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Analog Devices Inc. LTC3728LEGN-1
- Part No.:
- LTC3728LEGN-1
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3728LEGN-1.pdf
- Description:
- IC POWER MANAGEMENT
- Quantity:
- Payment:
- Shipping:
Inventory:2,351
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Product details
Overview
LTC3728LEGN-1 from Analog Devices (formerly Linear Technology) is a dual-phase, 550kHz synchronous step-down controller driving all-N-channel MOSFET stages in high-efficiency DC/DC converters. It features 180° out-of-phase operation, OPTI-LOOP® compensation, ±1.5% output voltage accuracy, and operates from 4.5V to 28V input - optimized for notebook computers and telecom power systems.
For engineers reviewing the LTC3728LEGN-1 datasheet, LTC3728LEGN-1 pinout, LTC3728LEGN-1 application, or LTC3728LEGN-1 equivalent, key selection criteria include dual-channel phase interleaving, absence of overcurrent latchoff, 0.8V reference precision, PGOOD monitoring for dual outputs, and compatibility with 28-lead narrow SSOP layout constraints.
Technical Context
The LTC3728LEGN-1 implements constant-frequency current-mode control across two independent channels, each with dedicated ITH, VOSENSE, RUN/SS, and SENSE pins. Its phase-locked loop supports synchronization via PLLIN and frequency tuning via PLLFLTR (260–550kHz range), while FCB pin selects among Burst Mode®, constant-frequency, or forced continuous PWM operation.
It integrates a 5V internal LDO (INTVCC), a 3.3V linear regulator (10mA output), and dual gate drivers (TG/BG) with <100ns transition times. The device lacks overcurrent latchoff - distinguishing it from the standard LTC3728L - and uses differential current sensing with foldback limiting during short-circuit conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 28V (30V absolute max); supports wide battery chemistries and industrial rails without external regulation. |
| Switching Frequency | 260kHz to 550kHz (PLL-tunable); enables EMI reduction and optimal magnetics sizing for dual-phase interleaving. |
| Output Voltage Accuracy | ±1.5% over temperature; ensures stable core/supply rail compliance for microprocessors and FPGAs. |
| Reference Voltage | 0.800V ±12mV; low-drift precision reference compatible with future low-voltage logic families. |
| Power Good Threshold | ±7.5% per output; open-drain PGOOD asserts low if either channel deviates beyond tolerance - critical for system sequencing. |
| Shutdown Quiescent Current | 20μA; enables ultra-low-power standby in battery-operated portable instruments. |
| Max Duty Cycle | 99.4%; supports very low dropout operation (e.g., 5V-out from 5.2V-in) without external boost assist. |
Pinout & Package
The LTC3728LEGN-1 is packaged in a 28-lead narrow plastic SSOP (GN package), with exposed pad not present - distinct from the 32-lead QFN (UH) variant. Thermal resistance θJA = 95°C/W; operating junction temperature up to 125°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN/SS1, RUN/SS2 | Soft-start & enable control | Capacitor-based ramp controls inrush; pulling below 1.0V shuts down respective channel - enables staggered startup and fault isolation. |
| SENSE1+, SENSE1− / SENSE2+, SENSE2− | Differential current sense inputs | Rejects common-mode noise on high-side shunt; sets peak current limit via RSENSE and ITH voltage - essential for accurate foldback protection. |
| VOSENSE1, VOSENSE2 | Feedback error amplifier inputs | Accepts remote-sensed voltage from resistor divider; referenced to 0.8V internal bandgap - enables precise regulation despite PCB trace IR drop. |
| TG1, TG2 / BG1, BG2 | Top/bottom N-MOSFET gate drivers | High-current (3A peak), fast-transition (<100ns) drivers with bootstrap (BOOST) support - eliminates need for external level shifters. |
| PGOOD | Open-drain status indicator | Asserts low if either output deviates >±7.5%; requires external pull-up to ≤7V - used for system power-good sequencing and fault reporting. |
| PLLIN, PLLFLTR | Phase-lock interface | Allows synchronization to external clock (PLLIN) or DC voltage tuning (PLLFLTR); enables multi-rail coherence and EMI spreading. |
| FCB | Operating mode selector | Three-state control: <0.8V → forced PWM; 0.8–2.8V → Burst Mode®; >2.8V → constant-frequency - simplifies dynamic efficiency optimization. |
Key Features
| Feature | Design Value |
|---|---|
| 180° Dual-Phase Interleaving | Reduces RMS input current by ~39% vs. single-phase - cuts input capacitor size/cost and lowers conducted EMI without added filtering. |
| OPTI-LOOP® Compensation | Enables stable loop response across wide COUT and ESR variations (e.g., ceramic vs. polymer caps) - eliminates re-tuning for BOM changes. |
| No Overcurrent Latchoff | Prevents permanent shutdown during transient overload; instead uses foldback limiting - improves robustness in intermittent fault environments. |
| Integrated 3.3V Linear Regulator | Delivers 10mA at 3.35V ±50mV; powers auxiliary circuitry (e.g., ADC references, level shifters) without external LDO - saves board space and BOM count. |
| EXTVCC Switchover | Automatically bypasses internal 5V LDO when EXTVCC >4.7V - improves overall converter efficiency by eliminating LDO dropout loss in high-current designs. |
Applications
| Notebook Power Rails | Telecom Intermediate Bus |
|---|---|
|
Use Scenario: Generating tightly regulated 5V and 3.3V rails from a 12V or 19V adapter in ultraportable notebooks with strict thermal and ripple limits. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing two independent output stages with interleaved switching to minimize input ripple. Use Value: Achieves >90% efficiency at 5A per rail while reducing input capacitance by 40% and lowering EMI emissions to meet FCC Class B requirements. |
Use Scenario: Providing isolated 5V/3.3V supplies from a 48V intermediate bus in telecom line cards where reliability and transient response are critical. IC Role / Device Role / Timing Role: High-voltage-input dual controller with UVLO (3.5V) and overvoltage lockout (0.86V) ensuring safe operation during brownouts or surges. Use Value: Maintains ±1.5% output accuracy across –40°C to 85°C and delivers 10μs PGOOD assertion delay - enabling deterministic system boot sequencing. |
| Portable Test Instruments | Battery-Powered Digital Systems |
|
Use Scenario: Powering mixed-signal circuits (ADCs, DACs, microcontrollers) in handheld multimeters and oscilloscopes with minimal noise coupling. IC Role / Device Role / Timing Role: Dual-output controller using separate RUN/SS pins and PGOOD to coordinate power-up of analog and digital subsystems. Use Value: Burst Mode® operation extends battery life by reducing no-load IQ to 20μA while maintaining <20mV output ripple during active measurement cycles. |
Use Scenario: Supplying core logic and I/O rails in ruggedized PDAs and industrial handhelds powered by Li-ion or LiFePO₄ batteries. IC Role / Device Role / Timing Role: Wide-input (4.5V–28V), high-duty-cycle (99.4%) controller supporting operation down to near-dead battery voltage. Use Value: Enables full functionality at 3.6V battery voltage via 99% duty cycle - avoids premature shutdown and maximizes usable battery capacity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-phase synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3728LEUH-1 | Same die, 32-lead 5mm × 5mm QFN package; θJA = 34°C/W vs. 95°C/W for GN; no exposed pad connection required in SSOP. | Preferred for thermally constrained layouts needing lower junction-to-ambient resistance; unsuitable for legacy SSOP footprints. | Select LTC3728LEUH-1 when thermal performance outweighs board area or when using automated optical inspection (AOI) that benefits from QFN solder joint visibility. |
| LTC3728LIGN-1 | Identical electrical specs but rated for –40°C to 85°C with guaranteed performance over full range (vs. assured-by-design for LTC3728LEGN-1). | Required for extended-temperature deployments (e.g., automotive under-hood, outdoor telecom enclosures) where data sheet min/max specs must be production-guaranteed. | Choose LTC3728LIGN-1 for mission-critical industrial or automotive applications demanding full-range characterization and statistical process control validation. |
Compared with LTC3728LEGN-1, the LTC3728LEUH-1 offers superior thermal dissipation in compact layouts, while the LTC3728LIGN-1 provides production-validated operation across the full industrial temperature range - neither is pin-compatible due to differing package types and pin counts.
Availability
LTC3728LEGN-1 is available at Aetrix Electronics and suitable for notebook computers, telecom power systems, and portable instrumentation requiring stable component supply, long-term lifecycle support, and consistent parametric performance across manufacturing lots.
Supply support for LTC3728LEGN-1 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 its high-performance power management portfolio with rigorous qualification and long-term product commitments.
The LTC3728L-1 family was designed specifically for dual-output, high-efficiency, phase-interleaved DC/DC conversion in space-constrained portable and telecom equipment - emphasizing low-noise regulation, flexible mode control, and robust fault handling.
FAQ
What is the key functional difference between LTC3728LEGN-1 and LTC3728L?
The LTC3728LEGN-1 lacks the overcurrent latchoff feature present in the base LTC3728L. Instead, it implements foldback current limiting during short-circuit events - allowing automatic recovery after fault clearance without requiring a reset signal. This behavior is confirmed in the "FEATURES" section of the datasheet and applies exclusively to the -1 variant.
Does LTC3728LEGN-1 support synchronization to an external clock source?
Yes, the LTC3728LEGN-1 supports external synchronization via the PLLIN pin, which connects to an internal phase detector. When driven with a clean square wave, the device aligns the rising edge of TG1 to the rising edge of the PLLIN signal. The PLLFLTR pin allows DC voltage tuning of oscillator frequency from 260kHz to 550kHz - both functions are fully operational in the LTC3728LEGN-1.
What package type and footprint does LTC3728LEGN-1 use?
The LTC3728LEGN-1 uses a 28-lead narrow plastic SSOP (GN package), with pin pitch of 0.65mm and body dimensions of 10.2mm × 5.3mm. It is not pin-compatible with the 32-lead QFN (UH) variants like LTC3728LEUH-1. The ordering part number LTC3728LEGN-1#TRPBF confirms tape-and-reel packaging for automated assembly.
How does the FCB pin affect operating mode selection in LTC3728LEGN-1?
The FCB pin on the LTC3728LEGN-1 selects among three modes: pulling below 0.8V forces continuous PWM; holding between 0.8V and INTVCC–2V enables Burst Mode®; tying to INTVCC disables Burst Mode for constant-frequency operation. These thresholds and behaviors are specified in the Electrical Characteristics table and validated across temperature.
Is the 3.3VOUT regulator on LTC3728LEGN-1 internally current-limited?
Yes, the 3.3VOUT pin on the LTC3728LEGN-1 is rated for 10mA DC load with 50mA peak capability, and includes leakage current specification (≤50μA in shutdown). The regulator is internally protected against overcurrent and thermal overload - no external current-limiting components are required for typical auxiliary loads such as reference buffers or level translators.
LTC3728LEGN-1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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 ~ 28V
- 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
LTC3728LEGN-1 FAQ
1.How can I place an order for LTC3728LEGN-1 through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3728LEGN-1 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 LTC3728LEGN-1 reliable?
The price and inventory of LTC3728LEGN-1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3728LEGN-1 is usually 5 days.
3.What payment methods are accepted for LTC3728LEGN-1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3728LEGN-1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3728LEGN-1?
LTC3728LEGN-1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3728LEGN-1 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 LTC3728LEGN-1?
For technical support, including LTC3728LEGN-1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3728LEGN-1 requirements.
6.How does Aetrix verify that LTC3728LEGN-1 is sourced from the original manufacturer or authorized distributors?
All LTC3728LEGN-1 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 LTC3728LEGN-1 meets industry standards.
7.What is the process for return or replacement of LTC3728LEGN-1?
All LTC3728LEGN-1 units undergo pre-shipment inspection (PSI). If there is an issue with LTC3728LEGN-1, 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 LTC3728LEGN-1 part is unused and in its original packaging.
Return procedure for LTC3728LEGN-1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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