Hall, MR and TMR Current Sensor ICs
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Hall, MR and TMR current sensor ICs let you measure high-voltage currents with low loss and built-in isolation, avoiding hot shunts and bulky transformers. This page shows how to choose the right technology, package and isolation level, then turn those decisions into practical layouts, diagnostics and BOM requirements.
System Role & Why Hall / MR / TMR Current Sensors
Hall, MR and TMR current sensor ICs measure current indirectly by sensing the magnetic field around a conductor or busbar. They sit directly in high-voltage power paths — traction inverters, on-board chargers, PFC stages and industrial drives — where shunt-based sensing would run hot or require complex galvanic isolation. Instead of dropping voltage across a resistor, these devices couple the field into an on-chip sensor and signal chain, providing a compact, board-friendly way to monitor tens to hundreds of amps.
Compared with low-side or high-side shunt solutions, Hall/MR/TMR current sensors trade a little absolute accuracy for intrinsic isolation, very low insertion loss and simplified thermal design. Isolation ratings in the 1–5 kV class, reinforced creepage distances and busbar-friendly packages make them a natural fit wherever you need non-contact, isolated current feedback on high-voltage rails rather than precision sense resistors plus separate digital isolators.
Hall vs MR vs TMR, Core vs Coreless and Open vs Closed Loop
Hall current sensor IC
Hall-effect current sensors are the mainstream choice for isolated current feedback on DC links and AC mains rails. They offer robust behaviour, wide current ranges and attractive cost, typically serving tens to a few hundred amps where 1–3 % accuracy is acceptable.
Many classic “isolated current sensor ICs” are Hall based. They tolerate harsh environments and switching noise, but show more offset, drift and noise than carefully designed shunt and amplifier solutions on low-voltage rails.
MR (AMR / GMR) sensor IC
Magnetoresistive (AMR/GMR) current sensor ICs use resistor elements whose value changes with magnetic field, arranged in precision bridges and amplified on chip. They deliver higher sensitivity and lower noise than basic Hall devices at similar current ranges.
MR sensors are attractive when you want better small-signal resolution and cleaner waveforms, for example in metering, industrial control or inverter monitoring that must capture detailed current shape rather than just coarse RMS levels.
TMR sensor IC
Tunnel magnetoresistance (TMR) current sensor ICs provide the highest sensitivity and best signal-to-noise ratio among mainstream magnetic sensing options. They can resolve smaller field changes and support tighter accuracy budgets on the same current range.
TMR parts are increasingly used in automotive and industrial designs that combine high-voltage isolation, high current and more demanding accuracy or resolution targets, at the cost of more premium pricing and careful layout around the sensing window.
Core-based transducers
Core-based current transducers route the primary conductor through a magnetic core, concentrating flux into a small sensing region. This improves linearity and immunity to external fields, but adds size, weight and cost compared with small IC-style packages.
They remain popular in cabinet-mounted modules and very high-current systems where bulky cores are acceptable and mechanical integration favours a standalone device rather than an SMT IC on the PCB.
Coreless isolated sensors
Coreless Hall/MR/TMR current sensor ICs remove the magnetic core and instead rely on leadframes or PCB structures to sample the field near the conductor. They are thin, fully SMT compatible and integrate easily on crowded power boards.
With careful layout, coreless sensors offer a good balance of bandwidth, cost and isolation for OBC, PFC, motor drives and DC bus monitoring, but they are more sensitive to conductor placement and external magnetic sources.
Busbar-integrated sensors
Busbar-integrated current sensors provide a defined window or cut-out that a copper bar passes through, locking in the geometry between conductor and sensing elements. This suits EV traction inverters and power modules where large currents must be monitored compactly.
When selecting these parts, you must match busbar size, tolerance and mounting scheme, and consider creepage and clearance rules between primary and secondary domains as part of the overall mechanical design.
Open-loop current sensors
Open-loop Hall/MR/TMR current sensors use a single magnetic sensing path and an internal amplifier to generate an output proportional to current. They are compact, low power and cost-effective, with modest latency that suits most monitoring and control tasks.
Their linearity and accuracy depend strongly on field geometry, sensor placement and on-chip trimming. For moderate bandwidth and accuracy targets they are usually the first option to consider.
Closed-loop current sensors
Closed-loop current sensors add a compensation winding or feedback path so the sensed flux is actively nulled. The drive required to cancel the field becomes the output signal, delivering excellent linearity, wider bandwidth and better stability over temperature.
They cost more and often use bulkier magnetics, but are attractive where fast, precise Isense feedback is central to control loop performance, such as high-end drives or power modules that justify the extra size and complexity.
Key Specifications & How to Choose Hall / MR / TMR Sensors
Datasheets for Hall, MR and TMR current sensor ICs expose many numbers, but a small set of parameters really drives selection. Start from the current range and isolation requirements, then layer bandwidth, accuracy and practical packaging constraints on top. The goal is to reject obviously unsuitable parts early, and then compare only a short list of candidates against your accuracy and safety budget.
Key parameters to read first
- Current range & polarity: IRMS, IPEAK, unidirectional or bidirectional measurement.
- Bandwidth & response time: typical 10–200 kHz and associated step response for your loop or monitoring needs.
- Linearity (%FS) & full-scale error: how closely the output follows ideal gain across the entire current range.
- Offset & drift: zero-current offset in mV or A, and temperature drift in mV/°C or A/°C over the specified range.
- Noise-equivalent current: sensor noise in nT/√Hz or equivalent Arms versus your desired resolution.
- Supply & output swing: 3.3 V or 5 V rails, ratiometric or fixed output, and usable voltage range into the ADC.
- Isolation ratings: working voltage (VIORM), basic vs reinforced VISO, and surge ratings for your mains or DC link.
- Package & geometry: SOIC, DIP, cut-out or busbar-slot footprints and conductor window dimensions.
- Safety & automotive grade: UL/IEC approvals and AEC-Q100 qualification where applicable.
Practical trade-offs when reading datasheets
Start with the primary current and rail voltage: they dictate which families even cover your range and isolation level. For example, a 30 A low-voltage rail may tolerate a compact coreless sensor, while a 400 A, 800 V traction bus will narrow you to reinforced, busbar-oriented devices very quickly.
Next, match bandwidth and response time to the job. Inverter control and PFC feedback often call for tens of kilohertz of usable bandwidth, whereas slow metering can accept heavy filtering. Higher bandwidth usually brings more noise, so the accuracy budget must consider gain error, offset, drift and noise together rather than one line item in isolation.
Finally, check that the output format and package will physically integrate: the ratiometric span should map cleanly into your ADC range, and the SOIC, cut-out or slot geometries must match busbar dimensions, creepage/clearance rules and the overall isolation design.
- Fix current range, polarity and required isolation voltage.
- Choose Hall vs MR vs TMR and core vs coreless vs busbar form factor.
- Check bandwidth, linearity, offset, drift and noise against error budget.
- Verify supply, output swing and ADC mapping on the control side.
- Filter by package, safety approvals and automotive grade if needed.
Analogue Behaviour, Filtering & MCU Hooks
Once you have picked a Hall, MR or TMR current sensor IC, the analogue behaviour into your MCU or control ASIC matters just as much as the raw datasheet numbers. Most devices expose a ratiometric or biased output that must be mapped cleanly into an ADC, with just enough analogue filtering to tame noise without hiding real current dynamics or fault signatures.
Output format & biasing
Most Hall, MR and TMR sensors provide a voltage output centred around mid-supply, typically VCC/2, with a gain that maps positive and negative currents to usable ADC codes. Others offer current outputs or PWM/period encoding, but the design questions are the same: where is zero, what is full-scale and how do you keep headroom for abnormal events?
- Check the zero-current level and confirm it sits safely inside the ADC input range.
- Map full-scale current to voltage so the ADC uses most of its span without clipping.
- Note whether the output is ratiometric to VCC or referenced to an internal reference when planning ADC VREF.
Filtering, bandwidth & latency
Vendors often include on-chip filtering, but a simple external RC between the sensor output and ADC pin is still common. The cutoff frequency sets how much switching ripple and noise you see versus how much delay is added to the measured current, so the values must reflect the control loop and protection strategy.
- Set RC bandwidth high enough for PWM frequency and loop dynamics, not just DC.
- For slow metering, heavier filtering can greatly reduce noise at the cost of response time.
- If fast overcurrent trips rely on this path, avoid over-filtering and consider a separate comparator or eFuse path for hard protection.
MCU / ADC hooks & noise translation
On the digital side, the key is to relate ADC codes back to real amps with meaningful resolution and noise. The sensor’s noise-equivalent current sets a practical floor, and the ADC’s LSB size should be smaller than that floor so the converter is not the limiting factor. Oversampling helps only after the basic analogue chain is clean.
- Translate ADC LSB size into equivalent current and compare it with datasheet noise-equivalent current.
- Budget for gain error, offset and drift when deciding whether Hall, MR or TMR meets your long-term accuracy target.
- Apply digital averaging or decimation only after RC filtering; otherwise you may simply average switching artefacts instead of removing them.
Magnetic Path, Placement & EMC for Hall / MR / TMR Sensors
Magnetic path & window usage
Layout for Hall, MR and TMR current sensors is driven by magnetic flux rather than copper resistance. Window or slot-type packages expect the primary conductor to pass through a defined sensing region so the field pattern matches what the device was trimmed for. Running a busbar past the outside corner of the package is not equivalent to routing it through the intended window.
- Treat cut-out and slot packages as true windows: route the current path through the opening, not merely alongside the housing.
- For coreless SOIC parts, follow the vendor’s recommended copper path beneath or around the body to keep the sensing region centred on the current.
- Avoid creative zig-zag or offset routes that change the effective magnetic geometry and invalidate datasheet linearity and gain figures.
Symmetry, return paths & external fields
For single conductors, placing the busbar centrally in the sensing window maximises symmetry and keeps the transfer function close to what the device was trimmed for. Multiple parallel conductors or a misplaced return path can distort the net field, pulling the apparent gain and offset away from the datasheet values even when the current itself is correct.
- Centre the primary conductor in the window wherever possible, and keep parallel paths arranged symmetrically.
- Avoid routing high-current returns directly under the package unless the datasheet shows that geometry as supported.
- Keep motors, contactors, inductors and large steel parts a safe distance away or use shielding to limit static bias and torque-dependent field offsets.
EMC, output filtering & creepage / clearance
High di/dt edges on inverter and PFC rails inject high-frequency content into the magnetic path as well as into supply and ground. The output RC network is your last analogue stage to shape what the ADC sees, and it must be chosen so that switching artefacts are tamed without hiding legitimate current dynamics or fault signatures. At the same time, PCB layout must preserve the creepage and clearance that the package was designed to provide.
- Choose RC bandwidth high enough for the control loop while reducing visible PWM ripple and conducted noise.
- Do not route copper across isolation slots or undercut clearances that the datasheet calls out for SOIC, cut-out or busbar packages.
- Treat creepage distances as part of the system isolation design; detailed limits and coordination with standards are covered in the Safety section.
Isolation, Standards & Diagnostics
Isolation is the defining feature of most Hall, MR and TMR current sensor ICs. Beyond basic accuracy, you must confirm that working voltage, surge capability, insulation type and long-term reliability align with your mains, DC link or traction environment. On-chip diagnostics and calibration hooks then help prove that the sensor remains trustworthy throughout its service life.
Isolation parameters
Datasheets usually specify working isolation voltage (VIORM), one-minute isolating voltage (VISO) and surge capability. Together with the insulation type (basic or reinforced), these numbers must be matched against the maximum DC link, AC mains, pollution degree and over-voltage category of your design.
- Check VIORM against your continuous rail voltage plus expected tolerances and common-mode swings.
- Verify that VISO and surge ratings are compatible with system-level dielectric tests and lightning or switching surges.
- Confirm whether the device provides basic or reinforced insulation and align this with standards such as UL 60950, IEC 62368 or traction-specific rules.
Safety & lifetime
Isolation capability and measurement accuracy both age over time. Manufacturers may provide insulation lifetime curves versus working voltage, as well as drift data for offset and sensitivity. High ambient and case temperatures accelerate both dielectric ageing and magnetic sensor drift, which must be reflected in your lifetime budget.
- Use insulation lifetime data with your target service life, ambient profile and worst-case DC link voltage.
- Check that offset and gain drift over years still keeps protection thresholds, efficiency and metering accuracy within acceptable limits.
- For automotive and traction systems, prefer AEC-Q100 qualified parts and validate drift and insulation margins under realistic mission profiles.
Diagnostics & calibration hooks
Many current sensor ICs add fault outputs, enable pins, calibration inputs or temperature readouts that help detect latent failures and track drift. These hooks are especially valuable when the sensor feeds safety functions or power stages that must enter a controlled state on abnormal behaviour.
- Look for overcurrent flags, saturation indicators or error amplifiers that can trigger supervisors or eFuse devices.
- Use calibration pins or digital trim paths to remove assembly offsets during production and re-check them at service intervals where possible.
- Combine sensor readings with plausibility checks, redundant channels or model-based estimates to detect stuck, drifting or saturated sensors in critical applications.
Brand roadmap for Hall / MR / TMR current sensor ICs
This section shows where to start when you are looking for Hall / MR / TMR based current sensors at the “seven majors”. It highlights each vendor’s typical focus, gives a few concrete part numbers and explains what kind of rails or current ranges they are best suited for.
| Vendor | Portfolio focus | Typical parts / series | Why you would pick them |
|---|---|---|---|
| Texas Instruments | Isolated Hall current sensors with integrated primary conductor and strong analog front ends for EV, industrial drives and on-board chargers. | TMCS1100 · TMCS1101 · TMCS1123 | Strong choice when you need reinforced isolation, integrated busbar-style conductors and simple, ratiometric voltage outputs that drop straight into an ADC. Good generic fit for ±50 A to ±200 A rails. |
| STMicroelectronics | Focus on high-side shunt current sensing around motor drives and traction inverters; pairs well with external Hall / TMR transducers in EV and industrial drives. | TSC2020 · TSC103 | When you already have shunt-based sensing in the power stage and only need a robust high-side sense amplifier with automotive qualification, ST’s TSC family is a natural fit. |
| NXP | Magnetoresistive and Hall sensors around motor control and e-mobility, plus system-level reference designs for traction and battery junction boxes. | NMH1000 (Hall switch) · RD-UAMP-SENSOR (reference design) | Good fit if you are already on NXP MCUs/PMICs and want application notes and reference designs that show how to integrate external Hall / MR current sensors into traction or inverter platforms. |
| Renesas | Mix of shunt-based current sense amplifiers and contactless current sensor ICs (Rogowski coil based) targeting industrial mains and harsh environments. | RAA788000 · ISL28006 | Use RAA788000 when you want a contactless AC rail sensor (2–5000 A). Use ISL current-sense amps when a precise shunt plus isolation barrier is more economical than a fully integrated Hall / TMR solution. |
| onsemi | Strong focus on power modules and motor drivers; current sensing is often integrated into drivers or protected high-side switches rather than standalone Hall ICs. | NCS213R · NCV84120 | Choose these when you are already using onsemi FETs, gate drivers or smart switches, and you prefer an integrated protection / sensing path rather than a discrete Hall rail sensor. |
| Microchip | Mainly shunt-based high-side current monitors and power monitors, suitable for lighter power paths or where isolation is provided elsewhere in the system. | HV7800 · HV7802 | Appropriate when your design already uses Microchip MCUs or PMICs and the current sense is on the low / high side of a modest rail (AC-DC adapters, small inverters) rather than a high-voltage isolated busbar. |
| Melexis | Deep portfolio of automotive Hall and TMR current sensors for busbars, PCB cut-outs and in-line cables, optimized for EV traction inverters, on-board chargers and battery monitoring. | MLX91220 · MLX91221 · MLX91211 | Often the go-to when you need automotive-grade isolation, high bandwidth and tight accuracy on battery busbars or motor phases, with many package options for cut-out and PCB slot mounting. |
BOM fields, sourcing risks and supplier hand-off
Use this section as a copy-ready checklist: the left card lists fields you should write into the BOM, the middle
card calls out sourcing risks and second-source options, and the right card points to your internal
/submit-bom workflow.
BOM fields for Hall / MR / TMR current sensors
These fields make it clear to suppliers what kind of magnetic current sensor you need, and avoid being silently swapped to a generic shunt monitor.
- Current range: IRMS and IPEAK (for example, 200 A RMS / 400 A peak)
- Polarity: unidirectional / bidirectional, DC only or AC+DC
- Isolation rating: working voltage, VIORM/VISO, surge class, insulation type
- Accuracy budget: total %FS, offset at 25 °C, drift over temperature and lifetime
- Bandwidth / response: small-signal bandwidth and step response time
- Output type: ratiometric analog, fixed gain, PWM / SENT / SPI
- Supply and reference: 3.3 V / 5 V, Vref source, allowed common-mode
- Package & mechanics: SOIC cut-out, busbar slot, module, creepage target
- Standards: AEC-Q100 grade, UL / IEC isolation standard, OEM-specific specs
Procurement risks & example part choices
Call out what must not be changed (technology, isolation class, bandwidth) and give 1–2 acceptable second sources for each risk level.
- Isolation class is non-negotiable: do not down-bin reinforced parts (for example, TMCS1100) to basic-insulated sensors just to save cost.
- Bandwidth vs. delay: traction inverters and fast e-fuse coordination often need >100 kHz small-signal bandwidth; make sure replacements meet your fault-detection timing.
- Mechanical form: busbar-style packages and PCB cut-outs constrain alternative parts; note allowed footprint families explicitly.
Example IC choices and why they are used
- TI TMCS1100 / TMCS1101: reinforced isolated Hall sensors with integrated primary conductor; good generic choice for ±50 A to ±200 A HV rails in EV inverters and OBC.
- Melexis MLX91220 / MLX91221: high-speed Hall sensors for traction phases; pick when you need high bandwidth and automotive diagnostics on PCB cut-out or busbar rails.
- Renesas RAA788000: Rogowski-based contactless sensor for 50/60 Hz mains (2–5000 A); ideal for AC busbars in industrial cabinets when continuous isolation and low insertion loss matter.
- ST TSC2020 + shunt: precision high-side current sense amplifier; use where isolation is provided elsewhere and you want a shunt-based alternative to Hall / TMR on high-voltage rails.
Hand-off to suppliers (/submit-bom)
Use a short description paragraph to tell distributors and design-in FAE teams exactly what you are trying to sense (rail, current, isolation, bandwidth) and where you are flexible.
- Attach the BOM fields above as a structured line item for each current rail.
- Include schematics showing conductor geometry (busbar, cable, PCB cut-out).
- State preferred brands (for example, “TI / Melexis primary, others as backup”).
- Flag rails that require automotive certification vs. industrial only.
Final step: send this section along with your schematic PDF to your internal /submit-bom form so that procurement and FAE teams can short-list 2–3 Hall / MR / TMR options per current path.
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FAQs on Hall / MR / TMR Current Sensors
Hall, MR and TMR current sensors let you measure high-voltage currents with low loss and built-in isolation, but choosing the right device is not always obvious. This FAQ gathers twelve practical questions to help you decide on technology, package, isolation level and BOM fields for real inverter, charger and industrial power-rail designs.
How do Hall, MR and TMR sensors differ in sensitivity, noise and usable current range?
Hall sensors offer robust mid-range performance with moderate sensitivity and higher noise, making them fine for tens to a few hundred amps. MR devices improve sensitivity and low-current resolution. TMR parts push sensitivity and signal-to-noise ratio further, enabling finer measurements, tighter error budgets and stable results in smaller current windows or when bandwidth and resolution are both important.
When should I choose coreless or busbar-integrated current sensors over core-based parts?
Core-based sensors use a magnetic core to concentrate flux and deliver excellent linearity, but they are bulky and suit modules or cabinets. Coreless devices are thin, SMT-friendly and easier to place near electronics. Busbar-integrated parts shine at high currents in EV and industrial rails where the copper bar is the mechanical backbone.
How does isolation rating (VIORM/VISO/surge) affect selection for 400–800 V traction systems?
VIORM defines the maximum continuous working isolation voltage. VISO covers short-term dielectric test levels, and surge ratings describe immunity to lightning or switching transients. For 400–800 volt traction rails, you want reinforced insulation, working voltage comfortably above the worst-case DC link, and surge capability aligned with your OEM and regional traction standards.
What bandwidth can Hall, MR and TMR sensors realistically achieve, and when is it not enough?
Hall sensors typically support small-signal bandwidths from a few kilohertz to several tens of kilohertz, with some families reaching toward one hundred kilohertz. MR and TMR technologies can extend usable bandwidth and phase accuracy further. Bandwidth becomes insufficient when control loops, protection comparators or diagnostic sampling demand microsecond-scale response that rivals current transformers or Rogowski coils.
How do external magnetic fields from motors or contactors impact offset and drift?
External magnetic fields from motors, contactors and large inductors add to the field generated by the measured conductor. The sensor can see this as a static offset plus a load-dependent component that changes with torque, duty-cycle or coil current. Keeping such sources at distance, using shielding and maintaining symmetric routing all help to reduce drift and false readings.
How do I map ratiometric output and VCC/2 offset into an MCU ADC with good resolution?
Ratiometric sensors typically place the zero-current output at VCC divided by two and scale positive and negative currents around that midpoint. To use them well, map zero and full-scale voltages into ADC codes with some headroom, then compute the current represented by one LSB. Resolution is acceptable when one LSB corresponds to less current than the sensor noise floor.
What filtering is recommended to balance noise and latency in inverter or PFC loops?
Filtering usually starts with a simple RC network between sensor and ADC input. For inverters and power factor correction stages, you want a cutoff comfortably above the control-loop bandwidth but low enough to reduce PWM ripple and high-frequency noise. If you rely on very fast hardware trips, keep a separate, less filtered path for overcurrent comparators or eFuse logic.
How does temperature affect sensitivity, offset and long-term accuracy?
Temperature affects both instantaneous and long-term accuracy. Sensitivity changes with temperature according to the device’s gain tempco, while offset drifts across the specified range and may increase near limits. Over years, high temperature and high working voltage accelerate ageing. A realistic budget should combine datasheet drift figures with mission profiles and, for critical rails, allow margin for periodic recalibration.
How to interpret linearity (%FS) and noise-equivalent current when comparing datasheets?
Linearity in percent of full scale describes how far the transfer curve deviates from an ideal straight line across the specified current range. Noise-equivalent current converts voltage or field noise into an effective current floor within a given bandwidth. When comparing datasheets, align bandwidth assumptions and then check whether noise and linearity both sit inside your total error budget.
When are closed-loop current sensors worth the cost compared to open-loop devices?
Closed-loop current sensors add a compensation winding and amplifier so that the magnetic core is driven back toward zero flux. The result is excellent linearity, wider bandwidth and reduced temperature dependence at the cost of more power, size and price. They are worth it when fast, precise current control or metering justifies higher complexity and per-channel cost.
What packaging (SOIC, cut-out, busbar) is suitable for given creepage/clearance rules?
SOIC packages suit medium-voltage applications where creepage can be extended with board slots or coatings. Cut-out and slot packages route the conductor through a defined window and offer longer creepage distances on the board. Busbar-oriented devices provide the largest mechanical clearances and are preferred on high-current EV or industrial rails that must meet stringent isolation requirements.
What fields should be written clearly into a BOM to avoid wrong Hall/MR/TMR replacements?
A robust BOM entry for Hall, MR or TMR sensors should state current range and polarity, isolation class and working voltage, target accuracy and bandwidth, supply and output format, and the required package style. Clearly mark non-negotiable fields, such as reinforced isolation or automotive qualification, and list acceptable primary brands so replacements do not silently downgrade safety or performance.
