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Analog Devices Inc. AD7821KPZ-REEL
- Part No.:
- AD7821KPZ-REEL
- Manufacturer:
- Analog Devices Inc.
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 20-LCC (J-Lead)
- Datasheet:
-
AD7821KPZ-REEL.pdf
- Description:
- IC ADC 8BIT PIPELINED 20PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:3,596
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Product details
Overview
AD7821KPZ-REEL 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 V to +5 V) or bipolar (±2.5 V) input ranges. It serves as a high-speed data acquisition front-end in DSP-based instrumentation.
For engineers reviewing the AD7821KPZ-REEL datasheet, AD7821KPZ-REEL pinout, AD7821KPZ-REEL application, or AD7821KPZ-REEL equivalent, key selection criteria include its 100 kHz track-and-hold bandwidth, ratiometric reference inputs, no-external-clock half-flash architecture, 20-pin PLCC package, and microprocessor-compatible control interface (CS, RD, WR, INT, RDY).
Technical Context
The AD7821KPZ-REEL implements a half-flash conversion architecture using two 4-bit flash ADCs - one for MSBs and one for LSBs - eliminating need for external clock generation. Its sampled-data comparators inherently provide track-and-hold functionality without external components.
It supports two digital interface modes: RD mode (conversion and read via single READ cycle) and WR-RD mode (separate WRITE-initiated conversion and READ access), both synchronized to falling edges of RD or WR. The MODE pin selects between them, and VSS (Pin 19) enables ±5 V bipolar operation or 0 V unipolar operation.
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 sampling rate; critical for real-time signal capture |
| Total Unadjusted Error | ±1 LSB max over –40°C to +85°C - ensures monotonicity and no missing codes across temperature |
| Track-and-Hold Bandwidth | 100 kHz max - digitizes full-scale 5 VPP sine waves without external THA |
| Signal-to-Noise Ratio | 45 dB min at 99.85 kHz input - meets baseline dynamic performance for voice and sensor digitization |
| Power Dissipation | 50 mW typ at +5 V - compatible with low-power embedded systems and thermally constrained layouts |
| Supply Range | +5 V ±5 % (VDD), –5 V ±5 % (VSS) - supports true bipolar input acquisition with ±2.5 V range |
Pinout & Package
AD7821KPZ-REEL is housed in a 20-terminal plastic leaded chip carrier (PLCC) package, surface-mountable, with 0.050" lead pitch and JEDEC MO-047 compliant outline. Pin 1 identifier is marked by a notch on the package body.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Analog Input | Accepts differential input voltage between VREF(–) and VREF(+); supports unipolar (0 V to +5 V) or bipolar (–2.5 V to +2.5 V) ranges |
| DB0–DB7 (Pins 2–5, 14–17) | Three-State Data Outputs | Latched 8-bit parallel output bus; tri-stated when CS high or RD low only in RD mode |
| WR/RDY (Pin 6) | Mode-Dependent Control/Status | In WR-RD mode: active-low write strobe; in RD mode: open-drain ready indicator tied to processor WAIT |
| MODE (Pin 7) | Interface Mode Select | High = WR-RD mode; low = RD mode; internally pulled low (50 µA), so external pull-down not required |
| RD (Pin 8) | Read Strobe | Active-low signal enabling data output; in RD mode initiates conversion and read; in WR-RD mode reads latched result |
| INT (Pin 9) | Interrupt Output | Active-low pulse signaling conversion completion; resets on rising edge of CS or RD |
| GND (Pin 10) | Signal Ground | Reference node for analog and digital sections; requires low-impedance connection to minimize noise coupling |
| VREF(–) (Pin 11) | Reference Lower Bound | Defines negative end of reference span; accepts VSS to VREF(+) - enables ratiometric and offset reference configurations |
| VREF(+) (Pin 12) | Reference Upper Bound | Defines positive end of reference span; must be ≤ VDD and > VREF(–); sets full-scale range with VREF(–) |
| CS (Pin 13) | Chip Select | Active-low enable; device disabled (outputs high-Z) when high; required assertion before RD/WR access |
| OFL (Pin 18) | Overflow Flag | Active-low open-collector output indicating VIN > VREF(+) – ½ LSB; used for cascading multiple AD7821s to extend resolution |
| VSS (Pin 19) | Negative Supply | –5 V for bipolar operation; grounded for unipolar +5 V supply; separates analog ground path from digital return |
| VDD (Pin 20) | Positive Supply | +5 V ±5 % main power rail; powers analog core and digital logic; decoupling capacitor required near pin |
Key Features
| Feature | Design Value |
|---|---|
| No external clock required | Half-flash architecture eliminates CLK generation circuitry, reducing BOM count and layout complexity |
| Built-in 100 kHz track-and-hold | Enables accurate digitization of fast-slewing signals (up to 1.6 V/µs) without external THA or anti-aliasing filter overhead |
| Ratiometric reference inputs | VREF(+) and VREF(–) allow direct connection to sensor bridge outputs or supply rails, rejecting common-mode drift |
| Microprocessor-compatible interface | Standard CS/RD/WR/INT timing aligns with 68000, 80x86, and Z80 buses; supports WAIT-state and non-WAIT configurations |
| Low power dissipation | 50 mW typical at +5 V enables use in thermally sensitive or battery-backed DAQ modules without forced cooling |
Applications
| Industrial Process Monitoring | DSP-Based Voice Recognition |
|---|---|
Use Scenario: Real-time acquisition of 4–20 mA loop signals conditioned through precision op-amps into ±2.5 V range. IC Role / Device Role / Timing Role: ADC front-end with built-in track-and-hold capturing transient valve position or pressure spikes at up to 100 kHz. Use Value: Eliminates external THA and reduces signal chain latency by 660 ns per sample, improving closed-loop response fidelity. | Use Scenario: Digitizing microphone preamp output in embedded voice command systems operating at ambient temperature. IC Role / Device Role / Timing Role: High-speed sampling engine interfaced to TI C54x or ADSP-21xx DSP via memory-mapped I/O. Use Value: 45 dB SNR and –50 dB THD support clean spectral analysis for MFCC extraction without oversampling penalty. |
| Automotive Sensor Interface | Portable Medical ECG Front-End |
Use Scenario: Converting throttle position sensor (TPS) or knock sensor outputs in engine control units under extended temperature stress. IC Role / Device Role / Timing Role: Ratiometric ADC referenced to same 5 V supply as sensor, rejecting supply ripple and thermal drift. Use Value: ±1 LSB total unadjusted error maintained from –40°C to +85°C ensures consistent calibration across vehicle lifetime. | Use Scenario: Sampling amplified, filtered ECG leads in handheld diagnostic devices powered by single Li-ion cell. IC Role / Device Role / Timing Role: Low-power 8-bit ADC acquiring 250–500 Hz band-limited biopotential signals with minimal board space. Use Value: 50 mW dissipation and PLCC package allow integration into compact PCBs without thermal derating concerns. |
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; single-supply only (no bipolar mode); no OFL output | Lacks bipolar input support and overflow flag; unsuitable for cascaded resolution extension or ±5 V sensor interfaces | Select AD7821KPZ-REEL when 660 ns speed, bipolar operation, or multi-ADC chaining is required |
| MAX1112CPE+ | Serial SPI interface; 2.5 µs conversion; internal reference; 16-pin PDIP; no track-and-hold | Requires external THA for >10 kHz signals; incompatible with parallel bus architectures; lower power (25 mW) | Choose AD7821KPZ-REEL for parallel microprocessor interfacing, higher speed, or integrated THA in space-constrained designs |
Compared with AD7820KN and MAX1112CPE+, the AD7821KPZ-REEL uniquely combines sub-µs conversion, bipolar capability, and hardware track-and-hold in a single 20-pin PLCC - making it optimal for legacy parallel-bus DAQ systems needing deterministic timing and wide input range flexibility.
Availability
AD7821KPZ-REEL is available at Aetrix Electronics and suitable for industrial process monitoring, DSP-based voice recognition, automotive sensor interface, and portable medical ECG front-end applications requiring stable component supply and long-term obsolescence management.
Supply support for AD7821KPZ-REEL 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, headquartered in Wilmington, MA.
The AD7821KPZ-REEL belongs to Analog Devices' LC2MOS precision ADC product line, engineered for high-speed data acquisition in industrial, instrumentation, and embedded control systems where accuracy, speed, and interface simplicity are critical.
FAQ
What is the maximum analog input frequency the AD7821KPZ-REEL can accurately digitize without an external track-and-hold?
The AD7821KPZ-REEL features an inherent track-and-hold function rated for 100 kHz maximum input frequency (full-scale 5 VPP sine wave). This is confirmed by its specified slew rate of 1.6 V/µs and dynamic test conditions in the datasheet. At frequencies above 100 kHz, amplitude and harmonic distortion errors increase beyond specification limits, necessitating an external THA. The AD7821KPZ-REEL achieves this performance without added components due to its sampled-data comparator architecture.
Does the AD7821KPZ-REEL require an external clock signal to operate?
No, the AD7821KPZ-REEL does not require an external clock. It uses a half-flash conversion technique that internally generates all necessary timing for both MSB and LSB conversions. Control is managed solely by the microprocessor's RD, WR, and CS signals. This eliminates clock distribution noise, simplifies layout, and avoids clock jitter-related SNR degradation - a key advantage over successive-approximation or pipeline ADCs requiring precise external clocks.
How does the MODE pin affect the digital interface behavior of the AD7821KPZ-REEL?
The MODE pin configures the AD7821KPZ-REEL's interface protocol: when low, it operates in RD mode (conversion and read initiated by a single READ cycle); when high, it enters WR-RD mode (WRITE starts conversion, READ retrieves result). Pin 6 functions as RDY in RD mode and WR in WR-RD mode. The pin is internally pulled low (50 µA), so default operation is RD mode unless actively driven high. This dual-mode flexibility allows seamless integration with both WAIT-capable and WAIT-free microprocessors.
Can the AD7821KPZ-REEL operate with a single +5 V supply while accepting bipolar input signals?
No, the AD7821KPZ-REEL cannot accept true bipolar inputs (e.g., ±2.5 V) on a single +5 V supply. Bipolar operation requires VSS = –5 V (Pin 19) to establish the negative reference rail. With VSS grounded, the device operates in unipolar mode only (0 V to +5 V input range). Attempting to apply negative voltages to VIN with VSS = 0 V violates absolute maximum ratings and risks latch-up or permanent damage. For bipolar acquisition, dual ±5 V supplies are mandatory.
What is the purpose of the OFL (overflow) output on the AD7821KPZ-REEL, and how is it used?
The OFL pin on the AD7821KPZ-REEL is an active-low, non-three-state output that asserts when the analog input exceeds VREF(+) – ½ LSB, indicating over-range condition. It is designed specifically for cascading multiple AD7821KPZ-REEL devices to build higher-resolution converters (e.g., two 8-bit parts for 16-bit output). In such configurations, OFL from the MSB device drives the WR input of the LSB device, synchronizing their conversions. OFL cannot be wire-OR'd with other outputs due to its open-collector-like behavior and lack of internal pull-up.
AD7821KPZ-REEL Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-LCC (J-Lead)
- Packaging:
- Tape & Reel (TR)
- 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-REEL FAQ
1.How can I place an order for AD7821KPZ-REEL through Aetrix?
Please submit a Request for Quotation (RFQ) for AD7821KPZ-REEL 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-REEL reliable?
The price and inventory of AD7821KPZ-REEL are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD7821KPZ-REEL is usually 5 days.
3.What payment methods are accepted for AD7821KPZ-REEL?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD7821KPZ-REEL transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD7821KPZ-REEL?
AD7821KPZ-REEL orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD7821KPZ-REEL 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-REEL?
For technical support, including AD7821KPZ-REEL datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD7821KPZ-REEL requirements.
6.How does Aetrix verify that AD7821KPZ-REEL is sourced from the original manufacturer or authorized distributors?
All AD7821KPZ-REEL 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-REEL meets industry standards.
7.What is the process for return or replacement of AD7821KPZ-REEL?
All AD7821KPZ-REEL units undergo pre-shipment inspection (PSI). If there is an issue with AD7821KPZ-REEL, 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-REEL part is unused and in its original packaging.
Return procedure for AD7821KPZ-REEL:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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