Part A
AD7654ASTZ
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 2675 PCS
- Package
- LQFP-48
- Series
- Acquisition de données - Convertisseur analogique - numérique (ADC)
Replacement verdict
Compatible functional replacement candidate
The AD7654ASTZ and AD7655AST are both 16-bit successive-approximation ADCs from Analog Devices in the same 48-lead LQFP package, sharing a common architecture and pin-compatible footprint. The AD7655AST offers dual simultaneous-sampling capability with four input channels versus the AD7654ASTZ's two-channel configuration, making it a viable functional upgrade candidate where additional channel count and simultaneous sampling are beneficial. Designers should validate the interface timing and input configuration against their specific application requirements before substitution.
Resolution
High match
Package Type
High match
Channel Count
Validation required
Sampling Architecture
Validation required
Parts at a glance
Part B
AD7655AST
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 5389 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 | AD7654ASTZ | AD7655AST | Why it matters |
|---|---|---|---|
| Number of ADC Channels | 4 (2 pseudo-differential pairs) | 4 (2 pseudo-differential pairs) | Channel count determines how many analog signals can be sampled; both offer 4 channels, so input multiplexing capability is equivalent. |
| Resolution | 16 bits | 16 bits | Resolution sets the smallest detectable signal change; identical 16-bit resolution means equivalent measurement precision. |
| Sampling Rate | 500 kSPS | 1 MSPS | Maximum throughput affects the highest signal frequency that can be captured; the AD7655 supports twice the sample rate, enabling faster acquisition. |
| Input Type | Pseudo-differential | Pseudo-differential | Input configuration determines common-mode rejection and wiring; both use pseudo-differential inputs, so signal conditioning requirements match. |
| Supply Voltage (Analog) | 5 V | 5 V | Analog supply defines the input voltage range and must match the system rail; both operate from a 5 V analog supply. |
| Interface | Parallel / Serial (SPI) | Parallel / Serial (SPI) | Digital interface compatibility determines whether the part can drop into an existing host design; both support parallel and serial modes. |
| Package | 48-lead LQFP | 48-lead LQFP | Package footprint and pinout affect PCB layout and rework; identical LQFP-48 packages allow board-level interchangeability. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Temperature range defines the environments where the part is guaranteed to meet specs; both cover the industrial range. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7654ASTZ | AD7655AST |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Series | PulSAR® | PulSAR® |
| Part Status | Active | Obsolete |
| Number of Bits | 16 | 16 |
| Sampling Rate(Per Second) | 500k | 1M |
| 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 differences between the AD7654ASTZ and the AD7655AST?
The AD7654ASTZ is a dual 16-bit successive-approximation ADC with two simultaneous-sampling channels, while the AD7655AST is a quad 16-bit ADC with four simultaneous-sampling channels. Both are pin-compatible in the same 48-lead LQFP package, but the AD7655AST provides twice the channel count. The AD7654ASTZ is specified for operation from −40°C to +85°C, whereas the AD7655AST is specified over the same industrial temperature range. Designers should confirm channel count, throughput, and power requirements against the respective datasheets before selecting between them.
Are the AD7654ASTZ and AD7655AST pin-compatible?
Yes. Both devices are offered in the same 48-lead LQFP (ST-48) package with a common pinout, which allows the AD7655AST to be used as a higher-channel-count upgrade path on an existing AD7654ASTZ footprint. However, because the AD7655AST uses the additional pins for its extra analog inputs, the surrounding circuitry must be designed to support four input channels rather than two.
What is the resolution and throughput of each device?
Both the AD7654ASTZ and the AD7655AST are 16-bit successive-approximation ADCs. The AD7654ASTZ provides two simultaneous-sampling channels, and the AD7655AST provides four simultaneous-sampling channels. Both families are specified for a maximum throughput of 500 kSPS per channel. Actual achievable throughput depends on the chosen interface mode and serial clock rate, so the datasheet timing specifications should be consulted for the target configuration.
Do both parts support simultaneous sampling?
Yes. Both the AD7654ASTZ and the AD7655AST are designed for simultaneous sampling, which preserves the relative phase information between channels. The AD7654ASTZ samples two channels at once, and the AD7655AST samples four channels at once. This makes both devices suitable for motor control, power monitoring, and multi-phase signal acquisition where channel-to-channel timing alignment is critical.
What analog input configuration do these ADCs support?
Both devices accept true bipolar analog input signals and are configured for simultaneous sampling of their respective channel pairs or groups. The AD7654ASTZ handles two input channels, and the AD7655AST handles four input channels. Input voltage range, reference requirements, and configuration options should be verified against the official Analog Devices datasheets for each specific part number before finalizing the analog front end.
What digital interface do the AD7654ASTZ and AD7655AST provide?
Both devices provide a serial digital interface for reading conversion results, along with a parallel interface option, supporting connection to common DSPs, FPGAs, and microcontrollers. The interface mode is selected via dedicated configuration pins. Because the AD7655AST outputs four channels of data versus two for the AD7654ASTZ, the readback timing and frame length differ, and the host interface must be sized accordingly.
Can the AD7654ASTZ be replaced by the AD7655AST in an existing design?
Replacement is possible only after validating the differences. Although the package and pinout are shared, the AD7655AST requires the additional analog input pins to be connected and the digital readback to accommodate four channels instead of two. The power supply decoupling, reference, and layout should also be reviewed against the AD7655AST datasheet. A direct drop-in substitution without design review is not recommended.
What are the typical applications for these simultaneous-sampling ADCs?
Both the AD7654ASTZ and AD7655AST are suited to applications requiring phase-coherent multi-channel acquisition, such as three-phase power metering and protection, motor control, industrial data acquisition, and instrumentation. The AD7655AST's four-channel capability is advantageous where four signals must be captured at the same instant, while the AD7654ASTZ fits two-channel simultaneous-sampling designs with a smaller channel count requirement.