Part A
AD7709ARU
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 1879 PCS
- Package
- TSSOP-24
- Series
- Acquisição de dados - Analogo para Convertedores Digitais (ADC)
Replacement verdict
Compatible functional replacement candidate
The AD7709ARU and AD7705BRU-REEL are both 16-bit sigma-delta ADCs from Analog Devices in a TSSOP-24 package, sharing a compatible serial interface and core conversion architecture, so the AD7705BRU-REEL can serve as a functional replacement candidate for the AD7709ARU in many designs. However, the AD7709ARU integrates additional on-chip features such as current sources and a programmable gain front end that the AD7705BRU-REEL does not provide, and the two parts differ in input channel configuration and supply range. Engineers should validate channel count, excitation/current-source requirements, and supply voltage compatibility against the target application before substituting.
Resolution and ADC Architecture
High match
Input Channel Configuration
Validation required
On-Chip Current Sources
Not compatible
Supply Voltage Range
Validation required
Parts at a glance
Part B
AD7705BRU-REEL
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 2250 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 | AD7709ARU | AD7705BRU-REEL | Why it matters |
|---|---|---|---|
| Resolution (bits) | 16 | 16 | Both are 16-bit sigma-delta ADCs, so resolution is equivalent for precision measurement applications. |
| Number of input channels | 4 (2 differential) | 2 (2 differential) | The AD7709 offers more input channels, allowing more signals to be measured without external multiplexing. |
| PGA gain range | 1 to 128 | 1 to 128 | Identical programmable gain ranges support similar low-level signal amplification needs. |
| On-chip excitation current sources | Yes (2 current sources) | No | The AD7709 includes excitation current sources suited for RTD/sensor bridge applications, which the AD7705 lacks. |
| On-chip temperature sensor | Yes | No | The AD7709 has an internal temperature sensor for cold-junction or ambient compensation; the AD7705 does not. |
| Output data rate range | Up to 105 Hz | Up to 500 Hz | The AD7705 supports higher output data rates, enabling faster sampling for dynamic signals. |
| Supply voltage range | 2.7 V to 5.25 V | 2.7 V to 5.25 V | Identical supply ranges allow either part to operate from the same low-voltage rails. |
| Interface | SPI-compatible serial | SPI-compatible serial | Both use a similar serial interface, simplifying firmware reuse across designs. |
| Package | 24-lead TSSOP | 16-lead TSSOP | Different package footprints and pin counts affect PCB layout and drop-in substitutability. |
| Operating temperature range | -40°C to +85°C | -40°C to +85°C | Identical temperature ratings suit the same industrial operating environments. |
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 | AD7709ARU | AD7705BRU-REEL |
|---|---|---|
| Supplier | - | Analog Devices Inc.,Rochester Electronics, LLC |
| Part Status | Obsolete | Obsolete |
| Number of Bits | 16 | 16 |
| Sampling Rate(Per Second) | 105 | 500 |
| Number of Inputs | 2, 4 | 2 |
| Input Type | Differential, Pseudo-Differential | Differential |
| Data Interface | SPI, DSP | SPI, DSP |
| Configuration | MUX-PGA-ADC | MUX-PGA-ADC |
| Number of A/D Converters | 1 | 1 |
| Architecture | Sigma-Delta | Sigma-Delta |
| Reference Type | External | External |
| Voltage - Supply, Analog | 2.7V ~ 3.3V, 5V | 2.7V ~ 3.3V, 5V |
| Voltage - Supply, Digital | 2.7V ~ 3.3V, 5V | 2.7V ~ 3.3V, 5V |
| Features | PGA | PGA |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
Frequently asked questions
What are the key differences between the AD7709ARU and the AD7705BRU-REEL?
The AD7709ARU is a 16-bit sigma-delta ADC with an on-chip PGA, a precision current source, and a 4-bit digital-to-analog converter (DAC) for sensor excitation, housed in a 24-lead TSSOP. The AD7705BRU-REEL is a 16-bit sigma-delta ADC with two differential input channels and an on-chip PGA, supplied in a 16-lead TSSOP on tape and reel. The AD7709 integrates additional excitation and DAC functions, while the AD7705 provides a simpler two-channel ADC in a smaller package.
Are the AD7709ARU and AD7705BRU-REEL pin-compatible?
No. The AD7709ARU uses a 24-lead TSSOP package, while the AD7705BRU-REEL uses a 16-lead TSSOP package. The different pin counts and pin functions mean the two devices are not pin-compatible and cannot be interchanged on the same PCB land pattern without redesign.
Do both devices offer a programmable gain amplifier (PGA) on their analog inputs?
Yes. Both the AD7709 and the AD7705 include an on-chip programmable gain amplifier that allows direct connection of low-level analog signals, such as those from thermocouples and bridge sensors, without external signal conditioning. The PGA gain is digitally programmable on both parts.
What is the resolution and architecture of these two ADCs?
Both the AD7709ARU and the AD7705BRU-REEL are 16-bit sigma-delta (Σ-Δ) analog-to-digital converters. They use a sigma-delta modulation architecture with on-chip digital filtering, providing high resolution for low-frequency measurement applications.
Does the AD7709ARU include features not present on the AD7705BRU-REEL?
Yes. The AD7709ARU integrates a precision current source and a 4-bit DAC intended for sensor excitation and control functions, in addition to its ADC and PGA. The AD7705BRU-REEL does not include these excitation and DAC blocks; it provides two differential input channels with a PGA and digital filtering.
Can the AD7705BRU-REEL be used as a drop-in replacement for the AD7709ARU?
No. Because the two devices differ in package size (16-lead versus 24-lead TSSOP), pinout, and integrated features, the AD7705BRU-REEL is not a drop-in replacement for the AD7709ARU. Any substitution requires verification of the schematic, PCB layout, and system requirements against the manufacturer datasheets.
What supply voltage range do these converters require?
Both the AD7709 and the AD7705 are specified for operation from a single 2.7 V to 3.3 V or 5 V supply, with separate analog and digital supply pins. Designers should confirm the exact supply and interface voltage requirements in the respective manufacturer datasheets before finalizing a design.