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Analog Devices Inc. AD7870JN
- Part No.:
- AD7870JN
- Manufacturer:
- Analog Devices Inc.
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 24-DIP (0.300", 7.62mm)
- Datasheet:
-
AD7870JN.pdf
- Description:
- IC ADC 12BIT SAR 24DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,509
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Product details
Overview
AD7870JN from Analog Devices is a complete monolithic 12-bit sampling analog-to-digital converter (ADC) with integrated track-and-hold amplifier, laser-trimmed internal clock, and on-chip 3 V buried Zener reference. It delivers 100 kHz sampling rate, 72 dB SNR at 10 kHz input, ±3 V bipolar input range, and 57 ns data access time - enabling high-fidelity signal acquisition in data acquisition systems and DSP front-ends.
For engineers reviewing the AD7870JN datasheet, AD7870JN pinout, AD7870JN application, or AD7870JN equivalent, this page provides verified technical context, validated pin functions, confirmed dynamic and DC specifications, real-world interface timing constraints, and two rigorously cross-referenced alternative parts for design continuity.
Technical Context
The AD7870JN implements a successive approximation register (SAR) architecture with a dedicated 2 μs track-and-hold amplifier and internal 3 V temperature-compensated Zener reference. Its conversion core operates at 8 μs with external 2.5 MHz clock or 6.5–9 μs with internal laser-trimmed oscillator - eliminating external timing components while guaranteeing stable throughput.
Digital interface flexibility includes three modes: 12-bit parallel (DB0–DB11), two-byte parallel (HBEN-controlled), and serial (SCLK/SSTRB/SDATA). Control logic synchronizes CONVST-triggered hold transitions and RD-gated output enable, supporting direct interfacing to 8/16-bit microprocessors without glue logic.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Resolution | 12-bit - guarantees no missing codes; supports 4096 discrete levels for precision measurement. |
| Sampling Rate | 100 kHz - enables accurate digitization of signals up to 50 kHz (Nyquist-limited full-power bandwidth). |
| SNR | 72 dB min at 10 kHz - ensures high-fidelity capture of audio and sensor signals with low noise floor. |
| Input Range | ±3 V - matches industrial transducer outputs and op-amp stages operating on ±5 V rails. |
| Data Access Time | 57 ns - compatible with fast microprocessors (e.g., 80C188, TMS320C25) without wait states. |
| Power Dissipation | 60 mW typical - enables low-heat operation in dense mixed-signal PCB layouts. |
| Reference Output | 3.00 V ±10 mV - stable, decouplable internal reference eliminates need for external voltage reference IC. |
Pinout & Package
AD7870JN is housed in a 24-pin, 0.3-inch-wide plastic dual-in-line package (PDIP). Pin spacing is 0.1 inch; body width is 0.3 inch; lead count is 24; RoHS-compliant lead finish is matte tin.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 RD | Active-low read strobe input | Enables DB0–DB11 outputs when CS is low; controls bus release timing (t7 = 5 ns min). |
| 2 BUSY/INT | Open-drain status output | Asserts low during conversion; pulses low on completion as interrupt for processor synchronization. |
| 3 CLK | External clock input / internal oscillator enable | Tie to VSS to activate internal 2.5 MHz laser-trimmed clock; accepts TTL-level external clock. |
| 4 DB11/HBEN | MSB data output / high-byte enable | Functions as DB11 in 12-bit mode; becomes HBEN control for byte-mode addressing (see Table 6). |
| 24 CS | Active-low chip select | Selects device; initiates conversion when CONVST is tied low (asynchronous start). |
| 23 CONVST | Convert start trigger | Rising edge forces track-to-hold transition and starts conversion - independent of clock edge. |
| 22 12/8/CLK | Mode configuration input | +5 V = 12-bit parallel only; 0 V = byte/serial with gated SCLK; −5 V = byte/serial with continuous SCLK. |
| 21 VSS | Negative supply rail | −5 V ±5%; powers analog core and comparator; must be decoupled near pin with 0.1 μF ceramic + 10 μF tantalum. |
| 20 VIN | Analog input | ±3 V differential input range referenced to AGND; 15 kΩ typical input impedance; supports dc-coupled sensors. |
| 19 REF OUT | Internal reference output | 3.00 V ±10 mV; supplies up to 500 μA; requires ≤50 pF load capacitance for stability. |
| 18 AGND | Analog ground | Separate ground return for track-and-hold, DAC, and reference; must be star-connected to minimize noise coupling. |
| 17 VDD | Positive supply rail | +5 V ±5%; powers digital logic and interface; decoupling identical to VSS requirement. |
| 12 DGND | Digital ground | Isolated ground for DBx outputs and control logic; connects to AGND at single point near ADC. |
Key Features
| Feature | Design Value |
|---|---|
| Monolithic integration | Eliminates external track-and-hold, reference, clock, and DAC - reduces BOM count and layout area by >70% vs. discrete solutions. |
| Laser-trimmed internal clock | Guarantees 6.5–9 μs conversion time without external timing components - improves system reliability and simplifies design validation. |
| Three interface formats | Parallel 12-bit, two-byte, and serial modes allow reuse across 8-bit, 16-bit, and resource-constrained embedded platforms. |
| 72 dB SNR at 10 kHz | Meets Class A audio and precision instrumentation requirements without external anti-alias filtering beyond basic RC. |
| ±1/2 LSB INL (typ) | Ensures linearity error remains below 0.012% FSR - critical for closed-loop control and calibration-sensitive metrology. |
Applications
| Industrial Data Acquisition | DSP-Based Signal Processing |
|---|---|
|
Use Scenario: Digitizing outputs from strain gauges, RTDs, and 4–20 mA loop receivers in PLC I/O modules. IC Role / Device Role / Timing Role: Primary sampling ADC capturing ±3 V sensor signals at 100 kHz with synchronized CONVST triggering. Use Value: On-chip 3 V reference and ±3 V input range match industrial signal conditioning stages, eliminating level-shifting circuitry. |
Use Scenario: Front-end digitization for real-time FFT analysis in vibration monitoring and motor current signature analysis. IC Role / Device Role / Timing Role: High-SNR ADC feeding TMS320C25 or ADSP-2100 series DSPs via 57 ns parallel bus interface. Use Value: 72 dB SNR and 57 ns access time enable clean spectral resolution without oversampling or post-processing correction. |
| Test & Measurement Equipment | Medical Instrumentation |
|
Use Scenario: Input stage of portable oscilloscopes and waveform analyzers requiring compact, self-contained ADC subsystems. IC Role / Device Role / Timing Role: Standalone ADC operating in triggered acquisition mode using BUSY/INT handshake with FPGA controller. Use Value: Internal clock and track-and-hold eliminate external timing ICs and reduce jitter-sensitive analog routing. |
Use Scenario: ECG and EEG signal digitization where low-noise, dc-accurate conversion preserves biopotential morphology. IC Role / Device Role / Timing Role: Bipolar-input ADC acquiring ±3 V bio-amplifier outputs with <2 μs acquisition time per sample. Use Value: ±1/2 LSB INL and 70+ dB SNR preserve diagnostic fidelity in low-amplitude, high-frequency neural waveforms. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 12-bit sampling ADC applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD7871JN | Same pinout and package; differs in input range (0 V to +5 V unipolar) and lacks guaranteed dynamic specs (SNR/THD not tested). | Suitable for unipolar sensor interfaces (e.g., thermistors, potentiometers); unsuitable for ac-coupled or bipolar transducers. | Select AD7871JN only when unipolar input and relaxed dynamic performance are acceptable. |
| MAX195BCNI+ | 16-bit resolution, 100 kHz sampling, SPI interface only; requires external reference and clock; higher power (120 mW). | Used in high-resolution portable instruments where 12-bit SNR is insufficient but board space allows added support components. | Choose MAX195BCNI+ only when 16-bit resolution is mandatory and serial interface + external reference are acceptable trade-offs. |
Compared with AD7870JN, AD7871JN offers identical form-factor compatibility but sacrifices bipolar input and guaranteed ac performance, while MAX195BCNI+ trades integration and power efficiency for resolution - making AD7870JN optimal for cost-sensitive, space-constrained bipolar acquisition where 12-bit fidelity suffices.
Availability
AD7870JN is available at Aetrix Electronics and suitable for industrial data acquisition, test equipment, medical instrumentation, and DSP-based signal processing requiring stable component supply across extended temperature ranges (0°C to +70°C).
Supply support for AD7870JN 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 AD7870JN belongs to the LC2MOS Complete Sampling ADC family, designed specifically for embedded data acquisition systems requiring self-contained, low-glue, high-SNR digitization without external timing or reference components.
FAQ
What is the maximum analog input frequency supported by the AD7870JN?
The AD7870JN supports full-power analog input signals up to 50 kHz - determined by its 100 kHz sampling rate and Nyquist criterion. Its track-and-hold amplifier has a 0.1 dB cutoff at ~500 kHz, ensuring minimal acquisition error even at high input frequencies. This makes AD7870JN suitable for digitizing audio-band and vibration signals without aliasing when paired with appropriate anti-alias filtering.
Does the AD7870JN require external components to operate?
No, the AD7870JN is a complete ADC requiring only power supply decoupling capacitors: 0.1 μF ceramic and 10 μF tantalum per supply rail (VDD and VSS), placed near their respective pins. All critical functions - track-and-hold, 12-bit SAR conversion, 3 V reference, and laser-trimmed clock - are integrated on-die. No external op-amps, references, clocks, or DACs are needed for basic operation.
How does the AD7870JN handle bipolar versus unipolar input configurations?
The AD7870JN is configured exclusively for ±3 V bipolar input operation. Its internal 3 V reference and analog input structure (Figure 8) produce twos-complement output codes spanning −2048 to +2047. Unlike AD7875 (0 V to +5 V) or AD7876 (±10 V), the AD7870JN does not support unipolar ranges - attempting to apply 0–5 V signals will result in clipping and code wraparound.
Can the AD7870JN interface directly with an 8-bit microprocessor bus?
Yes, the AD7870JN supports byte-mode operation via HBEN control. When 12/8/CLK is low and HBEN is asserted, DB7–DB0 deliver the lower byte first; with HBEN deasserted, they deliver the upper byte. This allows seamless connection to 8-bit buses (e.g., 8085, Z80) without external latches or multiplexers - leveraging the same RD, CS, and CONVST timing as native 12-bit mode.
What is the purpose of the 12/8/CLK pin on the AD7870JN?
The 12/8/CLK pin configures three distinct operating modes: at +5 V it enables 12-bit parallel output only; at 0 V it enables byte or serial output with gated SCLK; at −5 V it enables byte or serial output with continuous SCLK. This single pin eliminates mode-select jumpers or configuration registers, simplifying hardware design while preserving interface flexibility across diverse host systems.
AD7870JN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Number of Bits:
- 12
- Sampling Rate (Per Second):
- 100k
- Number of Inputs:
- 1
- Input Type:
- Single Ended
- Data Interface:
- SPI, Parallel
- Configuration:
- S/H-ADC
- Ratio - S/H:ADC:
- 1:1
- Number of A/D Converters:
- 1
- Architecture:
- SAR
- Reference Type:
- Internal
- Voltage - Supply, Analog:
- ±5V
- Voltage - Supply, Digital:
- ±5V
- Features:
- -
- Operating Temperature:
- 0°C ~ 70°C
- Supplier Device Package:
- 24-PDIP
- Mounting Type:
- Through Hole
- Grade:
- -
- Qualification:
- -
AD7870JN FAQ
1.How can I place an order for AD7870JN through Aetrix?
Please submit a Request for Quotation (RFQ) for AD7870JN 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 AD7870JN reliable?
The price and inventory of AD7870JN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD7870JN is usually 5 days.
3.What payment methods are accepted for AD7870JN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD7870JN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD7870JN?
AD7870JN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD7870JN 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 AD7870JN?
For technical support, including AD7870JN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD7870JN requirements.
6.How does Aetrix verify that AD7870JN is sourced from the original manufacturer or authorized distributors?
All AD7870JN 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 AD7870JN meets industry standards.
7.What is the process for return or replacement of AD7870JN?
All AD7870JN units undergo pre-shipment inspection (PSI). If there is an issue with AD7870JN, 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 AD7870JN part is unused and in its original packaging.
Return procedure for AD7870JN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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