Key facts
- Brand
- Analog Devices
- Model
- AD9985
- Category
- Other Electronics
- Documents
- 4
- Languages
- EN
- Last added
- 2012-08-02
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AN-745 AD9985 Auto-Offset Function Application Note
The document describes the implementation of the auto-offset feature in the AD9985 Analog-to-Digital Converter (ADC). This function monitors the output during the clamp period to calculate and adjust the required offset setting automatically. When enabled via Register 0x1D, the circuit compares the actual output code against target codes set in Registers 0x19 through 0x1B to compensate for signal levels.
The guide provides detailed definitions for offset registers (0x0B to 0x0D) and auto-offset related registers (0x19 to 0x1D), explaining their behavior in both manual and auto-offset modes. It includes specific instructions on programming target codes for RGB and YPbPr signals, setting update modes, and performing brightness adjustments using signed two's complement values.
Analog Devices AD9985 specifications
| Maximum conversion rate | 140 MSPS |
|---|---|
| Analog bandwidth (full power) | 300 MHz |
| Analog input voltage range | 0.5 V to 1.0 V |
| Typical power consumption | 500 mW |
| Output format | 4:2:2 |
All Analog Devices AD9985 documents by type
How to use the product for one specific task, with worked examples.
Ratings, dimensions and ordering codes, for selection and design work.
Questions answered in these manuals
How is the auto-offset function activated on the AD9985?
To activate the function, set Register 1Dh, Bit 7 to 1.
What is the effective range for adjusting offset when auto-offset is enabled?
The effective range for adjusting offset is +63 LSBs to -64 LSBs.
What is the primary function of the AD9985?
The AD9985 is a pin-for-pin replacement of the AD9883A that includes an automatic offset calibration feature.
From: Analog Devices AN-731 AD9985 Design Conversion Considerations Application Note
How does the AD9985 eliminate offset errors?
It monitors the output of each ADC during the back porch of the input signals to self-adjust and eliminate offset errors.
From: Analog Devices AN-731 AD9985 Design Conversion Considerations Application Note
What is the maximum conversion rate of the AD9985A?
The AD9985A can convert at up to 140 MSPS.
What analog input voltage range does the AD9985A accept?
It accepts an analog input range from 0.5 V to 1.0 V.