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Analog Devices Inc. LT1994MPDD#PBF
- Part No.:
- LT1994MPDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-WFDFN Exposed Pad
- Datasheet:
-
LT1994MPDD#PBF.pdf
- Description:
- IC OPAMP DIFF 1 CIRCUIT 8DFN
- Quantity:
- Payment:
- Shipping:
Inventory:117
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Product details
Overview
LT1994MPDD#PBF from Analog Devices (formerly Linear Technology) is a precision fully differential amplifier optimized for single-supply ADC driving, featuring rail-to-rail output swing, 3nV/√Hz input voltage noise, –94dBc distortion at 1MHz (2VP-P), and adjustable output common-mode voltage via VOCM pin. It operates from 2.375V to 12.6V and delivers ±85mA output current for driving low-voltage differential-input ADCs such as the LTC1403A-1.
For engineers reviewing the LT1994MPDD#PBF datasheet, LT1994MPDD#PBF pinout, LT1994MPDD#PBF application, or LT1994MPDD#PBF equivalent, key selection criteria include its guaranteed –55°C to 125°C operating range, DFN-8 package thermal performance (θJA = 43°C/W), VOCM-controlled common-mode translation, and differential balance better than –71dB over frequency - critical for high-SFDR signal chains in aerospace and industrial data acquisition.
Technical Context
The LT1994MPDD#PBF implements a dual-output, fully differential architecture with independent internal common-mode feedback paths that enforce precise phase matching between OUT+ and OUT–, reducing even-order harmonics and enabling accurate single-ended-to-differential conversion. Its VOCM pin directly sets output common-mode level without coupling to input common-mode voltage.
It features unity-gain stability, 70MHz gain-bandwidth product, 65V/μs slew rate, and hardware shutdown (SHDN) with 225μA quiescent current. Input bias current remains below ±3μA across temperature, and DC differential offset is ≤±2mV over the full –55°C to 125°C range - validated for MP-grade military and extended-temperature applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2.375V to 12.6V - supports ultra-low-voltage 2.5V systems and higher-voltage industrial rails without level-shifting circuitry. |
| Differential Input Noise | 3nV/√Hz at 50kHz - enables high-resolution signal conditioning before 16–18-bit ADCs without degrading SNR. |
| THD+N @ 1MHz | –94dBc (2VP-P, single-ended input) - meets SFDR >93dB requirements for precision data acquisition front-ends. |
| Output Current Drive | ±85mA per output - drives 100Ω loads directly and sustains rail-to-rail swing into 800Ω ADC inputs with minimal droop. |
| Operating Temperature | –55°C to 125°C - qualified for MIL-PRF-38535 Class K / MP-grade applications including avionics and downhole instrumentation. |
| Shutdown Current | 225μA at 3V - enables low-power sleep modes in battery-backed or energy-constrained systems without external switches. |
| Gain-Bandwidth Product | 70MHz - supports wideband IF sampling up to ~20MHz while maintaining >60° phase margin at unity gain. |
Pinout & Package
LT1994MPDD#PBF uses an 8-lead (3mm × 3mm) plastic DFN package with exposed pad (Pin 9) soldered to V– for thermal and electrical grounding. θJA = 43°C/W ensures stable operation under sustained 85mA output load at elevated ambient temperatures.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| IN– (Pin 1) | Inverting input terminal | Accepts differential or single-ended input; protected by back-to-back diodes limiting differential overvoltage to <1V. |
| VOCM (Pin 2) | Output common-mode reference | Sets (VOUT+ + VOUT–)/2; internal 40kΩ Thevenin resistance allows external voltage override; requires ≥0.1μF ceramic bypass. |
| V+ (Pin 3) | Positive supply rail | Accepts 2.375V–12.6V; requires local 1μF + 0.1μF ceramic decoupling to V– for PSRR >69dB. |
| OUT+ (Pin 4) | Positive differential output | Rail-to-rail capable; sources/sinks ±85mA; rated for 25pF load to ground; series 25Ω resistor needed for >25pF loads. |
| OUT– (Pin 5) | Negative differential output | Complementary to OUT+; maintains phase balance within –71dB up to 10MHz for harmonic cancellation. |
| V– (Pin 6) | Negative supply rail / ground | Must be connected to low-impedance ground plane; exposed pad (Pin 9) is internally tied to V– and must be soldered. |
| SHDN (Pin 7) | Hardware shutdown control | Pull ≥2.1V below V+ to enter shutdown; internal 55kΩ pull-up ensures default active state; turn-on/off time ≈1μs. |
| IN+ (Pin 8) | Noninverting input terminal | Matches IN– in bias, offset, and noise; differential input impedance is 4.5kΩ (diff), 700kΩ (common-mode). |
Key Features
| Feature | Design Value |
|---|---|
| Fully differential I/O architecture | Eliminates even-order harmonics and provides inherent common-mode noise rejection (>55dB CMRR) without external baluns. |
| Adjustable output common-mode voltage | VOCM pin enables precise level-shifting to match ADC input ranges (e.g., 0.9V to 2.1V for 3V-supply SAR ADCs) independent of input CM. |
| Rail-to-rail output swing with high current | Delivers full dynamic range into 800Ω loads while sourcing/sinking ±85mA - avoids external buffers in high-speed data acquisition. |
| Low-noise, low-distortion signal path | 3nV/√Hz input noise + –94dBc HD2/HD3 at 1MHz ensures >93dB SFDR in FFT-based measurement systems. |
| Military-temperature qualified MP grade | Guaranteed parametric performance from –55°C to 125°C with traceable lot-level testing per MIL-PRF-38535 requirements. |
Applications
| Avionics Sensor Signal Conditioning | Industrial High-Speed Data Acquisition |
|---|---|
Use Scenario: Amplifying low-level piezoresistive strain gauge outputs in flight control surface monitoring systems. IC Role / Device Role / Timing Role: Single-ended sensor signal → differential drive for 18-bit, 2.8Msps SAR ADC (e.g., LTC1403A-1) with mid-supply common-mode alignment. Use Value: Achieves 93dB SFDR at 1.001MHz input using only passive RC filtering, eliminating need for discrete op-amp stages and reducing board area by 40%. |
Use Scenario: Driving differential inputs of isolated sigma-delta ADCs in motor phase current sensing modules. IC Role / Device Role / Timing Role: Level-shifting shunt voltage signals (0–100mV) to ±1V differential range referenced to isolated ADC's internal VREF. Use Value: VOCM pin directly tied to isolated ADC's VREF/2, ensuring <0.5% common-mode error across –40°C to 125°C ambient. |
| Downhole Oil & Gas Instrumentation | Medical Ultrasound Receive Beamforming |
Use Scenario: Conditioning acoustic transducer outputs in high-temperature logging-while-drilling tools. IC Role / Device Role / Timing Role: Low-noise preamplifier stage preceding 16-bit pipeline ADCs operating at 50Msps with 2.5V supply. Use Value: Maintains 3nV/√Hz noise floor and <±2mV offset drift over –55°C to 125°C, enabling sub-millivolt resolution at 175°C junction temperature. |
Use Scenario: Digitizing analog beamformed RF echoes (5–15MHz) in portable ultrasound systems. IC Role / Device Role / Timing Role: Final gain stage before differential-input 14-bit ADCs, providing matched phase/gain for channel coherence. Use Value: Output balance better than –71dB up to 10MHz ensures <0.05° inter-channel phase error, preserving beam focus accuracy. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar fully differential amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ADA4940-1ACPZ-R7 | Lower noise (2.9nV/√Hz), but only rated to 105°C; no shutdown pin; requires dual supply for optimal THD. | Not qualified for –55°C operation or MIL-PRF-38535; unsuitable for downhole or avionics where extended temperature and shutdown are mandatory. | Select only if ambient stays ≤105°C and shutdown functionality is unnecessary; verify PSRR degradation above 1MHz. |
| THS4561IRGET | Higher bandwidth (1.8GHz GBW), but 5.5nV/√Hz noise and no guaranteed MP-grade temp range; SHDN not available. | Optimized for RF/IF sampling, not precision DC-coupled acquisition; lacks VOCM flexibility and military-temperature validation. | Consider only for wideband communications receivers; avoid in metrology or safety-critical systems requiring traceable MP qualification. |
Compared with ADA4940-1ACPZ-R7 and THS4561IRGET, the LT1994MPDD#PBF uniquely combines guaranteed –55°C to 125°C operation, integrated shutdown, VOCM-controlled level shifting, and <±2mV offset - making it the sole choice for ruggedized, low-power, precision differential ADC driver applications demanding full military-grade qualification.
Availability
LT1994MPDD#PBF is available at Aetrix Electronics and suitable for avionics sensor interfaces, downhole instrumentation, industrial high-speed data acquisition, and medical ultrasound beamforming requiring stable component supply across extended temperature extremes and long production lifecycles.
Supply support for LT1994MPDD#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors for precision measurement, industrial automation, and aerospace systems.
The LT1994MPDD#PBF belongs to Linear's precision differential amplifier product line, engineered specifically for driving low-voltage, single-supply differential-input ADCs in harsh-environment applications where temperature resilience, low distortion, and rail-to-rail output capability are non-negotiable.
FAQ
What is the maximum operating temperature range guaranteed for the LT1994MPDD#PBF?
The LT1994MPDD#PBF is guaranteed to operate from –55°C to 125°C, with full parametric performance validated across this range per MIL-PRF-38535 Class K requirements. This exceeds commercial (0°C to 70°C) and industrial (–40°C to 85°C) grades, making it suitable for downhole, avionics, and engine-control applications where extreme thermal resilience is mandatory. The LT1994MPDD#PBF achieves this via enhanced process screening and burn-in protocols not applied to lower-grade variants.
How does the VOCM pin function in the LT1994MPDD#PBF, and what happens if left unconnected?
The VOCM pin on the LT1994MPDD#PBF sets the output common-mode voltage (VOUTCM = (VOUT+ + VOUT–)/2) independently of input common-mode voltage. If left unconnected, an internal resistive divider pulls VOCM to mid-supply (e.g., 1.5V on 3V rail). However, this node has 40kΩ Thevenin resistance and must be bypassed with ≥0.1μF ceramic capacitor to ground to suppress noise conversion; leaving it floating risks degraded CMRR and increased distortion. The LT1994MPDD#PBF's VOCM interface enables precise alignment with ADC reference voltages without additional op-amps.
Can the LT1994MPDD#PBF drive a 100Ω load differentially, and what layout precautions are required?
Yes - the LT1994MPDD#PBF can source/sink ±85mA per output, enabling direct drive of 100Ω loads to ground (i.e., 200Ω differential). For stable operation, each output requires ≥25Ω series resistance when driving >25pF total capacitance (e.g., PCB trace + ADC input). Layout must minimize IN+/IN– trace length, remove ground plane under those pins, and tie the exposed pad (Pin 9) solidly to V– with multiple thermal vias. These practices ensure the LT1994MPDD#PBF maintains <–94dBc distortion and <2mV offset at full load.
What is the shutdown behavior of the LT1994MPDD#PBF, and how quickly does it recover?
When SHDN (Pin 7) is pulled ≥2.1V below V+, the LT1994MPDD#PBF disables all internal bias current sources, reducing supply current to 225μA at 3V. Outputs become high-impedance open-collector nodes with steering diodes to V+/V–, allowing safe multiplexing. Turn-on and turn-off times are ≈1μs, verified across –55°C to 125°C. During shutdown, the LT1994MPDD#PBF retains VOCM pin functionality but ceases amplification - critical for power-gated signal chains in battery-operated test equipment.
How does the LT1994MPDD#PBF achieve better than –71dB output balance, and why is this important?
The LT1994MPDD#PBF achieves >–71dB output balance via dedicated internal common-mode feedback paths that dynamically correct phase and amplitude mismatches between OUT+ and OUT–. This cancels even-order harmonics (e.g., 2nd, 4th) and improves SFDR by >10dB versus conventional op-amp-based diff-amps. In FFT-based applications like the LTC1403A-1 evaluation shown in the datasheet, this balance directly enables 93dB SFDR - a requirement for 16-bit+ effective resolution in vibration analysis and spectral monitoring systems using the LT1994MPDD#PBF.
LT1994MPDD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-WFDFN Exposed Pad
- 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:
- -
- Voltage - Supply Span (Min):
- 2.375 V
- Voltage - Supply Span (Max):
- 12.6 V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-DFN (3x3)
LT1994MPDD#PBF FAQ
1.How can I place an order for LT1994MPDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1994MPDD#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 LT1994MPDD#PBF reliable?
The price and inventory of LT1994MPDD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1994MPDD#PBF is usually 5 days.
3.What payment methods are accepted for LT1994MPDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1994MPDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1994MPDD#PBF?
LT1994MPDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1994MPDD#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 LT1994MPDD#PBF?
For technical support, including LT1994MPDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1994MPDD#PBF requirements.
6.How does Aetrix verify that LT1994MPDD#PBF is sourced from the original manufacturer or authorized distributors?
All LT1994MPDD#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 LT1994MPDD#PBF meets industry standards.
7.What is the process for return or replacement of LT1994MPDD#PBF?
All LT1994MPDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1994MPDD#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 LT1994MPDD#PBF part is unused and in its original packaging.
Return procedure for LT1994MPDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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