TDA3MV Datasheet, PDF (178/256 Pages) Texas Instruments – TDA3x SoC for Advanced Driver Assistance Systems (ADAS) 15mm Package (ABF) Silicon Revision 2.0

TDA3MV, TDA3MA
TDA3LX, TDA3LA
SPRS964C – JUNE 2016 – REVISED JULY 2017
www.ti.com
Trace
Capacitor
Via
3
DIE
Package
Power/Ground
Ground/Power
1
2
Note: 1. BGA via pair loop inductance
2. Power/Ground net spreading inductance
3. Capacitor trace inductance
Loop inductance
SPRS91v_PCB_STACKUP_01
Figure 8-1. Minimize Loop Inductance With Proper Layer Assignment
The placement of power and ground planes in the PCB stackup (determined by layer assignment) has a
significant impact on the parasitic inductances of power current path as shown in Figure 8-1. For this
reason, it is recommended to consider layer order in the early stages of the PCB PDN design cycle,
putting high-priority supplies in the top half of the stackup (assuming high load and priority components
are mounted on the top-side of PCB) and low-priority supplies in the bottom half of the stackup as shown
in the examples below (vias have parasitic inductances which impact the bottom layers more, so it is
advised to put the sensitive and high-priority power supplies on the top/same layers).
8.2.2 Step 2: Physical Placement
A critical step in designing an optimized PDN is that proper care must be taken to making sure that the
initial floor planning of the PCB layout is done with good power integrity design guidelines in mind. The
following points are important for optimizing a PCB’s PDN:
• Minimizing the physical distance between power sources and key high load components is the first
step toward optimization. Placing source and load components on the same side of the PCB is
desirable. This will minimize via inductance impact for high current loads and steps
• External trace routing between components must be as wide as possible. The wider the traces, the
lower the DC resistance and consequently the lower the static IR drop.
• Whenever possible for the internal layers (routing and plane), wide traces and copper area fills are
preferred for PDN layout. The routing of power nets in plane provide for more interplane capacitance
and improved high frequency performance of the PDN.
• Whenever possible, use a via to component pin/pad ratio of 1:1 or better (i.e. especially decoupling
capacitors, power inductors and current sensing resistors). Do not share vias among multiple
capacitors for connecting power supply and ground planes.
• Placement of vias must be as close as possible or even within a component’s solder pad if the PCB
technology you are using provides this capability.
• To avoid any "ampacity” issue – maximum current-carrying capacity of each transitional via should be
evaluated to determine the appropriate number of vias required to connect components.
Adding vias to bring the "via-to-pad” ratio to 1:1 will improve PDN performance.
• For noise sensitive power supplies (i.e. Phase Lock-Loops, analog signals like audio and video), a Gnd
shield can be used to isolate coplanar supplies that may have high step currents or high frequency
switching transitions from coupling into low-noise supplies.
178 Applications, Implementation, and Layout
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