8.3.2 Accurate Current Sense

High-accuracy current sense is implemented in the version-B device. It allows a better real-time monitoring effect and more-accurate diagnostics without further calibration.

One integrated current mirror can source 1 / K_(CS) of the load current, and the mirrored current flows into the external current sense resistor to become a voltage signal. The current mirror is shared by the four channels. K_(CS) is the ratio of the output current and the sense current. It is a constant value across the temperature and supply voltage. Each device is calibrated accurately during production, so post-calibration is not required. See Figure 21 for more details.

Figure 21. Current-Sense Block Diagram

When a fault occurs, the CS pin also works as a fault report with a pullup voltage, V_CS(H). See Figure 22 for more details.

Figure 22. Current-Sense Output-Voltage Curve

Use Equation 1 to calculate R_(CS).

Equation 1.

Take the following points into consideration when calculating R_(CS).

• Ensure V_CS is within the current-sense linear region (V_CS, I_OUTx(lin)) across the full range of the load current. Check R_(CS) with Equation 2.
Equation 2.
• In fault mode, ensure I_CS is within the source capacity of the CS pin (I_CS(H)). Check R_(CS) with Equation 3.
Equation 3.