Part A
ADS8691IPW
Texas Instruments
- Lifecycle
- Active
- Stock
- 7455 PCS
- Package
- TSSOP-16
- Series
- Acquisição de dados - Analogo para Convertedores Digitais (ADC)
Replacement verdict
Not a drop-in replacement
The ADS8688IDBTR and ADS8691IPW are not drop-in replacements for one another. The ADS8688IDBTR is an 8-channel, 16-bit SAR ADC in a TSSOP-38 package, while the ADS8691IPW is a single-channel, 18-bit SAR ADC in a TSSOP-16 package. The differences in channel count, resolution, package footprint, and input configuration make direct substitution impractical without redesign of the signal chain and PCB layout.
Different channel count
Different resolution
Different footprint
Different input configuration
Parts at a glance
Part B
ADS8688IDBTR
Texas Instruments
- Lifecycle
- Active
- Stock
- 1493 PCS
- Package
- TSSOP-38
- 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 | ADS8688IDBTR | ADS8691IPW | Why it matters |
|---|---|---|---|
| Number of ADC Channels | 8 (single-ended) | 1 (single-ended) | Channel count determines how many analog signals can be sampled; an 8-channel device cannot be directly substituted by a single-channel device in multi-signal systems. |
| Resolution | 16 bit | 18 bit | Higher resolution provides finer measurement granularity; an 18-bit converter offers 4x the code density of a 16-bit one, affecting precision-sensitive applications. |
| Maximum Sample Rate | 500 kSPS | 500 kSPS | Sample rate defines the maximum signal bandwidth that can be captured; matching rates ease timing compatibility but channel count still differs. |
| Input Voltage Range | ±10.24 V, ±5.12 V, ±2.56 V, 0 to 10.24 V, 0 to 5.12 V (software-selectable) | ±10.24 V, ±5.12 V, ±2.56 V, 0 to 10.24 V, 0 to 5.12 V (software-selectable) | Programmable input ranges allow direct connection to various sensor and industrial signal levels without external conditioning. |
| Interface Type | SPI (serial) | SPI (serial) | A compatible SPI interface simplifies digital host connection, though firmware must account for differing channel counts and command sets. |
| Supply Voltage (Analog) | 5 V (analog), 3.3 V to 5 V (digital) | 5 V (analog), 3.3 V to 5 V (digital) | Matching supply requirements allow reuse of the same power rail design when evaluating substitution. |
| Package | TSSOP-38 (DBT) | TSSOP-16 (PW) | Different package footprints and pin counts prevent drop-in board replacement and require PCB redesign. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Identical industrial temperature ratings ensure both parts suit harsh-environment applications equally. |
| Internal Reference | Integrated 4.096 V reference | Integrated 4.096 V reference | An on-chip reference reduces external component count and simplifies precision measurement design in both devices. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADS8691IPW | ADS8688IDBTR |
|---|---|---|
| Series | ADS869x | - |
| Part Status | Active | Active |
| Number of Bits | 18 | 16 |
| Sampling Rate(Per Second) | 1M | 500k |
| Number of Inputs | 1 | 8 |
| Input Type | Differential, Pseudo-Differential, Single Ended | Differential, Single Ended |
| Data Interface | SPI | SPI |
| Configuration | PGA-ADC | PGA-MUX-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 | 5V |
| 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 architectural differences between the ADS8688IDBTR and the ADS8691IPW?
The ADS8688IDBTR is an 8-channel, 16-bit successive-approximation register (SAR) analog-to-digital converter with an integrated analog front-end, offering a maximum aggregate throughput of 500 kSPS. The ADS8691IPW is a single-channel, 18-bit SAR ADC with an integrated analog front-end, capable of a maximum throughput of 1 MSPS. The ADS8688IDBTR provides eight multiplexed input channels, while the ADS8691IPW provides one channel.
Are the ADS8688IDBTR and ADS8691IPW pin-to-pin or package compatible?
No. The ADS8688IDBTR is supplied in a 38-pin TSSOP (DBT) package, whereas the ADS8691IPW is supplied in a 16-pin TSSOP (PW) package. The two devices have different pin counts, pin functions, and PCB land patterns, so they are not direct drop-in replacements for one another.
What input voltage ranges do the ADS8688IDBTR and ADS8691IPW support?
Both devices feature an integrated analog front-end with programmable input ranges. The ADS8688IDBTR supports bipolar input ranges of ±10.24 V, ±5.12 V, and ±2.56 V, as well as unipolar ranges of 0 V to 10.24 V and 0 V to 5.12 V. The ADS8691IPW supports bipolar ranges of ±10.24 V, ±5.12 V, and ±2.56 V, and unipolar ranges of 0 V to 10.24 V and 0 V to 5.12 V. Designers should confirm the exact range set against the respective datasheet for the specific grade.
How do the resolution and throughput of the ADS8688IDBTR and ADS8691IPW compare?
The ADS8688IDBTR offers 16-bit resolution with a maximum aggregate throughput of 500 kSPS across its eight channels. The ADS8691IPW offers 18-bit resolution with a maximum throughput of 1 MSPS on its single channel. The ADS8691IPW therefore provides higher resolution and higher per-channel throughput, while the ADS8688IDBTR provides channel density for multi-channel acquisition.
What digital interfaces do the ADS8688IDBTR and ADS8691IPW use?
Both devices use an SPI-compatible serial interface for configuration and data readback. The ADS8688IDBTR supports daisy-chain operation, which allows multiple devices to share a single SPI bus, making it suitable for multi-channel systems. The ADS8691IPW uses a standard SPI interface for single-device communication. Designers should verify timing and mode requirements in the respective datasheets.
What are the typical supply voltage requirements for the ADS8688IDBTR and ADS8691IPW?
Both devices operate from a single 5 V analog supply and a separate digital supply that supports 1.8 V to 5 V logic levels, allowing direct interfacing with low-voltage processors. The integrated analog front-end includes an internal reference and reference buffer. Exact supply tolerances and current consumption should be confirmed from the manufacturer datasheets for each device.
In what applications would the ADS8688IDBTR be preferred over the ADS8691IPW, and vice versa?
The ADS8688IDBTR is preferred in multi-channel data acquisition systems such as industrial process control, power monitoring, and multi-axis sensor interfaces where eight channels of 16-bit acquisition are required in a compact footprint. The ADS8691IPW is preferred in applications requiring higher resolution and higher throughput on a single channel, such as precision instrumentation, medical monitoring, and high-accuracy single-point measurement systems.
Can the ADS8688IDBTR and ADS8691IPW be used interchangeably in an existing design?
No. Because the two devices differ in package, pin count, channel count, resolution, and throughput, they cannot be used interchangeably without a complete redesign of the schematic, PCB layout, and firmware. Any substitution requires validation against the manufacturer datasheets and the target system requirements.