2 Enabling Broad Electrification

Electrification enables improvements in performance, reliability, and total lifetime cost, but these systems require isolation from their high-voltage AC or DC domains in increasingly dense form factors. Many existing isolated current-sensing solutions take up significant space on high-voltage PCB designs due to additional external components, housings or elements. Hall-effect current sensors provide a monolithic, single-chip solution incorporating both the isolation and sensing elements in surface-mount form factors, such as 8-pin small-outline integrated circuit (SOIC) packages with 5 mm by 6 mm of PCB space.

However, most sensors in 8-pin SOIC packages only provide around 400 V of a working lifetime isolation voltage, which limits the usability of these devices to systems operating below this level. For example, many high-power battery systems have 400-V nominal DC buses, and they can significantly exceed this level with load and switching transients. Industrial systems that operate from 240 V_AC and convert power to a 340-V_DC rectified voltage level will often include a boost stage, as Figure 2-1 shows, which can reach voltage levels of 400 V_DC–600 V_DC. Many solar string inverters operate with photovoltaic cell and maximum power-point tracker (MPPT) buses in the 480-V to 600-V range, which are also outside the capabilities of most available 8-pin SOIC Hall-effect current sensors.

To provide a sufficient lifetime isolation margin, the TMCS1100 and TMCS1101 devices provide 600 V of working voltage in an 8-pin SOIC form factor, with a higher lifetime margin than what is required by industry standards such as Verband der Elektrotechnik 0884-11 and Underwriters Laboratories 1577. This working voltage provides a sufficient isolation margin for equipment manufacturers without the need to transition to a larger solution size.

It is possible to extrapolate the expected lifetimes of a device from a qualification test known as time-dependent dielectric breakdown (TDDB), which measures the expected lifetime of a device versus the device voltage stress. Figure 2-2 shows the TMCS1100 family TDDB curve. The operating lifetime zone greatly exceeds industry standards for a 26-year lifetime with a 20% voltage safety margin.

The lifetime capability of these devices, coupled with 3 kV_RMS of 60-s basic isolation, makes them a good fit for grid-connected or high-energy systems that see high-voltage transients. Many systems in power delivery, motor control, and grid infrastructure place a premium on tight packing and high energy density, which is enabled by the optimized form factor and isolation capability of the TMCS1100.