In this TIDA design, there are 3pcs REF2030 devices being used for the reference voltage of the C2000. Why 3pcs REF2030 are necessary to be used, not only one pcs? What's the limitation here? Is it limited by the REF2030 output current? Thanks.
Regards
Brian W
Hello Brian,
A single reference for the bias voltage such as the REF2030 can be used for all three TMSC1100 sensing the phase current. When using a single reference we’d recommend to consider and validate the current drive capabilities of the reference (if different than REF2030) as well as the layout.
The reason that TIDA-010059 use a REF2030 for each TMSC1100 in each phase is due to the specific layout and related noise coupling. Due to the stacked PCB version with a GaN power PCB (TIDA-00915) and an a current sense PCB (TIDA-010059), the isolated GND (cold side) is cut by the high-voltage switch nodes for the three phases.
To minimize noise coupling into the trace which connects the RF2030 output to the TMCS1100 VREF input, the REF2030 was placed closed to each of the TMCS1100. See attached picture. If we placed a single REF2030 for example at the top middle of the PCB, there would have been an additional around 5cm long analog trace to each of the three TMCS1100, which would pick up additional switching noise.
In a real system, customers will typically have a single PCB for the power FETs or IGBTs and the TMCS1100. In that case the placement and layout of the phase current sensors TMCS1100 can be often done in a way to allow for a single reference with short traces to each of the TMCS1100. In that case we’d go for a single reference like REF2030. Other than lower BOM and less PCB space an advantage is that with a single reference the bias voltage for each phase tracks together, which could make offset drift compensation simpler. The REF2030 can drive up to 20mA and up to 10uF capacitive load, which should meet most configurations.
Regards,
Martin Staebler
Texas Instruments
