Part A
AD7705BR
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 6867 PCS
- Package
- SOIC-16
- Series
- Acquisition de données - Convertisseur analogique - numérique (ADC)
Replacement verdict
Not a drop-in replacement
The AD7705BR and AD7703AR-REEL are not drop-in replacements for each other. Although both are 16-bit sigma-delta ADCs from Analog Devices, they differ in resolution architecture, input channel configuration, package footprint, and digital interface, so a direct board-level substitution is not possible without redesign.
Different channel count
Different output interface
Different package footprint
Different input configuration
Parts at a glance
Part B
AD7703AR-REEL
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 71 PCS
- Package
- SOIC-20
- Series
- Acquisition de données - Convertisseur analogique - numérique (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 | AD7705BR | AD7703AR-REEL | Why it matters |
|---|---|---|---|
| Resolution (bits) | 16 | 20 | Higher resolution allows detection of smaller signal changes; the AD7703 offers 4 more bits, which can be critical for high-precision measurement applications. |
| Number of ADC channels | 2 (differential) | 1 (differential) | Channel count determines how many independent signals can be measured; the AD7705 supports two differential inputs while the AD7703 supports only one. |
| Interface type | SPI / 3-wire serial | Serial (SPI-compatible) | The digital interface must match the host microcontroller; both are serial but the AD7705 uses a standard SPI-compatible 3-wire interface, affecting firmware and wiring compatibility. |
| Maximum sample/output rate | 500 SPS | 4 kSPS | Output rate limits how fast the system can acquire data; the AD7703 supports a much higher throughput, which matters for faster-changing signals. |
| Supply voltage (analog) | 2.7 V to 3.3 V (or 5 V) | 5 V | Supply voltage compatibility affects power design; the AD7705 supports lower-voltage operation while the AD7703 requires a 5 V supply. |
| Package type | 16-lead SOIC | 20-lead SOIC | Package footprint and pin count must match the PCB layout; the two parts are not drop-in compatible due to different package sizes. |
| Input type | Differential (2 channels) | Differential (1 channel) | Differential inputs reject common-mode noise; both are differential but the channel count differs, affecting multi-signal designs. |
| On-chip PGA | Yes (gain 1 to 128) | No | An on-chip programmable gain amplifier allows direct connection of low-level sensors; the AD7705 includes a PGA while the AD7703 does not, affecting front-end design. |
| Operating temperature range | -40 °C to +85 °C | -40 °C to +85 °C | Both parts share the same industrial temperature range, so environmental operating limits are equivalent for either device. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7705BR | AD7703AR-REEL |
|---|---|---|
| Supplier | - | Analog Devices Inc.,Rochester Electronics, LLC |
| Part Status | Obsolete | Obsolete |
| Number of Bits | 16 | 20 |
| Sampling Rate(Per Second) | 500 | 4k |
| Number of Inputs | 2 | 1 |
| Input Type | Differential | Single Ended |
| Data Interface | SPI, DSP | SPI |
| Configuration | MUX-PGA-ADC | S/H-ADC |
| Ratio - S / H: ADC | - | 1:1 |
| Number of A/D Converters | 1 | 1 |
| Architecture | Sigma-Delta | Sigma-Delta |
| Reference Type | External | External |
| Voltage - Supply, Analog | 2.7V ~ 3.3V, 5V | 5V |
| Voltage - Supply, Digital | 2.7V ~ 3.3V, 5V | 5V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Features | PGA | - |
Frequently asked questions
What are the key architectural differences between the AD7705BR and the AD7703AR-REEL?
The AD7705BR is a 2-channel, 16-bit sigma-delta ADC with an on-chip programmable gain amplifier (PGA) and a serial interface, housed in a 16-lead SOIC. The AD7703AR-REEL is a single-channel, 20-bit sigma-delta ADC with a serial interface, housed in a 20-lead SOIC. The AD7705BR integrates two differential input channels and a PGA, while the AD7703AR-REEL provides one channel with higher resolution (20 bits vs 16 bits).
Can the AD7705BR and AD7703AR-REEL be used interchangeably in an existing design?
No. They differ in resolution (16-bit vs 20-bit), channel count (2 vs 1), package (16-lead SOIC vs 20-lead SOIC), and pinout. A direct drop-in replacement is not possible; any substitution requires a full schematic and layout review against the respective datasheets.
What are the supply voltage and power consumption specifications for each device?
The AD7705BR operates from a 2.7 V to 3.3 V or 4.75 V to 5.25 V supply (dual-supply capable) and typically consumes about 1 mW at 3 V. The AD7703AR-REEL operates from a single 5 V supply and typically consumes about 25 mW. Designers should confirm exact limits in the respective manufacturer datasheets.
How do the input configurations differ between the AD7705BR and AD7703AR-REEL?
The AD7705BR provides two fully differential input channels with a programmable gain amplifier selectable from 1 to 128, allowing direct connection of low-level sensors. The AD7703AR-REEL provides a single differential input channel without an integrated PGA, so external signal conditioning is typically required for low-level signals.
What output data rates are supported by each converter?
The AD7705BR supports programmable output update rates from 20 Hz to 500 Hz. The AD7703AR-REEL supports output word rates from 4 kHz down to 16 Hz, selectable via its serial interface. The appropriate rate depends on the required resolution and anti-aliasing needs of the application.
Do both parts use the same serial interface protocol?
Both devices use a serial interface, but they are not protocol-identical. The AD7705BR uses a SPI-compatible 3-wire serial interface with separate DIN and DOUT lines and a DRDY output. The AD7703AR-REEL uses a serial interface with separate data input and output lines and a frame synchronization signal. Firmware must be adapted accordingly.
Which device is better suited for multi-channel sensor applications?
The AD7705BR is better suited for multi-channel sensor applications because it integrates two differential input channels with a PGA, reducing external component count. The AD7703AR-REEL, with a single channel and higher 20-bit resolution, is better suited to precision single-channel measurement where maximum resolution is required.