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Analog Devices Inc. AD7705BN
- Part No.:
- AD7705BN
- Manufacturer:
- Analog Devices Inc.
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
AD7705BN.pdf
- Description:
- IC ADC 16BIT SIGMA-DELTA 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,722
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Product details
Overview
AD7705BN from Analog Devices is a 16-bit sigma-delta analog-to-digital converter with two fully differential input channels, programmable gain (1–128), 3-wire SPI-compatible serial interface, and operation at 2.7–3.3 V or 4.75–5.25 V. It delivers 0.003% nonlinearity, <600 nV rms noise, and 1 mW max power dissipation at 3 V - designed for precision low-frequency transducer signal acquisition in industrial sensor interfaces.
For engineers reviewing the AD7705BN datasheet, AD7705BN pinout, AD7705BN application, or AD7705BN equivalent, key selection criteria include its dual-channel fully differential architecture, on-chip calibration support, unipolar/bipolar input range flexibility, and compatibility with microcontroller-based data acquisition systems requiring high DC accuracy and low power.
Technical Context
The AD7705BN employs a charge-balancing sigma-delta modulator followed by an on-chip digital filter with programmable first-notch frequency, enabling configurable output update rates and rejection of 50/60 Hz line interference. Its analog front end integrates a programmable-gain amplifier (PGA) and optional input buffer, allowing direct connection to low-level transducer outputs such as strain gauges without external signal conditioning.
It supports both unipolar (0 mV to +VREF/gain) and bipolar (±VREF/gain) input ranges referenced to AIN(−), with common-mode rejection up to 130 dB at gains ≥8. The device features self-calibration and system calibration registers to eliminate zero-scale and full-scale errors, and operates with either an external master clock or an internal crystal oscillator across MCLK IN/MCLK OUT pins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Resolution | 16 bits with no missing codes - guarantees monotonicity and full code coverage for precision measurement applications. |
| Input Channels | 2 fully differential analog inputs - enables simultaneous or sequential measurement of two isolated sensor signals with inherent noise rejection. |
| PGA Gain Range | 1 to 128 - allows direct digitization of millivolt-level transducer outputs (e.g., ±20 mV to ±2.5 V) without external amplification. |
| Power Dissipation | 1 mW maximum at 3 V - supports battery-powered or thermally constrained embedded systems. |
| Integral Nonlinearity | ±0.003% of FSR - ensures high-end accuracy for calibration-critical instrumentation and smart transmitter designs. |
| Reference Input | Differential REF IN(+) and REF IN(−) - permits ratiometric measurement and flexible reference voltage selection (1.225 V or 2.5 V). |
| Serial Interface | 3-wire SPI/QSPI/MICROWIRE/DSP-compatible - reduces MCU GPIO count and simplifies isolation in industrial I/O modules. |
Pinout & Package
AD7705BN is housed in a 16-lead plastic dual in-line package (PDIP) with 0.3-inch wide body. Pin functions are electrically and functionally identical to the AD7705 family and validated per Analog Devices Rev. C datasheet Figure 3 and Table 4.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SCLK | Serial clock input | Schmitt-triggered logic input accepting discontinuous or continuous clocks; controls timing of DIN/DOUT data transfers. |
| MCLK IN | Master clock input | Accepts external CMOS clock or crystal/resonator; sets conversion throughput and filter notch frequency. |
| MCLK OUT | Master clock output | Provides inverted clock for external circuitry when crystal is used; disableable via CLKDIS bit to reduce power. |
| CS | Chip select | Active-low enable for 3-wire mode; allows multi-device sharing of SCLK/DIN/DOUT lines on same bus. |
| RESET | Hardware reset | Active-low signal that restores all registers, filter state, and calibration coefficients to power-on defaults. |
| AIN1(+), AIN1(−) | Channel 1 differential input | Primary fully differential analog input pair; supports bipolar/unipolar ranges referenced to AIN1(−). |
| AIN2(+), AIN2(−) | Channel 2 differential input | Secondary fully differential analog input pair; independent gain and polarity configuration from Channel 1. |
| REF IN(+), REF IN(−) | Differential reference input | Defines full-scale range; supports ratiometric sensing and eliminates reference drift impact on accuracy. |
| DRDY | Data ready indicator | Open-drain output signals valid conversion result; synchronizes read operations and indicates calibration completion. |
| DIN | Serial data input | Writes to communication, setup, clock, or calibration registers; supports register addressing and configuration updates. |
| DOUT | Serial data output | Reads from data, setup, or calibration registers; outputs MSB-first 16-bit conversion results or status information. |
| VDD, GND | Power supply | Single 2.7–3.3 V or 4.75–5.25 V supply; CMOS design enables low quiescent current (8 μA standby). |
Key Features
| Feature | Design Value |
|---|---|
| On-chip self-calibration | Eliminates zero-scale and full-scale errors internally, removing need for external calibration hardware in field-deployed sensors. |
| Programmable digital filter notch | Enables precise 50 Hz or 60 Hz line frequency rejection by setting first filter notch - critical for AC-coupled industrial environments. |
| Input buffer enable (BUF bit) | Reduces source impedance sensitivity and improves common-mode rejection when enabled, supporting high-impedance transducers. |
| Bipolar/unipolar mode selection | Configurable via B/U bit in setup register - supports both signed and unsigned sensor outputs without external level-shifting circuitry. |
| Low-power standby mode | Reduces current to 8 μA at 3 V, enabling wake-on-event architectures in battery-operated remote monitoring nodes. |
Applications
| Pressure Measurement | Temperature Measurement |
|---|---|
Use Scenario: High-accuracy pressure sensing in HVAC control panels using bridge-based piezoresistive sensors with mV-level output. IC Role / Device Role / Timing Role: ADC front end performing PGA gain scaling, sigma-delta conversion, and digital filtering of differential bridge signals. Use Value: Achieves ±0.003% linearity and 16-bit resolution without external op-amps or precision references - reducing BOM cost and board area. | Use Scenario: RTD or thermocouple signal conditioning in industrial process controllers requiring cold-junction compensation and linearization. IC Role / Device Role / Timing Role: Dual-channel ADC acquiring both sensor voltage and reference junction temperature simultaneously. Use Value: Fully differential inputs reject common-mode noise from heater elements; on-chip calibration maintains accuracy across −40°C to +85°C operating range. |
| Smart Transmitters | Battery Monitoring |
Use Scenario: 4–20 mA loop-powered field instruments transmitting calibrated analog sensor data over long cables. IC Role / Device Role / Timing Role: Precision ADC interfacing with microcontroller and HART modem; provides digitized sensor values for digital communication. Use Value: Low 1 mW power consumption extends loop budget; 3-wire interface minimizes isolation component count in intrinsically safe designs. | Use Scenario: State-of-charge estimation in portable medical devices using voltage and current sensing across Li-ion battery cells. IC Role / Device Role / Timing Role: Simultaneous sampling of cell voltage (unipolar) and shunt voltage (bipolar) for Coulomb counting and OCV tracking. Use Value: Programmable gain accommodates both 0–4.2 V cell range and µV-level shunt signals; standby current <8 μA preserves battery life during sleep cycles. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar sigma-delta ADC applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD7706BN | 3 pseudo-differential input channels vs. AD7705BN's 2 fully differential channels; identical core architecture, timing, and register map. | Supports three single-ended or pseudo-differential sensors instead of two fully differential ones; requires COMMON reference connection rather than dedicated AIN(−) per channel. | Select AD7706BN when system requires third analog input and can accept shared reference topology; pinout differs - not drop-in compatible. |
| ADS1115IDGSR | 16-bit delta-sigma ADC with 4-channel input multiplexer, programmable gain (2/4/8/16), I²C interface, and internal reference; higher sampling rate (860 sps) but no on-chip calibration registers. | Designed for compact, low-pin-count I²C systems; lacks self-calibration and 50/60 Hz notch programming - requires external calibration or software compensation. | Choose ADS1115IDGSR for space-constrained designs needing I²C simplicity and higher throughput; AD7705BN preferred where on-chip calibration and line-rejection configurability are mandatory. |
Compared with AD7706BN, AD7705BN offers superior noise rejection for fully differential sensor topologies, while ADS1115IDGSR trades calibration autonomy and flexible filtering for integration density and interface simplicity - making AD7705BN optimal for high-stability, low-noise industrial analog front ends.
Availability
AD7705BN is available at Aetrix Electronics and suitable for pressure measurement, temperature sensing, smart transmitter development, and battery monitoring applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for AD7705BN 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 Norwood, MA.
The AD7705/AD7706 product line was engineered specifically for low-frequency, high-accuracy industrial measurement systems - integrating PGA, sigma-delta conversion, digital filtering, and calibration into a single low-power IC for transducer interface applications.
FAQ
What is the maximum sampling rate of the AD7705BN at gain = 1 and MCLK IN = 2.4576 MHz?
The AD7705BN achieves a maximum output data rate of 38.4 Hz under those conditions. This is calculated as fCLKIN/64 = 2.4576 MHz / 64. The actual update rate depends on the selected digital filter notch frequency and gain setting - higher gains reduce effective throughput due to longer settling times in the sigma-delta modulator and filter stages. AD7705BN's filter architecture prioritizes noise rejection over speed, making it ideal for DC and low-frequency (<10 Hz) measurements.
Does the AD7705BN support true bipolar input ranges, and how is it configured?
Yes, the AD7705BN supports true bipolar input ranges (e.g., ±20 mV to ±2.5 V) by setting the B/U bit in the setup register to '0'. In this mode, the input voltage on AIN1(+) or AIN2(+) is measured differentially with respect to its corresponding AIN1(−) or AIN2(−) terminal, producing offset binary output coding. The device uses the same PGA and reference structure for both unipolar and bipolar modes - no external components are needed to switch between them. AD7705BN's differential architecture inherently rejects common-mode noise, preserving accuracy across the full bipolar span.
Can the AD7705BN operate with a 3.3 V supply and a 2.5 V reference voltage?
No - the AD7705BN requires the reference voltage to be compatible with the supply rail. When operating at 3.3 V (within the 2.7–3.3 V range), the specified reference is 1.225 V ±1%; using a 2.5 V reference violates the absolute maximum rating for REF IN(+) (must be ≤ VDD). Attempting this may cause inaccurate conversions or damage. AD7705BN's reference input range is GND to VDD, and VREF = REFIN(+) − REFIN(−) must be 1/1.75 V (min/max) for 3 V operation. For 2.5 V references, use the 5 V supply range (4.75–5.25 V) as specified in the datasheet.
How does the AD7705BN handle power-down mode, and what is the typical standby current?
The AD7705BN enters standby mode when the RESET pin is held low or when the device is idle with CLKDIS enabled and no master clock applied. Standby current is 8 μA maximum at 3 V and 16 μA maximum at 5 V, per the Rev. C datasheet. During standby, the analog modulator, digital filter, and interface logic are disabled - but calibration coefficients remain retained in registers. To resume operation, a valid master clock must be reapplied and a reset or register reinitialization performed. AD7705BN's ultra-low standby current makes it suitable for energy-harvesting and battery-backed sensor nodes.
Is the AD7705BN pin-compatible with other packages of the same part number, such as SOIC or TSSOP?
Yes - the AD7705BN (PDIP), AD7705BR (SOIC), and AD7705BRU (TSSOP) share identical pin numbering, signal definitions, and electrical characteristics per Analog Devices' ordering guide. All three packages use the same 16-pin layout shown in Figure 3 of the Rev. C datasheet. Mechanical dimensions and thermal performance differ (e.g., θJA = 105°C/W for PDIP vs. 75°C/W for SOIC), but PCB footprint and schematic symbol can be reused across variants. AD7705BN is the through-hole option optimized for prototyping and legacy industrial designs requiring DIP sockets.
AD7705BN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Number of Bits:
- 16
- Sampling Rate (Per Second):
- 500
- Number of Inputs:
- 2
- Input Type:
- Differential
- Data Interface:
- SPI, DSP
- Configuration:
- MUX-PGA-ADC
- Ratio - S/H:ADC:
- -
- Number of A/D Converters:
- 1
- Architecture:
- Sigma-Delta
- Reference Type:
- External
- Voltage - Supply, Analog:
- 2.7V ~ 3.3V, 5V
- Voltage - Supply, Digital:
- 2.7V ~ 3.3V, 5V
- Features:
- PGA
- Operating Temperature:
- -40°C ~ 85°C
- Supplier Device Package:
- 16-PDIP
- Mounting Type:
- Through Hole
- Grade:
- -
- Qualification:
- -
AD7705BN FAQ
1.How can I place an order for AD7705BN through Aetrix?
Please submit a Request for Quotation (RFQ) for AD7705BN 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 AD7705BN reliable?
The price and inventory of AD7705BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD7705BN is usually 5 days.
3.What payment methods are accepted for AD7705BN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD7705BN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD7705BN?
AD7705BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD7705BN 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 AD7705BN?
For technical support, including AD7705BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD7705BN requirements.
6.How does Aetrix verify that AD7705BN is sourced from the original manufacturer or authorized distributors?
All AD7705BN 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 AD7705BN meets industry standards.
7.What is the process for return or replacement of AD7705BN?
All AD7705BN units undergo pre-shipment inspection (PSI). If there is an issue with AD7705BN, 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 AD7705BN part is unused and in its original packaging.
Return procedure for AD7705BN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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