Part A
ADS1251U
Texas Instruments
- Lifecycle
- Active
- Stock
- 2748 PCS
- Package
- SOIC-8
- Series
- Acquisição de dados - Analogo para Convertedores Digitais (ADC)
Replacement verdict
Not a drop-in replacement
The ADS1251U and ADS1286U are not drop-in replacements for one another. Although both are 24-bit delta-sigma ADCs in the same SOIC-8 package, they differ in resolution architecture, input configuration, interface type, and reference scheme, so the ADS1286U cannot be substituted directly for the ADS1251U without circuit and firmware redesign.
Different input configuration
Different digital interface
Different reference scheme
Different conversion architecture
Parts at a glance
Part B
ADS1286U
Texas Instruments
- Lifecycle
- Active
- Stock
- 9431 PCS
- Package
- SOIC-8
- Series
- Acquisição de dados - Analogo para Convertedores Digitais (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 | ADS1286U | Why it matters |
|---|---|---|---|
| Resolution (bits) | 24 | 12 | Resolution determines the smallest signal change the ADC can distinguish; a 24-bit device offers far finer measurement granularity than a 12-bit device. |
| Architecture | Delta-Sigma | SAR | Delta-sigma converters excel at high-resolution, low-frequency signals, while SAR converters offer faster sampling and lower latency; this affects suitability for a given application. |
| Sample Rate (max) | 20 kSPS | 20 kSPS | Maximum sample rate defines how fast the ADC can capture changing signals; both parts share a similar throughput ceiling despite different architectures. |
| Input Type | Differential | Differential | Differential inputs reject common-mode noise and improve accuracy in noisy environments; both devices support this configuration. |
| Supply Voltage | 5 V (single supply) | 5 V (single supply) | Supply voltage must match the system rail; both parts operate from a single 5 V supply, simplifying power design. |
| Interface | SPI (serial) | SPI (serial) | A serial SPI interface reduces pin count and simplifies connection to microcontrollers; both devices use the same interface type. |
| Package | SOIC-8 | SOIC-8 | Package footprint affects PCB layout and assembly; matching packages allow drop-in replacement without board redesign. |
| Operating Temperature Range | -40°C to +85°C | -40°C to +85°C | The temperature range defines the environments in which the part can reliably operate; identical ranges mean equivalent environmental robustness. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADS1251U | ADS1286U |
|---|---|---|
| Supplier | - | Texas Instruments |
| Part Status | Active | Obsolete |
| Number of Bits | 24 | 12 |
| Sampling Rate(Per Second) | 20k | 20k |
| Number of Inputs | 1 | 1 |
| Input Type | Differential | Differential |
| Data Interface | SPI | SPI |
| Configuration | ADC | S/H-ADC |
| Ratio - S / H: ADC | - | 1:1 |
| Number of A/D Converters | 1 | 1 |
| Architecture | Sigma-Delta | SAR |
| Reference Type | External | External |
| Voltage - Supply, Analog | 5V | 5V |
| Voltage - Supply, Digital | 5V | 5V |
| Operating Temperature | -40°C ~ 85°C | 0°C ~ 70°C |
Frequently asked questions
What are the key architectural differences between the ADS1251U and ADS1286U?
The ADS1251U is a 24-bit delta-sigma analog-to-digital converter with a fixed data rate of 20.8 kSPS and a single differential input, while the ADS1286U is a 12-bit successive-approximation-register (SAR) ADC with a 20 kHz sampling rate and a single-ended input configuration. The ADS1251U targets high-resolution, low-speed precision measurement, whereas the ADS1286U targets faster, lower-resolution data acquisition.
Do the ADS1251U and ADS1286U have compatible package pinouts?
No. The ADS1251U is offered in an 8-pin SOIC package, and the ADS1286U is offered in an 8-pin SOIC package as well, but their pin functions differ: the ADS1251U uses a serial interface with dedicated clock and data pins plus differential analog inputs, while the ADS1286U uses a different serial interface arrangement with a single-ended input and reference pin. Pin functions and external component connections are not interchangeable, so the PCB layout must be redesigned.
Can the ADS1251U and ADS1286U be used interchangeably in an existing design?
No. The two devices differ in resolution (24-bit vs 12-bit), architecture (delta-sigma vs SAR), input configuration (differential vs single-ended), data rate (20.8 kSPS vs 20 kHz), and interface timing. A direct substitution would require validation of all electrical, timing, and layout differences against the respective manufacturer datasheets, and in most designs a board redesign is necessary.
How do the supply voltage and power consumption of the ADS1251U and ADS1286U compare?
The ADS1251U operates from a single 5 V supply and typically consumes about 25 mW. The ADS1286U operates from a single 5 V supply and typically consumes about 20 mW. Both are 5 V single-supply devices, but the ADS1251U's higher resolution delta-sigma architecture results in slightly higher power consumption.
What are the typical applications for the ADS1251U versus the ADS1286U?
The ADS1251U is suited to high-resolution, low-frequency precision measurement such as industrial process control, weigh scales, and transducer interfaces where 24-bit resolution is required. The ADS1286U is suited to general-purpose data acquisition, battery-powered instruments, and applications requiring a 12-bit SAR converter with a 20 kHz sampling rate and low power.
How do the reference input requirements differ between the ADS1251U and ADS1286U?
The ADS1251U uses an external differential reference input (VREF+ and VREF-) to set the full-scale range of its 24-bit conversion. The ADS1286U uses a single external reference input (VREF) that sets the full-scale range of its 12-bit conversion. In both cases the reference source must be low-noise and stable to achieve specified performance, but the reference topology and connection differ.
What serial interface differences exist between the ADS1251U and ADS1286U?
The ADS1251U provides a synchronous serial interface with a dedicated serial clock (SCLK) output and a data-ready (DRDY) signal, and it outputs conversion results as a 24-bit word. The ADS1286U provides a serial interface with a serial clock input and a chip-select/frame signal, outputting a 12-bit result. The interface timing, word length, and control signals are not compatible, so firmware must be rewritten when switching between the two devices.