Part A
AD7655ASTZ
Công ty Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 5580 PCS
- Package
- LQFP-48
- Series
- Data Acquisition - Analog to Digital Converters (ADC)
Replacement verdict
Compatible functional replacement candidate
The AD7655ASTZ and AD7651AST are both 16-bit successive-approximation ADCs from Analog Devices in the same 48-lead LQFP package, sharing a comparable analog input range and serial interface, so the AD7651AST can serve as a functional substitute for the AD7655ASTZ in many designs. However, the AD7655ASTZ provides four simultaneous-sampling channels versus a single channel on the AD7651AST, and the two devices differ in throughput rate and power consumption, so channel count, sampling rate, and power budget must be validated against the target application before committing to the replacement.
Channel Count
Validation required
Throughput Rate
Validation required
Package Type
High match
Power Consumption
Validation required
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AD7655ASTZ | AD7651AST | Why it matters |
|---|---|---|---|
| Number of ADC Channels | 2 (simultaneous sampling) | 1 | Determines how many independent analog signals can be digitized; the dual-channel AD7655 supports simultaneous two-channel acquisition while the AD7651 is single-channel. |
| Resolution | 16 bits | 16 bits | Both provide 16-bit resolution, so precision and dynamic range are equivalent for substitutability in that respect. |
| Sampling Rate | 1 MSPS | 100 kSPS | The maximum throughput differs by an order of magnitude; the AD7655 supports much faster sampling, which is critical for high-speed signal acquisition. |
| Input Configuration | 4-channel, 2 simultaneous (pseudo-differential) | Single-ended | Input topology affects how signals are wired and whether differential or simultaneous sampling is possible; these parts are not directly interchangeable in circuit topology. |
| Interface Type | Parallel and Serial (SPI/QSPI/MICROWIRE/DSP) | Serial (SPI/QSPI/MICROWIRE/DSP) | The AD7655 offers both parallel and serial interfaces, giving more host connectivity options, while the AD7651 is serial-only. |
| Package / Mounting | 48-LQFP | 48-LQFP | Both use the same 48-lead LQFP package, which simplifies board-level footprint compatibility. |
| Supply Voltage (Analog) | 5 V | 5 V | Matching analog supply requirements means the same power rail can be reused, aiding substitutability. |
| Power Consumption | ~120 mW (typical) | ~25 mW (typical) | Lower power dissipation in the AD7651 suits power-sensitive designs, while the AD7655 consumes more due to higher speed and dual channels. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Identical industrial temperature ranges mean both are suitable for the same environmental conditions. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7655ASTZ | AD7651AST |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Series | PulSAR® | PulSAR® |
| Part Status | Active | Obsolete |
| Number of Bits | 16 | 16 |
| Sampling Rate(Per Second) | 1M | 100k |
| Number of A/D Converters | 1 | 1 |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Number of Inputs | 2, 4 | - |
| Input Type | Pseudo-Differential, Single Ended | - |
| Data Interface | SPI, Parallel, DSP | - |
| Configuration | MUX-S/H-MUX-ADC | - |
| Ratio - S / H: ADC | 2:1 | - |
| Architecture | SAR | - |
| Reference Type | External | - |
| Voltage - Supply, Analog | 5V | - |
| Voltage - Supply, Digital | 5V | - |
| Features | Simultaneous Sampling | - |
Frequently asked questions
What are the primary differences between the AD7655ASTZ and the AD7651AST?
The AD7655ASTZ is a dual-channel, 16-bit, 1 MSPS successive-approximation ADC with two simultaneous-sampling SAR cores in a 48-lead LQFP package. The AD7651AST is a single-channel, 16-bit, 100 kSPS PulSAR ADC in a 48-lead LQFP package. Key differences include channel count (2 vs 1), throughput (1 MSPS vs 100 kSPS), and the AD7655's simultaneous sampling capability versus the AD7651's single-channel architecture.
Are the AD7655ASTZ and AD7651AST pin-compatible?
No. Although both devices are offered in a 48-lead LQFP package, their pinouts differ because the AD7655ASTZ provides two simultaneous-sampling ADC channels while the AD7651AST is a single-channel device. Pin functions and the digital interface assignments are not interchangeable, so the PCB layout must be designed specifically for each part.
Can the AD7651AST be used as a drop-in replacement for the AD7655ASTZ?
No. The AD7651AST is a single-channel 100 kSPS ADC, whereas the AD7655ASTZ is a dual simultaneous-sampling 1 MSPS ADC. The channel count, throughput, pinout, and internal architecture differ, so a direct drop-in substitution is not possible without redesigning the analog front end and digital interface.
What are the maximum throughput rates of the AD7655ASTZ and AD7651AST?
The AD7655ASTZ supports a maximum throughput of 1 MSPS per channel with two simultaneous-sampling channels. The AD7651AST supports a maximum throughput of 100 kSPS on its single channel. The AD7655ASTZ therefore offers roughly ten times the per-channel conversion rate of the AD7651AST.
Do both devices use the same digital interface?
Both parts provide a parallel digital interface, but the interface width and timing differ. The AD7655ASTZ provides a 16-bit parallel interface for its dual-channel output data, while the AD7651AST provides a parallel interface for its single-channel 16-bit output. The host must be configured according to each device's specific timing and control signals as defined in the respective datasheets.
What are the typical applications for each device?
The AD7655ASTZ, with dual simultaneous sampling and 1 MSPS throughput, is suited to applications requiring phase-coherent acquisition such as motor control, power monitoring, and multi-axis data acquisition. The AD7651AST, a single-channel 100 kSPS 16-bit ADC, is suited to lower-speed precision measurement applications such as industrial process control and instrumentation where a single high-resolution channel is sufficient.
Do both devices operate from the same analog supply voltage?
Both devices are specified for a 5 V analog supply (AVDD) with a separate digital supply (DVDD) that supports interfacing to lower-voltage logic. Designers should confirm the exact supply ranges and decoupling requirements in the respective manufacturer datasheets, since the internal architectures and current consumption differ between the dual-channel AD7655ASTZ and the single-channel AD7651AST.