High-accuracy current sense is implemented in the TPS7H2140-SEP. It allows a better real-time monitoring effect and more-accurate diagnostics without further calibration.

The integrated current mirror sources a ratio of the load current as: 1 / K_CS (where: K_CS = 300). This mirrored current flows into the external current sense resistor to become a voltage signal. The current mirror is shared by the four channels. Channel selection is accomplished by using the multiplexer digital inputs (SEL and SEH). I_CS can be calculated using Equation 1.

K_CS is the ratio of the output current and the sense current (CS). It is a constant value across the temperature and supply voltage (IN). Each device is calibrated accurately during production, so post-calibration is not required. See Figure 8-2 for more details.

Figure 8-2 Current-Sense Block Diagram

When a fault occurs, the CS pin also works as a fault report with a pullup voltage of V_{CS_FAULT}. During a fault the maximum available current in CS is I_{CS_FAULT} (15 mA). See Figure 8-3 for more details.

Figure 8-3 Current-Sense Output-Voltage Curve

Use Equation 2 to calculate R_CS.

Take the following points into consideration when calculating R_CS.

• Ensure V_CS is within the current-sense linear region (V_{CS_LINEAR}, I_{OUTx_LINEAR}) across the full range of the load current. Check R_CS with Equation 3.
  Equation 3. ${\mathrm{R}}_{\mathrm{C}\mathrm{S}}=\frac{{\mathrm{V}}_{\mathrm{C}\mathrm{S}}}{{\mathrm{I}}_{\mathrm{C}\mathrm{S}}}\le \frac{{\mathrm{V}}_{\mathrm{C}\mathrm{S}\_\mathrm{L}\mathrm{I}\mathrm{N}\mathrm{E}\mathrm{A}\mathrm{R}\left(\mathrm{M}\mathrm{A}\mathrm{X}\right)}\mathrm{ }\times \mathrm{ }{\mathrm{K}}_{\mathrm{C}\mathrm{S}}\mathrm{ }\mathrm{ }}{{\mathrm{I}}_{\mathrm{O}\mathrm{U}\mathrm{T}\mathrm{x}\left(\mathrm{M}\mathrm{A}\mathrm{X}\right)}}$
• In fault mode, ensure I_CS is within the source capacity of the CS pin (I_{CS_FAULT}). Check R_CS with Equation 4 .
  Equation 4. ${\mathrm{R}}_{\mathrm{C}\mathrm{S}}=\frac{{\mathrm{V}}_{\mathrm{C}\mathrm{S}}}{{\mathrm{I}}_{\mathrm{C}\mathrm{S}}}\ge \frac{{\mathrm{V}}_{\mathrm{C}\mathrm{S}\_\mathrm{F}\mathrm{A}\mathrm{U}\mathrm{L}\mathrm{T}\left(\mathrm{M}\mathrm{A}\mathrm{X}\right)}\mathrm{ }\mathrm{ }}{{\mathrm{I}}_{\mathrm{C}\mathrm{S}\_\mathrm{F}\mathrm{A}\mathrm{U}\mathrm{L}\mathrm{T}\left(\mathrm{M}\mathrm{I}\mathrm{N}\right)}}$