Part A
AD7656BSTZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 3438 PCS
- Package
- LQFP-64
- Series
- Acquisição de dados - Analogo para Convertedores Digitais (ADC)
Replacement verdict
Not a drop-in replacement
The AD7656BSTZ and AD7651ASTZRL are not drop-in replacements for one another. The AD7656BSTZ is a six-channel, 16-bit simultaneous-sampling bipolar ADC in a 64-lead LQFP, while the AD7651ASTZRL is a single-channel, 16-bit ADC in a 48-lead LQFP. The differences in channel count, package footprint, and digital interface architecture make direct substitution impractical without a full board redesign.
Different channel count
Different package footprint
Different digital interface
Different input configuration
Parts at a glance
Part B
AD7651ASTZRL
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 3821 PCS
- Package
- LQFP-48
- 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 | AD7656BSTZ | AD7651ASTZRL | Why it matters |
|---|---|---|---|
| Number of ADC Channels | 6 | 1 | Determines how many independent analog signals can be sampled simultaneously; a 6-channel part cannot be directly substituted where a single-channel converter is required and vice versa. |
| Resolution | 16 bits | 16 bits | Both provide 16-bit resolution, so precision and LSB size are comparable, which is important for measurement accuracy in signal-chain design. |
| Sampling Rate | 250 kSPS | 100 kSPS | Maximum throughput affects the bandwidth of signals that can be digitized; the higher-rate part supports faster acquisition and wider input bandwidth. |
| Input Type | Single-ended (true bipolar) | Single-ended (unipolar/bipolar) | Input configuration determines how the analog source must be conditioned and whether negative voltages can be directly measured. |
| Supply Voltage | 5 V analog (AVDD), 5 V digital (DVDD) | 5 V analog (AVDD), 5 V digital (DVDD) | Matching supply rails simplifies power-tree reuse and ensures compatible logic levels when swapping parts on an existing board. |
| Interface | Parallel and serial (SPI/QSPI/MICROWIRE/DSP) | Serial (SPI/QSPI/MICROWIRE/DSP) | The available digital interface must match the host controller; a parallel-only design cannot directly accept a serial-only converter without rework. |
| Package | 64-lead LQFP | 48-lead LQFP | Footprint and pin count must match the PCB layout; different packages require board redesign and cannot be drop-in substituted. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Identical industrial temperature ratings mean both parts suit the same environmental conditions without derating concerns. |
| Power Consumption | Approx. 160 mW (typical, 5 V) | Approx. 25 mW (typical, 5 V) | Power budget and thermal design differ significantly; the multi-channel part draws substantially more current, affecting supply sizing and heat dissipation. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7656BSTZ | AD7651ASTZRL |
|---|---|---|
| Supplier | - | Analog Devices Inc. |
| Series | iCMOS® | PulSAR® |
| Part Status | Active | Obsolete |
| Number of Bits | 16 | 16 |
| Sampling Rate(Per Second) | 250k | 100k |
| Number of Inputs | 6 | 1 |
| Input Type | Single Ended | Pseudo-Differential |
| Data Interface | SPI, Parallel, DSP | SPI, Parallel, DSP |
| Configuration | S/H-ADC | S/H-ADC |
| Ratio - S / H: ADC | 1:1 | 1:1 |
| Number of A/D Converters | 6 | 1 |
| Architecture | SAR | SAR |
| Reference Type | External, Internal | External, Internal |
| Voltage - Supply, Analog | 5V | 5V |
| Voltage - Supply, Digital | 5V | 5V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Features | Simultaneous Sampling, True Bipolar | - |
Frequently asked questions
What are the key differences between the AD7656BSTZ and the AD7651ASTZRL?
The AD7656BSTZ is a 16-bit, 6-channel, simultaneous-sampling bipolar SAR ADC offering 250 kSPS per channel, while the AD7651ASTZRL is a 16-bit, single-channel, bipolar SAR ADC offering 100 kSPS. The AD7656BSTZ is supplied in a 64-lead LQFP package, whereas the AD7651ASTZRL is supplied in a 48-lead LQFP package. The two devices differ in channel count, throughput, package footprint, and pinout, so they are not drop-in replacements for one another.
Are the AD7656BSTZ and AD7651ASTZRL pin-compatible or package-compatible?
No. The AD7656BSTZ uses a 64-lead LQFP package and the AD7651ASTZRL uses a 48-lead LQFP package. Because the package body size, lead count, and pin assignments differ, the PCB land patterns and pin functions are not interchangeable, and a direct board-level substitution is not possible without a redesign.
Can the AD7651ASTZRL be used as a direct substitute for the AD7656BSTZ in an existing design?
No. The AD7651ASTZRL provides only one analog input channel at 100 kSPS, while the AD7656BSTZ provides six simultaneously sampled channels at 250 kSPS per channel. In addition to the channel-count and throughput differences, the package and pinout are different, so the AD7651ASTZRL cannot directly replace the AD7656BSTZ without significant hardware and firmware changes.
What are the resolution and throughput specifications of each device?
Both devices offer 16-bit resolution. The AD7656BSTZ provides a throughput of 250 kSPS per channel across six simultaneous-sampling channels. The AD7651ASTZRL provides a throughput of 100 kSPS on a single channel. These throughput figures are specified in the respective manufacturer datasheets.
What analog input configuration do these ADCs support?
Both the AD7656BSTZ and the AD7651ASTZRL are bipolar-input SAR ADCs. The AD7656BSTZ provides six independent analog input channels that are sampled simultaneously, which is advantageous for applications requiring phase-coherent acquisition such as motor control and power monitoring. The AD7651ASTZRL provides a single bipolar input channel. Designers should consult the respective datasheets for the exact input voltage ranges and configuration options.
What are the typical applications for each device?
The AD7656BSTZ, with six simultaneous-sampling 16-bit channels at 250 kSPS, is typically used in applications such as three-phase power monitoring, motor control, and multi-axis data acquisition where simultaneous sampling of multiple channels is required. The AD7651ASTZRL, a single-channel 16-bit 100 kSPS ADC, is typically used in simpler signal-acquisition paths where only one channel is needed. Application suitability should be confirmed against the manufacturer datasheets.
Do both devices use the same digital interface?
Both devices are SAR ADCs that provide a parallel digital output interface, but the interface details, including bus width and control signal timing, differ between the two parts and are defined in their respective datasheets. Because the pinouts and package sizes differ, the digital interface connections are not interchangeable at the board level, and firmware must be adapted to the specific device.
What package and temperature-grade information is available for these parts?
The AD7656BSTZ is offered in a 64-lead LQFP package, and the AD7651ASTZRL is offered in a 48-lead LQFP package. Both part numbers use the "B" grade designation and are specified for the industrial temperature range as defined in the manufacturer datasheets. Designers should verify the exact operating temperature range and package outline from the official Analog Devices documentation before finalizing a design.