TDA3MV Datasheet, PDF (179/256 Pages) Texas Instruments – TDA3x SoC for Advanced Driver Assistance Systems (ADAS) 15mm Package (ABF) Silicon Revision 2.0

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TDA3MV, TDA3MA
TDA3LX, TDA3LA
SPRS964C – JUNE 2016 – REVISED JULY 2017
vdd_mpu
vss
vdd
SPRS91v_PCB_PHYS_05
Figure 8-2. Coplanar Shielding of Power Net Using Ground Guard-band
8.2.3 Step 3: Static Analysis
Delivering reliable power to circuits is always of critical importance because voltage drops (also known as
IR drops) can happen at every level within an electronic system, on-chip, within a package, and across the
board. Robust system performance can only be ensured by understanding how the system elements will
perform under typical stressful Use Cases. Therefore, it is a good practice to perform a Static or DC
Analysis.
Static or DC analysis and design methodology results in a PDN design that minimizes voltage or IR drops
across power and ground planes, traces and vias. This ensures the application processor’s internal
transistors will be operating within their specified voltage ranges for proper functionality. The amount of IR
drop that will be encounter is based upon amount power drawn for a desired Use Case and PCB trace
(widths, geometry and number of parallel traces) and via (size, type and number) characteristics.
Components that are distant from their power source are particularly susceptible to IR drop. Designs that
rely on battery power must minimize voltage drops to avoid unacceptable power loss that can negatively
impact system performance. Early assessments a PDN’s static (DC) performance helps to determine
basic power distribution parameters such as best system input power point, optimal PCB layer stackup,
and copper area needed for load currents.
The resistance Rs of a plane conductor
for a unit length and unit width is called
the surface resistivity (ohms per square).
L
t
W
1^r
Rs = =
σ×t t
l
R = Rs ×
w
SPRS91v_PCB_STATIC_01
Figure 8-3. Depiction of Sheet Resistivity and Resistance
Ohm’s Law (V = I × R) relates conduction current to voltage drop. At DC, the relation coefficient is a
constant and represents the resistance of the conductor. Even current carrying conductors will dissipate
power at high currents even though their resistance may be very small. Both voltage drop and power
dissipation are proportional to the resistance of the conductor.
Figure 8-4 shows a PCB-level static IR drop budget defined between the power management device
(PMIC) pins and the application processor’s balls when the PMIC is supplying power.
• It is highly recommended to physically place the PMIC as close as possible to the processor and on
the same side. The orientation of the PMIC vs. the processor should be aligned to minimize distance
for the highest current rail.
Copyright © 2016–2017, Texas Instruments Incorporated
Applications, Implementation, and Layout 179
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