Unsure of what to use, maybe an INA301?

Jason,

The INA300 and INA301 could both be good potential fits.  The INA300 has can accept a bus voltage of up to 36V and can respond in 10uS.  It doesn't have an analog output, just an alert line, perfect for use with a microcontroller.  The INA301 can also accept up to 36V bus supply and responds in 1uS.  The INA301 also has an analog output in addition to a digital output for use in other analog circuitry if you need it.  Each device will need a small value resistive shunt placed in the path of the load, and then a limit setting resistor to set the threshold.

For the INA300, this could mean something like choosing a 50mOhm shunt, which will create a 40mV drop across the inputs at 0.8A and a 65mV drop at 1.3A.  Total power lost through the shunt at 1.3A is only 84mW.  Now let's assume you want the 10uS response time.  The data sheet explains in section 7.3.2.1 how to calculate an limit-setting-resistor value.  I'll run you through it here though - let's say you want to have the system alert when you cross about 1.1A, which would be 55mV across the shunt.  Table 2 says to take your Trip/Limit voltage and use this equation: (Vlimit-NAF)/(Ilimit) = Rlimit.  NAF is a noise adjustment factor used in the 10uS setting, and is defined as 500uV.  It provides a good margin of operation.  Ilimit is 20uA, which is the current source defined in the INA300.  So in our case, this would be Rlimit = (55mV-500uV)/20uA = 2775ohms, or probably 2.7k would be alright.

Let's do the same thing with the INA301.  This time the Ilimit current source is 80uA, but you have to take into account the gain of the amplifier.  Let's use the A1 version, so gain = 20.  There's no NAF this time, so the calculations are just a little bit simpler.  The INA301 data sheet explains this in section 7.3.3.1.  Vlimit = Isense * Rsense * Gain = 1.1A * .05ohm * 20 = 1.1V.  So we need to set the Rlimit to give us a trip voltage of 1.1V, done like so: Rlimit = Vlimit/Ilimit = 1.1V/80uA = 13,750ohm.  I expect a 13k resistor would be alright. 

So to sum up, an INA300, a 50mOhm resistor and a 2.7k resistor would probably work for a 10uS response.  An INA301, a 50mOhm resistor and a 13k resistor would also probably work and have a 1uS response.

Hope this helps.