Part A
AD7656YSTZ
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 7772 PCS
- Package
- LQFP-64
- Series
- Acquisition de données - Convertisseur analogique - numérique (ADC)
Replacement verdict
Not a drop-in replacement
The AD7656YSTZ and AD7651ASTZRL are not functionally interchangeable. The AD7656YSTZ is a six-channel simultaneous-sampling bipolar ADC in a 64-lead LQFP, while the AD7651ASTZRL is a single-channel unipolar ADC in a 48-lead LQFP. The differences in channel count, input configuration, package footprint, and digital interface make direct substitution impractical without a full board and firmware redesign.
Different channel count
Different input configuration
Different package footprint
Different digital interface
Parts at a glance
Part B
AD7651ASTZRL
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 3821 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 | AD7656YSTZ | AD7651ASTZRL | Why it matters |
|---|---|---|---|
| Number of ADC Channels | 6 | 1 | Determines how many independent analog signals can be sampled simultaneously; a 6-channel device cannot be substituted by a single-channel device in multi-channel acquisition systems. |
| Resolution | 16 bits | 16 bits | Both provide 16-bit resolution, so precision level is equivalent, but channel count and architecture still differ. |
| Sampling Rate | 250 kSPS | 100 kSPS | Maximum throughput affects the ability to capture fast-changing signals; the higher-rate part can handle wider bandwidth applications. |
| Input Type | Single-ended (true bipolar) | Single-ended (unipolar/bipolar) | Input configuration must match the signal conditioning and sensor output range for correct digitization. |
| Package / Pin Count | 64-lead LQFP | 48-lead LQFP | Different footprints and pin counts prevent direct drop-in replacement on an existing PCB layout. |
| Supply Voltage | 5 V analog (AVDD), 5 V digital (DVDD) | 5 V analog (AVDD), 5 V digital (DVDD) | Supply requirements are similar, easing power-rail compatibility, though external reference and interface details still differ. |
| Interface | Parallel and serial (SPI/QSPI/MICROWIRE/DSP) | Parallel and serial (SPI/QSPI/MICROWIRE/DSP) | Both support flexible digital interfaces, but the host must be configured for the specific channel-count data format. |
| Internal Reference | Yes (2.5 V) | Yes (2.5 V) | An on-chip reference simplifies design, but external reference accuracy and drift still affect overall system performance. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +85 °C | The wider temperature range of the AD7656YSTZ suits harsher environments; the AD7651ASTZRL is limited to standard industrial conditions. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7656YSTZ | 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 ~ 125°C | -40°C ~ 85°C |
| Features | Simultaneous Sampling, True Bipolar | - |
Frequently asked questions
What are the key differences between the AD7656YSTZ and the AD7651ASTZRL?
The AD7656YSTZ 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 AD7656YSTZ is supplied in a 64-lead LQFP package, whereas the AD7651ASTZRL is supplied in a 48-lead LQFP package. They differ in channel count, throughput, and package, so they are not drop-in equivalents.
Are the AD7656YSTZ and AD7651ASTZRL pin-compatible or interchangeable?
No. The AD7656YSTZ uses a 64-lead LQFP package and the AD7651ASTZRL uses a 48-lead LQFP package, so the pin counts, pin functions, and PCB land patterns differ. A direct substitution is not possible without a board redesign and full validation against the respective datasheets.
What are the resolution and throughput specifications of each device?
Both devices provide 16-bit resolution. The AD7656YSTZ offers 250 kSPS per channel across six simultaneous-sampling channels, while the AD7651ASTZRL offers 100 kSPS on a single channel. Throughput requirements should be checked against the target application before selecting either part.
How do the input configurations of the AD7656YSTZ and AD7651ASTZRL differ?
The AD7656YSTZ provides six independent bipolar input channels that are sampled simultaneously, which suits multi-phase or multi-axis acquisition. The AD7651ASTZRL provides a single bipolar input channel. Designs requiring concurrent sampling of multiple signals cannot use the single-channel AD7651ASTZRL without external multiplexing and sample-and-hold circuitry.
What are the supply and interface requirements for these ADCs?
Both parts are bipolar SAR converters that require separate analog and digital supplies and provide a parallel digital interface for connection to a host processor or FPGA. Exact supply rails, reference requirements, and timing parameters must be taken from the respective manufacturer datasheets, as they differ between the two devices.
Which applications favor the AD7656YSTZ versus the AD7651ASTZRL?
The AD7656YSTZ is suited to applications needing simultaneous sampling of multiple channels, such as motor control, power monitoring, and multi-axis instrumentation. The AD7651ASTZRL is suited to single-channel precision acquisition where 100 kSPS is sufficient. Selection should be based on channel count, throughput, and package constraints.
Can the AD7651ASTZRL replace one channel of an AD7656YSTZ design?
Functionally, a single AD7651ASTZRL channel can perform 16-bit bipolar conversion similar to one AD7656YSTZ channel, but it cannot replicate simultaneous sampling across six channels. Replacing an AD7656YSTZ with AD7651ASTZRL devices would require multiple parts, additional board area, and revalidation of timing and accuracy.