply to be connected to the
LaunchPad.
JP5 and JP7 are provided as extra connection points for a 5 V supply to be connected to the LaunchPad.
2.1.9.4
5 V Step-up Converter
JP9 isolates the output of the LMR2421 Simple Switcher step-up voltage regulator(U3) from the 5 V power
domain of the LaunchPad. This voltage regulator can step up 3.3 V to 5 V if no other 5 V supply is
connected. Do not place a shunt on J9 unless JP3 is open and no other 5 V supply is connected to the
LaunchPad.
2.1.10
PGA
The F28004x MCU features on-chip Programmable Gain Amplifiers (PGA) to amplify an input voltage for
increasing the dynamic range of the downstream ADC and CMPSS modules. The integrated PGA helps to
reduce the cost and design effort for many control applications that traditionally require external, stand-
alone amplifiers. On-chip integration ensures that the PGA is compatible with the downstream ADC and
CMPSS modules. Software selectable gain and filter settings make the PGA adaptable to various
performance needs. For more information on the PGAs, see the device-specific data sheet and TRM.
The F28004x LaunchPad was designed to optimize the routing of certain PGA signals to the BoosterPack
connectors. This design choice allows for the evaluation of the on-chip PGA, if desired. Three PGA
modules are routed each BoosterPack Connector. An RC filter can be placed on each of these signals to
provide additional filtering of the input signal. By default, 0
Ω
series resistor and pads for a decoupling
capacitor are placed on each PGA input signal. These values can be modified based on application
requirements.
In addition to the PGA input signals, BoosterPack site 2 has the associated output filter signals routed.
Each output filter signal has two components: a 0
Ω
series resistor and a decoupling capacitor. If the PGA
output filters are used, remove the 0
Ω
series resistor to isolate it from the BoosterPack connector, and
place an appropriate filter capacitor. By default, a 330 pF capacitor is populated. An isolated ground plane
for the PGAs has been created to help limit outside noise coupling onto the PGA signals. By default, this
ground plane is shorted to the ground plane of the PCB through a resistor. If isolation between
PGAx_GND and the PCB ground is needed the resistor can be removed.
Wherever a PGA signal is brought to the BoosterPack connector, an ADC input is also provided.
Depending on the signal, the ADC is connected by either a short on the board or through on-chip
connections. Other than PGA4_IN and PGA6_IN, each PGA input signal can be isolated from the
connected ADC signal by removing the 0
Ω
resistor that is part of the input RC filter.
