Part A
AD7705BRZ
Công ty Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 5488 PCS
- Package
- SOIC-16
- Series
- Data Acquisition - Analog to Digital Converters (ADC)
Replacement verdict
Not a drop-in replacement
The AD7705BRZ and AD7703AR are both 16-bit sigma-delta ADCs from Analog Devices, but they differ fundamentally in resolution architecture, input channel configuration, digital interface, and package footprint. The AD7705BRZ offers two differential input channels with an SPI-compatible serial interface in a 16-lead SOIC package, while the AD7703AR provides a single-channel configuration with a different serial output format in a 20-lead SOIC package. Because these differences affect board layout, host interface firmware, and signal chain design, the AD7705BRZ cannot be considered a direct drop-in substitute for the AD7703AR without substantial redesign and validation.
Different channel count
Different digital interface
Different package footprint
Different input configuration
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 | AD7703AR | Why it matters |
|---|---|---|---|
| Resolution (bits) | 16 | 20 | Higher resolution allows detection of smaller signal changes; the AD7703 offers 4 extra bits, which may be required 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) | Interface compatibility affects how easily the part connects to a host microcontroller; both are serial but the AD7705 offers a more standard SPI interface. |
| Package / Mounting | 16-lead SOIC (surface mount) | 20-lead PDIP (through-hole) | Package and mounting style affect PCB layout, assembly process, and board space; these parts are not drop-in footprint compatible. |
| Supply voltage (analog) | 2.7 V to 3.3 V (or 5 V) | 5 V | Supply voltage compatibility determines whether the part can operate in a given system rail; the AD7705 supports lower-voltage rails while the AD7703 requires 5 V. |
| Input type | Differential (2 channels) | Differential (1 channel) | Differential inputs improve noise rejection; both are differential but the AD7705 provides two input pairs versus one on the AD7703. |
| Output data rate | Up to 500 Hz | Up to 4 kHz | Output data rate affects measurement speed; the AD7703 can sample faster, which matters for dynamic or multiplexed signals. |
| Operating temperature range | -40 °C to +85 °C | -40 °C to +85 °C | Temperature range indicates suitability for industrial environments; both parts share the same industrial-grade range. |
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 | AD7705BRZ | 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 primary differences between the AD7705BRZ and the AD7703AR?
The AD7705BRZ is a 16-bit, 2-channel sigma-delta ADC with an SPI-compatible serial interface, housed in a 16-lead SOIC package. The AD7703AR is a 20-bit, single-channel sigma-delta ADC with a serial interface, housed in a 20-lead SOIC package. Key differences include resolution (16-bit vs 20-bit), channel count (2 vs 1), and package footprint.
Are the AD7705BRZ and AD7703AR pin-compatible?
No. The AD7705BRZ uses a 16-lead SOIC package, while the AD7703AR uses a 20-lead SOIC package. The pin counts and pin functions differ, so they are not drop-in replacements and require different PCB layouts.
Can the AD7705BRZ and AD7703AR share the same power supply voltage?
Both devices operate from a single 5 V supply (VDD = 5 V nominal). The AD7705BRZ also supports a 3 V supply option. The AD7703AR is specified for 5 V operation. Designers should verify the specific supply range in the respective datasheets before sharing a rail.
How do the serial interfaces of the AD7705BRZ and AD7703AR differ?
The AD7705BRZ provides an SPI-compatible 3-wire serial interface with separate DIN and DOUT lines, supporting daisy-chaining. The AD7703AR uses a serial interface with a single data output line (SDATA) and a frame synchronization signal (FRAME), which is not directly SPI-compatible and requires different host controller firmware.
Which device offers higher resolution, and does that affect noise performance?
The AD7703AR offers 20-bit resolution, while the AD7705BRZ offers 16-bit resolution. The higher resolution of the AD7703AR generally provides lower noise relative to full scale, but actual noise performance depends on gain, update rate, and filter settings. Designers should consult the noise tables in each datasheet for the specific configuration.
Do the AD7705BRZ and AD7703AR support the same input signal ranges?
Both devices feature programmable gain amplifiers (PGAs) for direct sensor interfacing. The AD7705BRZ offers selectable gains of 1, 2, 4, 8, 16, 32, 64, and 128 with differential inputs. The AD7703AR offers gains of 1, 2, 4, and 8 with a differential input. The available gain settings and input ranges differ, so signal chain design must be matched to each part.
Can the AD7705BRZ be used as a direct replacement for the AD7703AR in an existing design?
No. Differences in package (16-lead vs 20-lead SOIC), resolution (16-bit vs 20-bit), channel count (2 vs 1), serial interface protocol, and PGA gain options prevent a direct replacement. A redesign of the PCB layout and firmware would be required.