Part A
AD7655ASTZRL
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 1730 PCS
- Package
- LQFP-48
- Series
- Acquisition de données - Convertisseur analogique - numérique (ADC)
Replacement verdict
Compatible functional replacement candidate
The AD7651AST is a functionally compatible replacement candidate for the AD7655ASTZRL in single-channel applications, sharing the same 16-bit SAR architecture, 48-lead LQFP footprint, and parallel/SPI interface family. However, the AD7655ASTZRL provides dual simultaneous-sampling channels and a higher throughput rate, so the AD7651AST is only a partial substitute where two-channel simultaneous conversion is not required. Designers must validate channel count, sample rate, and digital interface timing against the target application before committing to the substitution.
Channel Count
Validation required
Sample Rate
Validation required
Package Type
High match
Resolution
High match
Parts at a glance
Part B
AD7651AST
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 965 PCS
- Package
- LQFP-48
- Series
- Acquisition de données - Convertisseur analogique - numérique (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 | AD7655ASTZRL | AD7651AST | Why it matters |
|---|---|---|---|
| Number of ADC Channels | 2 (simultaneous sampling) | 1 | Determines how many 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 is equivalent; this is not a differentiator between the two parts. |
| Sampling Rate | 500 kSPS | 100 kSPS | Maximum throughput affects the bandwidth of signals that can be captured; the AD7655 is five times faster than the AD7651. |
| Input Configuration | Pseudo-differential, 2 channels | Single-ended / pseudo-differential, 1 channel | Defines how many inputs and what signal referencing is supported, affecting system topology and channel count. |
| Package / Pin Count | 48-lead LQFP | 48-lead LQFP | Package and pin count affect PCB footprint and layout; both share the same package, easing board-level substitution. |
| Supply Voltage | 5 V analog (AVDD), 2.7–5.25 V digital (DVDD) | 5 V analog (AVDD), 2.7–5.25 V digital (DVDD) | Supply requirements determine power rail compatibility; identical rails simplify replacement. |
| Interface | Parallel and serial (SPI/QSPI/MICROWIRE/DSP) | Parallel and serial (SPI/QSPI/MICROWIRE/DSP) | Interface options affect host connectivity; both support parallel and serial modes, aiding drop-in compatibility. |
| Power Consumption | ~120 mW typical | ~90 mW typical | Power draw impacts thermal design and energy budget; the dual-channel AD7655 consumes more due to its higher throughput. |
| Internal Reference | Yes (2.5 V) | Yes (2.5 V) | An on-chip reference reduces external component count; both include a 2.5 V reference. |
| Operating Temperature Range | -40°C to +85°C | -40°C to +85°C | Temperature range determines suitability for industrial environments; both cover the same industrial range. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7655ASTZRL | 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 key architectural differences between the AD7655ASTZRL and the AD7651AST?
The AD7655ASTZRL is a dual-channel, 16-bit, 1 MSPS successive-approximation (SAR) ADC with two simultaneous-sampling inputs, while the AD7651AST is a single-channel, 16-bit, 100 kSPS SAR ADC. The AD7655ASTZRL offers two independent ADC cores in one package, whereas the AD7651AST provides one ADC channel with a lower throughput rate.
Are the AD7655ASTZRL and AD7651AST pin-compatible?
No. The AD7655ASTZRL is supplied in a 48-lead LQFP package, and the AD7651AST is supplied in a 48-lead LQFP package, but the two devices have different pin functions and internal architectures. Pin assignments and control interfaces differ, so they are not direct drop-in replacements for each other.
What are the maximum sampling rates of these two ADCs?
The AD7655ASTZRL supports a maximum throughput of 1 MSPS per channel with simultaneous sampling on both channels. The AD7651AST supports a maximum throughput of 100 kSPS on its single channel.
Do both devices support the same analog input voltage range?
Both parts are specified for a 0 V to 2.5 V analog input range in their standard configurations, but the AD7655ASTZRL provides two independent input channels that can be configured for simultaneous sampling, while the AD7651AST provides a single input channel. Designers should confirm the exact input configuration and reference requirements in the respective datasheets.
What digital interfaces do the AD7655ASTZRL and AD7651AST provide?
Both devices provide a parallel digital interface for connection to a host processor or DSP. The AD7655ASTZRL offers a 16-bit parallel output with additional control signals for dual-channel readout, while the AD7651AST provides a parallel output for its single-channel conversion result. The exact timing and control signal definitions differ between the two parts.
Can the AD7651AST be used as a substitute for the AD7655ASTZRL in an existing design?
No, not without significant redesign. The AD7651AST has only one ADC channel and a much lower throughput (100 kSPS versus 1 MSPS), and its pinout and control interface differ from the AD7655ASTZRL. A direct substitution would not preserve the dual simultaneous-sampling capability or the higher speed of the AD7655ASTZRL.
What are the typical power supply requirements for these devices?
Both the AD7655ASTZRL and the AD7651AST operate from a 5 V analog supply and a 2.7 V to 5.25 V digital supply, consistent with the Analog Devices iCMOS process family. Designers should verify the exact supply tolerances and decoupling requirements in the respective datasheets before finalizing the power design.