Commit 21abf3fa authored by Ruben Castro's avatar Ruben Castro
parents 865a5621 17866ee4
This works
\ No newline at end of file
Hello!
This is my first attempt at a circuit board. It shall hold an H-bridge for
motor control, current sensing, and SPI pins for encoder implementation.
It is a board that revolves around the DRV8701 (http://www.ti.com/product/DRV8701)
gate driver chip. The DRV8701 is capable of driving a varied set of MOSFETS.
Chosen here are the AON7410 MOSFETS.
Design Rules:
-5A continuous/10A peak rating
-0-10A to 0-1.5V mapping current sensing
-12V Motor
-SPI breakout for encoder
-Not hotter than 70C
DRV8701 Rules:
Vgs(voltage applied to MOSFET gate) = 9.5V
Ivcp(current capable of being applied to MOSFET gate - dependent on Vm) = 12mA
20v/v conversion for current sense - for 0-10A to 0-1.5V mapping, you need a ~7 mOhm resistor rated for >=2watts
Lots of passive components need to be around the IC.
Basic definitions I learned in the process-
Bulk Capacitor - Capacitor used to be capable of taking over battery in certain sags. It is
set as close to the input as possible. In this case an electrolytic >=10uF.
Decoupling Capacitor- Capacitor used to give power to certain components or devices
similar function to bulk capacitor, except placed near individual components.
Like a local bulk capacitor.
Rsense -Shunt Resistor used for current sensing on the low side of the h-bridge.
In this case- 7mOhm. Current can be measured by taking the difference between
each side of the resistor to measure voltage drop, then V=IR
Net Ties- Just like a trace, except its meant to be isolated from other traces or
pours around it. Used here for Rsense, where we want to measure difference
between ground and the voltage before the resistor, but we want the traces
to look about the same and not be impacted by differences in voltage around it.
Kelvin Connection- Way of connecting traces to Rsense. It just makes sense
Take it for granted. Google how to do it. It's very simple.
PCB guides:
45 degree traces only
Kelvin Connection for Rsense
Always have a ground plane.
Try to be as symmetric as possible
Differential pairs routing for pairs of traces.
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