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Analog Devices Inc. LT1994CMS8#PBF
- Part No.:
- LT1994CMS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LT1994CMS8#PBF.pdf
- Description:
- IC OPAMP DIFF 1 CIRCUIT 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,757
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Product details
Overview
LT1994CMS8#PBF from Analog Devices (formerly Linear Technology) is a fully differential input/output amplifier optimized for single-supply ADC driving, featuring rail-to-rail output swing, adjustable output common mode voltage via VOCM pin, 3nV/√Hz input voltage noise, –94dBc distortion at 1MHz (2VP-P), and 70MHz gain-bandwidth. It enables precise single-ended-to-differential conversion in low-voltage data acquisition systems.
For engineers reviewing the LT1994CMS8#PBF datasheet, LT1994CMS8#PBF pinout, LT1994CMS8#PBF application, or LT1994CMS8#PBF equivalent, key selection criteria include VOCM-adjustable common mode translation, ±85mA output drive capability, shutdown current of 225μA, differential balance better than –71dB, and MSOP-8 package compatibility with space-constrained signal chains.
Technical Context
The LT1994CMS8#PBF employs a dual-output, fully differential architecture with independent internal common-mode feedback to enforce phase matching between OUT+ and OUT–, reducing even-order harmonics. Its VOCM pin directly sets output common-mode level without dependence on input common-mode voltage.
It operates from 2.375V to 12.6V supply, maintains unity-gain stability, and delivers 65V/μs slew rate with 120ns settling time (0.01%). Input bias current is ±3μA max (C-grade), and differential offset voltage is ±2mV max over 0°C to 70°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Gain-Bandwidth Product | 70MHz - supports high-fidelity amplification up to ~10MHz closed-loop bandwidth with moderate gain. |
| Slew Rate | 65V/μs - enables clean 2VP-P, 1MHz sine wave reproduction with <–94dBc THD. | Differential Input Noise | 3nV/√Hz - preserves SNR in precision sensor front-ends and low-level analog signal conditioning. |
| Output Drive Current | ±85mA - drives 100Ω loads directly, supporting fast settling into ADC input networks with minimal external buffering. |
| Supply Current (Active) | 13.3mA - balances performance and power efficiency for battery-sensitive or thermally constrained designs. |
| Shutdown Current | 225μA - reduces system standby power while retaining fast 1μs wake-up for duty-cycled signal acquisition. |
| Input Offset Voltage | ±2mV max - ensures DC accuracy in single-ended-to-differential conversion without post-amplifier trimming. |
Pinout & Package
LT1994CMS8#PBF is housed in an 8-lead plastic MSOP package (3mm × 3mm footprint, 0.65mm pitch), with exposed pad connected to V– for thermal and electrical grounding.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (IN–) | Inverting input | Accepts differential or single-ended input; requires matched layout to IN+ to preserve CMRR >55dB. |
| 2 (VOCM) | Output common-mode reference | Sets average of OUT+ and OUT–; internal 40kΩ Thevenin resistance; must be bypassed with ≥0.1μF ceramic capacitor. |
| 3 (V+) | Positive supply | Supports 2.375V–12.6V operation; requires local 1μF + 0.1μF ceramic decoupling to V–. |
| 4 (OUT+) | Positive differential output | Rail-to-rail capable; sources/sinks up to 85mA; limited to 25pF load unless series-resistor isolated. |
| 5 (OUT–) | Negative differential output | Complementary to OUT+; balanced phase ensures <–71dB output imbalance for harmonic cancellation. |
| 6 (V–) | Negative supply / ground | Reference for single-supply operation; exposed pad must be soldered to this node for thermal and noise integrity. |
| 7 (SHDN) | Shutdown control | Logic-high (≥V+–0.6V) enables operation; pulled ≥2.1V below V+ disables amplifier and reduces ICC to 225μA. |
| 8 (IN+) | Non-inverting input | Paired with IN–; input resistance 700kΩ (common-mode), 4.5kΩ (differential); protected by back-to-back diodes. |
Key Features
| Feature | Design Value |
|---|---|
| Fully differential I/O architecture | Enables true differential signaling with inherent common-mode noise rejection and even-harmonic cancellation. |
| VOCM-adjustable output common mode | Allows precise alignment of differential output midpoint to ADC's optimal input common-mode range (e.g., 1.5V for 3V ADCs). |
| Rail-to-rail output swing | Maximizes dynamic range in low-voltage systems (e.g., 2.375V supply), delivering full-scale differential signals without clipping. |
| Low 3nV/√Hz input voltage noise | Preserves signal integrity in high-resolution (≥16-bit) data acquisition where thermal and amplifier noise dominate SNR. |
| Hardware shutdown with 1μs transition | Supports power-gated signal chains in portable or energy-harvesting applications without sacrificing responsiveness. |
Applications
| Instrumentation Signal Conditioning | High-Speed Data Acquisition Front-End |
|---|---|
Use Scenario: Amplifying low-level bridge sensor outputs before digitization in portable multimeters or strain gauge systems. IC Role / Device Role / Timing Role: Single-ended-to-differential converter with programmable VOCM, providing level-shifted, noise-immune drive to SAR ADCs. Use Value: 3nV/√Hz noise floor and ±2mV offset ensure sub-LSB error in 16-bit measurements; rail-to-rail swing maximizes utilization of ADC input range. | Use Scenario: Driving LTC1403A-1 or similar 12-bit, 2.8Msps differential-input ADCs in oscilloscope or spectrum analyzer channels. IC Role / Device Role / Timing Role: High-fidelity differential line driver with 65V/μs slew rate and 120ns settling, enabling accurate capture of transient-rich waveforms. Use Value: –94dBc distortion at 1MHz and <–71dB output balance maintain SFDR >93dB, critical for FFT-based spectral analysis. |
| Medical ECG/EEG Analog Front-End | Industrial Process Monitoring Interface |
Use Scenario: Conditioning biopotential signals (e.g., ±5mV ECG) with high CMRR and low noise prior to isolation and digitization. IC Role / Device Role / Timing Role: Differential amplifier with VOCM set to mid-supply, rejecting power supply ripple and electrode half-cell offsets. Use Value: PSRR >69dB and CMRR >55dB suppress 50/60Hz interference; shutdown mode reduces idle power in battery-powered monitors. | Use Scenario: Interfacing 4–20mA loop receivers or RTD bridges to industrial PLC ADC modules operating from 3.3V supplies. IC Role / Device Role / Timing Role: Level-shifting driver translating ground-referenced transducer outputs to VOCM-aligned differential inputs compliant with ISA-100.11a or HART ADC requirements. Use Value: Adjustable VOCM (V–+1.1V to V+–0.8V) ensures compatibility across diverse ADC families; ±85mA drive handles long trace capacitance. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar differential amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ADA4940-1ACPZ-R7 | Lower noise (2.9nV/√Hz), higher GBW (600MHz), but 20mA quiescent current vs. 13.3mA; no hardware shutdown pin. | Better for wideband RF/IF applications; less suitable for low-power portable instrumentation due to higher IQ. | Choose ADA4940-1 when bandwidth >100MHz is required and power budget allows >2× IQ. |
| THS4561IRGET | Higher output current (±120mA), lower distortion (–105dBc @1MHz), but 18mA IQ; VOCM range narrower (V–+0.5V to V+–0.5V). | Preferred for driving heavy capacitive loads or ultra-low-distortion audio ADCs; less flexible VOCM adjustment for mid-supply ADCs. | Choose THS4561 when driving >50pF loads or requiring <–100dBc HD2/HD3; verify VOCM compatibility with target ADC. |
Compared with ADA4940-1 and THS4561, the LT1994CMS8#PBF offers the best trade-off of ultra-low noise, low power, integrated shutdown, and wide VOCM adjustability-making it uniquely suited for portable, battery-operated, precision data acquisition where supply headroom and standby power are constrained.
Availability
LT1994CMS8#PBF is available at Aetrix Electronics and suitable for instrumentation signal conditioning, high-speed data acquisition front-ends, medical ECG/EEG analog front-ends, and industrial process monitoring interfaces requiring stable component supply and guaranteed 0°C to 70°C performance.
Supply support for LT1994CMS8#PBF 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 acquired Linear Technology in 2017 and maintains its legacy of high-performance analog ICs for precision signal processing.
The LT1994CMS8#PBF belongs to Linear's precision differential amplifier product line, designed specifically to solve single-supply ADC interface challenges-including common-mode level shifting, noise-sensitive signal conditioning, and rail-to-rail drive capability in compact packages.
FAQ
What is the maximum supply voltage rating for the LT1994CMS8#PBF?
The LT1994CMS8#PBF has an absolute maximum total supply voltage (V+ to V–) of 12.6V. Operation beyond this risks permanent damage. For reliable long-term use, the recommended supply range is 2.375V to 12.6V, with full specified performance validated from 0°C to 70°C for the C-grade part. The LT1994CMS8#PBF maintains rail-to-rail output swing and low distortion across this entire voltage range.
How does the VOCM pin function in the LT1994CMS8#PBF, and what happens if left unconnected?
The VOCM pin on the LT1994CMS8#PBF sets the average voltage of the differential outputs (VOUTCM = (VOUT+ + VOUT–)/2). If left unconnected, an internal resistive divider pulls it to mid-supply (V+/2), establishing default output common-mode level. However, this node has ~40kΩ Thevenin resistance and is highly sensitive to noise; leaving it floating degrades common-mode rejection and increases distortion. The LT1994CMS8#PBF datasheet mandates bypassing VOCM with ≥0.1μF ceramic capacitor to a low-impedance ground plane.
Can the LT1994CMS8#PBF drive a 50Ω load differentially, and what layout precautions are needed?
The LT1994CMS8#PBF is rated to drive 100Ω loads per output (i.e., 200Ω differentially) with full performance. Driving 50Ω differentially (25Ω per output) exceeds its ±85mA short-circuit current limit and risks thermal overload or distortion increase. To interface with 50Ω systems, use series 25Ω resistors at each output (OUT+ and OUT–) to isolate capacitive loading and limit current. Keep PCB traces short, avoid ground plane cuts near IN+/IN–, and place 0.1μF VOCM bypass capacitor within 2mm of the pin-critical for maintaining LT1994CMS8#PBF's –71dB output balance.
What is the typical shutdown behavior of the LT1994CMS8#PBF, and how does it affect system-level power sequencing?
When the SHDN pin of the LT1994CMS8#PBF is pulled ≥2.1V below V+, the device enters shutdown, reducing supply current to 225μA. In this state, OUT+ and OUT– become high-impedance open collectors with steering diodes to the rails-capable of sinking small transients but not sourcing current. Turn-on/off time is ~1μs. For robust power sequencing, ensure SHDN is held high (or open, relying on internal pull-up) before V+ ramps, and avoid floating SHDN during brown-out conditions, as leakage >1μA may inadvertently trigger shutdown. This behavior makes LT1994CMS8#PBF suitable for microcontroller-controlled power gating.
Does the LT1994CMS8#PBF require external gain-setting resistors, and how does resistor mismatch impact performance?
Yes-the LT1994CMS8#PBF is a fixed-gain differential amplifier requiring external feedback resistors (RF) and input resistors (RI) to set closed-loop gain. Mismatch between RI1/RI2 or RF1/RF2 causes common-mode-to-differential conversion, degrading effective CMRR. Using 1% resistors yields ~28dB rejection; 0.1% resistors improve this to ~48dB. Layout symmetry-equal trace length, width, and proximity to ground-is equally critical. The LT1994CMS8#PBF's internal common-mode feedback cannot compensate for external resistor or layout asymmetry, so matching directly determines achievable THD and SFDR in final application.
LT1994CMS8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Amplifier Type:
- Differential
- Number of Circuits:
- 1
- Output Type:
- Rail-to-Rail
- Slew Rate:
- 65V/µs
- Gain Bandwidth Product:
- 70 MHz
- -3db Bandwidth:
- -
- Current - Input Bias:
- 18 µA
- Voltage - Input Offset:
- 3 mV
- Current - Supply:
- 14.8mA
- Current - Output / Channel:
- 85 mA
- Voltage - Supply Span (Min):
- 2.375 V
- Voltage - Supply Span (Max):
- 12.6 V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-MSOP
LT1994CMS8#PBF FAQ
1.How can I place an order for LT1994CMS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1994CMS8#PBF 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 LT1994CMS8#PBF reliable?
The price and inventory of LT1994CMS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1994CMS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1994CMS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1994CMS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1994CMS8#PBF?
LT1994CMS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1994CMS8#PBF 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 LT1994CMS8#PBF?
For technical support, including LT1994CMS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1994CMS8#PBF requirements.
6.How does Aetrix verify that LT1994CMS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1994CMS8#PBF 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 LT1994CMS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1994CMS8#PBF?
All LT1994CMS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1994CMS8#PBF, 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 LT1994CMS8#PBF part is unused and in its original packaging.
Return procedure for LT1994CMS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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