Part A
AD7709ARUZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 1974 Stückzahl
- Package
- TSSOP-24
- Series
- Datenerfassung mit Analog to Digital Converters (ADC)
Replacement verdict
Compatible functional replacement candidate
The AD7705BRUZ and AD7709ARUZ share the same TSSOP-16 footprint and core sigma-delta ADC architecture, making the AD7709ARUZ a viable functional candidate for the AD7705BRUZ in many designs. However, the AD7709ARUZ integrates additional on-chip features and differs in channel configuration and supply range, so schematic and firmware validation is required before committing to a drop-in substitution.
Package Type
High match
Channel Count
Validation required
Supply Voltage Range
Validation required
Integrated Features
Validation required
Parts at a glance
Part B
AD7705BRUZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 3428 Stückzahl
- Package
- TSSOP-16
- Series
- Datenerfassung mit Analog to Digital Converters (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 | AD7705BRUZ | AD7709ARUZ | 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 | 2 differential | 4 differential / 8 single-ended (with PGA and current sources) | The AD7709 offers more input channels, enabling more sensors to be connected to a single device. |
| On-chip PGA | Yes (gain 1 to 128) | Yes (gain 1 to 128) | Programmable gain allows direct interfacing with low-level sensor signals without external amplification. |
| On-chip current sources | No | Yes (two matched excitation current sources) | Integrated current sources simplify RTD and resistive sensor designs by removing external excitation circuitry. |
| Output data rate | 20 Hz to 500 Hz | Up to 105 Hz (typical update rate) | Different update rates affect how fast the system can respond to changing input signals. |
| Supply voltage | 2.7 V to 3.3 V (or 5 V) | 2.7 V to 3.3 V (or 5 V) | Compatible supply ranges allow both parts to operate in the same low-voltage system designs. |
| Interface | SPI-compatible serial | SPI-compatible serial | A common serial interface simplifies microcontroller integration and firmware reuse. |
| Package | 16-lead TSSOP | 20-lead TSSOP | Different package footprints affect PCB layout and may require board redesign for substitution. |
| Operating temperature range | -40°C to +85°C | -40°C to +85°C | Identical temperature ratings ensure both parts suit the same industrial 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 | AD7709ARUZ | AD7705BRUZ |
|---|---|---|
| Part Status | Active | Active |
| 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 architectural differences between the AD7705BRUZ and AD7709ARUZ?
The AD7705BRUZ is a 2-channel, 16-bit sigma-delta ADC with an on-chip PGA, operating from a 2.7 V to 3.3 V or 4.75 V to 5.25 V supply. The AD7709ARUZ is a 4-channel, 16-bit sigma-delta ADC that integrates a PGA, an on-chip oscillator, and a precision current source for RTD/excitation applications, operating from a 2.7 V to 5.25 V supply. The AD7709ARUZ provides twice the input channel count and additional on-chip excitation circuitry compared with the AD7705BRUZ.
Are the AD7705BRUZ and AD7709ARUZ pin-compatible?
No. Both devices are offered in a 16-lead TSSOP (RU-16) package, but their pin functions differ. The AD7709ARUZ includes additional pins for the on-chip current source and oscillator, and the channel input assignments differ from the AD7705BRUZ. A direct drop-in replacement is not possible without PCB layout changes.
How do the input channel counts compare?
The AD7705BRUZ provides two fully differential input channels (AIN1 and AIN2). The AD7709ARUZ provides four input channels, configurable as either differential or single-ended inputs, making it suitable for multi-sensor applications.
Do both devices include a programmable gain amplifier (PGA)?
Yes. Both the AD7705BRUZ and AD7709ARUZ integrate an on-chip PGA with selectable gains of 1, 2, 4, 8, 16, 32, 64, and 128, allowing direct interfacing with low-level sensor signals such as thermocouples and bridge transducers.
What is the difference in on-chip current source capability?
The AD7709ARUZ integrates two matched current sources (typically 200 µA) intended for RTD excitation and sensor biasing. The AD7705BRUZ does not include on-chip current sources, so external excitation circuitry must be provided when used with resistive sensors.
How do the supply voltage ranges differ?
The AD7705BRUZ operates from a 2.7 V to 3.3 V supply or a 4.75 V to 5.25 V supply. The AD7709ARUZ operates from a single 2.7 V to 5.25 V supply, giving it a wider continuous supply range and greater flexibility for 3 V and 5 V systems.
Do both parts support the same serial interface?
Yes. Both the AD7705BRUZ and AD7709ARUZ provide a 3-wire SPI-compatible serial interface for configuration and data readback, allowing connection to most microcontrollers and DSPs.
Which device is better suited for multi-channel RTD measurement?
The AD7709ARUZ is generally better suited for multi-channel RTD measurement because it offers four input channels, two on-chip matched current sources for excitation, and an on-chip oscillator. The AD7705BRUZ, with two channels and no on-chip current sources, requires external excitation circuitry for RTD applications.