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Analog Devices Inc. LTC3728LEGN-1#TRPBF
- Part No.:
- LTC3728LEGN-1#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3728LEGN-1#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 28SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,779
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Product details
Overview
LTC3728LEGN-1#TRPBF from Analog Devices (formerly Linear Technology) is a dual-phase, 180° out-of-phase, synchronous step-down controller driving two independent N-channel MOSFET stages for high-efficiency DC/DC conversion. It operates at a phase-lockable fixed frequency up to 550 kHz, features ±1.5% output voltage accuracy, 0.8 V reference, and power-good indication. It is used in notebook computers and telecom systems requiring tightly regulated dual-output rails (e.g., 5 V/3.3 V) with minimized input ripple.
For engineers reviewing the LTC3728LEGN-1#TRPBF datasheet, LTC3728LEGN-1#TRPBF pinout, LTC3728LEGN-1#TRPBF application, or LTC3728LEGN-1#TRPBF equivalent, key selection criteria include dual-phase interleaving capability, absence of overcurrent latchoff, OPTI-LOOP® compensation, 4.5 V–28 V input range, and support for Burst Mode®, constant-frequency, and forced continuous PWM operation.
Technical Context
The LTC3728LEGN-1#TRPBF implements a constant-frequency current-mode control architecture with two independent channels operating 180° out of phase. Each channel uses an error amplifier with ITH output, differential current sensing (SENSE±), and precision 0.8 V feedback reference to regulate output voltage. The absence of overcurrent latchoff distinguishes it from the LTC3728L.
Phase synchronization is achieved via PLLIN and PLLFLTR pins, enabling frequency locking from 260 kHz to 550 kHz. The FCB pin selects among Burst Mode®, constant-frequency discontinuous conduction mode, and forced continuous PWM - the latter enabling secondary winding regulation. OPTI-LOOP® compensation allows stable loop response across wide output capacitance and ESR ranges.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5 V to 28 V (30 V absolute max); supports all common battery chemistries and industrial DC supplies. |
| Output Voltage Accuracy | ±1.5% over temperature; ensures tight regulation for microprocessor core and I/O rail requirements. |
| Switching Frequency | 260 kHz to 550 kHz (phase-lockable); enables EMI reduction and optimized magnetics sizing. |
| Feedback Reference | 0.8 V ±1.5%; compatible with modern low-voltage microprocessors and FPGA I/O standards. |
| Power Good Threshold | ±7.5% of setpoint on both outputs; provides reliable system-level power sequencing and fault detection. |
| Shutdown Quiescent Current | 20 μA; minimizes battery drain in portable standby modes. |
| Duty Cycle Max | 99.4%; enables very low dropout operation near VIN ≈ VOUT, critical for battery end-of-life scenarios. |
Pinout & Package
Package: 28-Lead Narrow Plastic SSOP (GN), RoHS-compliant, –40°C to +85°C operating range. Exposed pad not present (UH QFN variant has exposed GND pad).
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| RUN/SS1, RUN/SS2 | Soft-start & enable control | Capacitor-to-ground sets ramp time; <1.0 V forces shutdown of respective channel. |
| VOSENSE1, VOSENSE2 | Feedback input | Connects to resistor divider; regulates output by comparing to internal 0.8 V reference. |
| SENSE1+, SENSE1− / SENSE2+, SENSE2− | Differential current sense inputs | Measure voltage across RSENSE to set peak inductor current limit per channel. |
| TG1, TG2 / BG1, BG2 | Top/bottom gate drivers | Drive external N-MOSFETs; TG swings referenced to SW node, BG swings 0 V to INTVCC. |
| PGOOD | Open-drain status indicator | Pulled low if either VOSENSE deviates >±7.5%; requires external pull-up to ≤7 V. |
| FCB | Mode selection input | Voltage <0.8 V forces continuous PWM; 0.8–2.8 V enables Burst Mode®; >2.8 V disables burst (constant freq). |
| PLLIN, PLLFLTR | Phase-lock interface | PLLIN accepts external sync signal; PLLFLTR sets oscillator frequency or receives phase detector output. |
Key Features
| Feature | Design Value |
|---|---|
| Dual 180° out-of-phase controllers | Reduces RMS input current by ~39% vs. in-phase dual controllers, lowering input capacitor cost and EMI. |
| OPTI-LOOP® compensation | Enables stable loop response across wide COUT/ESR variations without manual compensation redesign. |
| No overcurrent latchoff | Prevents lockout during transient overload; enables foldback current limiting instead for safe short-circuit recovery. |
| Three selectable operating modes | Burst Mode® (high efficiency at light load), constant-frequency (low noise), forced PWM (secondary regulation). |
| Integrated 3.3 V linear regulator | Supplies 10 mA (50 mA peak); powers auxiliary circuitry without external LDO. |
Applications
| High-Efficiency Notebook Power | Telecom Intermediate Bus Converter |
|---|---|
|
Use Scenario: Dual-output power supply for CPU core (5 V) and I/O (3.3 V) in space-constrained notebooks. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing interleaved switching, soft-start sequencing, and PGOOD coordination. Use Value: 180° phase shift cuts input RMS current by >35%, reducing ceramic input cap count and PCB area while maintaining <±1.5% regulation. |
Use Scenario: Intermediate bus converter in 48 V telecom systems stepping down to 12 V/5 V for downstream POL modules. IC Role / Device Role / Timing Role: High-input-voltage dual controller with 28 V max VIN rating and robust current sensing for reliable 10 A/channel operation. Use Value: Wide 4.5 V–28 V input range accommodates brownout conditions; foldback current limiting protects MOSFETs during hot-swap events. |
| Portable Instrument Dual Rail Supply | Battery-Powered Digital Signal Processor (DSP) Platform |
|
Use Scenario: Compact dual-rail supply for analog front-end (3.3 V) and digital logic (5 V) in handheld test equipment. IC Role / Device Role / Timing Role: Dual-channel controller with independent RUN/SS pins enabling staggered startup and independent fault shutdown. Use Value: 20 μA shutdown IQ extends battery life; integrated 3.3 V LDO eliminates need for discrete regulator in auxiliary circuits. |
Use Scenario: Power management for DSP-based edge AI devices powered by Li-ion (3.0–4.2 V/cell) or 12 V lead-acid batteries. IC Role / Device Role / Timing Role: Phase-locked dual controller synchronizing to system clock (via PLLIN) to minimize beat-frequency noise in sensitive ADC/DAC paths. Use Value: PLL synchronization reduces spectral spreading; 99.4% max duty cycle maintains regulation as battery discharges below 5 V. |
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#TRPBF | Same die, 32-lead 5 mm × 5 mm QFN package with exposed thermal pad; θJA = 34°C/W vs. 95°C/W for SSOP. | Better thermal performance in high-power-density designs; requires different PCB layout and reflow profile. | Select when thermal dissipation >1.2 W or board space permits smaller footprint with improved cooling. |
| LTC3728LIGN-1#TRPBF | Same GN package but rated for –40°C to +85°C industrial temp range; identical electrical specs and pinout. | No functional difference; intended for extended reliability validation in harsh environments. | Select when full industrial temperature qualification and traceability are required for production release. |
Compared with LTC3728LEGN-1#TRPBF, the QFN variant offers superior thermal resistance for higher ambient or power-dense layouts, while the I-grade variant provides certified industrial temperature compliance - neither changes functionality, pinout, or electrical behavior.
Availability
LTC3728LEGN-1#TRPBF is available at Aetrix Electronics and suitable for notebook computers, telecom intermediate bus converters, and portable instrumentation requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LTC3728LEGN-1#TRPBF 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 acquired Linear Technology in 2017 and maintains its high-performance power management portfolio with rigorous automotive and industrial qualification standards.
The LTC3728L family was designed for dual-output, high-efficiency DC/DC conversion in portable and telecom infrastructure where input ripple reduction, thermal efficiency, and precise multi-rail sequencing are critical.
FAQ
What is the key functional difference between LTC3728LEGN-1#TRPBF and LTC3728L?
The LTC3728LEGN-1#TRPBF lacks the overcurrent latchoff feature present in the base LTC3728L. Instead, it implements foldback current limiting during short-circuit conditions - allowing automatic recovery without manual reset. This behavior is confirmed in the device description and absolute maximum ratings section of the official datasheet, and applies identically to all variants bearing the "-1" suffix including LTC3728LEGN-1#TRPBF.
Does LTC3728LEGN-1#TRPBF support phase synchronization with an external clock?
Yes, LTC3728LEGN-1#TRPBF supports full phase synchronization via the PLLIN pin, which accepts an external TTL/CMOS clock signal. The internal phase-locked loop aligns the rising edge of TG1 to the rising edge of the PLLIN signal, and the PLLFLTR pin allows DC voltage tuning of oscillator frequency from 260 kHz to 550 kHz. This capability is documented in the Functional Diagram and OPERATION sections of the datasheet.
What are the supported operating modes of LTC3728LEGN-1#TRPBF and how are they selected?
LTC3728LEGN-1#TRPBF supports three modes via the FCB pin: Burst Mode® (FCB = 0.8–2.8 V), constant-frequency discontinuous conduction (FCB > 2.8 V), and forced continuous PWM (FCB < 0.8 V). These modes directly affect light-load efficiency, EMI profile, and ability to regulate secondary windings. Selection is voltage-based and does not require external logic - confirmed in the FEATURES and OPERATION sections.
Can LTC3728LEGN-1#TRPBF drive both high-side and low-side N-channel MOSFETs?
Yes, LTC3728LEGN-1#TRPBF integrates dedicated high-current gate drivers for both top-side (TG1/TG2) and bottom-side (BG1/BG2) N-channel MOSFETs. TG outputs are floating, referenced to SW nodes, and swing from (SW + INTVCC − 0.5 V) to SW; BG outputs swing from 0 V to INTVCC. This is explicitly stated in the PIN FUNCTIONS section and verified in the Functional Diagram.
What is the purpose of the 3.3VOUT pin on LTC3728LEGN-1#TRPBF?
The 3.3VOUT pin on LTC3728LEGN-1#TRPBF is an integrated linear regulator output delivering up to 10 mA DC (50 mA peak), intended for powering auxiliary circuitry such as level shifters, bias networks, or monitoring ICs. Its line/load regulation (0.05%/V and 0.5%) and shutdown leakage (<50 μA) are specified in the ELECTRICAL CHARACTERISTICS table, confirming its role as a self-contained auxiliary supply.
LTC3728LEGN-1#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- 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 ~ 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#TRPBF FAQ
1.How can I place an order for LTC3728LEGN-1#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3728LEGN-1#TRPBF 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#TRPBF reliable?
The price and inventory of LTC3728LEGN-1#TRPBF 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#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3728LEGN-1#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3728LEGN-1#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3728LEGN-1#TRPBF?
LTC3728LEGN-1#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3728LEGN-1#TRPBF 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#TRPBF?
For technical support, including LTC3728LEGN-1#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3728LEGN-1#TRPBF requirements.
6.How does Aetrix verify that LTC3728LEGN-1#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3728LEGN-1#TRPBF 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#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3728LEGN-1#TRPBF?
All LTC3728LEGN-1#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3728LEGN-1#TRPBF, 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#TRPBF part is unused and in its original packaging.
Return procedure for LTC3728LEGN-1#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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