One example of an integrated design for HV measurement is the TPS4141-Q1, shown in Figure 2-2, which is capable of voltage sensing up to ± 1200V and includes resistors, a switch, and a programmable gain amplifier (PGA) all in a single package.

The TPS4141-Q1 has 30MΩ of total resistance from the precision matched divider. The resistors meet creepage and clearance requirements within the package and take up less area than discrete counterparts.

Figure 2-3 and Figure 2-4 illustrates the reduction in board space, showing a discrete design using resistor ladders on the left and the TPS4141-Q1 on the right. The TPS4141-Q1 takes up 180mm², demonstrating a >60% decrease in area compared to the 488mm² taken up in the discrete design (even excluding switches or buffers). This offers more flexibility in the design and accommodates scaling trends in the EV market.

The resistor ratio is precisely designed for high accuracy – all the resistors are made of the same material and are deposited at the same time. This contributes to excellent ratio matching and practically non-existent temperature/lifetime drift. Integration into a single, small package further protects the ratio precision by providing shielding from contamination and spatially-distributed environmental factors like humidity and temperature. Additionally, high impedance nodes are not exposed as the nodes are in the discrete design, so leakage and parasitics are not of great concern.

A switch in series with the resistor network is also present within the package. Not only does this offer more robust control, the FET reduces leakage current when measurements are not being performed, enabling lower power consumption. Just as well, this adds a layer of protection in the case of fault conditions. This is increasingly important as EV batteries trend towards higher voltages for faster charging.

The integrated programmable-gain amplifier (PGA) supports four divider ratios to match the full-scale input voltage of the analog-to-digital converter. The divider ratios can be set and changed dynamically using DIV0 and DIV1 inputs. This saves development time as each HV measurement circuit in the BMS does not need to be designed from scratch, but rather can be changed spontaneously. This also enhances flexibility of the design, allowing this to interface with a host of analog-to-digital converters without sacrificing resolution. Such simplicity and versatility make this easier to develop BMS across EV platforms.

The TPS4141-Q1 also supports bi-directional voltage measurement by supplying an external precision voltage to REF. This allows the product to measure both positive and negative voltages with respect to HVGND. In combination with the dynamically adjustable divider ratio, the TPS4141-Q1 optimizes the AOUT output swing over the full voltage range present on HV, improving accuracy.

Integration of the resistors, switch, and PGA — in conjunction with control offered by the DIV0, DIV1, and REF pins — maximizes performance in the smallest area possible. Compared to the discrete design, saving cost on components, assembly, and board space. Discrete designs can also have extra costs associated with safety measures to counter issues non-experienced by the integrated design, like the coating of exposed nodes.