Part A
AD7705BRZ-REEL
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 7181 PCS
- Package
- SOIC-16
- Series
- Acquisição de dados - Analogo para Convertedores Digitais (ADC)
Replacement verdict
Not a drop-in replacement
The AD7705BRZ-REEL and AD7703AR are both 16-bit sigma-delta ADCs, but they differ fundamentally in resolution architecture, interface type, channel configuration, and package footprint. The AD7705BRZ-REEL offers a dual-channel, SPI-compatible serial interface in a 16-lead SOIC, while the AD7703AR is a single-channel device with a parallel interface in a 20-lead PDIP. These differences in pinout, communication protocol, and channel count prevent direct board-level substitution without redesign.
Different interface type
Different channel count
Different package footprint
Different supply architecture
Parts at a glance
Part B
AD7703AR
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 4078 PCS
- Package
- SOIC-20
- 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 | AD7705BRZ-REEL | AD7703AR | Why it matters |
|---|---|---|---|
| Resolution (bits) | 16 | 20 | Higher resolution provides finer measurement granularity; the 20-bit AD7703 can resolve smaller signal changes than the 16-bit AD7705. |
| Number of ADC channels | 2 (differential) | 1 (differential) | Channel count determines how many independent input signals can be measured; the AD7705 supports two differential inputs while the AD7703 supports one. |
| Interface type | SPI / 3-wire serial | Serial (SPI-compatible) | Interface compatibility affects how easily the part connects to a host microcontroller; both are serial but differ in protocol details and register access. |
| Maximum output data rate | 500 SPS | 4 kSPS | Data rate determines how fast measurements can be updated; the AD7703 supports higher throughput for faster-changing signals. |
| Supply voltage (analog) | 2.7 V to 5.25 V | 5 V (single supply) | Supply range affects system-level power design; the AD7705 supports lower-voltage operation while the AD7703 requires a 5 V supply. |
| Package | 16-lead SOIC | 20-lead SOIC | Package footprint and pin count affect PCB layout and drop-in compatibility; the two parts are not footprint-compatible. |
| Input type | Differential (2 channels) | Differential (1 channel) | Differential inputs reject common-mode noise; both are differential but the AD7705 offers two such inputs versus one on the AD7703. |
| PGA / gain stage | On-chip PGA (gain 1 to 128) | No on-chip PGA | An integrated PGA allows direct amplification of small signals; the AD7705 includes one while the AD7703 requires external signal conditioning. |
| Operating temperature range | -40 °C to +85 °C | -40 °C to +85 °C | Temperature range indicates environmental robustness; both parts share the same industrial temperature range. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7705BRZ-REEL | AD7703AR |
|---|---|---|
| Supplier | - | Analog Devices Inc.,Rochester Electronics, LLC |
| Part Status | Active | 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 AD7705BRZ-REEL and the AD7703AR?
The AD7705BRZ-REEL is a 2-channel, 16-bit sigma-delta ADC with an on-chip programmable gain amplifier (PGA) and a serial SPI-compatible interface, housed in a 16-lead SOIC. The AD7703AR is a single-channel, 20-bit sigma-delta ADC with a serial interface, housed in a 20-lead SOIC. The AD7705 offers two differential input channels and selectable gain of 1 to 128, while the AD7703 provides one channel with a fixed gain of 1 to 8 depending on the input range configuration.
Do the AD7705BRZ-REEL and AD7703AR have the same resolution and accuracy?
No. The AD7705BRZ-REEL provides 16-bit resolution, while the AD7703AR provides 20-bit resolution. The AD7703AR therefore offers higher resolution and correspondingly lower quantization noise, but the AD7705BRZ-REEL includes a PGA that allows direct connection of low-level sensors without external amplification.
Are the AD7705BRZ-REEL and AD7703AR pin-compatible or package-compatible?
No. The AD7705BRZ-REEL is supplied in a 16-lead SOIC (0.295 inch body width), and the AD7703AR is supplied in a 20-lead SOIC (0.295 inch body width). The pin counts and pin functions differ, so the two devices are not drop-in replacements and require different PCB land patterns.
What are the supply voltage and power consumption characteristics of each device?
The AD7705BRZ-REEL operates from a single 2.7 V to 3.3 V or 4.75 V to 5.25 V supply (with separate AVDD and DVDD options) and typically consumes about 1 mW at 3 V. The AD7703AR operates from a 5 V supply (AVDD = +5 V, DVDD = +5 V) and typically consumes about 25 mW. The AD7705BRZ-REEL is therefore better suited to low-power, battery-operated designs.
Which device is more suitable for multi-channel sensor applications?
The AD7705BRZ-REEL is more suitable for multi-channel applications because it provides two differential input channels with a software-selectable PGA (gain 1 to 128), allowing two sensors to be interfaced without external multiplexing or amplification. The AD7703AR provides only a single channel and is intended for high-resolution single-channel measurement.
Do both devices support a serial interface compatible with microcontrollers?
Yes. Both devices provide a serial interface. The AD7705BRZ-REEL uses an SPI-compatible 3-wire serial interface with separate DIN, DOUT, and SCLK lines. The AD7703AR uses a serial interface with a clock output and data output, configured for direct connection to a microcontroller or DSP serial port. The exact timing and register protocols differ and must be implemented per each datasheet.
Can the AD7705BRZ-REEL and AD7703AR 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 vs 20-lead SOIC), supply requirements, and interface protocol. A direct substitution is not possible; any replacement requires a redesign of the PCB layout, power supply, and firmware.