MP6570 Input Current Sense Clarification

working on BLDC drive design with MP6570, need clarification on DC bus current limit sensing part

From datasheet page no. 39
IIN_LIMIT[9:0] = (Vs+0.9)*1023/1.6

It is having 0 to 9 bits value under that decimal equivalent value is 511 (Decimal) = 1FF (Hex)

Rewriting above equation 511 = (Vs + 0.9)*1023/1.6 returns Vs max value as -0.1 Volts

value is in negative which is confusing.

Kindly clarify

with warm regards
Vasanthakumar M

Hi Vasanthkumar,

I’ll look into your request and post an update in 2-3 days.

Hi, Bryan

waiting for your update.

with warm regards
Vasanthakumar M

Hi Vasanthakumar,

Thank you for your patience. I’m working with our applications engineers to clarify the units in the equation and will post another update soon.

IIN_LIMIT[9:0] has 10bits, so the value range is 0 – 1023.

Vs = (IIN_LIMIT *1.6)/1023-0.9 = -0.9V – 0.7V. So, the Vs voltage range is -0.9V to 0.7V.
The DC current can flow in both directions so the voltage on a current sensing resistor can be negative or positive.
The IIN_LIMIT protection is also used to avoid DC voltage rising to a high value which may cause the device damage. This function can also be realized by VIN_LIMIT function.

Please ignore the IIN_LIMIT register. We recommend connecting the IDC pin to ground in most applications.
The motor phase current can be limited by IQ_LMT (register 06h) during normal operation.


Thanks for the clarification.

with warm regards
Vasanthakumar M

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