Part A
AD7705BR
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 6867 PCS
- Package
- SOIC-16
- Series
- Acquisição de dados - Analogo para Convertedores Digitais (ADC)
Replacement verdict
Not a drop-in replacement
The AD7705BR and AD7703BR-REEL are both 16-bit sigma-delta ADCs from Analog Devices, but they differ fundamentally in resolution architecture, input channel configuration, output interface, and package footprint. The AD7705BR offers two differential input channels with a serial SPI-compatible interface in a 16-lead SOIC, while the AD7703BR-REEL provides a single-channel 20-bit sigma-delta converter with a serial output in a 20-lead SOIC. Because the channel count, output word length, interface protocol, and package pinout are not interchangeable, the AD7703BR-REEL cannot directly replace the AD7705BR without redesign of the circuit, layout, and firmware.
Different channel count
Different resolution
Different package footprint
Different interface protocol
Parts at a glance
Part B
AD7703BR-REEL
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 444 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 | AD7705BR | AD7703BR-REEL | Why it matters |
|---|---|---|---|
| Number of ADC Channels | 2 (differential) | 1 (differential) | Determines how many independent analog signals can be measured; a 2-channel part can replace a 1-channel part only if the second channel is unused. |
| Resolution | 16 bits | 20 bits | Higher resolution provides finer measurement granularity; a 20-bit device can resolve smaller signal changes than a 16-bit device. |
| Maximum Sampling Rate | 500 SPS | 4 kSPS | Sets the highest frequency signal that can be captured; the AD7703 supports faster throughput for higher-bandwidth inputs. |
| Input Type | Differential (2 channels) | Differential (single channel) | Differential inputs reject common-mode noise; channel count affects how many sensors can be connected directly. |
| Interface | SPI / 3-wire serial | Serial (SPI-compatible) | Interface compatibility determines whether the part can drop into an existing digital bus without firmware or hardware changes. |
| Supply Voltage | 2.7 V to 3.3 V (DVDD), 2.7 V to 5.25 V (AVDD) | 5 V (single supply) | Supply range must match the system rail; a 5 V-only device cannot operate directly on a 3.3 V rail. |
| Package | 16-lead SOIC | 20-lead SOIC | Footprint and pin count must match the PCB layout; different packages require board redesign. |
| Power Consumption | ~1 mW (typical, 3 V) | ~25 mW (typical, 5 V) | Affects thermal budget and battery life; the lower-power AD7705 suits portable or low-power designs. |
| On-Chip PGA | Yes (gain 1 to 128) | No | A programmable gain amplifier allows direct connection of low-level sensors without external amplification. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Both parts share the same industrial temperature range, so environmental tolerance is equivalent. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7705BR | AD7703BR-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 AD7703BR-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 AD7703BR-REEL is a single-channel, 20-bit sigma-delta ADC without an integrated PGA, offered in a 20-lead SOIC and supplied on tape and reel. The AD7705BR provides two differential input channels and selectable gains of 1 to 128, while the AD7703BR offers one differential input channel with a fixed input range and 20-bit resolution.
Are the AD7705BR and AD7703BR-REEL pin-to-pin compatible?
No. The AD7705BR uses a 16-lead SOIC package, while the AD7703BR-REEL uses a 20-lead SOIC package. The differing package sizes and pin counts mean the two devices are not pin-to-pin compatible and cannot be interchanged on the same PCB land pattern without redesign.
How do the resolution and channel count of the two devices compare?
The AD7705BR provides 16-bit resolution with two differential input channels, making it suitable for multi-channel low-frequency measurement systems. The AD7703BR-REEL provides 20-bit resolution on a single differential input channel, offering higher resolution for single-channel precision applications. The choice depends on whether channel count or resolution is the priority.
Do both devices include an on-chip programmable gain amplifier?
The AD7705BR includes an on-chip PGA with selectable gains, allowing direct connection of low-level signals such as thermocouples and strain gauges. The AD7703BR-REEL does not include an integrated PGA; its input range is fixed, so external signal conditioning may be required for low-level inputs.
What are the supply voltage and interface characteristics of each part?
Both devices operate from a single 5 V supply (with the AD7705BR also supporting 3 V operation) and use a serial interface for communication with a microcontroller or DSP. The AD7705BR provides a bidirectional serial interface supporting both read and write operations, while the AD7703BR-REEL provides a serial output interface for reading conversion results. Designers should confirm the exact interface timing and supply requirements against the respective manufacturer datasheets.
What is the significance of the "BR" and "REEL" suffixes in these part numbers?
The "BR" suffix in AD7705BR and AD7703BR denotes the industrial temperature grade and SOIC package option per Analog Devices nomenclature. The "REEL" suffix on AD7703BR-REEL indicates the device is supplied in tape-and-reel packaging for automated assembly, rather than the tube or tray packaging used for the standard AD7703BR. The reel option does not change the electrical specifications of the device.
Can the AD7705BR be used as a drop-in replacement for the AD7703BR-REEL in an existing design?
No. Because the two devices differ in package size (16-lead versus 20-lead SOIC), channel count (2 versus 1), resolution (16-bit versus 20-bit), and PGA integration, the AD7705BR cannot be used as a drop-in replacement for the AD7703BR-REEL. Any substitution requires PCB redesign and revalidation of the signal chain against the target specifications.
Which device is better suited for multi-channel low-frequency measurement applications?
The AD7705BR is better suited for multi-channel low-frequency measurement because it integrates two differential input channels and a PGA in a single 16-lead SOIC, reducing external component count. The AD7703BR-REEL, with a single channel and 20-bit resolution, is better suited to single-channel high-resolution applications where channel count is not a requirement.