TPS1HC30-Q1: I_load and I_out relationship

Hi Chen, 

1.) Yes I_out = I_load here. Yes there are different current sense accuracies based on the I_load chosen. This is due to the nature of current mirrors. 

2.) The K_SNS value is a constant. This does represent the ratio between I_out = 1.5 and I_SNS. The value is still applicable for different I_loads chosen since this is a ratio that is used in equations that take into account the I_load being used. For example, equation 1 in section "8.3.1 Accurate Current Sense" of the data sheet demonstrates how to select the correct R_SNS value accounting for the I_load chosen and using the K_SNS ratio constant. 

3.) I understand the confusion here. The graph shown in Figure 8-1 is intended to demonstrate how the accuracy scales with load. The values given in the Current Sense Characteristics portion of the table should be used to help gauge the accuracy for a given I_load. 

Thank you,

Sarah

Dear Sarah,

Thanks for your reply.

3) I am performing WCA calculations.

Should I primarily use the 6.5 table first? Based on my I_Load conditions, how should I refer to the Error%?

Thank you!

Yufang Chen

Hi Chen, 

Yes, please refer to the table in section 6.5. 

I would suggest selecting the error closest to your chosen Iload. Or choose to work with the error value that give you a worst case condition. 

Alternatively, you could plot the values as Figure 8-1 attempts to do to find a more precise match for your values. 

Thanks,

Sarah

Dear  Sarah,

Sorry, I'm still a little confused.

For example, with I_load = 50mA, according to Table 6.5, the error value between ±40% and ±25%. However, in Figure 8-1, the error for I_load = 50mA is shown as ±7%. Which error value should I refer to?

Thank you!

Best Regards,

YuFang Chen