CIRCUIT060074: Design a 3A and 6A current comparator.

Hi Guohai,

From your application requirements, it seems like you already know the specifications that you will need to design the circuit following the instructions from CIRCUIT060074. If the common-mode voltage is required to be 40V, our 40V open-drain comparator is the TLV1861. Please let me know if you run into problems following the calculations detailed in the cookbook.

I'll answer the customer's questions here:

1. The accuracy of the current sensing is dependent on the resistor tolerances and the offset voltage of the comparator. In order for the comparator to transition low and indicate an overcurrent event, the shunt voltage needs to overcome the comparator's offset voltage. This is indicated in Design Note 3 and 4. Design step 1 also notes the tradeoff between accuracy and supply headroom.

2. The response time is dependent on the propagation delay of the comparator. The TLV1861 has a T_PDHL of 13us with a VOD = 100mV. TLV1861 is a slower part due to it being a high voltage part. For current sensing applications, a low propagation delay is usually required. I recommend looking for a way to divide down your common-mode voltage so a faster, lower voltage part can be used.

3. We don't have EVM for cookbooks, but we do have EVMs for individual devices for evaluation.

Hi Guohai,

In my last reply, I linked the nanopower 40V device. For overcurrent detection, the TLV182x would be more appropriate due to its lower propagation delay. Let's continue this offline.