Low side current measurement
simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Common ground for all logic.

I haven't come across that chip before but I'd suggest a layout like this. It avoids any sneak paths between ground and common - such as when programming your MCU through a USB port on your laptop, etc., and is common practice in current measuring applications.

The gain is only 20 so if you want, for example, 3 V out at 30 A then your shunt would need to drop \$ \frac {3~V}{20} = 0.15~V\$ and its resistance would be \$ \frac {0.15~V}{30~A} = 5~m\Omega\$.

Perhaps a better option based on your comment is to use high-side monitoring.



Figure 36 of the datasheet shows a high-side monitor. (They seem to have the battery symbol upside-down.)


  High-Side Current Sense with a High-Side Switch
  
  This configuration minimizes the possibility of unexpected 
  solenoid activation and excessive corrosion (see 
  Figure 36). In 
  Figure 36, both the switch and the shunt are on the high side. 
  When the switch is off, the battery is removed from the load, 
  which prevents damage from potential shorts to ground, while 
  still allowing the recirculation current to be measured and 
  providing for diagnostics. Removing the power supply from the 
  load for the majority of the time minimizes the corrosive effects 
  that can be caused by the differential voltage between the load 
  and ground. When using a high-side switch, the battery voltage 
  is connected to the load when the switch is closed, causing the 
  common-mode voltage to increase to the battery voltage. When 
  the switch is opened, the voltage reversal across the inductive 
  load causes the common-mode voltage to be held one diode 
  drop below ground by the clamp diode.