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Analog Devices Inc. LTC3728LEGN#TRPBF
- Part No.:
- LTC3728LEGN#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3728LEGN#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 28SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,277
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Product details
Overview
LTC3728LEGN#TRPBF from Analog Devices (formerly Linear Technology) is a dual-phase, synchronous step-down switching regulator controller driving two independent N-channel MOSFET stages in 180° out-of-phase operation. It delivers up to 5A per channel, supports 4.5V–28V input, features 0.8V ±1% reference accuracy, and operates at phase-lockable frequencies from 250kHz to 550kHz. It is used in high-efficiency dual-output power supplies for notebook computers and telecom systems.
For engineers reviewing the LTC3728LEGN#TRPBF datasheet, LTC3728LEGN#TRPBF pinout, LTC3728LEGN#TRPBF application, or LTC3728LEGN#TRPBF equivalent, key selection considerations include its dual-channel current-mode control architecture, OPTI-LOOP compensation for wide output capacitance tolerance, integrated 3.3V LDO, PGOOD monitoring, and FCB-selectable operating modes (Burst Mode, constant-frequency, forced continuous).
Technical Context
The LTC3728LEGN#TRPBF implements a constant-frequency, peak-current-mode control architecture with independent error amplifiers (ITH1/ITH2), differential current sensing (SENSE1±/SENSE2±), and dual 180°-phased PWM generators synchronized via PLLIN. Its OPTI-LOOP compensation allows stable loop response across diverse COUT/ESR combinations without external component changes.
It integrates dual gate drivers (TG1/BG1 and TG2/BG2) with 55ns rise/fall times, a precision 0.8V reference with ±1% tolerance over –40°C to +85°C, and protection features including output overvoltage latch (VOSENSE > 0.86V), foldback current limiting, and RUN/SS-based short-circuit shutdown with defeat option.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 28V - supports all common battery chemistries and industrial DC rails; absolute max 30V. |
| Output Voltage Reference | 0.800V ±1% - enables accurate regulation of 1.2V, 1.5V, 1.8V, 3.3V, and 5V outputs using standard resistor dividers. |
| Switching Frequency Range | 250kHz to 550kHz - adjustable via PLLFLTR voltage or external sync on PLLIN; reduces EMI and enables compact magnetics. |
| Phase Configuration | 180° dual-phase - cuts input ripple current by ~70%, allowing smaller input capacitors and lower noise in shared input bus designs. |
| Operating Temperature | –40°C to +85°C - qualified for industrial and extended commercial environments; no derating required up to 85°C ambient. |
| Shutdown Quiescent Current | 20µA - enables ultra-low-power system standby with minimal battery drain during sleep states. |
| Integrated 3.3V LDO | 3.3V ±2% @ 10mA - powers auxiliary circuitry (e.g., microcontroller I/O, sensors) without requiring a separate regulator. |
Pinout & Package
Package: 28-Lead Narrow Plastic SSOP (GN), 5.6mm × 10.2mm body, exposed pad not present (UH QFN variant has exposed SGND pad; GN does not).
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| RUN/SS1, RUN/SS2 | Soft-start / Run Control / Short-Circuit Timer | Capacitor-connected pins controlling startup ramp rate and enabling timed latchoff during sustained overcurrent (e.g., 100nF = ~120ms timeout). |
| SENSE1+, SENSE1−, SENSE2+, SENSE2− | Differential Current Sense Inputs | Measure voltage drop across RSENSE to regulate peak inductor current; reject common-mode noise up to 5V. |
| VOSENSE1, VOSENSE2 | Feedback Input for Output Regulation | High-impedance (–50nA) inputs for remote sensing; compare against 0.8V reference to adjust ITH voltage and maintain regulation. |
| TG1, TG2, BG1, BG2 | N-Channel MOSFET Gate Drivers | TG drives high-side FETs with bootstrapped swing; BG drives low-side FETs from ground to INTVCC (5V); 3A peak drive capability. |
| PGOOD | Open-Drain Power-Good Indicator | Asserts low when either VOSENSE deviates >±7.5% from setpoint; enables sequencing and system fault detection. |
| FCB | Forced Continuous/Burst Mode Control | Selects operating mode: <0.8V = forced PWM, 0.8–2.7V = Burst Mode, >4.3V = constant-frequency (Burst inhibit). |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP Compensation | Enables stable loop response across 10× variation in output capacitance and ESR without redesigning compensation network. |
| Dual 180° Phased Operation | Reduces RMS input capacitor current by ~70%, enabling smaller, lower-cost ceramic input banks and easing EMI filtering. |
| Three Selectable Operating Modes | Burst Mode (high efficiency at light load), constant-frequency (low-noise), and forced continuous (bidirectional current support). |
| Integrated 3.3V Linear Regulator | Supplies 10mA with ±2% load regulation - eliminates need for discrete LDO in auxiliary rail generation. |
| Output Overvoltage Protection | Latches bottom FET ON until VOSENSE returns within ±7.5%; prevents damage to downstream logic during transient overshoot. |
| Low Dropout Capability | 99.4% maximum duty cycle - supports VIN-to-VOUT ratios as low as 1.01:1 (e.g., 5.05V → 5V), critical for battery end-of-discharge operation. |
Applications
| Notebook Dual-Output Power Supply | Telecom DC/DC Distribution |
|---|---|
Use Scenario: Generating tightly regulated 5V/3.3V rails from a 12V or 19V adapter or Li-ion battery pack in ultraportable notebooks. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing two independent output stages with coordinated timing to minimize input ripple. Use Value: Reduces total input capacitance by 50% vs single-phase design while maintaining <20mV output ripple under 5A load steps. |
Use Scenario: Providing isolated 3.3V and 5V supplies for line-card processors and interface ICs in modular telecom chassis. IC Role / Device Role / Timing Role: High-reliability dual controller with PGOOD sequencing and overvoltage protection for hot-swap-capable power domains. Use Value: Enables precise power-up sequencing and fault isolation between processor and PHY rails via independent RUN/SS control. |
| Portable Instrumentation Power | Battery-Powered Digital Systems |
Use Scenario: Powering mixed-signal FPGA, ADC, and analog front-end circuits in handheld test equipment with strict noise budgets. IC Role / Device Role / Timing Role: Constant-frequency mode controller delivering low-noise, jitter-free 1.2V core and 3.3V I/O supplies. Use Value: Achieves <15mVpp output noise in constant-frequency mode, meeting ADC reference stability requirements. |
Use Scenario: Efficiently converting 7.4V (2S LiPo) to 5V/3.3V for embedded controllers and wireless modules in portable IoT devices. IC Role / Device Role / Timing Role: Burst Mode controller minimizing quiescent consumption during deep sleep while supporting fast wake-up. Use Value: Delivers 85% efficiency at 1mA load and drops to only 20µA shutdown IQ, extending battery life by >3× vs linear regulators. |
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 |
|---|---|---|---|
| MP2918GL-Z | Single-chip dual-phase controller with integrated MOSFETs; 4.5V–16V input; fixed 500kHz frequency; no PLL sync or FCB mode selection. | Lacks programmable frequency, external sync, and multi-mode operation - suitable only for fixed-rail, space-constrained designs where integration outweighs flexibility. | Choose MP2918GL-Z only if board area is critical and input voltage never exceeds 16V; LTC3728LEGN#TRPBF remains preferred for 28V input, thermal robustness, and design adaptability. |
| ISL95836IRZ-T | Intel VR12.5-compliant dual-phase controller; supports DVID, SVID; 4.5V–24V input; includes telemetry and PMBus interface. | Targeted at CPU VR applications with dynamic voltage identification; adds complexity and cost unnecessary for generic dual-rail DC/DC. | Select ISL95836IRZ-T only for Intel-compatible platforms requiring SVID communication; LTC3728LEGN#TRPBF offers superior simplicity, wider VIN, and broader temperature range for general-purpose use. |
Compared with MP2918GL-Z and ISL95836IRZ-T, the LTC3728LEGN#TRPBF provides unmatched flexibility in frequency tuning, operating mode selection, and input voltage range - making it ideal for industrial, telecom, and portable designs where reliability, adaptability, and thermal margin are prioritized over monolithic integration or protocol compliance.
Availability
LTC3728LEGN#TRPBF is available at Aetrix Electronics and suitable for notebook computing, telecom power distribution, and portable instrumentation requiring stable component supply, long-term lifecycle support, and guaranteed –40°C to +85°C operation.
Supply support for LTC3728LEGN#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 full product support, documentation, and manufacturing continuity for all Linear ICs including the LTC3728 family.
The LTC3728L series was designed specifically for high-efficiency, dual-output, synchronous buck regulation in space- and thermal-constrained portable and industrial systems - emphasizing phase interleaving, low IQ, and robust protection.
FAQ
What is the maximum input voltage rating for the LTC3728LEGN#TRPBF?
The LTC3728LEGN#TRPBF has an absolute maximum input voltage (VIN) rating of 30V. Continuous operation is specified from 4.5V to 28V. Exceeding 30V risks permanent damage to internal circuitry, especially the INTVCC regulator and gate drivers. Always include input transient suppression if operating near the 28V upper limit.
Does the LTC3728LEGN#TRPBF support external frequency synchronization?
Yes, the LTC3728LEGN#TRPBF supports external synchronization via the PLLIN pin. When an external clock signal is applied to PLLIN, the internal phase-locked loop aligns the rising edge of TG1 with the rising edge of that signal. The PLLIN pin has a 50kΩ internal pull-down, so it must be actively driven for reliable sync - floating PLLIN forces minimum oscillator frequency.
How does the FCB pin affect operating mode selection in the LTC3728LEGN#TRPBF?
The FCB pin selects among three distinct operating modes in the LTC3728LEGN#TRPBF: below 0.8V enables forced continuous PWM; between 0.8V and VINTVCC–2V enables Burst Mode for high light-load efficiency; above 4.3V disables Burst Mode for constant-frequency operation. This pin controls both channels simultaneously and requires no external components for basic mode selection.
What is the purpose of the RUN/SS pins on the LTC3728LEGN#TRPBF?
The RUN/SS1 and RUN/SS2 pins on the LTC3728LEGN#TRPBF serve three functions: soft-start timing (via external capacitor), run enable/disable control, and short-circuit timeout detection. During startup, an internal 1.2µA current charges the CSS capacitor; when voltage reaches 1.5V, the controller enables. Under sustained overcurrent, the same capacitor discharges to trigger latchoff - configurable for 10ms to 10s timeouts.
Can the LTC3728LEGN#TRPBF drive high-side MOSFETs without external bootstrap diodes?
No - the LTC3728LEGN#TRPBF requires external Schottky bootstrap diodes (e.g., 1N5817) between INTVCC and BOOST1/BOOST2. These diodes recharge the external bootstrap capacitors during each low-side conduction period. Omitting them causes loss of high-side gate drive after initial startup, resulting in unregulated output or thermal shutdown due to shoot-through.
LTC3728LEGN#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#TRPBF FAQ
1.How can I place an order for LTC3728LEGN#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3728LEGN#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#TRPBF reliable?
The price and inventory of LTC3728LEGN#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#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3728LEGN#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3728LEGN#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3728LEGN#TRPBF?
LTC3728LEGN#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3728LEGN#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#TRPBF?
For technical support, including LTC3728LEGN#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3728LEGN#TRPBF requirements.
6.How does Aetrix verify that LTC3728LEGN#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3728LEGN#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#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3728LEGN#TRPBF?
All LTC3728LEGN#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3728LEGN#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#TRPBF part is unused and in its original packaging.
Return procedure for LTC3728LEGN#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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