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Texas Instruments LMH6518SQX/NOPB
- Part No.:
- LMH6518SQX/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LMH6518SQX/NOPB.pdf
- Description:
- IC VARIABLE GAIN 1 CIRC 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,890
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Product details
Overview
LMH6518SQX/NOPB from Texas Instruments is a digitally controlled variable gain amplifier (DVGA) with 40 dB gain range in 2 dB steps, −3 dB bandwidth of 900 MHz across all gains, and differential main/auxiliary outputs for oscilloscope trigger and ADC driver applications. It features SPI interface, programmable bandwidth limiting (20–750 MHz), and overvoltage clamps enabling fast recovery in high-speed signal chains.
For engineers reviewing the LMH6518SQX/NOPB datasheet, LMH6518SQX/NOPB pinout, LMH6518SQX/NOPB application, or LMH6518SQX/NOPB equivalent, key selection criteria include its 8.5 mdB combined resolution with GSPS ADCs, ±0.1 dB gain matching between main and auxiliary paths, and dual common-mode control (VCM/VCM_AUX) for precision differential signal conditioning in RF/IF and medical instrumentation.
Technical Context
The LMH6518SQX/NOPB implements a two-stage architecture: a digitally selectable preamplifier (high-gain or low-gain mode) followed by a 10-step 2 dB ladder attenuator, enabling precise gain control from −1.16 dB to 38.8 dB. Its fully differential signal path supports dc-coupled operation with independent common-mode voltage control on both main and auxiliary outputs.
Bandwidth limiting is implemented via a shared filter network supporting seven selectable −3 dB points (20/100/200/350/650/750 MHz or full BW), and the auxiliary output replicates the main path's gain/phase response with <100 ps propagation delay mismatch and ±0.2 dB gain matching - critical for synchronized trigger and acquisition in high-bandwidth oscilloscopes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Gain Range | 40 dB (−1.16 dB to 38.8 dB), enabling full-scale input scaling from 6.8 mVPP to 920 mVPP at GSPS ADC inputs |
| Gain Step Size | 2 dB per step (±0.2 dB tolerance), with 8.5 mdB effective resolution when coordinated with ADC full-scale adjustment |
| −3 dB Bandwidth | 900 MHz at all gain settings, supporting wideband RF/IF signal processing up to 250 MHz with >−44 dBc HD2 |
| Rise/Fall Time | <460 ps / <450 ps, ensuring sub-nanosecond transient response for pulse-based test equipment |
| Input Noise Density | 0.98 nV/√Hz at maximum gain, optimizing SNR in low-amplitude signal amplification |
| Harmonic Distortion | −50 dBc HD2 / −53 dBc HD3 at 100 MHz, meeting spectral purity requirements in precision measurement systems |
| Power Consumption | 1.1 W (aux enabled) to 0.75 W (aux disabled), balancing performance and thermal management in dense PCB layouts |
Pinout & Package
LMH6518SQX/NOPB uses a 16-pin WQFN package (RGH), 4 mm × 4 mm, with exposed thermal pad electrically connected to pins 5 and 8 (GND).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| +OUT AUX (Pin 1) | Auxiliary positive output | Replicates main output for oscilloscope trigger circuitry; supports independent VCM_AUX biasing |
| −OUT AUX (Pin 2) | Auxiliary negative output | Differential complement to +OUT AUX; enables true differential trigger signal generation |
| VCC (Pins 3, 4) | Analog power supply | 5 V ±5% analog rail; dual pins reduce IR drop and improve PSRR in high-frequency operation |
| GND (Pins 5, 8) | Ground reference | Electrically tied to thermal pad; provides low-inductance return path for analog and digital sections |
| +IN (Pin 6) | Positive input | Differential input node with 150 kΩ || 1.5 pF impedance; accepts single-ended or differential drive |
| −IN (Pin 7) | Negative input | Complementary input node; CMVR supported from 1.9 V to 3.1 V with ≥40 dB CMRR |
| CS (Pin 9) | SPI chip select | Active-low enable for serial programming; disables SDIO I/O when deasserted to prevent crosstalk |
| SDIO (Pin 10) | SPI data I/O | Bidirectional 24-bit command/data port (8-bit cmd + 16-bit data); high-impedance when CS inactive |
| SCLK (Pin 11) | SPI clock | Up to 10 MHz synchronous clock; must be halted during idle to minimize digital noise coupling |
| VDD (Pin 12) | Digital power supply | 3.3 V ±5% digital rail; isolated from analog VCC to suppress supply noise injection into signal path |
| +OUT (Pin 15) | Main positive output | Differential output with 100 Ω nominal impedance; supports 800 mVPP full-scale swing at ≤−40 dBc THD |
| −OUT (Pin 14) | Main negative output | Complement to +OUT; matched rise/fall time and propagation delay (<100 ps mismatch) vs auxiliary path |
| VCM (Pin 13) | Main output CM control | Analog input setting main output common-mode voltage (1.2 V typical); enables level-shifting to match ADC input range |
| VCM_AUX (Pin 16) | Auxiliary output CM control | Independent bias input for auxiliary output; allows asynchronous trigger-level adjustment without affecting main path |
Key Features
| Feature | Design Value |
|---|---|
| Dual differential outputs with matched timing | Main and auxiliary outputs track within ±0.2 dB gain, ±100 ps propagation delay, and 5% rise-time matching - essential for correlated acquisition and trigger |
| Programmable bandwidth limiting | Seven user-selectable −3 dB points (20–750 MHz) applied identically to main and auxiliary paths, enabling flexible anti-aliasing and noise filtering |
| Overvoltage clamps with fast recovery | Clamps output excursions to safe levels and recover in <5 ns, preventing latch-up and preserving signal integrity after transient overload |
| SPI-compatible digital interface | 24-bit command/data protocol (8-bit opcode + 16-bit payload) with CS-controlled tri-state SDIO, minimizing interference in mixed-signal PCBs |
| Independent common-mode control | Separate VCM and VCM_AUX inputs allow simultaneous optimization of main-path ADC interface and auxiliary-path trigger threshold |
Applications
| Oscilloscope Programmable Gain Amplifier | Differential ADC Driver |
|---|---|
Use Scenario: High-bandwidth real-time oscilloscope front-end where input signal amplitude varies widely across measurement ranges. IC Role / Device Role / Timing Role: Digitally adjusts gain in 2 dB steps to maintain ADC input at 700 mVPP nominal while preserving 900 MHz bandwidth and sub-ns timing fidelity. Use Value: Enables automatic range switching without sacrificing rise time or introducing gain-dependent phase shift - critical for accurate waveform reconstruction. |
Use Scenario: Driving TI's GSPS ADCs (e.g., ADC12DJ3200) in radar or communications test equipment requiring full-scale flexibility. IC Role / Device Role / Timing Role: Serves as dc-coupled, differential driver with programmable VCM to match ADC input common-mode range and optimize SNR. Use Value: Combined 8.5 mdB resolution with ADC full-scale tuning allows precise signal scaling across 60+ dB dynamic range without analog recalibration. |
| RF/IF Signal Conditioning | Medical Ultrasound Receiver |
Use Scenario: IF stage in wideband spectrum analyzers or software-defined radios operating up to 250 MHz. IC Role / Device Role / Timing Role: Provides gain control and harmonic suppression (−50 dBc HD2 at 100 MHz) before digitization, with selectable bandwidth limiting to reject out-of-band noise. Use Value: Maintains linearity and low noise figure (3.8 dB at max gain) across gain settings, improving spurious-free dynamic range (SFDR) in crowded RF environments. |
Use Scenario: Time-gain compensation (TGC) amplifier in portable ultrasound beamformers requiring low-noise, high-linearity amplification of weak echo signals. IC Role / Device Role / Timing Role: Digitally adjusts gain per channel to compensate for acoustic attenuation with minimal added noise (0.98 nV/√Hz) and fast settling (<14 ns). Use Value: Supports high-resolution B-mode imaging by preserving signal fidelity across 40 dB gain sweep while enabling compact, low-power system integration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar digitally controlled variable gain amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ADL5330ACPZ-R7 | 50 Ω single-ended RF VGA (30 dB range, 2.5 GHz BW); no auxiliary output or VCM control | Optimized for 50 Ω RF systems (e.g., cellular infrastructure); lacks dc-coupling and differential ADC driving capability | Select when interfacing directly to 50 Ω mixers or filters; avoid for dc-coupled, differential ADC interfaces requiring common-mode control |
| MAX19707ETX+ | Integrated 12-bit ADC + DVGA (25 dB range, 1.2 GHz BW); fixed 2.5 V CM output | Single-chip solution for space-constrained receivers; no separate auxiliary output or programmable bandwidth filter | Choose for simplified BOM and layout in portable instruments; not suitable when independent trigger path or multi-bandwidth filtering is required |
Compared with ADL5330ACPZ-R7 and MAX19707ETX+, the LMH6518SQX/NOPB uniquely delivers matched dual differential outputs with independent VCM control, programmable bandwidth limiting, and SPI-configurable gain - making it the only option among the three that supports synchronized acquisition and trigger in high-fidelity oscilloscopes and modular test systems.
Availability
LMH6518SQX/NOPB is available at Aetrix Electronics and suitable for oscilloscope front-ends, GSPS ADC driver stages, and medical ultrasound TGC modules requiring stable component supply, long-term manufacturability, and guaranteed traceability.
Supply support for LMH6518SQX/NOPB 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
Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and high-performance signal chain solutions for industrial, automotive, and test & measurement markets.
The LMH6518SQX/NOPB belongs to TI's high-speed amplifier portfolio, designed specifically for wideband, digitally programmable gain control in precision instrumentation, where timing accuracy, distortion performance, and dual-output correlation are critical.
FAQ
What is the absolute maximum supply voltage rating for LMH6518SQX/NOPB?
The LMH6518SQX/NOPB has an absolute maximum analog supply voltage (VCC) of 5.5 V and digital supply voltage (VDD) of 3.6 V. Exceeding these ratings may cause permanent damage. Recommended operating conditions specify VCC = 5 V ±5% and VDD = 3.3 V ±5%. Operation outside recommended ranges compromises performance and reliability, and the LMH6518SQX/NOPB is not guaranteed to function correctly beyond these limits.
Does LMH6518SQX/NOPB support dc-coupled input and output operation?
Yes, the LMH6518SQX/NOPB supports fully dc-coupled signal paths on both input and output. Its differential inputs accept dc-coupled signals with common-mode voltage range of 1.9 V to 3.1 V, and both main and auxiliary differential outputs are dc-coupled with independently controllable common-mode voltages (VCM and VCM_AUX). This enables precise level-shifting for direct interfacing with dc-coupled ADCs or downstream stages.
How does the bandwidth limiting feature work on LMH6518SQX/NOPB?
The LMH6518SQX/NOPB implements a shared, digitally selectable low-pass filter network with seven −3 dB bandwidth options: 20 MHz, 100 MHz, 200 MHz, 350 MHz, 650 MHz, 750 MHz, or full 900 MHz bandwidth. The setting applies identically to both main and auxiliary outputs. Filter selection is programmed via SPI register bits, and passband tolerance is ±25% for higher bands and ±10% for 350/650/750 MHz when using low-gain preamp mode.
What is the purpose of the auxiliary output on LMH6518SQX/NOPB?
The auxiliary output (+OUT AUX/−OUT AUX) on LMH6518SQX/NOPB replicates the main output's gain, phase, and timing characteristics with <100 ps propagation delay mismatch and ±0.2 dB gain matching. It is intended primarily for oscilloscope trigger circuitry but can also serve as a secondary monitoring path. Independent VCM_AUX control allows setting a different common-mode voltage than the main output, enabling asynchronous trigger threshold adjustment without affecting acquisition path integrity.
Can LMH6518SQX/NOPB operate with a single 3.3 V supply?
No, the LMH6518SQX/NOPB requires dual supplies: 5 V ±5% for analog operation (VCC pins 3 and 4) and 3.3 V ±5% for digital logic (VDD pin 12). These rails are internally isolated. Using only a 3.3 V supply on VCC will result in severely degraded gain, bandwidth, and output swing - the LMH6518SQX/NOPB is not specified or characterized for single-supply operation, and its 900 MHz bandwidth depends on proper 5 V analog biasing.
LMH6518SQX/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Amplifier Type:
- Variable Gain
- Number of Circuits:
- 1
- Output Type:
- Differential
- Slew Rate:
- -
- Gain Bandwidth Product:
- -
- -3db Bandwidth:
- 900 MHz
- Current - Input Bias:
- 40 µA
- Voltage - Input Offset:
- -
- Current - Supply:
- 210mA
- Current - Output / Channel:
- -
- Voltage - Supply Span (Min):
- 4.75 V
- Voltage - Supply Span (Max):
- 5.25 V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-WQFN (4x4)
LMH6518SQX/NOPB FAQ
1.How can I place an order for LMH6518SQX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LMH6518SQX/NOPB 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 LMH6518SQX/NOPB reliable?
The price and inventory of LMH6518SQX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LMH6518SQX/NOPB is usually 5 days.
3.What payment methods are accepted for LMH6518SQX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LMH6518SQX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LMH6518SQX/NOPB?
LMH6518SQX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LMH6518SQX/NOPB 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 LMH6518SQX/NOPB?
For technical support, including LMH6518SQX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LMH6518SQX/NOPB requirements.
6.How does Aetrix verify that LMH6518SQX/NOPB is sourced from the original manufacturer or authorized distributors?
All LMH6518SQX/NOPB 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 LMH6518SQX/NOPB meets industry standards.
7.What is the process for return or replacement of LMH6518SQX/NOPB?
All LMH6518SQX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LMH6518SQX/NOPB, 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 LMH6518SQX/NOPB part is unused and in its original packaging.
Return procedure for LMH6518SQX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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