Problem understanding connecting power and logic ground in schematic
Problem understanding connecting power and logic ground in schematic
(OP)
Hi all,
I'm designing V2 of a PCB that uses a TI TPS6102x boost converter (http://www.ti.com/lit/ds/symlink/tps61020.pdf). I don't understand the schematic concerning the logic ground and power ground. All the caps and R2 are tied to PGND while PS and GND are tied to power ground. What's the purpose of separating these grounds in the chip but then tying them together in the PCB? Am I misunderstanding something?
I'm designing V2 of a PCB that uses a TI TPS6102x boost converter (http://www.ti.com/lit/ds/symlink/tps61020.pdf). I don't understand the schematic concerning the logic ground and power ground. All the caps and R2 are tied to PGND while PS and GND are tied to power ground. What's the purpose of separating these grounds in the chip but then tying them together in the PCB? Am I misunderstanding something?
-Russ





RE: Problem understanding connecting power and logic ground in schematic
If PG and SG were tied together inside the chip, there would be interaction betwee voltage drop in the PG, aka ground noise, and the SG. Keeping them separate until they meet solid copper outside the chip avoids that problem.
Sometimes, there are several SG pins available around the chip and it is good education to measure resistance between them. You will find that it isn't zero ohms.
For HF applications, also inductivity plays a role.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Problem understanding connecting power and logic ground in schematic
TTFN

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RE: Problem understanding connecting power and logic ground in schematic
-Russ
RE: Problem understanding connecting power and logic ground in schematic
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Problem understanding connecting power and logic ground in schematic
If I can ask one closely related question: is it recommended to have a copper pour on this PCB? If so, should it be localized or on one or both sides of this 2-layer PCB? There are components on both sides.
-Russ
RE: Problem understanding connecting power and logic ground in schematic
TTFN

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