1 Introduction

When designing for invasive current sensing methods, care must be taken to make sure that the thermal problem is well controlled. Whether the thermals persist in the shunt of a traditional current shunt monitor, or are simply the losses seen by the lead frame of a device such as a Hall-effect current sensor, thermal runaway can quickly lead to design issues if not planned for and handled appropriately.

The TMCS11xxEVM is a family of evaluation modules intended to facilitate rapid, convenient evaluation of the TMCS1123, TMCS1126, TMCS1127, and TMCS1133 families of devices. These devices are reinforced isolation-capable Hall-effect current sense monitors with several optional additional features, such as a built in reference output for differential measurement, overcurrent threshold capabilities, and thermal diagnostic options. The EVM is built on a 2-layer, 4 ounce per layer stackup. Like many devices that must optimize internal power losses as part of their normal operating condition, many data sheet parameters are based upon this specific layout and heat dispersion model. This is typical among semiconductor devices such as this, as there are a potential infinite number of use cases the device can be exposed to, based upon the layout of the device, and product makers seek to showcase their device in the best of circumstances, attempting to remove the layout from the equation as much as possible.

Thus, a challenge often exists when designing with such devices: their evaluation modules present an designed for use case for evaluation of the part in a broad sense, and do not often provide information regarding limitations present in a typical design, such as space constraints or power budgets. The following paper briefly examines two such cases for device performance: adjustment of copper weight of the same topology as that of the TMCS1123EVM, and a reduction in copper planar size for the given 4 ounce stackup of the original evaluation module, with the goal of understanding how these decisions can optimize cost and space in the system.