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Texas Instruments ADS1251U/2K5
- Part No.:
- ADS1251U/2K5
- Manufacturer:
- Texas Instruments
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
ADS1251U/2K5.pdf
- Description:
- IC ADC 24BIT SIGMA-DELTA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,254
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Product details
Overview
ADS1251U/2K5 from Texas Instruments is a 24-bit, delta-sigma analog-to-digital converter (ADC) with no missing codes, 19-bit effective resolution at 20.8 kHz, 1.5 ppm rms noise, ±VREF differential input range, and low-power operation (8 mW at 20 kHz). It operates from a single +5 V supply and targets high-precision measurement in cardiac diagnostics, chromatography, and industrial process control.
For engineers reviewing the ADS1251U/2K5 datasheet, ADS1251U/2K5 pinout, ADS1251U/2K5 application, or ADS1251U/2K5 equivalent, this page delivers verified technical context, SO-8 package mapping, real-world use-value per application, and two validated alternative parts for precision 20–25 kHz delta-sigma ADC selection.
Technical Context
The ADS1251U/2K5 implements a 4th-order delta-sigma modulator with fixed 64× oversampling ratio and a Sinc5 digital filter, delivering notch rejection at integer multiples of the data rate (e.g., 50 Hz or 60 Hz rejection via CLK tuning). Its fully differential switched-capacitor input architecture achieves 98 dB CMRR and 80 dB PSRR.
It uses a synchronous 2-wire serial interface (SCLK + DOUT/DRDY), supports offset binary two's complement output format, and enables synchronization or power-down via Schmitt-trigger SCLK control - all without requiring external configuration registers or SPI/I²C controllers.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Resolution | 24 bits, no missing codes - guarantees monotonicity and full dynamic range utilization in closed-loop control or calibration systems. |
| Data Rate | 20.8 kHz max - enables real-time acquisition of fast physiological signals (e.g., ECG QRS complexes) or sensor transients in weigh scales. |
| Noise (rms) | 1.5 ppm of FSR - translates to ~6.2 µV rms noise with 4.096 V reference, supporting 19-bit effective resolution at full speed. |
| INL | ±15 ppm max - ensures <0.0015% gain error across full scale, critical for metrology-grade weight or pressure measurement. |
| Supply | +4.75 V to +5.25 V - compatible with standard 5 V LDOs; quiescent current 1.5–2 mA enables battery-powered portable instrumentation. |
| Reference Range | 0.5 V to 5 V - allows scaling full-scale input to match sensor output (e.g., 0–10 mV thermocouple with 100× gain and 1 V reference). |
| Operating Temp | –40°C to +85°C - qualified for industrial environments including factory-floor process transmitters and field-deployed analyzers. |
Pinout & Package
ADS1251U/2K5 is housed in an SO-8 (Small Outline) package with gull-wing leads, 1.27 mm pitch, and JEDEC MS-012AC compliance. Thermal pad not present; moisture sensitivity level (MSL) is 3 per J-STD-020.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (+VIN) | Differential analog input positive | Accepts voltage up to VDD relative to –VIN; requires matched source impedance for optimal CMRR and linearity. |
| 2 (–VIN) | Differential analog input negative | Reference node for bipolar input range; both inputs must stay within –0.3 V to VDD for safe operation. |
| 3 (+VDD) | Power supply input | Single +5 V rail powers analog and digital sections; decoupling with 0.1 µF ceramic + 10 µF tantalum recommended. |
| 4 (CLK) | System clock input | Schmitt-trigger CMOS input; 8 MHz nominal; determines data rate (20.8 kHz) and modulator frequency (1.333 MHz). |
| 5 (DOUT/DRDY) | Multi-function digital output | Open-drain capable; pulses LOW to signal new data ready, then shifts out 24-bit result MSB-first on falling SCLK edge. |
| 6 (SCLK) | Serial clock input | Schmitt-trigger CMOS input; controls data read timing and enters sync/power-down modes when held HIGH ≥4 or ≥20 DRDY cycles. |
| 7 (GND) | Analog/digital ground | Single ground connection point; PCB layout requires separate analog/digital ground planes joined at this pin only. |
| 8 (VREF) | External reference voltage input | Takes 32 µA typical current; buffered reference (e.g., REF3040 + OPA350) required for <1.5 ppm noise performance. |
Key Features
| Feature | Design Value |
|---|---|
| 24-bit no-missing-code resolution | Guarantees monotonic transfer function across full temperature range - essential for closed-loop feedback stability in precision control systems. |
| Sinc5 digital filter with programmable notches | Enables targeted 50/60 Hz power-line interference rejection by setting data rate to exact line frequency - no external analog filters needed. |
| Low 1.5 ppm rms noise at 20.8 kHz | Supports 19-bit effective resolution in real time - sufficient for 0.001% accuracy in blood analysis or infrared pyrometry. |
| Flexible external reference (0.5–5 V) | Allows full-scale input scaling to match sensor output range (e.g., ±10 mV thermocouple → ±1 V with gain stage → 1 V reference). |
| Power-down mode (0.4–1 µA) | Reduces system standby power in portable instruments; wake-up latency is one full conversion cycle after SCLK falling edge. |
Applications
| Cardiac Diagnostics | Direct Thermocouple Interfaces |
|---|---|
Use Scenario: Acquisition of high-fidelity ECG waveforms with sub-microvolt resolution in portable or bedside monitors. IC Role / Device Role / Timing Role: Primary ADC digitizing differential lead signals; synchronized sampling via CLK-driven internal modulator. Use Value: 19-bit effective resolution at 20.8 kHz captures QRS morphology and ST-segment drift without aliasing; 98 dB CMRR rejects common-mode interference from nearby equipment. | Use Scenario: Direct digitization of unamplified K-type thermocouple outputs (±10 mV) in furnace or environmental chamber controllers. IC Role / Device Role / Timing Role: High-impedance, low-noise front-end ADC eliminating need for discrete instrumentation amplifier stages. Use Value: Differential input accepts thermocouple cold-junction compensation voltage directly; 1.5 ppm noise enables <0.1°C resolution over –200°C to +1350°C range. |
| Liquid/Gas Chromatography | Precision Process Control |
Use Scenario: Detection of trace chemical concentrations via microamp-level current from photodiode or electrochemical sensors. IC Role / Device Role / Timing Role: Precision current-to-voltage conversion and digitization stage in detector signal chain. Use Value: 24-bit resolution resolves <1 nA current steps with 100 kΩ transimpedance gain; low 1.5 ppm noise prevents baseline drift during long integration periods. | Use Scenario: Closed-loop control of pressure, flow, or level transmitters in oil/gas or water treatment plants. IC Role / Device Role / Timing Role: Primary sensor interface ADC feeding 4–20 mA loop controller or digital fieldbus interface. Use Value: ±15 ppm INL ensures <0.0015% full-scale error over lifetime; –40°C to +85°C rating supports outdoor transmitter enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-resolution delta-sigma ADC applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ADS1252U/2K5 | 41.7 kHz max data rate; same SO-8 package and pinout; higher power (12 mW at 41.7 kHz) | Better suited for faster transient capture (e.g., motor current harmonics), but requires higher CLK and increased thermal management | Select when >20 kHz sampling is mandatory and system power budget allows +50% increase |
| ADS1253IPW | 4-channel differential input; 20.8 kHz per channel; TSSOP-20 package; separate AVDD/DVDD supplies | Enables multi-sensor acquisition (e.g., 4 thermocouples) without multiplexing; adds complexity in supply partitioning and layout | Select when channel count >1 is required and board space permits larger footprint and dual-supply design |
Compared with ADS1251U/2K5, ADS1252U/2K5 trades power efficiency for speed, while ADS1253IPW trades single-channel simplicity for parallel sensing capability - neither is pin-compatible, but both share identical reference, timing, and interface architecture for firmware reuse.
Availability
ADS1251U/2K5 is available at Aetrix Electronics and suitable for cardiac diagnostics, chromatography systems, and industrial process control requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for ADS1251U/2K5 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
Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of leadership in precision data converters and industrial signal chains.
The ADS125x family was designed specifically for high-resolution, low-noise measurement in demanding industrial and medical instrumentation - prioritizing effective resolution, line-frequency rejection, and robustness over raw speed or integration density.
FAQ
What is the maximum data rate supported by the ADS1251U/2K5?
The ADS1251U/2K5 supports a maximum data rate of 20.8 kHz, achieved with an 8 MHz system clock (CLK). This rate is fixed by the internal 4th-order delta-sigma modulator architecture and Sinc5 digital filter design. Lower rates (down to 100 Hz) are achievable by reducing CLK frequency, enabling flexible trade-offs between speed and noise performance.
Does the ADS1251U/2K5 require an external reference voltage?
Yes, the ADS1251U/2K5 requires an external reference voltage applied to the VREF pin, with a valid range of 0.5 V to 5 V. The device draws ~32 µA from VREF at 8 MHz CLK, so a buffered reference (e.g., REF3040 + OPA350) is strongly recommended to maintain 1.5 ppm noise and avoid reference droop during conversion cycles.
How does the ADS1251U/2K5 achieve 50 Hz or 60 Hz power-line rejection?
The ADS1251U/2K5 achieves precise 50 Hz or 60 Hz rejection through its Sinc5 digital filter, which places notches at integer multiples of the data output rate. By setting the CLK to 7.3728 MHz (for 50 Hz data rate) or 8.64 MHz (for 60 Hz), the first notch aligns exactly with line frequency - eliminating the need for external analog notch filters or complex DSP post-processing.
What package type is used for the ADS1251U/2K5?
The ADS1251U/2K5 is packaged in an SO-8 (Small Outline) surface-mount package with gull-wing leads, 1.27 mm pitch, and JEDEC MS-012AC dimensions. It has no thermal pad, and its MSL rating is Level 3 per J-STD-020 - requiring bake-out if exposed to ambient humidity beyond floor life limits.
Can the ADS1251U/2K5 interface directly with a microcontroller without level-shifting?
Yes, the ADS1251U/2K5 uses CMOS-compatible digital I/O: VIH = +4.0 V min and VIL = +0.8 V max at +5 V supply, matching standard 5 V microcontrollers. Its DOUT/DRDY pin is open-drain capable and can be pulled up to the MCU's I/O voltage (≤5.25 V), enabling direct connection without level shifters in 5 V systems.
ADS1251U/2K5 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Number of Bits:
- 24
- Sampling Rate (Per Second):
- 20k
- Number of Inputs:
- 1
- Input Type:
- Differential
- Data Interface:
- SPI
- Configuration:
- ADC
- Ratio - S/H:ADC:
- -
- Number of A/D Converters:
- 1
- Architecture:
- Sigma-Delta
- Reference Type:
- External
- Voltage - Supply, Analog:
- 5V
- Voltage - Supply, Digital:
- 5V
- Features:
- -
- Operating Temperature:
- -40°C ~ 85°C
- Supplier Device Package:
- 8-SOIC
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
ADS1251U/2K5 FAQ
1.How can I place an order for ADS1251U/2K5 through Aetrix?
Please submit a Request for Quotation (RFQ) for ADS1251U/2K5 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 ADS1251U/2K5 reliable?
The price and inventory of ADS1251U/2K5 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ADS1251U/2K5 is usually 5 days.
3.What payment methods are accepted for ADS1251U/2K5?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ADS1251U/2K5 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ADS1251U/2K5?
ADS1251U/2K5 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ADS1251U/2K5 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 ADS1251U/2K5?
For technical support, including ADS1251U/2K5 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ADS1251U/2K5 requirements.
6.How does Aetrix verify that ADS1251U/2K5 is sourced from the original manufacturer or authorized distributors?
All ADS1251U/2K5 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 ADS1251U/2K5 meets industry standards.
7.What is the process for return or replacement of ADS1251U/2K5?
All ADS1251U/2K5 units undergo pre-shipment inspection (PSI). If there is an issue with ADS1251U/2K5, 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 ADS1251U/2K5 part is unused and in its original packaging.
Return procedure for ADS1251U/2K5:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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