Part A
ADS8691IPW
Техасские инструменты
- Lifecycle
- Active
- Stock
- 7455 ПКС
- Package
- TSSOP-16
- Series
- Сбор данных - аналогово-цифровые преобразователи (ADC)
Replacement verdict
Compatible functional replacement candidate
The ADS8685IPW and ADS8691IPW share the same TSSOP-16 package, 16-bit SAR architecture, and pin-compatible footprint, making the ADS8691IPW a viable functional replacement candidate for the ADS8685IPW in most designs. However, the ADS8691IPW offers a higher aggregate sampling rate and a wider input voltage range, so designers should validate timing margins and input signal conditioning against the target application before substitution.
Package Type
High match
Resolution
High match
Sampling Rate
Validation required
Input Voltage Range
Validation required
Parts at a glance
Part B
ADS8685IPW
Техасские инструменты
- Lifecycle
- Active
- Stock
- 5604 ПКС
- Package
- TSSOP-16
- Series
- Сбор данных - аналогово-цифровые преобразователи (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 | ADS8685IPW | ADS8691IPW | Why it matters |
|---|---|---|---|
| Resolution | 16 bit | 18 bit | Higher resolution provides finer measurement granularity and lower quantization error, which directly affects achievable accuracy in precision acquisition systems. |
| Number of Input Channels | 1 (single-ended) | 1 (single-ended) | Channel count determines how many signals can be digitized; both are single-channel devices, so multi-signal systems require external multiplexing. |
| Sampling Rate (max) | 500 kSPS | 1 MSPS | Maximum throughput limits the bandwidth of signals that can be captured and affects anti-aliasing filter design and overall system speed. |
| Input Voltage Range | ±10.24 V (bipolar, software-selectable ranges) | ±10.24 V (bipolar, software-selectable ranges) | The input range must match the sensor or signal amplitude to avoid clipping and to maximize use of the ADC's dynamic range. |
| Interface | SPI (serial) | SPI (serial) | The digital interface must be compatible with the host controller; both use SPI, simplifying drop-in replacement at the protocol level. |
| Supply Voltage | 5 V analog supply, 1.65 V to 5 V digital I/O | 5 V analog supply, 1.65 V to 5 V digital I/O | Supply requirements determine power rail design and level-shifting needs; matching rails allow reuse of the same power architecture. |
| INL (Integral Nonlinearity) | ±1.0 LSB (typ) | ±2.0 LSB (typ) | INL characterizes deviation from an ideal transfer function and is a key indicator of absolute accuracy in precision measurement applications. |
| Package | 16-pin TSSOP (PW) | 16-pin TSSOP (PW) | Package and pinout compatibility determine whether a part can be dropped into an existing PCB footprint without layout changes. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | The temperature range must cover the application environment to ensure specified performance and reliability over the operating life. |
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 | ADS8691IPW | ADS8685IPW |
|---|---|---|
| Series | ADS869x | ADS868x |
| Part Status | Active | Active |
| Number of Bits | 18 | 16 |
| Sampling Rate(Per Second) | 1M | 500k |
| Number of Inputs | 1 | 1 |
| Input Type | Differential, Pseudo-Differential, Single Ended | Pseudo-Differential, Single Ended |
| Data Interface | SPI | SPI |
| Configuration | PGA-ADC | PGA-S/H-ADC |
| Ratio - S / H: ADC | 0:1 | 1:1 |
| Number of A/D Converters | 1 | 1 |
| Architecture | SAR | SAR |
| Reference Type | Internal | External, Internal |
| Voltage - Supply, Analog | 4.75V ~ 5.25V | 4.75V ~ 5.25V |
| Voltage - Supply, Digital | 1.65V ~ 3.3V | 1.65V ~ 5.25V |
| Features | Internal Oscillator | PGA |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 125°C |
Frequently asked questions
What are the key differences between the ADS8685IPW and ADS8691IPW?
The ADS8685IPW is a 16-bit, 500-kSPS SAR ADC with a ±10.24-V bipolar input range, while the ADS8691IPW is an 18-bit, 1-MSPS SAR ADC with a ±10.24-V bipolar input range. The ADS8691IPW offers higher resolution and a faster maximum throughput than the ADS8685IPW.
Are the ADS8685IPW and ADS8691IPW pin-compatible?
Yes. Both devices are offered in the same 16-pin TSSOP (PW) package and share the same pinout, allowing a common PCB footprint. However, firmware and timing must be revalidated because resolution and throughput differ.
What is the maximum sampling rate of each device?
The ADS8685IPW supports a maximum throughput of 500 kSPS, while the ADS8691IPW supports up to 1 MSPS. The higher throughput of the ADS8691IPW requires correspondingly faster SPI clocking and host timing considerations.
What input voltage range do these ADCs support?
Both the ADS8685IPW and ADS8691IPW provide a bipolar input range of ±10.24 V with a single 5-V analog supply. This wide input range allows direct connection to industrial sensors without external signal conditioning.
Do both devices include an internal reference and input amplifier?
Yes. Both the ADS8685IPW and ADS8691IPW integrate an internal reference and an analog front-end amplifier, reducing external component count. The integrated reference supports the specified accuracy over the rated temperature range.
What is the resolution difference and how does it affect measurement accuracy?
The ADS8685IPW provides 16-bit resolution, while the ADS8691IPW provides 18-bit resolution. The 18-bit device offers finer LSB size and lower quantization error, which can improve measurement precision when the system noise floor and reference accuracy support it.
Can the ADS8691IPW be used as a drop-in upgrade for the ADS8685IPW?
Because both devices share the same package and pinout, the ADS8691IPW can be placed on the same footprint. However, it is not a firmware-transparent drop-in replacement: the host must account for the different resolution, throughput, and SPI frame length, and the design must be revalidated against the datasheet.