Part A
AD7655ASTZ
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 is a functionally compatible replacement candidate for the AD7655AST, as both parts share the same core 16-bit SAR ADC architecture, pinout, and package. The primary distinction is the AD7655ASTZ's RoHS-compliant lead-free construction, which may require reflow profile validation. Designers should confirm solder process compatibility before substituting in existing assemblies.
Package Type
High match
Pin Configuration
High match
Resolution and Architecture
High match
RoHS Compliance
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 | AD7655AST | Why it matters |
|---|---|---|---|
| Resolution | 16 bits | 16 bits | Determines the quantization step and achievable dynamic range; identical resolution means equivalent measurement precision. |
| Number of ADC Inputs / Channels | 4 (2 differential / 4 single-ended) | 4 (2 differential / 4 single-ended) | Defines how many signal sources can be multiplexed into the converter; matching channel count preserves system signal routing. |
| Sampling Rate | 1 MSPS | 1 MSPS | Sets the maximum throughput and Nyquist bandwidth; identical rate ensures the same timing budget and anti-alias requirements. |
| Architecture | SAR | SAR | Successive-approximation architecture affects latency, power, and no-cycle-latency behavior; same architecture means equivalent conversion timing. |
| Supply Voltage (Analog/Digital) | 5 V analog, 5 V digital | 5 V analog, 5 V digital | Determines power rail compatibility and input range; matching rails allow drop-in replacement without supply redesign. |
| Interface Type | Parallel (byte/word) | Parallel (byte/word) | Defines how the host reads conversion data; identical parallel interface preserves firmware and bus timing. |
| Package / Mounting | 48-LQFP, surface mount | 48-LQFP, surface mount | Footprint and mounting must match for board-level interchangeability; identical package allows the same PCB land pattern. |
| RoHS / Lead-Free Status | RoHS compliant, lead-free (Z suffix) | Non-RoHS, contains lead | Affects regulatory compliance and solder process; the leaded version cannot be used where RoHS is mandated, so substitution requires compliance review. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C (industrial) | Defines the environmental envelope for reliable operation; matching ranges ensure the part meets the same application conditions. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7655ASTZ | AD7655AST |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Series | PulSAR® | PulSAR® |
| Part Status | Active | Obsolete |
| Number of Bits | 16 | 16 |
| Sampling Rate(Per Second) | 1M | 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 is the difference between the AD7655ASTZ and the AD7655AST?
The AD7655ASTZ and AD7655AST are functionally identical 16-bit, 500 kSPS, 4-channel successive approximation ADCs from Analog Devices. The suffix difference is packaging/ordering status: the AD7655ASTZ is the RoHS-compliant, lead-free (Pb-free) version supplied in a 48-lead LQFP, while the AD7655AST is the non-RoHS leaded (Pb/Sn) version of the same die in the same 48-lead LQFP package.
Are the AD7655ASTZ and AD7655AST electrically and functionally interchangeable?
Yes. Both parts share the same datasheet specifications: 16-bit resolution, 500 kSPS throughput, 4-channel input with two simultaneous sample-and-hold amplifiers, pseudo-differential or single-ended inputs, parallel and serial interfaces, and a 5 V analog supply with 2.7 V to 5.25 V digital supply. The only documented difference is the RoHS/lead-free status of the package finish.
Does the AD7655ASTZ require a different PCB footprint than the AD7655AST?
No. Both devices are offered in the same 48-lead LQFP (ST-48) package with identical pinout and land pattern, so the PCB footprint is unchanged between the two orderable part numbers.
Which part should be selected for a RoHS-compliant design?
The AD7655ASTZ should be selected for RoHS-compliant and lead-free assembly requirements, as the "Z" suffix denotes the Pb-free, RoHS-compliant package finish. The AD7655AST is the leaded (non-RoHS) variant and is not suitable where RoHS compliance is mandated.
Do the AD7655ASTZ and AD7655AST have the same temperature range and accuracy specifications?
Yes. Both are specified over the industrial temperature range of −40 °C to +85 °C and share the same accuracy specifications per the Analog Devices datasheet, including 16-bit no-missing-codes performance, since they are the same silicon device differing only in package finish.
Can the AD7655ASTZ be used as a drop-in replacement for the AD7655AST in an existing design?
Yes, from an electrical and footprint standpoint the AD7655ASTZ is a drop-in replacement for the AD7655AST because both use the identical 48-lead LQFP package and pinout. The only consideration is that the AD7655ASTZ has a Pb-free/RoHS-compliant finish, which may require adjustment of the soldering process profile to match lead-free assembly requirements.
What are the key performance specifications shared by the AD7655ASTZ and AD7655AST?
Both devices are 16-bit, 500 kSPS successive approximation ADCs with four input channels, two simultaneous sample-and-hold amplifiers, a pseudo-differential input range, parallel and serial digital interfaces, and operation from a 5 V analog supply with a separate 2.7 V to 5.25 V digital supply, as documented in the Analog Devices AD7655 datasheet.