Part A
AD7705BRZ-REEL
テキサス・インスツルメンツ
- Lifecycle
- Active
- Stock
- 7181 個数
- Package
- SOIC-16
- Series
- データ取得 - アナログ/デジタルコンバータ (ADC)
Replacement verdict
Not a drop-in replacement
The AD7705BRZ-REEL and AD7703BR are both 16-bit sigma-delta ADCs, but they differ fundamentally in resolution architecture, interface type, channel configuration, and package footprint, so the AD7705BRZ-REEL cannot serve as a direct drop-in substitute for the AD7703BR without redesign of the interface, signal chain, and PCB layout.
Different interface type
Different channel count
Different package footprint
Different conversion architecture
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 | AD7703BR | Why it matters |
|---|---|---|---|
| Resolution (bits) | 16 | 20 | Higher resolution allows detection of smaller signal changes; the AD7703 offers 4 extra bits, improving dynamic range and precision for low-level measurements. |
| 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 differ in protocol details and register access. |
| Maximum output data rate | 500 SPS | 4 kSPS | Data rate sets how fast measurements can be updated; the AD7703 supports much higher throughput, suiting faster-changing signals. |
| Supply voltage (analog) | 2.7 V to 3.3 V (or 5 V) | 5 V | Supply requirements affect system 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. |
| PGA / gain stage | Yes (on-chip PGA, gain 1–128) | No (external gain required) | An on-chip PGA simplifies small-signal measurement without external amplifiers; the AD7705 includes one while the AD7703 does not. |
| Calibration | Self-calibration and system calibration | Self-calibration and system calibration | Calibration removes offset and gain errors; both support calibration, but the register/protocol implementation differs between the parts. |
| Operating temperature range | -40 °C to +85 °C | -40 °C to +85 °C | Temperature range indicates suitability for industrial environments; both cover the standard industrial range. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7705BRZ-REEL | AD7703BR |
|---|---|---|
| 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 AD7703BR?
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 AD7703BR is a single-channel, 20-bit sigma-delta ADC with a serial interface and no on-chip PGA, housed in a 20-lead SOIC. The AD7705 provides two differential input channels and selectable gains of 1 to 128, while the AD7703 offers one channel with a fixed input range and 20-bit resolution.
Can the AD7705BRZ-REEL and AD7703BR 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), pinout, and register/interface architecture. The AD7705 includes an on-chip PGA and calibration registers accessed via a different serial protocol than the AD7703. A direct drop-in replacement is not possible without redesigning the PCB layout and firmware.
What are the supply voltage and power consumption specifications for each device?
The AD7705BRZ-REEL 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 AD7703BR operates from a single 5 V supply and typically dissipates about 25 mW. These differences affect power budget and supply rail requirements in portable versus line-powered designs.
How do the serial interfaces of the AD7705BRZ-REEL and AD7703BR differ?
The AD7705BRZ-REEL uses a 3-wire or 4-wire SPI-compatible serial interface with separate DIN, DOUT, SCLK, and CS lines, supporting daisy-chaining and read/write register access. The AD7703BR uses a simpler serial output interface with a frame sync signal and does not support register readback in the same manner. Firmware drivers are not compatible between the two parts.
What are the input signal range and PGA capabilities of each converter?
The AD7705BRZ-REEL includes an on-chip PGA with selectable gains of 1, 2, 4, 8, 16, 32, 64, and 128, allowing direct connection of low-level sensors such as thermocouples and strain gauges. The AD7703BR does not include a PGA; its input range is fixed and typically spans ±2.5 V with a 5 V reference, requiring external signal conditioning for low-level inputs.
Which device is better suited for multi-channel sensor applications?
The AD7705BRZ-REEL is better suited for multi-channel applications because it provides two differential input channels with independently programmable gain and a multiplexer, allowing two sensors to be interfaced without external switching. The AD7703BR is a single-channel device and would require external multiplexing for multi-sensor designs.
What are the package and pin count differences that affect PCB layout?
The AD7705BRZ-REEL is supplied in a 16-lead SOIC (0.295-inch body width), while the AD7703BR is supplied in a 20-lead SOIC (0.295-inch body width). The different pin counts and pin functions mean the PCB land patterns are not compatible, and layout changes are required when migrating between the two devices.
Do both parts support the same reference voltage configuration?
Both devices use an external reference input, but the AD7705BRZ-REEL supports ratiometric operation with a reference range from 1 V to VDD, while the AD7703BR typically operates with a 2.5 V reference for a ±2.5 V input range at 5 V supply. The reference requirements and input span scaling differ, so the reference circuit must be reviewed when comparing the two.