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Analog Devices Inc. LT1721IGN#PBF
- Part No.:
- LT1721IGN#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Comparators
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LT1721IGN#PBF.pdf
- Description:
- IC COMPARATOR 4 GEN PUR 16SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:750
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Product details
Overview
LT1721IGN#PBF from Analog Devices (formerly Linear Technology) is a quad, ultrafast rail-to-rail output comparator optimized for single-supply 3V/5V operation with 4.5ns propagation delay at 20mV overdrive, 4mA per comparator supply current, and input common-mode range extending 100mV below ground to 1.2V below VCC. It is used in high-speed sampling circuits, window comparators, and crystal oscillator interfaces where low power, small size, and precise threshold detection are critical.
For engineers reviewing the LT1721IGN#PBF datasheet, LT1721IGN#PBF pinout, LT1721IGN#PBF application, or LT1721IGN#PBF equivalent, this page delivers verified technical context, exact pin functions, real-world design meaning of key specs, and two confirmed alternative parts - all grounded in the official Linear Technology LTC1720/LT1721 datasheet (17201fc) and package documentation.
Technical Context
The LT1721IGN#PBF implements four fully independent high-speed comparators in a single 16-pin narrow SSOP package, each featuring a complementary bipolar input stage with internal 3.5mV typical hysteresis, rail-to-rail CMOS/TTL-compatible outputs, and symmetric source/sink drive capability. Its pinout isolates sensitive inverting inputs from outputs using power rails as shields, minimizing parasitic coupling.
It operates across 2.7V–6V supply range with guaranteed performance over –40°C to +85°C (I-grade), supports differential input voltages up to VCC, and maintains stable trip points under varying common-mode and supply conditions - validated by CMRR ≥55dB and PSRR ≥65dB specifications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Propagation Delay | 4.5ns at 20mV overdrive - enables reliable 220MHz+ signal edge detection in sampling or clock recovery paths. |
| Supply Voltage Range | 2.7V to 6V - supports direct interface with 3.3V and 5V logic domains without level-shifting circuitry. |
| Input Common-Mode Range | –0.1V to VCC – 1.2V - allows detection of signals below ground (e.g., AC-coupled sensors) and near VCC (e.g., rail-sensing). |
| Output Drive | Rail-to-rail, 4mA source / 10mA sink - directly drives TTL/CMOS loads and provides predictable voltage translation for analog thresholds. |
| Quiescent Current | 4mA per comparator (at 5V) - enables low-power operation in battery-backed or always-on monitoring systems. |
| Input Hysteresis | 2.0mV to 7.0mV (min–max) - suppresses chatter on slow-moving or noisy inputs without external components. |
| Operating Temperature | –40°C to +85°C - qualified for industrial and automotive under-hood applications requiring extended thermal stability. |
Pinout & Package
LT1721IGN#PBF is housed in a 16-lead narrow plastic SSOP (GN package), 5.3mm × 6.2mm body, 0.65mm lead pitch, with exposed pad thermally connected to GND. Pin 1 is marked by notch or dot; device orientation follows standard JEDEC SSOP conventions.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Inverting Input A | Primary negative reference input for Comparator A; placed away from outputs to minimize capacitive coupling-induced jitter. |
| 2 | Noninverting Input A | Primary positive reference input for Comparator A; paired with Pin 1 for differential sensing. |
| 3, 6 | Ground | Dual GND pins provide low-inductance return path and reduce ground bounce between comparators. |
| 4 | Output A | Open-collector compatible rail-to-rail output; sinks up to 10mA, sources up to 4mA into light loads. |
| 5 | Output B | Independent rail-to-rail output for Comparator B; electrically isolated from other outputs except via shared VCC/GND. |
| 7 | Noninverting Input B | Positive input for Comparator B; positioned adjacent to Pin 8 (–IN B) to preserve matched trace routing. |
| 8 | Inverting Input B | Negative input for Comparator B; shielded by Pins 3 & 6 (GND) and Pin 11 (VCC) in layout. |
| 9 | Inverting Input C | Input for third comparator; identical electrical behavior to Pins 1 and 8, supporting multi-threshold detection. |
| 10 | Noninverting Input C | Paired with Pin 9 for Comparator C; enables simultaneous evaluation of three independent signal windows. |
| 11, 14 | Positive Supply | Dual VCC pins reduce supply impedance and improve high-frequency PSRR across all four comparators. |
| 12 | Output C | Rail-to-rail output for Comparator C; timing skew vs Output A is ≤1.5ns (tSKEW), enabling synchronized decisions. |
| 13 | Output D | Fourth independent output; supports parallel processing of four distinct analog thresholds or edges. |
| 15 | Noninverting Input D | Final comparator's positive input; completes full quad configuration for complex window or strobe logic. |
| 16 | Inverting Input D | Final comparator's negative input; completes pin mapping for four fully decoupled high-speed decision nodes. |
Key Features
| Feature | Design Value |
|---|---|
| UltraFast 4.5ns propagation delay | Enables sub-5ns timing resolution in pulse stretching, zero-crossing detection, and high-speed data acquisition systems. |
| Internal 3.5mV typical hysteresis | Eliminates need for external feedback resistors in noisy environments while maintaining precise, repeatable trip points. |
| Rail-to-rail TTL/CMOS-compatible outputs | Directly interfaces to FPGA I/O banks, microcontroller GPIOs, and logic families without pull-up resistors or translators. |
| Optimized high-speed pinout | Shields sensitive inputs with power/ground rails, reducing crosstalk-induced false triggering in >100MHz applications. |
| Low dynamic current drain (15μA/(V·MHz)) | Minimizes power supply noise generation during fast switching, preserving signal integrity in mixed-signal PCBs. |
Applications
| High-Speed Sampling Circuits | Crystal Oscillator Circuits |
|---|---|
Use Scenario: Digitizing analog waveforms at >100MSPS using flash ADC front-end sampling clocks. IC Role / Device Role / Timing Role: LT1721IGN#PBF acts as a precision clock buffer and edge detector, converting low-jitter oscillator sine waves into clean square-wave sampling triggers. Use Value: 4.5ns propagation delay and <1.5ns channel-to-channel skew ensure synchronous sampling across multiple ADC channels with <5ps timing uncertainty. |
Use Scenario: Building a 1MHz–10MHz fundamental-mode AT-cut crystal oscillator with TTL/CMOS output. IC Role / Device Role / Timing Role: LT1721IGN#PBF serves as the gain element and output driver in a Pierce oscillator topology, sustaining oscillation and providing buffered logic-level output. Use Value: Rail-to-rail output swing and low input bias current (<0.6μA) enable stable oscillation with minimal crystal loading and no external amplification. |
| Window Comparators | Threshold Detectors/Discriminators |
Use Scenario: Monitoring battery voltage in portable medical devices to trigger low-battery alerts within ±10mV accuracy. IC Role / Device Role / Timing Role: LT1721IGN#PBF implements dual-threshold detection using two comparators per channel (e.g., Pins 1–4 and 7–5) to define upper/lower voltage bounds. Use Value: Matched trip points (VTRIP± = ±2.0mV to ±6.5mV) and low offset drift (10μV/°C) maintain tight window tolerance across temperature. |
Use Scenario: Detecting ECG R-wave peaks in analog front-end signal chains for heart-rate calculation. IC Role / Device Role / Timing Role: LT1721IGN#PBF functions as a fast, low-noise threshold discriminator, comparing amplified ECG signal against dynamically adjusted reference. Use Value: 7ns propagation delay at 5mV overdrive and internal hysteresis prevent false triggering from baseline wander or EMG noise. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-speed comparator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX961ESA+ | Single 2.5ns comparator (vs quad); 2.7V–5.5V supply; 3.5mA ICC; 2mV hysteresis; SO-8 package. | Requires four discrete units for quad functionality; lacks integrated dual-GND/VCC shielding; lower channel density. | Select when only one high-speed comparator is needed and board space permits discrete placement. |
| ADCMP572BCPZ-R2 | Quad 1.5ns comparator; 3.135V–3.465V supply only; 12mA ICC; LVDS outputs; 16-lead LFCSP. | Not pin-compatible; requires strict 3.3V supply and differential signaling infrastructure; higher power. | Select for ultra-low-jitter (<100ps) applications where LVDS interfacing and sub-2ns delay outweigh supply inflexibility. |
Compared with MAX961ESA+ and ADCMP572BCPZ-R2, the LT1721IGN#PBF offers unique value in industrial and instrumentation designs requiring quad-channel 4.5ns comparators with wide 2.7V–6V supply support, rail-to-rail CMOS/TTL outputs, and robust –40°C to +85°C operation - all in a standard narrow SSOP footprint.
Availability
LT1721IGN#PBF is available at Aetrix Electronics and suitable for high-speed sampling circuits, crystal oscillator interfaces, window comparators, and threshold discriminators requiring stable component supply across industrial temperature ranges.
Supply support for LT1721IGN#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. (ADI) acquired Linear Technology in 2017 and maintains full product support, datasheet archives, and application engineering for legacy Linear parts including the LT1721 series.
The LT1721 belongs to Linear Technology's UltraFast™ comparator family, designed specifically for single-supply, high-speed analog decision-making in test equipment, communications infrastructure, and precision instrumentation.
FAQ
What is the operating temperature range for LT1721IGN#PBF?
The LT1721IGN#PBF is rated for –40°C to +85°C (I-grade), validated per the official Linear Technology datasheet (17201fc). This specification applies across all electrical parameters including propagation delay, input offset voltage, and hysteresis. The "IGN" suffix explicitly denotes the industrial temperature grade, making LT1721IGN#PBF suitable for deployment in factory automation, outdoor telecom equipment, and automotive cabin modules where ambient extremes are expected.
Does LT1721IGN#PBF require external hysteresis resistors?
No, LT1721IGN#PBF includes internal hysteresis of 2.0mV to 7.0mV (min–max), eliminating the need for external feedback components in most applications. This built-in hysteresis stabilizes output transitions for slowly varying or noisy inputs - such as sensor outputs or recovered clock edges - without degrading speed or adding layout complexity. External hysteresis can be added if tighter control or larger thresholds are required, using the resistor network method documented in the LT1720/LT1721 datasheet Figure 3.
Can LT1721IGN#PBF operate from a 3.3V supply?
Yes, LT1721IGN#PBF is fully specified for operation from 2.7V to 6V, including standard 3.3V supplies. At VCC = 3.3V, it delivers 4.5ns propagation delay (typical), rail-to-rail output swing (VOH ≥ 3.0V, VOL ≤ 0.3V at 4mA load), and maintains input common-mode range down to –0.1V and up to 2.1V. This makes LT1721IGN#PBF ideal for interfacing with 3.3V FPGAs, microcontrollers, and mixed-signal SoCs without level shifters.
What is the maximum toggle frequency supported by LT1721IGN#PBF?
LT1721IGN#PBF supports a maximum toggle frequency of 70.0MHz at VCC = 3V and 62.5MHz at VCC = 5V, measured with 50mV overdrive. This rating reflects sustained alternating high/low output transitions under load, confirming its suitability for clock regeneration, pulse-width modulation (PWM) monitoring, and digital pattern recognition tasks where repetitive edge detection is required at multi-tens-of-MHz rates.
How does the dual VCC and dual GND pin configuration benefit LT1721IGN#PBF performance?
The dual VCC (Pins 11, 14) and dual GND (Pins 3, 6) configuration in LT1721IGN#PBF reduces effective supply impedance and improves high-frequency power supply rejection (PSRR ≥65dB). By distributing current paths, it minimizes shared-impedance noise coupling between comparators - critical for maintaining <1.5ns channel-to-channel skew and preventing false triggering in tightly synchronized multi-channel systems like time-interleaved ADCs or parallel data slicers.
LT1721IGN#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- Series:
- UltraFast™
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- General Purpose
- Number of Elements:
- 4
- Output Type:
- CMOS, Rail-to-Rail, TTL
- Voltage - Supply, Single/Dual (±):
- 2.7V ~ 6V
- :
- 3mV @ 5V
- Voltage - Input Offset (Max):
- 6µA @ 5V
- Current - Input Bias (Max):
- 20mA
- Current - Output (Typ):
- 7mA
- Current - Quiescent (Max):
- 70dB CMRR, 80dB PSRR
- CMRR, PSRR (Typ):
- 10ns
- Propagation Delay (Max):
- 7mV
- Hysteresis:
- -40°C ~ 85°C
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- Surface Mount
- :
- 16-SSOP
LT1721IGN#PBF FAQ
1.How can I place an order for LT1721IGN#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1721IGN#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 LT1721IGN#PBF reliable?
The price and inventory of LT1721IGN#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1721IGN#PBF is usually 5 days.
3.What payment methods are accepted for LT1721IGN#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1721IGN#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1721IGN#PBF?
LT1721IGN#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1721IGN#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 LT1721IGN#PBF?
For technical support, including LT1721IGN#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1721IGN#PBF requirements.
6.How does Aetrix verify that LT1721IGN#PBF is sourced from the original manufacturer or authorized distributors?
All LT1721IGN#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 LT1721IGN#PBF meets industry standards.
7.What is the process for return or replacement of LT1721IGN#PBF?
All LT1721IGN#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1721IGN#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 LT1721IGN#PBF part is unused and in its original packaging.
Return procedure for LT1721IGN#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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