Hi All,
I'm using the TLC5943 in a multi-channel rgb module - 6 drivers for 2 channels of 4:1 scan rgb leds.
The Vled is 12V with voltage dropping series resistors inline with each led column. 5V for Vcc.
I seem to be getting a reset of the 5943 drivers with noise spikes external to the system - ac line side.
These are getting through the power supply and filtering on the module itself.
All I see on the scope is a 8 ns dip to 4.49 V. I'm not thinking this should be enough to reset the internals of the driver.
But when I load the brightness register back with valid data - they resume normal operation. Same operation as expected at startup.
This is on my test bench - the external event is turning on/off my magnifying lens. It has happened with other events in test, but this
reliably causes the apparent reset/clr of the brightness register/chip.
Scope results taken right at pin 28 with a short spring clip to gnd at the gnd side of the bypass cap (0.1uF).
Looking for ideas as to if I'm right about the internal reset and what other things I might look at or try to absorb this event or similar ones.
I have added a clc pi filter, and increased bulk capacitance to 1000uF - still happens. I have thought about a common mode choke - but not sure how I'm going to add this to the input power path on the board. Total draw for the 5V on the board is ~70mA. Also this event seems to have no affect on my omap cpu board on the same 5V rail.
Any thoughts - anyone?
Thx,
Matt
