Part A
AD7656YSTZ
Công ty Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 7772 PCS
- Package
- LQFP-64
- Series
- Data Acquisition - Analog to Digital Converters (ADC)
Replacement verdict
Not a drop-in replacement
The AD7654ASTZ and AD7656YSTZ are not drop-in replacements for one another. The AD7654ASTZ is a dual-channel 16-bit SAR ADC in a 48-lead LQFP package, while the AD7656YSTZ is a six-channel 16-bit SAR ADC in a 64-lead LQFP package with a different pinout, channel count, and supply architecture. Designers must account for differences in channel count, package footprint, digital interface, and power supply requirements before considering substitution.
Different channel count
Different package footprint
Different digital interface
Different supply architecture
Parts at a glance
Part B
AD7654ASTZ
Công ty Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 2675 PCS
- Package
- LQFP-48
- Series
- Data Acquisition - Analog to Digital Converters (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 | AD7656YSTZ | Why it matters |
|---|---|---|---|
| Number of ADC Channels | 2 (2 single-ended / 1 differential) | 6 (6 single-ended / 3 differential) | Channel count determines how many analog signals can be sampled; a 6-channel part can replace a 2-channel part only if the extra channels are unused or the system is redesigned. |
| Resolution | 16 bits | 16 bits | Both provide 16-bit resolution, so measurement precision and LSB size are equivalent, supporting functional substitutability in accuracy-critical designs. |
| Maximum Sampling Rate | 500 kSPS | 250 kSPS | The throughput difference affects the maximum signal bandwidth and settling requirements; the faster AD7654 can handle higher-frequency inputs than the AD7656. |
| Input Configuration | Pseudo-differential / single-ended | True differential / single-ended | Differential inputs improve common-mode noise rejection; the AD7656 offers true differential capability while the AD7654 is pseudo-differential, affecting noise immunity and signal conditioning needs. |
| Supply Voltage (Analog) | 5 V | 5 V | Matching analog supply simplifies power rail design and ensures comparable input voltage range and performance. |
| Interface Type | SPI / Serial (SPI-compatible) | SPI / Serial (SPI-compatible) | Both use a serial SPI-compatible interface, so the digital host connection and firmware protocol can remain largely unchanged. |
| Package / Mounting | 48-LQFP (Surface Mount) | 64-LQFP (Surface Mount) | Different package footprints and pin counts require PCB layout changes; the parts are not drop-in replacements despite similar functionality. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Identical temperature ratings mean both are suitable for the same industrial-grade environments. |
| Power Consumption (Typical) | ~120 mW | ~160 mW | Lower power dissipation in the AD7654 reduces thermal load and supply current demands, which matters in power-sensitive or thermally constrained designs. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7656YSTZ | AD7654ASTZ |
|---|---|---|
| Series | iCMOS® | PulSAR® |
| Part Status | Active | Active |
| Number of Bits | 16 | 16 |
| Sampling Rate(Per Second) | 250k | 500k |
| Number of Inputs | 6 | 2, 4 |
| Input Type | Single Ended | Pseudo-Differential, Single Ended |
| Data Interface | SPI, Parallel, DSP | SPI, Parallel, DSP |
| Configuration | S/H-ADC | MUX-S/H-MUX-ADC |
| Ratio - S / H: ADC | 1:1 | 2:1 |
| Number of A/D Converters | 6 | 1 |
| Architecture | SAR | SAR |
| Reference Type | External, Internal | External |
| Voltage - Supply, Analog | 5V | 5V |
| Voltage - Supply, Digital | 5V | 5V |
| Features | Simultaneous Sampling, True Bipolar | Simultaneous Sampling |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 85°C |
Frequently asked questions
What are the primary differences between the AD7654ASTZ and the AD7656YSTZ?
The AD7654ASTZ is a dual-channel, 16-bit successive-approximation ADC with a throughput of 500 kSPS, housed in a 48-lead LQFP package. The AD7656YSTZ is a six-channel, 16-bit SAR ADC with a throughput of 250 kSPS, housed in a 64-lead LQFP package. The AD7654ASTZ offers two simultaneous-sampling channels at higher per-channel speed, while the AD7656YSTZ provides six channels for higher channel density at a lower per-channel throughput.
Are the AD7654ASTZ and AD7656YSTZ pin-to-pin or package compatible?
No. The AD7654ASTZ uses a 48-lead LQFP package, while the AD7656YSTZ uses a 64-lead LQFP package. The differing lead counts and pin assignments mean they are not drop-in replacements and require different PCB footprints.
Can the AD7654ASTZ be used as a direct substitute for the AD7656YSTZ in an existing design?
No. Beyond the package and pinout differences, the two devices differ in channel count (2 vs 6), maximum throughput (500 kSPS vs 250 kSPS), and package size. A direct substitution is not possible without redesigning the analog front end, digital interface, and PCB layout.
What are the resolution and throughput specifications of each device?
Both devices provide 16-bit resolution. The AD7654ASTZ achieves a maximum throughput of 500 kSPS, while the AD7656YSTZ achieves a maximum throughput of 250 kSPS. The higher throughput of the AD7654ASTZ is associated with its lower channel count.
How do the input configurations of the AD7654ASTZ and AD7656YSTZ differ?
The AD7654ASTZ provides two analog input channels that can be configured as two single-ended inputs or one differential input pair. The AD7656YSTZ provides six analog input channels, each configurable as single-ended or as part of a differential pair, supporting simultaneous sampling across multiple channels.
Which device is better suited for multi-channel simultaneous-sampling applications?
The AD7656YSTZ is better suited for multi-channel simultaneous-sampling applications because it integrates six ADC channels in a single package, allowing more signals to be sampled concurrently. The AD7654ASTZ supports only two channels, so it would require multiple devices to match the channel count of the AD7656YSTZ.
Do both devices support the same digital interface and supply voltages?
Both devices provide a parallel digital interface and an SPI-compatible serial interface, and both operate from a 5 V analog supply with a separate digital supply. However, because the channel counts and package pinouts differ, the interface timing and pin assignments must be verified against the respective datasheets before reuse in a common design.
What are the typical applications for each device?
The AD7654ASTZ is typically used in applications requiring two high-speed, simultaneous-sampled channels, such as power monitoring and motor control. The AD7656YSTZ is typically used in multi-channel data acquisition systems, industrial instrumentation, and power-line monitoring where six simultaneous channels are needed.