ONET1151L: external zero temperature coefficient resistor for RZTC pin

Steven Yan

Part Number: ONET1151L

Tool/software:

Hi Team,

I am helping my customer with a debug and they would like some clarification on the RZTC pin operation. Please see inquiry below:

From Datasheet: An external zero temperature coefficient resistor must be connected from the RZTC pin of the device to ground

(GND). This resistor is used to generate a precise, zero TC current, which is required as a reference current for

the on-chip DACs.

For the external zero temperature coefficient resistor, what sort of behavior will happen when this resistor is not a zero temperature coefficient? Is this zero coefficient required for proper operation? The reference design for these parts do not have a zero coefficient resistor in the BOM so I was wondering if that was intentional or a mistake.

Looking forward to your expertise.

Best,
Steven

over 1 year ago

0 Nasser Mohammadi over 1 year ago

TI__Guru* 93570 points

Hi Steven,

This part supports APC - Automatic Power Control. Some of the parameters to allow APC operation within the range mentioned in the parametric table requires this type of accuracy For example, temperature sensor can maintain within +/-3deg C. To maintain this accuracy and other parameters such as average power stability.

Regards, Nasser

0 Steven Yan over 1 year ago in reply to Nasser Mohammadi

TI__Expert 3185 points

Hi Nasser,

Thanks, do we have a recommended ZTC Resistor for use? Please see last question from customer: The reference design for these parts do not have a zero coefficient resistor in the BOM so I was wondering if that was intentional or a mistake.

Thanks,
Steven

+1 Nasser Mohammadi over 1 year ago in reply to Steven Yan

TI__Guru* 93570 points

Searched online and found these:

https://nz.apexelex.com/htm/resistor_leaded_resistors.php?cl=0&islv=0&rh=0&st=0&csot=0&type=up&page=1&search=1&rspage=0&ckey=2011120000&sel1=~~1~~&sel2=~~28700~~&sel3=0&sel4=0&sel5=0&sel6=~~50~~&sel7=&sel8=&sel9=&sel10=&sel11=&sel12=&sel13=&sel14=&sel15=&sel16=&sel17=&sel18=0&sel19=0&sel20=0&sel21=0&sel22=0&sel23=0&sel24=&sel25=0&sel26=0&sel27=0#found

Maybe customer can fine tune the criteria:

https://nz.apexelex.com/htm/resistor_leaded_resistors.php?cl=0&islv=0&rh=0&st=0&csot=0&type=up&page=1&search=1&rspage=0&ckey=2011120000&sel1=~~0.1~~&sel2=~~28700~~&sel3=0&sel4=0&sel5=0&sel6=~~50~~&sel7=&sel8=&sel9=&sel10=&sel11=&sel12=&sel13=&sel14=&sel15=&sel16=&sel17=&sel18=0&sel19=0&sel20=0&sel21=0&sel22=0&sel23=0&sel24=&sel25=0&sel26=0&sel27=0#found

Regards, Nasser

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ONET1151L: external zero temperature coefficient resistor for RZTC pin