TPS92602-Q1: Voltages at the DIAGx Pin

Hi Dear Lorenz,

Could you tell me your application and the precision of current you need.

Hi Dear Mr. Qiu,

I had designed a Lamp for a automotive application. The max. current designed is 177mA. There are several steps of needed current 175mA; 100mA; 62mA;10mA (analog dimming to 10% - PWM 56%); 8mA (analog dimming to 10% - PWM 45%) and 4mA (analog dimming to 10% - PWM 23%). If I could read the 4mA within 10% would be nice.

What precision will be allowed here?

Best regards Markus

Hi Markus,

Can I calculate it as an linear equation?

A:YES 

The datasheed says the DIAGfactor will be 12.5 and the EVM users guide says this factor will be 16, but neither the datasheet factor nor the EVM users guide factor will correspond to a linear equation of 200mV to 2.85V!

A:You can use the gain as 12.5 but it have a offset.

4mA (analog dimming to 10% - PWM 23%). If I could read the 4mA within 10% would be nice.What precision will be allowed here?

A:the dimming factor is as below, but we don't have the traise and tfall of pwm, so if you use in a slow dimming frequency,i think it may match your precision.

Hi Frank,

I can not reache the 4mA by analog dimming. If we dimm to 10% we will have 17mA and if we dimm additional with a PWM of 23% at 400Hz we will reach a middle value of 4mA.

Will it be possible to get a signal at the Diag Pin of the IC? Because I can not measure any signal at this PIN.

The datasheed says the DIAGfactor will be 12.5 and the EVM users guide says this factor will be 16, but neither the datasheet factor nor the EVM users guide factor will correspond to a linear equation of 200mV to 2.85V!

A:You can use the gain as 12.5 but it have a offset.

Q: Is the offset special to our application or is it a constant value?

Best regards

Markus Lorenz

Hi

In your schematic i see the rled_sns is 0.5ohm.If the dc current is 10%(17mA) the Vsns is 8.5mv and the accuracy of sns is 6mv.So you may not measure at diag pin.You can increase the rled_sn.

And for ovp of led:in buck to battery topology, the voltage between is Vin-Vo,so the max voltage between led is Vin,So I think it's no use for OVP of LED.

Hi

The question referring to the Diag is be on another chanel with rled_sns is 1.69ohm. This will make a Vsns of about 28.73mV at 17mA.

Q: Which min. Vsns will be good for measuring?

Q: Will the PWM influence the measurement?

Best Regards

Markus Lorenz