The power supply design challenges for
TI radar processors are described below, and the TI radar processors are addressed
in this design.
- 1.0 V/1.3 V RF and 1.8 V RF rails have very tight ripple
specifications in (μV range) and it is very challenging to meet such a low
ripple specifications for switching regulators.
- Traditionally, LDO’s are used on RF rails, but LDO solution
suffers from poor thermal performance and it increases cost.
- A low cost LC filter is used between switching regulators
and AWR supply rails to filter the ripple. An LC filter should be carefully
selected as a large inductance will cause load transient settling or ringing
issues and also an increased voltage drop across them. A smaller inductance
won’t provide enough filtering performance.
- All the power rails should be within ±5 % (except 1.2 V
with -5% and +10% requirement) of nominal voltage level and increased
ringing will result in violation of specification.
- All the ringing should ideally settle very quickly (before
ADC start-time) to avoid spurs related to power supply settling noise.
- Higher regulator switching frequency helps to reduce the LC
filter size and also increases regulator bandwidth to minimize the
undershoot or overshoot during the load transient. All TI radar PMICs
supplying the RF rails use 4 MHz or higher switching frequency.
- LC filter is placed outside the switching regulator
regulation loop. L (ferrite bead) is placed close to the regulator output
and C of this LC filter includes the decoupling capacitors of the AWR supply
- The PCB size is very limited and hence it is necessary to
have a very small power management solution size in case of USRR, SRR, and
some MRR applications.
- Increased board temperature will affect the AWR RF
performance and hence it is necessary to reduce the effect of the board
temperature rise due to the PMIC and regulators heating. Also some of the
radar applications have plastic housing and thermal management becomes very
- System level safety requirements for radar sensors are
increasing and hence it is necessary to have PMICs which meet system level
safety goals (ASIL-B or ASIL-C at PMIC level).