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Analog Devices Inc. AD7821KPZ
- Part No.:
- AD7821KPZ
- Manufacturer:
- Analog Devices Inc.
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 20-LCC (J-Lead)
- Datasheet:
-
AD7821KPZ.pdf
- Description:
- IC ADC 8BIT PIPELINED 20PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:2,261
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Product details
Overview
AD7821KPZ from Analog Devices is an LC2MOS 8-bit analog-to-digital converter with integrated track-and-hold, 660 ns conversion time (WR-RD mode), ±1 LSB total unadjusted error over –40°C to +85°C, and dual-supply (±5 V) or single-supply (+5 V) operation for unipolar (0–5 V) or bipolar (±2.5 V) input ranges. It serves as a high-speed data acquisition front-end in real-time signal conditioning systems.
For engineers reviewing the AD7821KPZ datasheet, AD7821KPZ pinout, AD7821KPZ application, or AD7821KPZ equivalent, key selection criteria include its 100 kHz track-and-hold bandwidth, ratiometric reference inputs, no-external-clock half-flash architecture, microprocessor-compatible control interface (CS/WR/RD/INT/RDY), and 20-pin PLCC package compatibility with industrial temperature-grade ADC replacements.
Technical Context
The AD7821KPZ implements a half-flash conversion architecture using two cascaded 4-bit flash ADCs - one for MSBs and one for LSBs - eliminating need for external clock generation. Its sampled-data comparators inherently perform track-and-hold, enabling accurate digitization of 100 kHz full-scale sine waves without external circuitry.
It supports two microprocessor interface modes: RD mode (conversion and read via single READ cycle) and WR-RD mode (separate WRITE-start and READ-fetch), with precise sampling instants defined on falling edges of WR or RD. The MODE pin selects between these, and VSS (Pin 19) enables ±5 V dual-supply operation for true bipolar input handling.
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 ≥1 MHz effective sample rate with proper timing margins. |
| Total Unadjusted Error | ±1 LSB max over –40°C to +85°C - ensures monotonicity and no missing codes across full temperature range. |
| Track-and-Hold Bandwidth | 100 kHz max - supports digitization of full-scale 5 VPP sine wave without external T/H. |
| Supply Configuration | Single +5 V (VSS = GND) or dual ±5 V (VSS = –5 V) - selectable via Pin 19 for unipolar/bipolar input flexibility. |
| Reference Input | Ratiometric VREF(+) and VREF(–) - allows direct connection to supply rails or precision references for system-level gain matching. |
| Dynamic Performance | SNR = 45 dB min, THD = –50 dB max at 99.85 kHz - validated for DSP applications including voice and adaptive filtering. |
Pinout & Package
AD7821KPZ is housed in a 20-terminal plastic leaded chip carrier (PLCC) package (P-20A), surface-mount compatible with standard reflow profiles and IPC-7351 land patterns.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | VIN | Analog input node; accepts differential voltage range VREF(–) ≤ VIN ≤ VREF(+); supports ±2.5 V or 0–5 V full-scale. |
| 2–5, 14–17 | DB0–DB7 | Three-state parallel data outputs (LSB to MSB); latched and driven only when CS and RD are low. |
| 6 | WR/RDY | Configurable: WR input in WR-RD mode; RDY open-drain status output in RD mode - drives µP WAIT line. |
| 7 | MODE | Interface mode selector: low = RD mode; high = WR-RD mode; internally pulled low (50 µA source). |
| 8 | RD | Read strobe; active-low control that enables data bus drivers and triggers internal timing in both modes. |
| 9 | INT | Interrupt output; goes low upon conversion completion; reset by rising edge of CS or RD. |
| 10 | GND | Digital ground reference; separate from analog ground in layout-sensitive designs. |
| 11–12 | VREF(–), VREF(+) | Differential reference span inputs; define zero and full-scale; support ratiometric operation. |
| 13 | CS | Chip select; device enabled only when low; required for all control and data transactions. |
| 18 | OFL | Overflow flag; active-low non-three-state output indicating VIN > VREF(+) – ½ LSB; used for cascading. |
| 19 | VSS | Negative supply terminal; tied to 0 V for unipolar mode; –5 V for bipolar mode. |
| 20 | VDD | Positive supply; +5 V ±5%; powers analog and digital sections; decoupling required per datasheet. |
Key Features
| Feature | Design Value |
|---|---|
| No external clock required | Half-flash architecture self-times conversion - eliminates clock routing, jitter, and synchronization overhead. |
| Built-in track-and-hold | Supports 1.6 V/µs input slew rate - captures 100 kHz full-scale signals without external components or aperture uncertainty. |
| Microprocessor-compatible interface | Standard CS/WR/RD/INT/RDY signals - integrates directly with 68000, 80x86, and Z80 buses without glue logic. |
| Ratiometric reference inputs | VREF(+) and VREF(–) accept supply-derived or precision references - maintains accuracy under varying rail conditions. |
| Industrial temperature grade | Specified from –40°C to +85°C - suitable for embedded control, test equipment, and factory automation environments. |
Applications
| Motor Control Feedback Sampling | DSP-Based Voice Recognition Front-End |
|---|---|
|
Use Scenario: Real-time acquisition of current/voltage feedback from three-phase inverter legs in servo drives. IC Role / Device Role / Timing Role: ADC front-end capturing synchronized analog samples at ≥20 kSPS with deterministic sampling edge on WR falling edge. Use Value: 660 ns conversion + 100 kHz T/H bandwidth enables accurate reconstruction of motor phase currents without aliasing or hold droop. |
Use Scenario: Digitizing microphone preamp output in embedded voice command systems operating at 50–100 kHz bandwidth. IC Role / Device Role / Timing Role: High-fidelity signal acquisition stage feeding fixed-point DSP core with SNR ≥45 dB and THD ≤–50 dB. Use Value: Validated dynamic specs ensure clean spectral representation for FFT-based feature extraction and pattern matching. |
| Industrial Data Acquisition Module | Programmable Logic Controller (PLC) Analog Input Card |
|
Use Scenario: Multi-channel voltage monitoring in modular I/O systems with isolated sensor interfaces. IC Role / Device Role / Timing Role: Standalone ADC in WR-RD mode (CS/RD grounded), triggered by FPGA logic with tINTL < 700 ns latency. Use Value: Ratiometric reference support and ±1 LSB error guarantee stable measurement accuracy across supply and temperature variations. |
Use Scenario: 8-channel analog input expansion for DIN-rail mounted PLCs requiring robust, field-deployable performance. IC Role / Device Role / Timing Role: Microprocessor-mapped peripheral interfaced via RD mode with DTACK handshake to 68K-family CPUs. Use Value: RDY output integration with µP WAIT state simplifies timing-critical firmware and reduces interrupt latency. |
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 |
|---|---|---|---|
| AD7820KN | Slower 1.36 µs conversion time; no VSS pin; unipolar-only (0–5 V); lacks built-in T/H function. | Requires external track-and-hold for >6.4 kHz signals; limited to single-supply systems. | Select AD7821KPZ when 100 kHz signal bandwidth, bipolar input, or reduced BOM count is required. |
| MAX1112ACPP+ | Serial SPI interface; 2.5 µs conversion; 2.7–5.25 V supply; internal reference; 16-pin SSOP. | Lower pin count but serial interface increases µP overhead; no parallel bus compatibility. | Choose AD7821KPZ for legacy parallel-bus systems, deterministic timing, or higher throughput in WR-RD mode. |
Compared with AD7820KN and MAX1112ACPP+, the AD7821KPZ uniquely combines parallel microprocessor interface, integrated track-and-hold, bipolar capability, and sub-µs conversion - making it optimal for real-time industrial control where timing predictability and analog interface simplicity are critical.
Availability
AD7821KPZ is available at Aetrix Electronics and suitable for motor control feedback sampling, DSP-based voice recognition front-ends, industrial data acquisition modules, programmable logic controller analog input cards, and test instrumentation requiring stable component supply across extended lifecycle programs.
Supply support for AD7821KPZ 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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, founded in 1965 and headquartered in Wilmington, MA.
The AD7821KPZ belongs to Analog Devices' legacy high-speed ADC product line, designed specifically for industrial and instrumentation applications demanding fast, accurate, and microprocessor-friendly analog-to-digital conversion without external timing or signal conditioning.
FAQ
What is the maximum analog input frequency the AD7821KPZ can accurately digitize without an external track-and-hold?
The AD7821KPZ features an inherent track-and-hold function rated for 100 kHz maximum signal bandwidth. This means it can accurately digitize full-scale 5 VPP sine waves up to 100 kHz without external components. The specification is verified with SNR ≥45 dB and THD ≤–50 dB at 99.85 kHz input under fSAMPLE = 500 kHz conditions. For reliable Nyquist compliance, sampling rates ≥200 kHz are recommended.
Does the AD7821KPZ require an external clock signal to operate?
No, the AD7821KPZ does not require an external clock. It uses a half-flash conversion architecture that self-times the conversion process. All timing is controlled by the WR and RD strobes in WR-RD mode or by the RD pulse in RD mode. This eliminates clock distribution, jitter sensitivity, and external oscillator BOM cost - a key differentiator versus successive-approximation or pipeline ADCs.
How does the MODE pin affect the AD7821KPZ interface behavior?
The MODE pin determines the AD7821KPZ's digital interface protocol: when low, it configures the device for RD mode (conversion and read initiated by a single READ cycle); when high, it enables WR-RD mode (WRITE starts conversion, READ fetches result). Pin 6 functions as RDY output in RD mode and WR input in WR-RD mode. The pin is internally pulled low (50 µA), so a pull-up resistor is required for WR-RD operation.
Can the AD7821KPZ operate with a single +5 V supply while accepting bipolar input signals?
No. Bipolar input operation (±2.5 V range) requires dual supplies: VDD = +5 V and VSS = –5 V. The VSS pin (Pin 19) must be connected to –5 V to enable the internal circuitry for negative input handling. With VSS = GND, the AD7821KPZ operates only in unipolar mode (0–5 V input range). Attempting bipolar input with single supply will cause clipping and invalid codes.
What is the meaning of "total unadjusted error" for the AD7821KPZ, and how is it guaranteed?
Total unadjusted error for the AD7821KPZ is a composite specification encompassing offset error, full-scale error, and relative accuracy (integral nonlinearity), measured across –40°C to +85°C. It is guaranteed at ±1 LSB maximum - meaning all 256 output codes are monotonic and no code is missing. This is verified per the AD7821KPZ ordering guide (K version) and confirmed in the REV. B datasheet specifications table under "Total Unadjusted Error".
AD7821KPZ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-LCC (J-Lead)
- 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-PLCC (9x9)
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
AD7821KPZ FAQ
1.How can I place an order for AD7821KPZ through Aetrix?
Please submit a Request for Quotation (RFQ) for AD7821KPZ 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 AD7821KPZ reliable?
The price and inventory of AD7821KPZ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD7821KPZ is usually 5 days.
3.What payment methods are accepted for AD7821KPZ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD7821KPZ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD7821KPZ?
AD7821KPZ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD7821KPZ 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 AD7821KPZ?
For technical support, including AD7821KPZ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD7821KPZ requirements.
6.How does Aetrix verify that AD7821KPZ is sourced from the original manufacturer or authorized distributors?
All AD7821KPZ 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 AD7821KPZ meets industry standards.
7.What is the process for return or replacement of AD7821KPZ?
All AD7821KPZ units undergo pre-shipment inspection (PSI). If there is an issue with AD7821KPZ, 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 AD7821KPZ part is unused and in its original packaging.
Return procedure for AD7821KPZ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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