Part A
ADS8685IPWR
Texas Instruments
- Lifecycle
- Active
- Stock
- 3202 PCS
- Series
- Acquisição de dados - Analogo para Convertedores Digitais (ADC)
Replacement verdict
Compatible functional replacement candidate
The ADS8685IPWR and ADS8691IPW are both single-channel, 16-bit SAR ADCs from Texas Instruments in a TSSOP-16 package, sharing a compatible serial interface and reference architecture. The ADS8691IPW offers a higher maximum sampling rate and a wider input voltage range, making it a viable functional upgrade candidate for the ADS8685IPWR in most designs, provided the system timing and analog front-end are validated against the higher throughput and extended input span.
Resolution and Architecture
High match
Package and Pinout
High match
Sampling Rate
Validation required
Input Voltage Range
Validation required
Parts at a glance
Part B
ADS8691IPW
Texas Instruments
- Lifecycle
- Active
- Stock
- 7455 PCS
- Package
- TSSOP-16
- 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 | ADS8685IPWR | ADS8691IPW | Why it matters |
|---|---|---|---|
| Resolution | 16 bit | 18 bit | Higher resolution provides finer measurement granularity and lower quantization error, which is critical for precision sensing applications. |
| 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 channel count is not a differentiator here. |
| Sampling Rate (max) | 500 kSPS | 500 kSPS | Maximum throughput defines the highest signal bandwidth that can be captured without aliasing. |
| Input Voltage Range | ±10.24 V (bipolar, programmable) | ±10.24 V (bipolar, programmable) | The input range must match the sensor or signal amplitude to avoid clipping and to maximize dynamic range utilization. |
| Interface Type | SPI (serial) | SPI (serial) | The digital interface must be compatible with the host controller; both use SPI, simplifying drop-in replacement at the system level. |
| Supply Voltage | 5 V analog, 1.65–5 V digital | 5 V analog, 1.65–5 V digital | Supply requirements affect power rail design and level-shifting needs when substituting one part for another. |
| INL (Integral Nonlinearity) | ±1 LSB (typ) | ±2 LSB (typ) | INL quantifies deviation from an ideal transfer function; lower INL yields better absolute accuracy in precision measurement systems. |
| Package | TSSOP-16 | TSSOP-16 | Package and pinout compatibility determine whether a part can be dropped into an existing PCB footprint without redesign. |
| 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. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADS8685IPWR | ADS8691IPW |
|---|---|---|
| Series | - | ADS869x |
| Part Status | Active | Active |
| Number of Bits | 16 | 18 |
| Sampling Rate(Per Second) | - | 1M |
| Number of Inputs | 1 | 1 |
| Input Type | Pseudo-Differential, Single Ended | Differential, Pseudo-Differential, Single Ended |
| Data Interface | SPI | SPI |
| Configuration | PGA-S/H-ADC | PGA-ADC |
| Ratio - S / H: ADC | 1:1 | 0:1 |
| Number of A/D Converters | - | 1 |
| Architecture | SAR | SAR |
| Reference Type | External, Internal | Internal |
| Voltage - Supply, Analog | 5V | 4.75V ~ 5.25V |
| Voltage - Supply, Digital | 1.65V ~ 5.25V | 1.65V ~ 3.3V |
| Features | PGA | Internal Oscillator |
| Operating Temperature | -40°C ~ 125°C (TA) | -40°C ~ 125°C |
| Base Product Number | ADS8685 | - |
| Sampling Rate (Per Second) | 500k | - |
| Number of A / D Converters | 1 | - |
| Mounting Type | Surface Mount | - |
| Packaging | Cut Tape (CT), Tape & Reel (TR) | - |
Frequently asked questions
What are the key differences between the ADS8685IPWR and ADS8691IPW?
The ADS8685IPWR is a 16-bit, 500-kSPS SAR ADC with a ±10.24-V input range, while the ADS8691IPW is an 18-bit, 1-MSPS SAR ADC with a ±10.24-V input range. The ADS8691IPW offers higher resolution and a faster maximum throughput, whereas the ADS8685IPWR provides 16-bit resolution at 500 kSPS. Both integrate an analog front end with programmable gain and an internal reference.
Are the ADS8685IPWR 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, throughput, and configuration register behavior differ between the two devices.
What is the maximum sampling rate of each device?
The ADS8685IPWR supports a maximum throughput of 500 kSPS. The ADS8691IPW supports a maximum throughput of 1 MSPS. The actual achievable rate depends on the serial interface clock frequency and the selected configuration.
What input voltage range do these ADCs support?
Both the ADS8685IPWR and ADS8691IPW support a bipolar input range of ±10.24 V with an integrated programmable gain amplifier, allowing direct connection to industrial signal levels without external attenuation. The input range is configured through the device registers.
Do both devices include an internal voltage reference?
Yes. Both the ADS8685IPWR and ADS8691IPW integrate an internal reference and reference buffer, reducing external component count. An external reference can also be applied if required by the application.
What digital interface do the ADS8685IPWR and ADS8691IPW use?
Both devices use an SPI-compatible serial interface for configuration and data readback. The interface supports daisy-chain operation and is compatible with common host controllers. The maximum SCLK frequency must be observed to achieve the rated throughput of each device.
What are the typical applications for these ADCs?
Both devices target industrial data acquisition, programmable logic controllers, power monitoring, and test and measurement systems where high-voltage bipolar inputs and integrated signal conditioning are required. The ADS8691IPW is preferred where higher resolution and throughput are needed, while the ADS8685IPWR suits 16-bit applications with lower speed requirements.