Part A
ADS1251U
Texas Instruments
- Lifecycle
- Active
- Stock
- 2748 PCS
- Package
- SOIC-8
- Series
- Acquisition de données - Convertisseur analogique - numérique (ADC)
Replacement verdict
Not a drop-in replacement
The ADS1231IDR and ADS1251U are both 24-bit delta-sigma ADCs, but they differ fundamentally in resolution architecture, input configuration, interface timing, and package footprint, so the ADS1251U cannot serve as a direct drop-in substitute for the ADS1231IDR without redesign of the analog front end, digital interface, and PCB layout.
Different input configuration
Different interface timing
Different package footprint
Different reference architecture
Parts at a glance
Part B
ADS1231IDR
Texas Instruments
- Lifecycle
- Active
- Stock
- 4314 PCS
- Package
- SOIC-16
- 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 | ADS1231IDR | ADS1251U | Why it matters |
|---|---|---|---|
| Resolution (bits) | 24 | 24 | Both are 24-bit delta-sigma ADCs, so resolution alone does not differentiate them for substitutability. |
| Number of input channels | 1 (differential) | 1 (differential) | Both provide a single differential input, so channel count is equivalent for single-sensor applications. |
| Data rate (SPS) | 10 or 80 | Up to 20k | The ADS1251U supports much higher output rates, making it suitable for faster signals while the ADS1231IDR targets slow, high-resolution measurements. |
| Interface | Serial (SPI-compatible, 2-wire) | Serial (SPI-compatible) | Both use a serial interface, but pin/timing details differ, affecting drop-in compatibility with existing firmware. |
| Supply voltage | 2.7 V to 5.3 V | 4.75 V to 5.25 V | The ADS1231IDR operates over a wider low-voltage range, while the ADS1251U requires a nominal 5 V supply. |
| Internal PGA / gain | Fixed gain 128 | No internal PGA (gain 1) | The ADS1231IDR includes a fixed gain stage suited to low-level bridge sensors, whereas the ADS1251U needs external amplification for small signals. |
| Package | SOIC-8 | SOIC-8 | Both use an 8-pin SOIC package, so board footprint is compatible, though pin functions must be verified. |
| Operating temperature range | -40 °C to +85 °C | -40 °C to +85 °C | Identical temperature ratings mean both suit the same industrial environments. |
| Input type / sensor interface | Bridge sensor (differential, low-level) | General-purpose differential analog | The ADS1231IDR is optimized for bridge sensors with on-chip gain, while the ADS1251U is a general-purpose high-speed ADC requiring external front-end design. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADS1251U | ADS1231IDR |
|---|---|---|
| Part Status | Active | Active |
| Number of Bits | 24 | 24 |
| Sampling Rate(Per Second) | 20k | 80 |
| Number of Inputs | 1 | 1 |
| Input Type | Differential | Differential |
| Data Interface | SPI | SPI |
| Configuration | ADC | ADC |
| Number of A/D Converters | 1 | 1 |
| Architecture | Sigma-Delta | Sigma-Delta |
| Reference Type | External | External |
| Voltage - Supply, Analog | 5V | 3V ~ 5.3V |
| Voltage - Supply, Digital | 5V | 3V ~ 5.3V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
Frequently asked questions
What are the primary differences between the ADS1231IDR and the ADS1251U?
The ADS1231IDR is a 24-bit, single-channel delta-sigma ADC with an integrated low-noise PGA and a low-drift voltage reference, housed in an SOIC-8 package and specified for a 2.7 V to 5.3 V analog supply. The ADS1251U is a 24-bit, single-channel delta-sigma ADC without an integrated PGA or reference, housed in an SOIC-8 package, and specified for a 4.75 V to 5.25 V analog supply. The ADS1231 targets bridge/sensor applications requiring a complete front end, while the ADS1251 requires external signal conditioning and reference circuitry.
Are the ADS1231IDR and ADS1251U pin-compatible and directly interchangeable?
No. Although both devices are offered in an SOIC-8 package, their pin functions differ. The ADS1231IDR integrates a PGA and reference, so its pinout is dedicated to those functions, whereas the ADS1251U exposes differential analog inputs and requires an external reference. A direct drop-in substitution is not supported; the PCB layout and external circuitry must be redesigned or validated against the respective datasheets.
What are the maximum output data rates of the ADS1231IDR and ADS1251U?
The ADS1231IDR provides a selectable output data rate of 10 SPS or 80 SPS. The ADS1251U provides a fixed output data rate of 20.8 kSPS. The ADS1231 is therefore optimized for low-frequency, high-resolution sensor measurements, while the ADS1251 supports higher-speed data acquisition.
Do the ADS1231IDR and ADS1251U include an integrated voltage reference?
The ADS1231IDR includes an integrated, low-drift voltage reference, which reduces external component count for ratiometric bridge measurements. The ADS1251U does not include an integrated voltage reference and requires an external reference voltage to be supplied by the user. This difference affects system accuracy budgeting and board space.
What analog supply voltage ranges do the ADS1231IDR and ADS1251U support?
The ADS1231IDR operates from an analog supply of 2.7 V to 5.3 V. The ADS1251U operates from an analog supply of 4.75 V to 5.25 V. Designs migrating between the two devices must verify that the system supply rail falls within the respective specified range.
Which device is better suited for directly interfacing a resistive bridge sensor?
The ADS1231IDR is better suited for direct resistive bridge interfacing because it integrates a low-noise PGA and a voltage reference, allowing the bridge output to be connected with minimal external circuitry. The ADS1251U lacks an integrated PGA and reference, so an external amplifier and reference are required to achieve comparable bridge-sensor signal conditioning.
What serial interface do the ADS1231IDR and ADS1251U use?
Both devices provide a serial digital output interface for connection to a host microcontroller or DSP. The ADS1231IDR uses a simple two-wire serial interface for data retrieval, while the ADS1251U provides a serial output with a data-ready signal. System firmware must be adapted to the specific timing and protocol of each device; the interfaces are not protocol-identical.
Can the ADS1231IDR and ADS1251U operate from the same digital supply voltage?
Both devices support a digital supply (DVDD) in the 2.7 V to 5.25 V range, allowing either to interface with common 3.3 V or 5 V logic systems. However, the analog supply requirements differ, so the analog rail must be verified separately for each device before reuse in a common design.