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Analog Devices Inc. AD7821KNZ
- Part No.:
- AD7821KNZ
- Manufacturer:
- Analog Devices Inc.
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
AD7821KNZ.pdf
- Description:
- IC ADC 8BIT PIPELINED 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,948
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Product details
Overview
AD7821KNZ from Analog Devices is a high-speed, 8-bit LC2MOS analog-to-digital converter with integrated track-and-hold, 660 ns max conversion time (WR-RD mode), ±1 LSB total unadjusted error over –40°C to +85°C, and support for both unipolar (0 V to +5 V) and bipolar (±2.5 V) input ranges. It interfaces directly to microprocessor buses via CS, RD, WR, INT, and RDY signals and operates from single +5 V or dual ±5 V supplies.
For engineers reviewing the AD7821KNZ datasheet, AD7821KNZ pinout, AD7821KNZ application, or AD7821KNZ equivalent, key selection considerations include its half-flash architecture eliminating external clock dependency, 100 kHz signal bandwidth without external T/H, ratiometric reference capability, and compatibility with 68008/8086-style bus timing in RD or WR-RD modes.
Technical Context
The AD7821KNZ employs a half-flash conversion architecture using two cascaded 4-bit flash ADCs - one for MSBs and one for LSBs - with internal DAC feedback and comparator-based sampling. Its sampling instant is precisely defined on the falling edge of WR (WR-RD mode) or RD (RD mode), enabling deterministic jitter control critical for DSP applications.
It features standard microprocessor control logic (CS, RD, WR, INT, RDY), latched three-state data outputs (DB0–DB7), overflow flag (OFL), and MODE-selectable operation. The VSS pin (Pin 19) enables dual-supply bipolar operation (±5 V) or single-supply unipolar operation (VSS = GND), while ratiometric reference inputs (VREF(+) and VREF(–)) allow supply- or sensor-referenced measurements.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Resolution | 8 bits - delivers 256 discrete output codes; 1 LSB = 19.53 mV for 5 V full-scale range. |
| Conversion Time | 660 ns max (WR-RD mode) - enables up to 1 MHz sampling rate; supports real-time acquisition of 100 kHz signals. |
| Total Unadjusted Error | ±1 LSB max over –40°C to +85°C - ensures monotonicity and no missing codes without calibration. |
| Signal-to-Noise Ratio | 45 dB min at 99.85 kHz input - sufficient for voice-band and medium-fidelity digitization. |
| Track-and-Hold Bandwidth | 100 kHz max - digitizes full-scale 5 VPP sine waves without external T/H circuitry. |
| Power Dissipation | 50 mW typ at +5 V - low power for embedded systems; IDD = 20 mA max, ISS = 100 µA max. |
| Slew Rate (Tracking) | 1.6 V/µs max - supports accurate sampling of fast-rising analog transients within spec. |
Pinout & Package
AD7821KNZ is packaged in a 20-lead plastic DIP (N-20), with through-hole mounting and 0.3-inch body width. Pin 1 is marked with a notch or dot; Pin 10 is GND; Pin 20 is VDD (+5 V).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | VIN | Analog input node; accepts differential reference-defined range (VREF(–) to VREF(+)); supports ±2.5 V or 0 V to +5 V. |
| 2–5, 14–17 | DB0–DB7 | Three-state digital outputs; latched 8-bit parallel data bus; compatible with 5 V TTL/CMOS logic levels. |
| 6 | WR/RDY | Mode-dependent: WR input (WR-RD mode) or RDY status output (RD mode); open-drain RDY requires external pull-up. |
| 7 | MODE | Selects interface mode: low = RD mode (WAIT-state compatible), high = WR-RD mode (asynchronous control). |
| 8 | RD | Active-low read strobe; enables DB0–DB7 outputs when CS is low; resets INT on rising edge. |
| 9 | INT | Active-low interrupt; signals conversion completion; reset by rising edge of CS or RD. |
| 10 | GND | Digital ground reference; common return for logic and reference circuitry. |
| 11–12 | VREF(–), VREF(+) | Differential reference inputs; define zero and full-scale; enable ratiometric measurement and bipolar/unipolar configuration. |
| 13 | CS | Active-low chip select; enables device and synchronizes control timing; resets INT on rising edge. |
| 18 | OFL | Open-collector overflow flag; active-low when VIN > VREF(+) – ½ LSB; used for multi-device resolution extension. |
| 19 | VSS | Negative supply terminal; tied to 0 V for unipolar operation or –5 V for bipolar operation. |
| 20 | VDD | Positive supply input; +5 V ±5%; powers analog core and digital interface. |
Key Features
| Feature | Design Value |
|---|---|
| No external clock required | Half-flash architecture eliminates CLK generation circuitry, reducing BOM count and layout complexity. |
| Built-in track-and-hold function | Supports 100 kHz full-scale input signals without external components; tracking slew rate up to 1.6 V/µs. |
| Ratiometric reference inputs | VREF(+) and VREF(–) allow direct connection to sensor bridges or supply rails, maintaining accuracy despite supply drift. |
| Microprocessor-compatible interface | Standard CS/RD/WR/INT signals with WAIT-state support (RD mode) or asynchronous timing (WR-RD mode). |
| Unipolar/bipolar input flexibility | VSS pin enables seamless transition between 0 V to +5 V (VSS = GND) and ±2.5 V (VSS = –5 V) input ranges. |
Applications
| Data Acquisition System | DSP Front-End |
|---|---|
|
Use Scenario: High-speed industrial monitoring of motor current, temperature, and vibration waveforms sampled at ≥500 kHz. IC Role / Device Role / Timing Role: Primary ADC capturing analog sensor outputs with precise sampling edges synchronized to WR/RD falling edges. Use Value: 660 ns conversion time and 100 kHz T/H bandwidth eliminate need for external sample-hold, reducing board area and component count. |
Use Scenario: Real-time audio preprocessing in voice recognition hardware, digitizing microphone signals with minimal latency. IC Role / Device Role / Timing Role: Signal conditioning ADC providing 8-bit samples to fixed-point DSP; INT-driven interrupt handling ensures deterministic timing. Use Value: 45 dB SNR and –50 dB THD meet voice-band fidelity requirements while supporting 1 MHz sampling for oversampling noise shaping. |
| Motor Control Feedback | Test & Measurement Instrumentation |
|
Use Scenario: Closed-loop servo drive measuring back-EMF and phase current in brushless DC motor controllers. IC Role / Device Role / Timing Role: Bipolar-input ADC digitizing ±2.5 V current-sense amplifier outputs; VSS = –5 V enables true bipolar operation. Use Value: ±1 LSB total unadjusted error ensures accurate torque estimation across –40°C to +85°C industrial temperature range. |
Use Scenario: Portable oscilloscope module acquiring transient waveforms with trigger-synchronized sampling. IC Role / Device Role / Timing Role: Standalone ADC in WR-RD mode (CS/RD = GND), triggered by external logic; OFL flag enables multi-channel resolution extension. Use Value: 1 MHz max sampling rate and precise edge-triggered sampling (WR falling edge) support sub-microsecond time-domain resolution. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-bit, high-speed ADC applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD7820KNZ | Slower conversion (1.36 µs), no built-in T/H, 6.4 kHz signal bandwidth, single-supply only (no VSS pin). | Limited to low-frequency DC or slow-varying signals; unsuitable for 100 kHz+ AC acquisition. | Choose AD7821KNZ when T/H integration, speed, or bipolar input capability is required. |
| MAX118BCNG+ | Successive-approximation architecture, 1.6 µs conversion, 2.5 V internal reference, SPI interface only. | Requires serial interface design and external T/H for >10 kHz signals; incompatible with parallel MPU buses. | Choose AD7821KNZ for parallel bus compatibility, deterministic sampling, and self-contained T/H functionality. |
Compared with AD7820KNZ and MAX118BCNG+, the AD7821KNZ uniquely combines sub-microsecond conversion, integrated track-and-hold, parallel MPU interface, and dual-supply flexibility - making it optimal for cost-sensitive, space-constrained embedded systems requiring deterministic analog capture without external support circuitry.
Availability
AD7821KNZ is available at Aetrix Electronics and suitable for industrial data acquisition, motor control feedback loops, and test instrumentation requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for AD7821KNZ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, founded in 1965 and headquartered in Wilmington, MA.
The AD7821KNZ belongs to Analog Devices' legacy high-speed precision ADC family designed for embedded systems requiring fast, accurate, and easy-to-interface analog digitization without external clock or track-and-hold components.
FAQ
What is the maximum sampling rate supported by the AD7821KNZ?
The AD7821KNZ achieves a maximum sampling rate of 1 MHz in WR-RD mode under optimal timing conditions (tWR + tRD + tRI + tP). This is derived from its 660 ns conversion time and supports Nyquist-compliant digitization of up to 100 kHz analog signals. Actual achievable rate depends on system-level timing margins, load capacitance, and microprocessor bus speed.
Does the AD7821KNZ require an external clock signal?
No, the AD7821KNZ does not require an external clock signal. Its half-flash conversion architecture generates internal timing, allowing operation with only CS, RD, and WR control lines. This eliminates clock distribution challenges and reduces EMI sensitivity compared to externally clocked ADCs.
Can the AD7821KNZ operate with a single +5 V supply?
Yes, the AD7821KNZ can operate with a single +5 V supply by connecting Pin 19 (VSS) to GND. In this configuration, it supports unipolar input ranges from 0 V to +5 V. For bipolar operation (±2.5 V), VSS must be connected to –5 V, requiring dual ±5 V supplies.
What is the purpose of the OFL pin on the AD7821KNZ?
The OFL (Overflow) pin on the AD7821KNZ is an active-low, non-three-state output that indicates when the analog input exceeds VREF(+) – ½ LSB. It is designed for cascading multiple AD7821KNZ devices to construct higher-resolution converters (e.g., 12-bit or 16-bit) by routing OFL to the CS of the next stage.
How does the MODE pin affect the AD7821KNZ interface behavior?
The MODE pin selects between two interface protocols: when low, AD7821KNZ operates in RD mode (conversion starts and data reads via CS+RD); when high, it uses WR-RD mode (WR initiates conversion, RD reads data). RD mode suits processors with WAIT-state capability; WR-RD mode offers greater timing control and avoids bus wait cycles.
AD7821KNZ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Number of Bits:
- 8
- Sampling Rate (Per Second):
- 1M
- Number of Inputs:
- 1
- Input Type:
- Single Ended
- Data Interface:
- Parallel
- Configuration:
- S/H-ADC
- Ratio - S/H:ADC:
- 1:1
- Number of A/D Converters:
- 1
- Architecture:
- Pipelined
- Reference Type:
- External
- Voltage - Supply, Analog:
- 5V
- Voltage - Supply, Digital:
- 5V
- Features:
- -
- Operating Temperature:
- -40°C ~ 85°C
- Supplier Device Package:
- 20-PDIP
- Mounting Type:
- Through Hole
- Grade:
- -
- Qualification:
- -
AD7821KNZ FAQ
1.How can I place an order for AD7821KNZ through Aetrix?
Please submit a Request for Quotation (RFQ) for AD7821KNZ on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for AD7821KNZ reliable?
The price and inventory of AD7821KNZ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD7821KNZ is usually 5 days.
3.What payment methods are accepted for AD7821KNZ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD7821KNZ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD7821KNZ?
AD7821KNZ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD7821KNZ order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for AD7821KNZ?
For technical support, including AD7821KNZ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD7821KNZ requirements.
6.How does Aetrix verify that AD7821KNZ is sourced from the original manufacturer or authorized distributors?
All AD7821KNZ products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AD7821KNZ meets industry standards.
7.What is the process for return or replacement of AD7821KNZ?
All AD7821KNZ units undergo pre-shipment inspection (PSI). If there is an issue with AD7821KNZ, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The AD7821KNZ part is unused and in its original packaging.
Return procedure for AD7821KNZ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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