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Messages - dttworld

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Evaluation Tools / Re: NHD-TFT40 PWM pin
« on: September 05, 2017, 01:24:37 PM »
I believe I understand my problem now. The backlight converter on the eval board is a boost converter designed to drive a series LED backlight. I actually need a buck converter designed to drive the parallel LED backlight found on the HD-1.8-128160EF-CSXN-F.

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Evaluation Tools / Re: NHD-TFT40 PWM pin
« on: September 01, 2017, 01:23:00 PM »
So I swapped out the backlight IC with one bought from Mouser. Unfortunately, the PWM pin tied to gnd still doesn't turn off the backlight current. For this test I am actually lighting up 5 LEDs in parallel with the demo board. This really doesn't make sense to me.

Could you run a test where you light up 5 parallel LEDs and see if tying PWM to gnd turns the LEDs off?

Thank you

3
Evaluation Tools / Re: NHD-TFT40 PWM pin
« on: August 29, 2017, 06:10:41 PM »
Thanks for running the test on your end.

I am using the eval board for just the backlight function set to 90mA.

 I should be receiving my parts from Mouser on Wednesday and will provide an update after I do some testing.

4
Evaluation Tools / Re: NHD-TFT40 PWM pin
« on: August 28, 2017, 05:00:13 PM »
Hi -

I am connecting to the display through a FPC breakout board. The backlight connections have been double checked and things are wired properly (including multiple cathode connections). The backlight lights up properly but does not shutoff with PWM pin tied low. I am suspecting a problem with the backlight IC and have ordered some "genuine" parts from Mouser Electronics.

Please verify in your lab that the PWM works as intended. I'm not going to draw conclusions until I do an IC swap.

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Evaluation Tools / Re: NHD-TFT40 PWM pin
« on: August 28, 2017, 02:46:04 PM »
Hi -

I am trying to control the backlight current using the PWM signal. Right now I am using the NHD-TFT40 board to supply 90mA to the backlight off an NHD-1.8-128160EF-CSXN# display. I don't understand why tying the PWM pin to GND doesn't turn off the backlight completely (PWM duty cycle = 0%). This is also labeled as a /shutdown pin on the FAN5333BSX backlight IC. 




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Evaluation Tools / NHD-TFT40 PWM pin
« on: August 28, 2017, 12:15:04 PM »
Hi -

I have 2 "NHD-TFT40" boards that do the same strange thing. When the PWM pin is connected to ground the display current does not shut off.  Can someone at Newhaven replicate this test?

Thank you

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