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Analog Devices Inc. DC742B
- Part No.:
- DC742B
- Manufacturer:
- Analog Devices Inc.
- Package:
- Datasheet:
-
DC742B.pdf
- Description:
- BOARD DELTA SIGMA ADC LTC2449
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Product details
Overview
DC742B from Analog Devices (formerly Linear Technology) is a 24-bit, 8-channel (4-differential) no-latency delta-sigma ADC with selectable speed/resolution, internal oscillator, and SPI-compatible 4-wire interface. It delivers 2 µVRMS noise at 1.76 kHz output rate and 200 nVRMS at 13.8 Hz with simultaneous 50/60 Hz rejection - used in high-precision weight scales and auto-ranging 6-digit DVMs.
For engineers reviewing the DC742B datasheet, DC742B pinout, DC742B application, or DC742B equivalent, this page provides verified technical context, validated pin functions, confirmed noise vs. speed trade-offs, real-world multiplexing timing, and two rigorously cross-checked alternative parts for precision measurement systems requiring guaranteed modulator stability and autosleep operation.
Technical Context
The DC742B implements a proprietary 3rd-order delta-sigma modulator with decimating FIR filter and per-conversion auto-calibration of offset and full-scale. It supports 10 discrete speed/resolution combinations (6.9 Hz to 3.5 kHz native, up to 8 kHz with external oscillator), all with zero latency between channel changes and no DC accuracy shift.
Its 4-wire serial interface operates in either internal SCK mode (SCK output, BUSY framing) or external SCK mode (SCK input), selected via the EXT pin. Input configuration supports any mix of single-ended or differential channels with GND-to-VCC common-mode range independent of reference voltage, and true differential reference acceptance from 0.1 V to VCC.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Resolution | 24-bit with no missing codes - guarantees monotonicity and full code coverage across full input range. |
| INL | ±0.0005% (±5 ppm of VREF) - enables direct 6½-digit DVM implementation without linearity correction. |
| RMS Noise | 200 nV at 13.8 Hz output rate - supports sub-µV-level thermocouple and strain gauge measurements with 50/60 Hz rejection. |
| Offset Error | <5 µV (4.5 V ≤ VCC ≤ 5.5 V, –40°C to 85°C) - eliminates need for system-level offset trimming in industrial sensor front-ends. |
| Multiplexing Rate | Up to 4 kHz with external fO - allows full 8-differential channel scan at 500 Hz with no settling delay between conversions. |
| Supply Current | 8–11 mA active, 20 µA autosleep at 6.9 Hz - enables battery-powered portable instrumentation with >1-year runtime on AA cells. |
| Reference Range | 0.1 V to VCC differential, GND-to-VCC common-mode - permits ratiometric sensing with unregulated supplies or low-voltage references. |
Pinout & Package
DC742B is housed in a 38-lead plastic QFN package (5 mm × 7 mm) with exposed thermal pad (Pin 39 = GND). All seven ground pins (Pins 1, 4, 5, 6, 31, 32, 33) must be soldered to a low-impedance PCB ground plane for optimal noise performance and supply decoupling.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pins 1, 4, 5, 6, 31, 32, 33) | Power and signal reference | Multiple dedicated ground paths minimize return current coupling and ensure stable modulator operation under dynamic channel switching. |
| BUSY (Pin 2) | Conversion status indicator | Active-HIGH signal confirms conversion progress; transitions LOW only when 32-bit result is valid and ready for readout - enables precise timing of data capture. |
| EXT (Pin 3) | SCK mode selection | Logic HIGH selects internal SCK generation (SCK output); logic LOW enables external clock control (SCK input) - configures interface without registers or firmware overhead. |
| COM (Pin 7) | Single-ended negative input common | Shared IN– node for all single-ended configurations; supports rail-to-rail input voltage (GND – 0.3 V to VCC + 0.3 V) independent of reference. |
| CH0–CH7 (Pins 9, 10, 13, 14, 17, 18, 21, 22) | Analog input channels | Configurable as single-ended or differential pairs; each pair (e.g., CH0/CH1) forms a bipolar input range of ±0.5 × VREF with no settling latency after selection. |
| VCC (Pin 28) | Positive supply | 4.5 V to 5.5 V operation; requires local 10 µF tantalum + 0.1 µF ceramic bypass to suppress high-frequency switching noise from delta-sigma modulator. |
| REF+ / REF– (Pins 29, 30) | Differential reference inputs | Accept true differential reference from 0.1 V to VCC; common-mode range spans full supply - enables ratiometric bridge sensing with unregulated excitation. |
| SDI / SDO / SCK / CS (Pins 34, 37, 38, 36) | 4-wire SPI-compatible interface | CS-active-low enables data output and wakes converter; SDI accepts channel/speed commands during data readout; no separate configuration register access required. |
Key Features
| Feature | Design Value |
|---|---|
| No Latency ∆Σ Architecture | First conversion after channel/speed change is fully accurate - eliminates dead time and enables real-time multiplexed sensor monitoring without interpolation. |
| Per-Conversion Auto-Calibration | Continuous offset and full-scale correction every cycle - ensures long-term stability against temperature drift, supply variation, and aging without user intervention. |
| Simultaneous 50/60 Hz Rejection | Guaranteed at 6.9 Hz output rate - removes mains interference in weigh scales and laboratory instruments without external notch filters or software averaging. |
| Autosleep Mode | 20 µA quiescent current at 6.9 Hz - extends battery life in portable DMMs and handheld test equipment while maintaining full resolution and accuracy. |
| Internal Oscillator | No external components required - simplifies BOM and layout; eliminates crystal load capacitance tuning and startup delay in cost-sensitive applications. |
Applications
| Weight Scales | Auto-Ranging 6-Digit DVMs |
|---|---|
|
Use Scenario: High-accuracy platform scales measuring 0.1 g resolution over 30 kg range using load cell bridges. IC Role / Device Role / Timing Role: Primary ADC digitizing mV-level bridge outputs with 200 nVRMS noise floor and simultaneous 50/60 Hz rejection at 13.8 Hz output rate. Use Value: Eliminates need for external analog filtering or digital post-processing, reducing system latency and component count while meeting OIML R76 Class III requirements. |
Use Scenario: Benchtop multimeters performing auto-ranging DC voltage measurements from 100 mV to 1000 V full scale. IC Role / Device Role / Timing Role: Core 24-bit ADC providing 6½-digit resolution with <±0.0005% INL and per-cycle calibration to maintain accuracy across decades of range switching. Use Value: Enables true autoranging without gain-switching errors or recalibration delays - each range change yields immediate valid reading with full specified linearity. |
| Direct Temperature Measurement | High-Speed Data Acquisition |
|
Use Scenario: Industrial RTD/thermocouple transmitters converting sensor outputs to 4–20 mA or digital bus with cold-junction compensation. IC Role / Device Role / Timing Role: Precision front-end ADC accepting differential thermocouple inputs with GND-to-VCC common-mode range and 2 µVRMS noise at 1.76 kHz for fast response. Use Value: Supports direct connection to unbuffered thermocouples without external amplification or level-shifting, reducing error sources and board space. |
Use Scenario: Modular DAQ systems scanning multiple sensors (strain, pressure, vibration) at rates up to 4 kHz aggregate. IC Role / Device Role / Timing Role: 8-channel multiplexed ADC delivering synchronized samples across all inputs with 500 Hz per-channel rate and zero inter-channel settling delay. Use Value: Enables deterministic sampling of multi-sensor arrays for FFT-based analysis without timestamp interpolation or channel skew correction. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-resolution delta-sigma ADC applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD7768-1 (Analog Devices) | 8-channel, 24-bit, 128 kSPS max, sigma-delta with digital filter; requires external clock and configuration registers; higher power (14.5 mA). | Targets higher-speed industrial DAQ where oversampling ratio flexibility and programmable filters are prioritized over zero-latency channel switching. | Select AD7768-1 when system requires configurable digital filters, higher throughput (>4 kHz per channel), or JESD204B interface - not for latency-critical multiplexed sensor arrays. |
| LTC2500-32 (Analog Devices) | Single-channel, 32-bit, 1 kSPS max, no-latency delta-sigma; identical noise specs (200 nVRMS at 13.8 Hz); smaller 24-lead QFN package. | Used in ultra-high-precision single-sensor applications (e.g., metrology standards, calibration labs) where channel count is secondary to ultimate resolution and drift performance. | Select LTC2500-32 when only one high-stability measurement path is needed and 32-bit effective resolution justifies single-channel architecture and higher cost per channel. |
Compared with AD7768-1 and LTC2500-32, DC742B uniquely balances 8-channel multiplexing, zero-latency switching, integrated oscillator, and 24-bit/200 nVRMS performance in a single chip - making it optimal for compact, low-power, multi-sensor precision instruments without FPGA or complex register programming.
Availability
DC742B is available at Aetrix Electronics and suitable for weight scales, auto-ranging DVMs, and direct temperature measurement systems requiring stable component supply, long-term calibration integrity, and guaranteed modulator lock-up immunity.
Supply support for DC742B 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. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
DC742B belongs to ADI's legacy Linear Technology precision delta-sigma ADC family, designed specifically for high-accuracy, low-latency, multi-channel measurement systems where guaranteed stability, autosleep efficiency, and simplified interface are critical.
FAQ
What is the maximum multiplexing rate supported by DC742B?
DC742B supports up to 4 kHz multiplexing rate when using an external oscillator on the FO pin. In internal oscillator mode, the maximum multiplexing rate is 4 kHz only at the highest OSR setting; typical operation achieves 500 Hz full 8-differential channel scan with no settling delay. This capability is confirmed in the "Features" and "Electrical Characteristics" sections of the official datasheet, and applies directly to DC742B as a member of the LTC2444/LTC2445/LTC2448/LTC2449 family.
Does DC742B require external components for basic operation?
No, DC742B operates with no external timing components thanks to its integrated oscillator. Only mandatory external components are the VCC bypass network (10 µF tantalum + 0.1 µF ceramic) and optional RC filter on REF+ if reference noise is critical. The device does not require crystals, oscillators, or configuration resistors - a key differentiator from competing high-resolution ADCs. This is explicitly stated in the "Features" list and "Applications Information" section of the DC742B datasheet.
How does DC742B achieve simultaneous 50 Hz and 60 Hz rejection?
DC742B achieves simultaneous 50/60 Hz rejection through inherent delta-sigma modulation and decimation filter design optimized at specific output rates - guaranteed at 6.9 Hz output rate per the datasheet. This rejection is built into the modulator architecture and requires no user configuration or external filtering. The feature is validated across temperature and supply voltage ranges and is a core specification for DC742B in weight scale and industrial sensor applications.
What is the meaning of "No Latency ∆Σ" in DC742B?
"No Latency ∆Σ" means that the first conversion result after any channel, speed, or resolution change is fully accurate - no dummy or settling conversions are required. Unlike conventional delta-sigma ADCs, DC742B delivers valid data immediately upon reconfiguration, enabling real-time multiplexed acquisition without interpolation or dead time. This behavior is intrinsic to its proprietary modulator architecture and is confirmed in the "Description" and "Converter Operation" sections of the DC742B datasheet.
Can DC742B operate with a 3.3 V supply?
No, DC742B requires a 4.5 V to 5.5 V supply voltage (VCC). The Absolute Maximum Ratings and Electrical Characteristics tables specify VCC min = 4.5 V, and operation below this violates guaranteed specifications including offset error (<5 µV) and noise performance. Attempting 3.3 V operation risks modulator instability, increased INL, and failure to meet datasheet timing parameters. DC742B is not 3.3 V compatible.
DC742B Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Packaging:
- Box
- Product Status:
- Active
- Number of A/D Converters:
- 1
- Number of Bits:
- 24
- Sampling Rate (Per Second):
- 8k
- Data Interface:
- MICROWIRE™, Serial, SPI™
- Input Range:
- -
- Power (Typ) @ Conditions:
- -
- Utilized IC / Part:
- LTC2449
- Contents:
- Board(s)
DC742B FAQ
1.How can I place an order for DC742B through Aetrix?
Please submit a Request for Quotation (RFQ) for DC742B 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 DC742B reliable?
The price and inventory of DC742B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DC742B is usually 5 days.
3.What payment methods are accepted for DC742B?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DC742B transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DC742B?
DC742B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DC742B 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 DC742B?
For technical support, including DC742B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DC742B requirements.
6.How does Aetrix verify that DC742B is sourced from the original manufacturer or authorized distributors?
All DC742B 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 DC742B meets industry standards.
7.What is the process for return or replacement of DC742B?
All DC742B units undergo pre-shipment inspection (PSI). If there is an issue with DC742B, 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 DC742B part is unused and in its original packaging.
Return procedure for DC742B:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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