Newhaven Display Forum

Newhaven Products => Character LCDs => Topic started by: Nimrod on February 19, 2016, 11:12:36 AM

Title: NHD-C0216CZ-NSW-BBW-3V3 Interface Voltage
Post by: Nimrod on February 19, 2016, 11:12:36 AM
Hi I've been using the NHD-C0216CZ-NSW-BBW-3V3 run at 3 volts, but had an occasion where the PIC16F  controller was sending SPI which was running at 5v. This did not seem to do any damage, and looking at the controller chip (ST7032) on the LCD, it would appear to be capable of taking 2.7v to 5.5v  from an interface point of view. Is it okay to continue, as it will save having to put in level shifting logic, or am I slowly cooking the LCD unit? The backlight was only 3v, under PWM control.
Title: Re: NHD-C0216CZ-NSW-BBW-3V3 Interface Voltage
Post by: Paul_B on February 19, 2016, 12:40:05 PM
Hi,

Correct, the displays built-in controller is capable of taking 2.7v to 5.5v  from an interface point of view. 

However the COG display as a whole is a 3.3V max device, so you'll need to do some level-shifting between the PIC16F and NHD-C0216CZ-NSW-BBW-3V3.

Series resistors on the SDA and SCL lines should do the trick (~330Ohm) or a level shifting IC  ;)




Title: Re: NHD-C0216CZ-NSW-BBW-3V3 Interface Voltage
Post by: perky on March 03, 2016, 07:03:02 PM
According to the ST7032 the absolute max input voltage Vin is VDD+0.3V which means the controller has substrate diodes and is not 5V tolerant, the controller cannot take interface signals from 2.7V to 5.5V if it is powered from 3.3V unless they are current limited. You will need either a level shifter or resistor-dividers on your SPI lines to the display (CS#, MOSI and CLK) . The MISO will only be driven to 3.3V by the display, so you might want to check the Vih of the PIC is compatible when running it at 5V, there's a good chance it isn't.
Mark.