Part A
AD9850BRS
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 3838 PCS
- Package
- SSOP-28
- Series
- Interface - Sintese Digital Direta (DDS)
Replacement verdict
Compatible functional replacement candidate
The AD9851BRS is a functionally compatible upgrade candidate for the AD9850BRS, sharing the same 28-lead SSOP footprint, 125 MHz maximum clock, and 5 V supply architecture while adding an integrated 6-bit reference clock multiplier and selectable 5-bit phase control. Designers can generally substitute the AD9851BRS in existing AD9850BRS sockets with minimal layout changes, though firmware must account for the additional control-word bits and the higher power consumption of the multiplier-enabled mode.
Package and Pinout
High match
Supply Voltage
High match
Maximum Clock Frequency
High match
Control Interface and Power Consumption
Validation required
Parts at a glance
Part B
AD9851BRS
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 4415 PCS
- Package
- SSOP-28
- Series
- Interface - Sintese Digital Direta (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 | AD9851BRS | AD9850BRS | Why it matters |
|---|---|---|---|
| Maximum Clock Frequency | 180 MHz | 125 MHz | Higher clock frequency allows generation of higher output frequencies and finer frequency resolution, directly affecting the usable frequency range. |
| On-Chip Comparator | Yes | Yes | The integrated high-speed comparator enables square-wave output generation for clock and signal applications. |
| Internal Reference Clock Multiplier | 6x REFCLK multiplier | None | The 6x multiplier lets the AD9851 use a lower external reference clock while still achieving high internal clock rates, simplifying system clock design. |
| Maximum DAC Output Frequency | ~72 MHz | ~50 MHz | The DAC output bandwidth determines the highest practical analog output frequency before filtering and attenuation become significant. |
| Frequency Resolution (at max clock) | ~0.04 Hz | ~0.03 Hz | Frequency resolution affects how finely the output frequency can be tuned, which is critical for precision signal generation. |
| Supply Voltage | 2.7 V to 5.25 V | 3.3 V to 5.25 V | A wider supply range allows operation in lower-voltage systems, improving compatibility with modern low-power logic. |
| Power Consumption | ~155 mW at 3.3 V | ~155 mW at 3.3 V | Power consumption affects thermal design and suitability for portable or power-sensitive applications. |
| Package | 28-Lead SSOP | 28-Lead SSOP | Package compatibility determines whether the parts are drop-in replacements on an existing PCB footprint. |
| Control Interface | Parallel/Serial (SPI-compatible) | Parallel/Serial (SPI-compatible) | The control interface determines how the device is programmed by a host microcontroller or FPGA. |
| Operating Temperature Range | -40°C to +85°C | -40°C to +85°C | The temperature range indicates suitability for industrial versus commercial environments. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD9850BRS | AD9851BRS |
|---|---|---|
| Part Status | Active | Active |
| Resolution(Bits) | 10 b | 10 b |
| Masterfclk | 125 MHz | 180 MHz |
| Tuning Word Width(Bits) | 32 b | 32 b |
| Voltage - Supply | 3.3V, 5V | 2.7V ~ 5.25V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the key differences between the AD9851BRS and AD9850BRS DDS chips?
The AD9851BRS includes an integrated 6x reference clock multiplier and operates from a 2.7 V to 5.25 V supply, while the AD9850BRS has no internal multiplier and operates from a 3.3 V to 5 V supply. The AD9851 also supports a 180 MHz system clock with the multiplier enabled, whereas the AD9850 supports up to 125 MHz.
Are the AD9851BRS and AD9850BRS pin-compatible?
Yes, both devices are offered in the same 28-lead SSOP (RS) package and share a compatible pinout, which allows the AD9851BRS to be used as a drop-in upgrade for the AD9850BRS in many existing designs.
What is the maximum output frequency of each device?
The AD9850BRS produces a maximum output frequency of 62.5 MHz with a 125 MHz clock. The AD9851BRS produces a maximum output frequency of 90 MHz with a 180 MHz clock and the 6x multiplier enabled.
Do both parts support the same serial and parallel control interfaces?
Yes, both the AD9851BRS and AD9850BRS support 40-bit serial and 8-bit parallel loading of the frequency and phase control words, allowing either device to be configured through the same interface type.
How does the integrated clock multiplier in the AD9851BRS affect system design?
The AD9851BRS's on-chip 6x reference clock multiplier allows a lower-frequency external reference oscillator to generate the internal 180 MHz system clock, reducing the need for a separate high-frequency clock source that the AD9850BRS would require to reach comparable output frequencies.
What are the power supply requirements for the AD9851BRS versus the AD9850BRS?
The AD9851BRS operates from a single 2.7 V to 5.25 V supply, while the AD9850BRS operates from a 3.3 V to 5 V supply. Both are CMOS devices with low power consumption, but the AD9851's wider supply range offers greater flexibility in low-voltage systems.
Can the AD9851BRS replace the AD9850BRS without firmware changes?
In most cases yes, because both devices use the same 40-bit control word format and interface protocols. However, the AD9851BRS adds a control bit for enabling the 6x reference clock multiplier, so firmware should be reviewed to ensure that bit is set appropriately for the intended clock configuration.