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Analog Devices Inc. AD737KR-REEL
- Part No.:
- AD737KR-REEL
- Manufacturer:
- Analog Devices Inc.
- Category:
- RMS to DC Converters
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
AD737KR-REEL.pdf
- Description:
- IC RMS TO DC CONVERTER 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,424
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Product details
Overview
AD737KR-REEL from Analog Devices is a monolithic, laser-trimmed true RMS-to-DC converter IC designed for precision ac/dc voltage measurement in portable and battery-powered instrumentation. It computes true RMS, average rectified, and absolute values of input signals with ±0.2 mV ± 0.3% reading accuracy, 10¹² Ω high-Z FET input impedance, and 25 µA typical standby current. It operates from ±2.5 V to ±16.5 V dual supplies and delivers negative-going DC output suitable for direct interfacing with 3½-digit CMOS ADCs in multimeters and power analyzers.
For engineers reviewing the AD737KR-REEL datasheet, AD737KR-REEL pinout, AD737KR-REEL application, or AD737KR-REEL equivalent, key selection considerations include its dual-input architecture (Pin 1 low-Z, Pin 2 high-Z), crest factor support up to 5, 10 kHz bandwidth at 20–200 mV rms, absence of output buffer amplifier, and requirement for only one external averaging capacitor (CAV) to achieve true RMS operation.
Technical Context
The AD737KR-REEL implements a four-stage analog signal path: high-impedance FET input amplifier, full-wave precision rectifier, analog RMS core (squaring/averaging/square-rooting), and bias-controlled power-down section. Its RMS computation relies on an external averaging capacitor (CAV) connected to Pin 5, while optional external coupling capacitor (CC) at Pin 1 enables indirect DC coupling and low-Z input scaling.
It supports both ac-coupled and dc-coupled configurations, delivers negative-polarity output referenced to COM (Pin 8), and achieves 1% error bandwidth exceeding 10 kHz for 20–200 mV rms inputs. Power-down mode (enabled by pulling Pin 3 high) reduces supply current from 160 µA to 25 µA, making it suitable for handheld DVMs and energy-monitoring sensors.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Accuracy | ±0.2 mV ± 0.3% of reading - enables sub-millivolt RMS measurement fidelity without external trimming |
| Input Impedance | 10¹² Ω (Pin 2) - preserves signal integrity when measuring high-impedance sources like piezoelectric sensors |
| Input Bias Current | 25 pA max - minimizes voltage drop across high-value source impedances |
| Supply Range | ±2.5 V to ±16.5 V - supports single-cell Li-ion (±2.5 V) and industrial rail systems (±15 V) |
| Standby Current | 25 µA typical - extends battery life in portable multimeters and field test equipment |
| Crest Factor Support | Up to 5 - maintains accuracy on phase-controlled sine waves, triac outputs, and pulsed waveforms |
| Bandwidth (1% error) | 33 kHz at 200 mV rms - captures fast-rising AC transients in motor drive diagnostics |
| Output Polarity | Negative-going - simplifies interface with CMOS ADCs requiring negative reference or inverted input stages |
Pinout & Package
AD737KR-REEL is housed in an 8-lead SOIC_N (R-8) package with standard 1.27 mm pitch, 5.0 mm × 6.2 mm body size, and exposed pad not present. Thermal resistance θJA = 155°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (CC) | Coupling Capacitor / Low-Z Input | Provides alternative 8 kΩ low-impedance input path; also serves as series coupling node for ac-coupled high-Z mode |
| 2 (VIN) | High-Z RMS Input | FET-gated input accepting up to ±200 mV rms directly; enables ultra-low bias current measurement |
| 3 (POWER DOWN) | Power-Down Control | Active-high enable: logic high disables device, reducing supply current to 25 µA |
| 4 (–VS) | Negative Supply Rail | Connects to negative supply; must be within ±16.5 V absolute rating |
| 5 (CAV) | Averaging Capacitor Terminal | External capacitor (e.g., 33 µF) sets RMS time constant and determines low-frequency accuracy |
| 6 (OUTPUT) | Negative-Going DC Output | Unbuffered output; requires high-impedance load (e.g., >1 MΩ) to avoid dc offset degradation |
| 7 (+VS) | Positive Supply Rail | Connects to positive supply; supports asymmetric rails (e.g., +2.8 V/−3.2 V) |
| 8 (COM) | Common Reference | Output and supply return; defines 0 V reference for all voltages including OUTPUT and CAV |
Key Features
| Feature | Design Value |
|---|---|
| True RMS + Average + Absolute modes | Single IC replaces three discrete measurement topologies; selectable via external capacitor configuration |
| No external trims required | Laser-trimmed internal resistors ensure ±0.2 mV ± 0.3% accuracy over temperature without user calibration |
| Two-input topology (high-Z/low-Z) | Enables simultaneous optimization: high-Z for sensor interfaces, low-Z for attenuator-driven signals |
| Direct 3½-digit ADC interface | Negative output polarity and low output impedance match common CMOS ADC input requirements |
| Low-power power-down mode | 25 µA standby current allows integration into always-on monitoring nodes without compromising battery runtime |
| Wide supply range (±2.5 V to ±16.5 V) | Eliminates need for external voltage regulators in mixed-rail systems such as industrial data loggers |
Applications
| Portable Digital Multimeters | Industrial Power Quality Analyzers |
|---|---|
Use Scenario: Handheld DVM measuring RMS voltage of variable-speed motor drives and non-sinusoidal utility feeds. IC Role / Device Role / Timing Role: True RMS conversion engine generating calibrated DC output proportional to input waveform heating value. Use Value: Delivers ±0.3% accuracy on crest factors up to 5, enabling reliable measurement of SCR-phase-controlled and PWM-modulated outputs without waveform assumption errors. | Use Scenario: Rack-mounted analyzer monitoring harmonics, THD, and RMS fluctuations in factory mains distribution panels. IC Role / Device Role / Timing Role: Precision front-end RMS detector feeding isolated ADC and microcontroller-based firmware analysis stack. Use Value: 10¹² Ω input impedance prevents loading of high-impedance voltage dividers used in Class I metering circuits, preserving measurement integrity. |
| Battery-Powered Energy Monitors | Audio Signal Level Meters |
Use Scenario: IoT-connected residential energy monitor logging real-time RMS current/voltage using coin-cell or LiPo battery. IC Role / Device Role / Timing Role: Low-quiescent-current RMS converter operating in burst-mode sampling to extend multi-year battery life. Use Value: 25 µA power-down current and ±2.5 V minimum supply enable direct connection to single Li-ion cell (3.0–4.2 V) with simple LDO, minimizing BOM count. | Use Scenario: Studio-grade VU meter or loudness analyzer processing speech/music signals with dynamic crest factors (3–10). IC Role / Device Role / Timing Role: Real-time RMS envelope detector driving LED bar graph or digital display with logarithmic scaling. Use Value: 33 µF CAV configuration achieves <1% averaging error at 300 Hz for speech, while 100 µF supports music with 10:1 crest factor and <2.4 sec settling time. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar true RMS-to-DC conversion applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD736JRZ-R7 | Positive-output polarity; identical accuracy, bandwidth, and pinout except OUTPUT polarity reversed | Requires inverted signal chain or level-shifting circuitry when replacing AD737KR-REEL in existing negative-output designs | Select when system-level signal flow expects positive-going RMS output and no redesign of downstream ADC interface is feasible |
| MAX9926ASA+ | Higher supply current (350 µA active); integrated output buffer; wider input range (±2 V); no power-down mode | Better suited for high-speed, high-dynamic-range applications but incompatible with ultra-low-power battery operation | Choose for industrial test equipment needing faster settling and buffered output, accepting higher power budget |
Compared with AD737KR-REEL, AD736JRZ-R7 offers identical performance with inverted output polarity-ideal for retrofitting positive-output systems-while MAX9926ASA+ trades 14× higher active current for integrated buffering and extended input range, targeting fixed-power applications where speed and drive strength outweigh quiescent power constraints.
Availability
AD737KR-REEL is available at Aetrix Electronics and suitable for portable multimeters, industrial power quality analyzers, and battery-powered energy monitors requiring stable component supply, long-lifecycle assurance, and guaranteed traceable sourcing.
Supply support for AD737KR-REEL includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, communications, automotive, and healthcare markets.
The AD737 product line delivers precision, low-power true RMS conversion for instrumentation-grade measurement systems, specifically engineered to replace legacy average-responding circuits with minimal external components and no calibration overhead.
FAQ
What is the function of Pin 3 (POWER DOWN) on the AD737KR-REEL?
Pin 3 is the active-high power-down control input. When pulled high to +VS, the AD737KR-REEL enters low-power mode, reducing supply current from 160 µA to 25 µA. When grounded or held low, the device operates normally. This feature is essential for extending battery life in portable multimeters and handheld testers using the AD737KR-REEL.
Can the AD737KR-REEL measure DC signals, and how does it handle DC offset?
Yes, the AD737KR-REEL computes the true RMS value of both AC and DC input voltages. For DC-coupled operation, apply the signal directly to Pin 2 (VIN). AC coupling is achieved by adding a capacitor between the source and Pin 2. The AD737KR-REEL resolves input signal levels down to 100 µV rms despite variations in temperature or supply voltage, and its input offset voltage is specified at ±31 mV for AC-coupled configurations.
What external components are required for basic true RMS operation of the AD737KR-REEL?
The AD737KR-REEL requires only one mandatory external component for true RMS operation: an averaging capacitor (CAV) connected between Pin 5 and COM (Pin 8). Typical values range from 3.3 µF to 150 µF depending on input frequency and crest factor. Optional components include CC (coupling capacitor at Pin 1) for low-Z input scaling and CF (post-filter capacitor) to reduce output ripple when interfacing with low-impedance loads.
How does the AD737KR-REEL differ from the AD736 in terms of output polarity and application compatibility?
The AD737KR-REEL provides a negative-going DC output, while the AD736 is its functional counterpart with positive-going output polarity. Both share identical accuracy, bandwidth, pinout, and internal architecture. Therefore, the AD737KR-REEL cannot be directly substituted for the AD736 in circuits expecting positive output without modifying downstream signal conditioning-making polarity a critical selection criterion when designing or replacing RMS converter stages.
What is the maximum crest factor the AD737KR-REEL supports, and how does it affect accuracy?
The AD737KR-REEL maintains specified accuracy for input waveforms with crest factors up to 5. Crest factor error increases with higher ratios of peak-to-RMS voltage; for example, at crest factor 5 with CAV = 100 µF, additional error is ≤2.5%. Applications involving triac phase control, pulse-width modulation, or low-duty-cycle switching benefit from this capability, as the AD737KR-REEL avoids the >80% errors seen in average-responding converters under the same conditions.
AD737KR-REEL Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Current - Supply:
- 170 µA
- Voltage - Supply:
- 2.8V, -3.2V ~ ±16.5V
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
AD737KR-REEL FAQ
1.How can I place an order for AD737KR-REEL through Aetrix?
Please submit a Request for Quotation (RFQ) for AD737KR-REEL on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for AD737KR-REEL reliable?
The price and inventory of AD737KR-REEL are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD737KR-REEL is usually 5 days.
3.What payment methods are accepted for AD737KR-REEL?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD737KR-REEL transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD737KR-REEL?
AD737KR-REEL orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD737KR-REEL order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for AD737KR-REEL?
For technical support, including AD737KR-REEL datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD737KR-REEL requirements.
6.How does Aetrix verify that AD737KR-REEL is sourced from the original manufacturer or authorized distributors?
All AD737KR-REEL products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AD737KR-REEL meets industry standards.
7.What is the process for return or replacement of AD737KR-REEL?
All AD737KR-REEL units undergo pre-shipment inspection (PSI). If there is an issue with AD737KR-REEL, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The AD737KR-REEL part is unused and in its original packaging.
Return procedure for AD737KR-REEL:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AD737KR-REEL Tags
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