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Analog Devices Inc. LTC3728LIGN-1#PBF
- Part No.:
- LTC3728LIGN-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3728LIGN-1#PBF.pdf
- Description:
- IC REG CTRLR BUCK 28SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,505
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Product details
Overview
LTC3728LIGN-1#PBF from Analog Devices (formerly Linear Technology) is a dual, 180° out-of-phase, synchronous step-down controller driving all-N-channel MOSFET stages for high-efficiency DC/DC conversion. It operates at a phase-lockable constant frequency up to 550 kHz, features ±1.5% output voltage accuracy, 0.8 V reference, and power-good monitoring for both outputs. It is used in notebook computers and telecom systems requiring tightly regulated dual-rail supplies with minimized input ripple.
For engineers reviewing the LTC3728LIGN-1#PBF datasheet, LTC3728LIGN-1#PBF pinout, LTC3728LIGN-1#PBF application, or LTC3728LIGN-1#PBF equivalent, key selection criteria include dual-phase interleaving capability, absence of overcurrent latchoff, OPTI-LOOP® compensation for wide output capacitor/ESR tolerance, and support for Burst Mode®, constant-frequency, and forced continuous PWM operation via FCB pin control.
Technical Context
The LTC3728LIGN-1#PBF implements a current-mode, dual-channel architecture with independent error amplifiers (ITH1/ITH2), differential current sense inputs (SENSE1±/SENSE2±), and 180° phase offset between channels to reduce RMS input current and EMI. Its PLLIN/PLLFLTR interface enables external synchronization or DC voltage-controlled frequency tuning from 260 kHz to 550 kHz.
It integrates a 5 V internal LDO (INTVCC), a 3.3 V linear regulator (3.3VOUT), and dual gate drivers (TG1/BG1/TG2/BG2) with precise timing control (tON(MIN) = 100 ns, TG/BG delays ≤ 80 ns). The RUN/SS pins provide per-channel soft-start and shutdown, while PGOOD asserts open-drain low if either VOSENSE1 or VOSENSE2 deviates >±7.5% from setpoint.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Dual synchronous buck controller - drives external N-MOSFETs for two independent output rails. |
| Switching Frequency Range | 260 kHz to 550 kHz - adjustable via PLLFLTR voltage or external sync on PLLIN; supports phase-locking. |
| Output Voltage Accuracy | ±1.5% - guaranteed over temperature and line/load, enabling precision regulation for microprocessor core and I/O rails. |
| Reference Voltage | 0.800 V ±12 mV - stable, low-drift feedback reference compatible with future low-voltage processors. |
| Input Voltage Range | 4.5 V to 28 V - supports single-cell Li-ion through 24 V industrial rails; absolute max 30 V. |
| Power Good Threshold | ±7.5% window on VOSENSE - ensures system-level power sequencing integrity before asserting PGOOD high. |
| Shutdown Quiescent Current | 20 μA - enables ultra-low-power standby in battery-operated systems when both RUN/SS pins are pulled low. |
Pinout & Package
Package: 28-Lead Narrow Plastic SSOP (GN package), exposed pad not present (UH QFN variant has exposed pad; GN does not).
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| RUN/SS1, RUN/SS2 | Per-channel soft-start and enable input | Capacitor-to-ground sets ramp time; <1.0 V forces shutdown of respective channel; internal 1.2 μA current source enables controlled startup. |
| VOSENSE1, VOSENSE2 | Feedback input for error amplifier | Connects to resistor divider across output rail; regulates to 0.8 V reference with ±1.5% accuracy. |
| SENSE1+, SENSE1−, SENSE2+, SENSE2− | Differential current sense inputs | Measure voltage across RSENSE; trip threshold programmable up to 88 mV with foldback behavior under overload. |
| TG1, TG2, BG1, BG2 | High-current gate drivers | TG drives top N-MOSFET (floating, bootstrapped); BG drives bottom N-MOSFET (ground-referenced); rise/fall times <100 ns. |
| SW1, SW2 | Switch node connections | Interface to inductor and external Schottky diode or synchronous rectifier; voltage swings from GND to VIN. |
| PGOOD | Open-drain power-good indicator | Pulled low if either output is outside ±7.5%; requires external pull-up to ≤7 V; responds within 10 μs after fault clearance. |
| FCB | Forced continuous/burst mode select | Voltage-selectable: <0.8 V → forced PWM; 0.8–2.8 V → Burst Mode; >4.3 V → constant-frequency mode. |
| PLLIN, PLLFLTR | Phase-locked loop interface | PLLIN accepts external clock (50 kΩ internal termination); PLLFLTR sets oscillator frequency or receives phase detector output. |
| INTVCC | Internal 5 V LDO output | Powers control circuitry and gate drivers; bypassed with ≥4.7 μF tantalum; switchover to EXTVCC occurs at 4.7 V. |
| 3.3VOUT | Dedicated 3.3 V linear regulator | Supplies 10 mA DC / 50 mA peak; independent of main regulators; used for auxiliary bias or logic rails. |
Key Features
| Feature | Design Value |
|---|---|
| 180° Interleaved Dual-Phase Operation | Reduces RMS input current by ~39% vs. in-phase dual controllers, enabling smaller input capacitors and lower EMI without added magnetics. |
| OPTI-LOOP® Compensation | Allows stable loop response across wide range of output capacitor values (ceramic, polymer, electrolytic) and ESR (0.5 mΩ to 100 mΩ), simplifying design reuse. |
| No Overcurrent Latchoff | Distinguishes LTC3728LIGN-1#PBF from LTC3728L - enables automatic recovery from short-circuit events without manual reset or external circuitry. |
| Three-Mode Operating Selection (FCB) | Single-pin control of Burst Mode® (high efficiency at light load), constant-frequency (low noise), or forced continuous PWM (output sink capability). |
| Very Low Dropout Support | 99.4% maximum duty cycle and dropout detector allow operation with VIN as low as VOUT + 0.1 V, critical for battery end-of-life conditions. |
Applications
| Notebook Power Management | Telecom Intermediate Bus Conversion |
|---|---|
Use Scenario: Dual-rail CPU core (5 V) and I/O (3.3 V) supply in space-constrained notebook platforms with strict thermal and ripple budgets. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller providing interleaved switching, phase-aligned clock distribution, and coordinated soft-start sequencing. Use Value: 39% lower RMS input current reduces required input capacitance by >50%, cuts board area, and lowers conducted EMI to meet FCC Class B limits without added shielding. | Use Scenario: Converting 48 V intermediate bus to 5 V/3.3 V for line cards and baseband processing units in telecom infrastructure. IC Role / Device Role / Timing Role: High-input-voltage dual controller managing two independent loads with tight cross-regulation and fast transient response. Use Value: ±1.5% output accuracy and 0.8 V reference ensure compatibility with next-generation ASICs; 28 V max input rating covers 48 V bus transients with margin. |
| Battery-Powered Portable Instruments | Industrial DC Power Distribution |
Use Scenario: Portable test equipment powered by 2-cell Li-ion (6–8.4 V) requiring clean, efficient 5 V and 3.3 V rails for analog front-end and digital logic. IC Role / Device Role / Timing Role: Dual-channel controller with Burst Mode® operation to extend battery life and 3.3VOUT linear regulator for low-noise sensor bias. Use Value: 20 μA shutdown IQ preserves battery charge during sleep; Burst Mode® maintains >85% efficiency down to 10 mA load per rail. | Use Scenario: Distributed power architecture in factory automation PLCs where multiple 5 V/3.3 V point-of-load supplies must track and sequence reliably. IC Role / Device Role / Timing Role: Dual controller with independent RUN/SS pins enabling staggered startup and PGOOD monitoring for system-level fault reporting. Use Value: Open-drain PGOOD with ±7.5% window provides deterministic power-good assertion for FPGA configuration and microcontroller boot sequencing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3728LEGN-1#PBF | Identical electrical specs and pinout; differs only in lead-free finish marking (EGN vs IGN) and RoHS compliance documentation path. | No functional difference; suitable for same designs; IGN denotes industrial temp grade with identical –40°C to 85°C range. | Select LTC3728LIGN-1#PBF for standard industrial-grade sourcing; LTC3728LEGN-1#PBF is functionally interchangeable but may differ in traceability documentation. |
| LTC3728LIUH-1#PBF | Same functionality but in 32-lead 5 mm × 5 mm QFN (UH) package with exposed thermal pad; higher thermal performance (θJA = 34°C/W vs 95°C/W). | Requires PCB redesign due to different footprint, pad layout, and thermal via requirements; better suited for high-power-density or thermally constrained layouts. | Choose LTC3728LIUH-1#PBF only when thermal dissipation exceeds SSOP capability or board space permits QFN migration. |
Compared with LTC3728LEGN-1#PBF, LTC3728LIGN-1#PBF offers identical performance in the same SSOP package but with distinct industrial-grade qualification documentation; versus LTC3728LIUH-1#PBF, it trades superior thermal metrics for proven SSOP manufacturability and legacy footprint compatibility.
Availability
LTC3728LIGN-1#PBF is available at Aetrix Electronics and suitable for notebook power management, telecom intermediate bus conversion, and portable instrumentation requiring stable component supply with full industrial temperature support (–40°C to 85°C).
Supply support for LTC3728LIGN-1#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 power management semiconductors.
The LTC3728L family was designed specifically for high-efficiency, dual-output, interleaved synchronous buck conversion in portable and telecom applications where input ripple reduction and thermal efficiency are critical.
FAQ
What is the key functional difference between LTC3728LIGN-1#PBF and LTC3728L?
The LTC3728LIGN-1#PBF lacks the overcurrent latchoff feature present in the base LTC3728L. This means that under short-circuit conditions, LTC3728LIGN-1#PBF enters foldback current limiting and automatically recovers when the fault clears, whereas LTC3728L latches off and requires a RUN/SS reset. This makes LTC3728LIGN-1#PBF more suitable for self-recovering power systems where manual intervention is impractical.
Does LTC3728LIGN-1#PBF support external frequency synchronization?
Yes, LTC3728LIGN-1#PBF supports full external synchronization via the PLLIN pin, which accepts a CMOS/TTL clock signal. The internal phase-locked loop aligns the rising edge of TG1 to the rising edge of the PLLIN signal. When PLLIN is left unconnected, the internal 50 kΩ pull-down forces the oscillator to its minimum frequency (~260 kHz), and PLLFLTR can be used for DC voltage-based frequency tuning instead.
How does the FCB pin configure operating modes in LTC3728LIGN-1#PBF?
The FCB pin on LTC3728LIGN-1#PBF selects among three distinct operating modes: pulling FCB <0.8 V forces continuous PWM operation on both channels; holding FCB between 0.8 V and ~2.8 V enables Burst Mode® for highest light-load efficiency; tying FCB >4.3 V disables Burst Mode® and enforces constant-frequency discontinuous conduction mode. Each mode affects efficiency, ripple, and EMI profile distinctly.
What is the purpose of the 3.3VOUT pin on LTC3728LIGN-1#PBF?
The 3.3VOUT pin on LTC3728LIGN-1#PBF is an integrated linear regulator delivering a stable 3.3 V ±2% output capable of supplying up to 10 mA DC (50 mA peak). It operates independently of the main switching regulators and is commonly used to power auxiliary circuitry such as level shifters, sensors, or logic bias rails-reducing need for external LDOs and improving system integration.
Can LTC3728LIGN-1#PBF operate with input voltages below 4.5 V?
No, LTC3728LIGN-1#PBF has a specified minimum input voltage of 4.5 V per absolute maximum and electrical characteristics tables. Below this, undervoltage lockout (UVLO) activates at 3.5 V (typical), disabling operation. Attempting to operate below 4.5 V risks unstable regulation, failure to start, or undefined behavior-designs requiring sub-4.5 V input must use alternative controllers such as LTC3850 or LTC3851 series.
LTC3728LIGN-1#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 2
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 4.5V ~ 35V
- Frequency - Switching:
- 260kHz ~ 550kHz
- Duty Cycle (Max):
- 99.4%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Enable, Power Good, Soft Start
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SSOP
LTC3728LIGN-1#PBF FAQ
1.How can I place an order for LTC3728LIGN-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3728LIGN-1#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 LTC3728LIGN-1#PBF reliable?
The price and inventory of LTC3728LIGN-1#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3728LIGN-1#PBF is usually 5 days.
3.What payment methods are accepted for LTC3728LIGN-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3728LIGN-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3728LIGN-1#PBF?
LTC3728LIGN-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3728LIGN-1#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 LTC3728LIGN-1#PBF?
For technical support, including LTC3728LIGN-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3728LIGN-1#PBF requirements.
6.How does Aetrix verify that LTC3728LIGN-1#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3728LIGN-1#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 LTC3728LIGN-1#PBF meets industry standards.
7.What is the process for return or replacement of LTC3728LIGN-1#PBF?
All LTC3728LIGN-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3728LIGN-1#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 LTC3728LIGN-1#PBF part is unused and in its original packaging.
Return procedure for LTC3728LIGN-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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