The ATM90E26 is a practical metering front end for custom single-phase energy-monitoring equipment. It measures active and reactive energy, voltage, current, power, power factor, phase angle and frequency, then exposes those results to a host microcontroller through SPI or UART. Microchip specifies 0.1% active-energy accuracy, 0.2% reactive-energy accuracy and a 5000:1 dynamic range under the conditions and calibration procedures in its documentation.
Its cost advantage is not that it creates a complete $1–$2 energy monitor. The chip still needs current and voltage sensors, protection, a power supply, a controller, calibration and a safe mains-rated product design. It is cost-effective when a project needs dependable single-phase metrology without burdening a general-purpose MCU with the entire measurement algorithm.
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What the ATM90E26 does
The ATM90E26 is a single-phase energy-metering IC intended for single-phase two-wire and three-wire meters, anti-tampering applications and power-monitoring instruments. It combines analog measurement channels with dedicated digital signal processing and measurement registers.
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Depending on the circuit and operating mode, it can provide:
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- Comprehensive Testing Capabilities: This electric monitoring test module effectively measures power, energy, voltage, and current for various applications.
- Connection Design: The connection of this module is divided into 2 parts: voltage, current input connection and serial port communication, and you can use different TTL adapters to make it communicate with various terminals
- High-Power Equipment Testing: The test module is design to test high power equipment and you can observe the accumulative process intuitively for the low-power(within 100W)load test
- Simple Energy Reset Function: There is a button on module for energy reset, simply press and hold the button for 5 seconds and release, then press the button again to finish energy reset
- Flexible Display Options: It displays through PC or other terminals, and you can download the software for PC. For other terminals, it need to be programmed by yourself
- Active, reactive and apparent power
- Forward and reverse active and reactive energy
- RMS voltage and current
- Mean active and reactive power
- Power factor, phase angle and line frequency
- Energy pulse outputs for active and reactive energy
- Voltage-sag detection and zero-crossing output
- Programmable startup and no-load thresholds
- Voltage and current gain, offset and phase compensation
- Line-neutral comparison for suitable anti-tampering configurations
The IC is therefore a metrology component, not a finished monitoring system. Connectivity, logging, display, control and cloud functions remain the responsibility of the host product.
Why it can reduce project cost
Dedicated metrology instead of MCU-only sampling
An MCU-only design must synchronously sample voltage and current, remove offsets, calculate RMS quantities, determine real and reactive power, integrate energy over time, compensate sensor phase error and manage calibration. The ATM90E26 performs those core metering functions and makes the results available through registers and pulse outputs. The host MCU can concentrate on communications, control and the user interface.
This may allow a product to use a modest MCU that it already needs for Wi-Fi, Bluetooth, RS-485, a display or appliance control. The saving is design-dependent: a more expensive metering IC can still reduce firmware development, validation effort and processor requirements.
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DigiKey listed the ATM90E26-YU-R at approximately $1.66 for one unit, $1.6216 at 25 units and $1.39001 at 2,000 units when checked on August 16, 2026. Those are time-specific distributor observations, not guaranteed future prices; shipping, taxes, tariffs and production terms are excluded. Check the current distributor listing before costing a design.
The complete cost stack can include:
- A shunt, current transformer or neutral current transformer
- High-voltage divider resistors or a potential transformer
- Burden resistors, filters and surge-protection components
- A 3.3-V-class regulator, decoupling components and an 8.192-MHz crystal
- An MCU, memory and communications hardware
- Isolation components, where the architecture requires them
- Mains-rated connectors, fusing, enclosure and PCB area
- Calibration fixtures, production test time and traceability
- EMC, safety and applicable regulatory testing
For a one-off installation or hobby project, a complete pre-engineered smart plug or energy-monitoring module may be cheaper in total effort. For a product made in volume, the ATM90E26 can make the custom metrology portion economical.
Key specifications and their limits
| Characteristic | ATM90E26 information |
|---|---|
| Measurement | Single-phase two-wire, single-phase three-wire and suitable line-neutral/anti-tampering configurations |
| Active-energy accuracy | 0.1% specified by Microchip under stated conditions |
| Reactive-energy accuracy | 0.2% specified by Microchip under stated conditions |
| Dynamic range | 5000:1 |
| Host interface | SPI or UART |
| Supply | Approximately 2.8–3.6 V nominal operating range; metering accuracy is guaranteed over 3.0–3.6 V in the cited datasheet |
| Temperature | −40 °C to +85 °C in the cited product documentation |
| Package | 28-pin SSOP |
| Clock | 8.192-MHz crystal oscillator frequency |
| Outputs | Active- and reactive-energy pulses, interrupt/warning functions and zero-crossing output |
Refer to the ATM90E26 datasheet for the conditions behind each specification. A 0.1% IC-level figure is not a guarantee that a completed monitor will read a wall outlet to 0.1%. Divider tolerance and drift, sensor linearity, CT phase shift, shunt heating, reference behavior, PCB noise, temperature and calibration all affect the result.
Similarly, a 5000:1 dynamic range does not mean that every real load down to one five-thousandth of full scale will meet headline accuracy. Low-current noise, offsets, sensor behavior and the programmed startup threshold determine the useful range of the finished product.
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- Comprehensive Parameter Measurement: Includes voltage, current, active power, and energy measurement.
- High Power Equipment Testing: Allows for low-power (within 100W) load test observation.
- Voltage and Current Capacity: AC 80-260V Voltage Test Range; working voltage of 80-260V; maximum current of 100A.
- Communication Interface: Comes with a TTL serial data communication interface for parameter reading and setting.
- Energy Reset Feature: Panel key enables energy reset for user convenience.
How a typical measurement chain works
Mains voltage
│
├── Fuse / surge protection / protection network
│
├── High-value resistor divider ───────┐
│ │
Line conductor ├── ATM90E26 ── SPI/UART ── MCU
│ │ │
├── Shunt or current transformer ──────┘ Wi-Fi/BLE/RS-485/display
│
Neutral conductor
└── Optional neutral CT
ATM90E26 CF1 / CF2 ── pulse counter or calibration interfaceThe voltage channel normally uses a resistor-divider network or potential transformer. The line-current channel can use a shunt or current transformer; a current transformer can also be used on neutral in configurations that compare line and neutral current.
Microchip’s ATM90E2x-DB demonstration board illustrates this type of arrangement. It samples single-phase voltage and current, measures active and reactive energy, produces energy pulses and communicates through a SAM4C-based control board.
Hardware design decisions
Choose the current sensor around the whole operating range
Shunt: A shunt is compact and usually inexpensive, with a direct relationship between current and voltage. Its disadvantages are power dissipation, thermal drift, overload considerations and the fact that it may be electrically connected to the mains. The shunt’s resistance, power rating, layout and fault behavior must be engineered for the maximum continuous and transient current.
Current transformer: A CT provides galvanic separation for the measured current path and is often attractive for mains monitoring. It adds a burden resistor, physical volume and phase error. It can saturate under overload or an unsuitable burden condition, and its phase behavior may be especially important at low current or when measuring reactive power.
Neutral CT: A second CT can support line-neutral comparison and anti-tampering functions. A mismatch is not automatically proof of tampering; it can also result from wiring errors, sensor mismatch, leakage, saturation or poor threshold selection.
Define nominal voltage and frequency, maximum continuous and transient current, minimum useful current, insertion-loss limits, overload behavior and required power-factor range before selecting the sensor.
Scale and protect the voltage input
The voltage input is a mains-connected measurement circuit, not a spare MCU ADC pin. Use the datasheet’s recommended input range and application circuit as a starting point. The divider must account for resistor voltage rating, pulse withstand, power dissipation, tolerance, thermal drift, noise, creepage and clearance. A potential transformer changes the isolation and accuracy trade-offs but is not automatically a complete safety solution.
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- 【Real Time Monitoring】PZEM energy meter tracks AC 80 to 260V voltage 0 to 100A current active power frequency power factor and active energy for circuit monitoring.
- 【V3 Module Design】PZEM 004T V3 para module includes mutual inductor and supports measurement up to 23kW with 0.1V voltage resolution 0.001A current resolution and 0.1Hz frequency resolution.
- 【Multi Data Display】Measures voltage current active power power factor 0.00 to 1.00 frequency 45Hz to 65Hz and active energy 0 to 9999.99kWh for power usage observation.
- 【Compact Size】Module size is approx. 78 x 37 x 19mm making it suitable for electrical boxes test benches DIY electronics projects and home power monitoring setups with limited space.
- 【For DIY And Monitoring】Designed for users who need to monitor household circuits equipment load and power consumption trends with a 100A current transformer for AC measurement tasks.
Microchip’s AN46102 application note and its reference PDF include a reference implementation and component BOM. Treat those values as design guidance, not a universal production BOM: mains voltage, current range, sensor, enclosure, overvoltage category and compliance requirements may all require changes.
Supply, clock and layout
Provide a clean, regulated supply in the datasheet’s specified range. Although the device is a mixed-signal metering IC, supply decoupling and noise control directly affect measurement quality. Follow the recommended crystal arrangement, grounding, analog routing and input filtering. Keep noisy digital, switching-power and communications paths from coupling into the measurement network.
PCB spacing must be designed for the actual mains environment, including the applicable working voltage, overvoltage category, pollution degree, insulation system and enclosure. Fusing, surge protection, touch protection and an appropriate power supply are system-design responsibilities; the metering IC does not provide them.
Firmware integration
The host MCU normally needs to:
- Initialize the ATM90E26 and select the correct metering mode.
- Read voltage, current, power, power factor, frequency and energy registers at the required intervals.
- Monitor status, warning, interrupt, voltage-sag and zero-crossing signals where used.
- Count or process CF1 and CF2 energy pulses for calibration or downstream accumulation.
- Apply application-level filtering, averaging, unit conversion and reporting rules.
- Store calibration constants and associate them with the product, sensor configuration and firmware revision.
- Recover cleanly from reset, brownout, communication timeout or corrupted transactions.
SPI is convenient when the MCU has a shared bus and tight transaction control is useful. UART can be attractive for a simple point-to-point connection or when SPI resources are constrained. Either interface must follow the applicable datasheet revision for timing, transaction framing, checksum handling and timeout behavior. Do not assume that a generic MCU library or hobbyist driver is officially supported by Microchip.
Configure the metering mode carefully. A single-phase two-wire setup, single-phase three-wire setup and line-plus-neutral anti-tampering setup do not use identical assumptions. Incorrect initialization can produce plausible values that are nevertheless wrong.
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Calibration: where system accuracy is won
Practical designs should include calibration even though Microchip describes single-point active-energy calibration and states that reactive-energy calibration is unnecessary under specified conditions. That statement concerns the IC and defined operating conditions; it does not remove errors from the chosen sensors, divider, PCB or complete product.
A useful production workflow is:
- Verify supply voltage, crystal, reset and communications.
- Apply a known voltage and current from a controlled reference.
- Measure at a defined power factor and operating point.
- Adjust voltage and current gain.
- Apply offset correction where required.
- Correct sensor phase error when the current sensor requires it.
- Set the active-energy constant and verify pulse output.
- Check reactive-energy readings if the application uses them.
- Test low, nominal, high and reverse-energy conditions.
- Store calibration data with product identity and firmware revision.
- Repeat verification after thermal or environmental testing.
The exact register sequence and constants must come from the applicable datasheet and application-note revision, together with the selected sensor network.
Rank #4
- 1. Monitors key AC power readings in one panel display: This hardwired AC power meter shows voltage, current, wattage, kWh energy, frequency and power factor, helping you watch generator load, RV power, workshop circuits or appliance consumption in real time
- 2. Split-core CT makes installation easier: The included 100A current transformer clamps around one live conductor, so you do not need to cut the monitored wire; for 120/240V split-phase systems, monitor one leg per meter or use separate meters as needed
- 3. Wide AC range for common electrical panels: Designed for 80-260VAC circuits with 0-100A current measurement and up to 22,000W rated power, this meter is useful for household, garage, generator, RV and light commercial monitoring projects
- 4. Power-off memory and visual overload alarm: The meter can store energy data and settings after power loss, and the backlight/power display flashes when the preset power threshold is exceeded, giving a clear visual warning for load monitoring
- 5. Clear LCD display for practical troubleshooting: The compact panel meter provides quick readings for energy use and load balancing, with 1.0 grade monitoring accuracy; it is intended for hardwired installation and should be installed with proper electrical safety precautions
Verification test matrix
| Test | What it can reveal |
|---|---|
| No load | Unwanted accumulation, noise and no-load threshold errors |
| Startup and low current | Offset, sensor linearity and missed-load behavior |
| Nominal and maximum current | Gain error, heating, overload margin and sensor saturation |
| Resistive load | Basic active-energy calibration |
| Inductive and capacitive power factor | Phase compensation and reactive-energy behavior |
| Switch-mode, LED or motor loads | Performance with distorted current and high crest factor |
| Reverse current | Forward/reverse register and reporting policy |
| Voltage variation and sag | Thresholds, warnings and scaling |
| Temperature variation | Divider, shunt, CT and overall drift |
| Brownout and communication faults | Reset recovery, register reinitialization and data integrity |
| EMC and mains transients | Robustness and compliance risks |
Safety: the non-negotiable part
Do not connect an ATM90E26 circuit to mains merely because the IC operates at low voltage. A low-voltage logic interface is not the same thing as an isolated or touch-safe product.
The complete design must address the intended mains voltage, overvoltage category, pollution degree, fuse coordination, surge environment, PCB creepage and clearance, insulation barriers, component ratings, enclosure, connectors, accessible surfaces and power-supply isolation. It also needs review against the regulations and standards applicable to the installation and market.
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Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →The datasheet references IEC 62052-11, IEC 62053-21 and IEC 62053-23 for specified meter applications. That does not mean a finished product is certified simply because it uses the IC or follows a demonstration circuit. Prototype mains work should use appropriate test equipment, protection and procedures; commercial equipment requires a formal safety and compliance assessment.
Where the ATM90E26 fits
Strong candidates
- Smart plugs and connected appliance monitors
- Single-phase load monitors and embedded displays
- Residential submeters
- Single-phase industrial equipment monitors
- Power instruments that need active and reactive measurements
- Line-neutral comparison or anti-tampering products
Consider another architecture when
- The product needs three-phase metering in one device.
- Both AC and DC power must be measured.
- Extensive harmonic or high-end power-quality analysis is required.
- The environment exceeds the cited +85 °C temperature range.
- Wireless connectivity or an isolated complete measurement system must be integrated.
- The team cannot take responsibility for mains analog design, calibration and compliance.
- A one-off project can use a certified commercial meter or complete module instead.
For polyphase designs, Microchip lists families such as ATM90E32AS and ATM90E36A. They are not direct low-cost substitutes for a single-phase design, but they are more appropriate starting points when additional phases must be measured.
Alternatives
MCP39F511A
DigiKey’s energy-metering listings showed the MCP39F511A with approximately 0.1% listed measurement error, a 2.7–3.6 V supply, a −40 °C to +125 °C range and a 28-pin QFN listing. A single-unit price signal was approximately $3.59 when checked. It may be preferable where temperature range or its feature balance outweighs the ATM90E26’s lower observed price, but QFN assembly and a different firmware and analog design still have to be evaluated. See the specific distributor listing for current information.
ADE7953
The ADE7953 is another single-phase metering IC. It may suit teams already using Analog Devices’ metering ecosystem or needing its particular interface and measurement characteristics. The evidence available here does not establish a complete current price or feature comparison, so it should not be described as cheaper or more accurate without checking the exact ordering code and current documentation.
STPM32
STPM32 appeared in distributor comparison results as a single-phase energy-metering option, with an observed price signal of approximately $2.66. Treat that as a time-specific comparison signal only. Verify the exact part, package, lifecycle status, interface, calibration flow and availability before considering it for a design.
Best Value
- It can set active power threshold, and it will alarm when the measured active power exceeds the threshold.
- With reset energy, which can be used to reset software.
- Its communication interface is RS485.
- High precision, fast response and stable communication.
- Comes with a for shell to protect the module.
Complete monitoring platforms
A certified smart plug, submeter or development module can be the better commercial choice when engineering time, mains safety, calibration, connectivity and certification dominate. The trade-off is less control over the sensor, enclosure, firmware and long-term product architecture.
Buying guidance
Buy the ATM90E26 IC when the product is single-phase, a separate MCU is already present, active-energy metering around the IC’s specified accuracy class is valuable, and the team can design and validate the mains-side circuitry.
Start with the ATM90E2x-DB when the immediate need is register exploration, firmware development, sensor experiments or early metrology validation. It is an evaluation platform, not a production-ready connected meter, and its availability and price should be checked with Microchip or an authorized distributor.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsChoose a more integrated or complete platform when the project needs three-phase measurement, AC/DC capability, wireless connectivity, a certified finished product or minimal external circuitry. The correct comparison is total engineering and compliance cost, not just the metering IC’s line item.
Verdict
The ATM90E26 is compelling for a custom single-phase monitor that needs dedicated active and reactive metrology at a low IC cost. Its 0.1% active-energy and 0.2% reactive-energy specifications, broad measurement features, pulse outputs and SPI/UART interfaces can simplify the controller and firmware architecture.
It is not a shortcut around current-sensor selection, mains safety, isolation, calibration or product certification. For an engineered product, those surrounding decisions determine both the final accuracy and the real cost. Use the ATM90E26 when you are prepared to build and validate the complete measurement system; use a complete smart-metering platform when reducing development risk matters more than customizing the electronics.
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