Part A
AD9857ASTZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 6382 Stückzahl
- Package
- LQFP-80
- Series
- RF Verschiedene ICs und Module
Replacement verdict
Not a drop-in replacement
The AD9854ASTZ and AD9857ASTZ are not functionally interchangeable despite sharing the same Analog Devices DDS family and 80-lead LQFP package. The AD9854ASTZ is a dual 12-bit quadrature DDS/DAC synthesizer operating up to 300 MSPS, while the AD9857ASTZ is a single-channel 14-bit quadrature digital upconverter with integrated interpolation filters and a 200 MSPS maximum update rate. Their differing channel architecture, DAC resolution, maximum clock rate, and on-chip signal-processing blocks make direct substitution infeasible without redesign of the surrounding signal chain and clocking scheme.
Different channel architecture
Different DAC resolution
Different maximum clock rate
Different on-chip signal processing
Parts at a glance
Part B
AD9854ASTZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 6529 Stückzahl
- Package
- LQFP-80
- Series
- Schnittstelle für digitale Synthese (DDS)
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AD9854ASTZ | AD9857ASTZ | Why it matters |
|---|---|---|---|
| Primary Function | Dual-channel DDS/DAC synthesizer (quadrature output) | Quadrature digital upconverter (QDUC) with integrated DAC | Defines the core signal-chain role; a DDS synthesizer generates waveforms directly, while a QDUC upconverts baseband I/Q to an intermediate frequency, so they are not drop-in substitutes. |
| Maximum DAC Update / Sample Rate | 300 MSPS | 200 MSPS | Sets the highest output frequency and bandwidth achievable; a higher update rate allows wider tuning range and finer frequency resolution at high output frequencies. |
| DAC Resolution | 12-bit (dual DAC) | 14-bit | Higher resolution improves output signal-to-noise ratio and spurious-free dynamic range, directly affecting spectral purity of the generated signal. |
| On-chip Input Data Path | Frequency/phase/amplitude tuning words via parallel or serial interface | 14-bit I/Q input with interpolation filters and upconversion mixer | Determines how the device is driven; the DDS accepts tuning words to synthesize a tone, whereas the QDUC accepts baseband I/Q samples, requiring a different host interface and signal source. |
| Maximum Output Frequency | Up to ~150 MHz (at 300 MSPS) | Up to ~100 MHz (at 200 MSPS) | Constrains the usable RF/IF band; systems requiring higher output tones cannot substitute the lower-frequency part without redesign. |
| Package | 80-lead LQFP | 80-lead LQFP | Board footprint and pinout compatibility; identical package type aids layout reuse but pin functions still differ between the two devices. |
| Supply Voltage | 3.3 V single supply (with 1.8 V core option) | 3.3 V single supply | Affects power-rail design and level compatibility with surrounding logic; matching rails simplify substitution but core-voltage differences may require review. |
| Integrated Mixer / Upconversion | No (direct DDS output) | Yes (quadrature upconversion mixer) | The presence of an upconversion mixer in the QDUC enables direct IF output from baseband I/Q, a function the DDS lacks, so the two serve different transmit architectures. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD9857ASTZ | AD9854ASTZ |
|---|---|---|
| Series | AD9857 | - |
| Part Status | Active | Active |
| Function | Upconverter | - |
| Frequency | 5MHz ~ 200MHz | - |
| RF Type | HFC Cable Network | - |
| Mounting Type | Surface Mount | Surface Mount |
| Resolution(Bits) | - | 12 b |
| Masterfclk | - | 300 MHz |
| Tuning Word Width(Bits) | - | 48 b |
| Voltage - Supply | - | 3.14V ~ 3.47V |
| Operating Temperature | - | -40°C ~ 85°C |
Frequently asked questions
What are the primary functional differences between the AD9854ASTZ and AD9857ASTZ?
The AD9854ASTZ is a dual-channel, 300 MSPS quadrature DDS/DAC synthesizer with 48-bit frequency tuning and 14-bit phase offset, while the AD9857ASTZ is a single-channel, 200 MSPS quadrature digital upconverter with a 14-bit DAC and integrated interpolation filters. The AD9854 is optimized for direct digital synthesis, whereas the AD9857 is designed for transmit signal processing in communications systems.
Are the AD9854ASTZ and AD9857ASTZ pin-compatible?
No. Both devices are offered in a 80-lead LQFP package, but their pin functions and internal architectures differ significantly. The AD9854ASTZ provides dual DDS channels with separate frequency and phase registers, while the AD9857ASTZ integrates a single upconversion path with interpolation filters. Pin assignments and control interfaces are not interchangeable, so direct PCB substitution is not possible.
What are the maximum clock speeds of the AD9854ASTZ and AD9857ASTZ?
The AD9854ASTZ supports a maximum system clock of 300 MSPS. The AD9857ASTZ supports a maximum input clock of 200 MSPS. These values are specified in the respective manufacturer datasheets and determine the maximum output frequency and signal processing bandwidth for each device.
Do both devices include an integrated DAC?
Yes. The AD9854ASTZ integrates two 12-bit DACs for its dual DDS channels, while the AD9857ASTZ integrates a single 14-bit DAC. The DAC resolution and channel count differ, which affects output signal quality and the number of independent synthesis channels available.
Which device is better suited for quadrature modulation applications?
The AD9854ASTZ is specifically designed for quadrature synthesis with dual DDS channels, programmable phase offset, and I/Q output capability, making it suitable for quadrature modulation. The AD9857ASTZ is a quadrature digital upconverter intended for transmit path interpolation and upconversion. Selection depends on whether the application requires dual-channel DDS synthesis or single-channel upconversion with interpolation filtering.
What are the power supply requirements for the AD9854ASTZ and AD9857ASTZ?
Both devices operate from a 3.3 V analog supply and a 3.3 V digital supply, with separate analog and digital power pins to reduce noise coupling. The AD9854ASTZ also requires a reference clock input and provides programmable power-down modes. Exact current consumption and power dissipation figures should be verified from the respective datasheets, as they depend on clock frequency and operating mode.
Can the AD9857ASTZ replace the AD9854ASTZ in an existing design?
No. The AD9857ASTZ is a single-channel quadrature digital upconverter, while the AD9854ASTZ is a dual-channel DDS synthesizer. Differences in channel count, clock rate, DAC resolution, pinout, and control register architecture prevent a direct replacement. Any substitution would require a complete redesign of the signal chain and PCB layout, validated against the manufacturer datasheets.