Part A
ADS1251U/2K5
Texas Instruments
- Lifecycle
- Active
- Stock
- 4208 PCS
- Package
- SOIC-8
- Series
- Acquisition de données - Convertisseur analogique - numérique (ADC)
Replacement verdict
Not a drop-in replacement
The ADS1251U/2K5 and ADS1211UG4 are not drop-in replacements for one another. The ADS1251U/2K5 is a single-channel, 24-bit delta-sigma ADC with a serial SPI-compatible interface in a small SOIC-8 package, while the ADS1211UG4 is a four-channel, 24-bit delta-sigma ADC with a wider input multiplexer and a different package and interface configuration. Designers must account for differences in channel count, package footprint, digital interface, and reference/supply architecture before considering either device in an existing socket.
Different channel count
Different package footprint
Different digital interface
Different input architecture
Parts at a glance
Part B
ADS1211UG4
Texas Instruments
- Lifecycle
- Active
- Stock
- 7896 PCS
- Package
- SOIC-24
- Series
- Acquisition de données - Convertisseur analogique - numérique (ADC)
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | ADS1251U/2K5 | ADS1211UG4 | Why it matters |
|---|---|---|---|
| Resolution (bits) | 24 | 24 | Both are 24-bit delta-sigma ADCs, so resolution alone does not distinguish them for substitutability. |
| Number of input channels | 1 (single-ended) | 4 (differential) / 8 (single-ended) | Channel count determines how many signals can be measured; the ADS1211 supports multi-channel systems while the ADS1251 is single-channel only. |
| Maximum data rate (SPS) | 20k | 19.5k | Sample rate affects achievable throughput and anti-alias filtering requirements; the two parts are close but not identical. |
| Interface type | SPI (serial) | SPI (serial) | Both use a serial SPI-compatible interface, easing digital-side substitution, though protocol details differ. |
| Supply voltage (analog) | 5 V | 5 V | Analog supply compatibility is essential for direct board-level replacement without reworking the power rail. |
| Package / mounting | 8-SOIC (surface mount) | 24-SOIC (surface mount) | Different package footprints and pin counts prevent drop-in replacement; PCB layout changes are required. |
| Input type | Differential | Differential / single-ended | Input configuration affects sensor interfacing and noise rejection; the ADS1211 offers more flexibility. |
| Operating temperature range | -40°C to +85°C | -40°C to +85°C | Matching temperature ranges confirm both parts suit the same industrial environments. |
| Internal PGA | No | Yes (1 to 16) | A programmable gain amplifier allows direct connection of low-level sensors; its absence in the ADS1251 requires external signal conditioning. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADS1251U/2K5 | ADS1211UG4 |
|---|---|---|
| Supplier | - | Texas Instruments |
| Part Status | Active | Discontinued at Digi-Key |
| Number of Bits | 24 | 24 |
| Sampling Rate(Per Second) | 20k | 16k |
| Number of Inputs | 1 | 4 |
| Input Type | Differential | Differential |
| Data Interface | SPI | SPI |
| Configuration | ADC | MUX-PGA-ADC |
| Number of A/D Converters | 1 | 1 |
| Architecture | Sigma-Delta | Sigma-Delta |
| Reference Type | External | External, Internal |
| Voltage - Supply, Analog | 5V | 5V |
| Voltage - Supply, Digital | 5V | 5V |
| Features | - | PGA |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
Frequently asked questions
What are the key architectural differences between the ADS1251U/2K5 and the ADS1211UG4?
The ADS1251U/2K5 is a single-channel, 24-bit delta-sigma ADC with a fixed gain of 1 and a serial interface, supplied in an SOIC-8 package. The ADS1211UG4 is a 4-channel (differential/multiplexed) 24-bit delta-sigma ADC featuring a programmable gain amplifier (PGA) with gains from 1 to 128, an on-chip reference, and a serial interface, supplied in a SOIC-28 package. The ADS1211UG4 integrates more signal conditioning and multiplexing, while the ADS1251U/2K5 is a simpler, single-channel converter.
Can the ADS1251U/2K5 and ADS1211UG4 be used interchangeably in the same PCB footprint?
No. The ADS1251U/2K5 is packaged in an SOIC-8 (D package), whereas the ADS1211UG4 is packaged in an SOIC-28 (DW package). The pin counts, pin functions, and PCB land patterns differ, so they are not footprint-compatible and cannot be directly substituted without a board redesign.
How do the input configurations of the ADS1251U/2K5 and ADS1211UG4 differ?
The ADS1251U/2K5 provides a single differential input channel with a fixed gain of 1. The ADS1211UG4 provides a 4-channel input multiplexer that can be configured for differential or single-ended inputs, and includes a PGA offering gains of 1, 2, 4, 8, 16, 32, 64, and 128. This makes the ADS1211UG4 suitable for low-level signal applications requiring gain, while the ADS1251U/2K5 is limited to unity-gain single-channel acquisition.
Do both devices support an on-chip voltage reference?
The ADS1211UG4 includes an on-chip reference (nominally 2.5 V) that can be used for ratiometric or absolute measurements. The ADS1251U/2K5 does not include an internal voltage reference and requires an external reference voltage to be supplied for conversion. This is a significant difference for system design and bill-of-materials planning.
What are the data output rates of the ADS1251U/2K5 and ADS1211UG4?
The ADS1251U/2K5 offers a fixed output data rate of approximately 20 kSPS (with a 4 MHz clock), as specified in its datasheet. The ADS1211UG4 provides a programmable output data rate that can be configured via its internal registers, typically ranging from a few samples per second up to approximately 19.5 kSPS depending on the turbo mode and gain settings. Designers should consult the respective datasheets for exact rate configurations.
Which device is better suited for multi-channel data acquisition systems?
The ADS1211UG4 is better suited for multi-channel systems because it integrates a 4-channel input multiplexer and a PGA, allowing multiple sensors to be digitized by a single converter. The ADS1251U/2K5 is a single-channel device, so multi-channel systems would require external multiplexing and additional board space.
How do the power supply requirements compare between the ADS1251U/2K5 and ADS1211UG4?
Both devices operate from a single 5 V analog supply (AVDD) with a separate digital supply (DVDD) that can range from 2.7 V to 5.25 V, per their datasheets. The ADS1211UG4 includes additional internal circuitry (PGA, multiplexer, reference) that may influence total power consumption, so designers should verify the specified supply current and power dissipation for each device in the manufacturer datasheet for their target operating conditions.
Are the serial interfaces of the ADS1251U/2K5 and ADS1211UG4 compatible?
Both devices provide a serial interface for communication with a host controller, but the protocols differ. The ADS1251U/2K5 uses a simple synchronous serial interface with a data-ready signal and a serial clock. The ADS1211UG4 uses a more feature-rich serial interface supporting command registers and multiple operating modes. Firmware and host interface logic are therefore not directly interchangeable between the two devices.