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Analog Devices Inc. LTC3728LCUH#PBF
- Part No.:
- LTC3728LCUH#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3728LCUH#PBF.pdf
- Description:
- IC REG CTRLR BUCK 32QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,246
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Product details
Overview
LTC3728LCUH#PBF from Analog Devices (formerly Linear Technology) is a dual-phase, 550kHz synchronous step-down controller IC driving two independent N-channel MOSFET stages in 180° out-of-phase operation. It features ±1% output voltage accuracy (0.8V reference), 4.5V–28V input range, and integrated 5V/3.3V auxiliary regulators - designed for high-efficiency dual-output power supplies in notebook computers and telecom systems.
For engineers reviewing the LTC3728LCUH#PBF datasheet, LTC3728LCUH#PBF pinout, LTC3728LCUH#PBF application, or LTC3728LCUH#PBF equivalent, key selection considerations include phase-lockable 250–550kHz frequency, OPTI-LOOP™ compensation for wide output capacitance tolerance, dual current-mode control with foldback protection, and QFN-32 package thermal performance (θJA = 34°C/W).
Technical Context
The LTC3728LCUH#PBF implements a constant-frequency, current-mode architecture with two independent control loops, each featuring an error amplifier (ITH1/ITH2), differential current sense inputs (SENSE1±/SENSE2±), and 0.8V precision reference. Phase synchronization is achieved via PLLIN/PLLFLTR pins, enabling precise 180° interleaving to reduce input ripple and capacitor stress.
Its dual-channel design supports three operating modes-Burst Mode®, constant-frequency, and forced continuous PWM-selected by the FCB pin. Output overvoltage protection latches the bottom MOSFET until VOSENSE returns within ±7.5%, while RUN/SS pins provide soft-start ramping (1.2µA charge current) and timed short-circuit shutdown with latchoff defeat capability.
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. |
| Switching Frequency | 250kHz to 550kHz - phase-lockable via PLLIN; adjustable with PLLFLTR voltage (0–2.4V). |
| Output Voltage Accuracy | ±1% at 0.8V feedback reference - ensures tight regulation for modern microprocessor core supplies. |
| PGOOD Threshold | ±7.5% of setpoint on either channel - open-drain indicator enables system power sequencing and fault monitoring. |
| Shutdown Quiescent Current | 20µA - enables ultra-low-power standby in battery-operated devices. |
| Thermal Resistance (θJA) | 34°C/W - measured for 5mm × 5mm QFN package with exposed pad soldered to PCB ground plane. |
| Operating Temperature | 0°C to +85°C - commercial-grade rating suitable for notebooks, portable instruments, and telecom line cards. |
Pinout & Package
Package: 32-lead (5mm × 5mm) plastic QFN with exposed thermal pad (Pin 33 = SGND). Requires soldering of exposed pad to PCB for optimal thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main power input | Supplies internal circuitry and gate drivers; bypassed to SGND with ≥22µF ceramic capacitor. |
| TG1/TG2 | Top gate drivers | Floating high-side N-MOSFET drivers; swing = INTVCC – 0.5V above SW node. |
| BG1/BG2 | Bottom gate drivers | Low-side N-MOSFET drivers; swing = 0V to INTVCC. |
| SW1/SW2 | Switch nodes | Connect to inductor high-side terminals; voltage swings from GND to VIN. |
| BOOST1/BOOST2 | Bootstrap supplies | Charge reservoirs for top gate drivers; require external bootstrap capacitors and Schottky diodes. |
| SENSE1±/SENSE2± | Differential current sense | Measure RSENSE voltage drop to regulate peak inductor current per channel. |
| VOSENSE1/VOSENSE2 | Feedback inputs | Remote sensing of output voltage via resistive divider; referenced to 0.8V internal reference. |
| RUN/SS1/RUN/SS2 | Soft-start & fault control | Capacitor-based ramp for controlled startup; also triggers timed latchoff during sustained overcurrent. |
| FCB | Mode select | Selects Burst Mode® (0.8–VINTVCC–2V), constant-frequency (tied to INTVCC), or forced PWM (grounded). |
| PGOOD | Power-good indicator | Open-drain output pulled low if either VOSENSE deviates >±7.5% from target. |
| INTVCC | Internal 5V LDO output | Powers control logic and drivers; can be bypassed by EXTVCC ≥4.7V for higher efficiency. |
| 3.3VOUT | Auxiliary linear regulator | Stable 3.3V output capable of 10mA DC / 50mA peak - powers bias rails or low-power peripherals. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP™ Compensation | Enables stable loop response across wide COUT and ESR variations without redesigning compensation network. |
| 180° Interleaved Dual-Phase Operation | Halves input RMS current and reduces required input capacitance by ~70% versus single-phase design. |
| Programmable Operating Modes | Three distinct low-power modes (Burst, constant-frequency, forced PWM) optimized for light-load efficiency or noise-sensitive applications. |
| Integrated 5V/3.3V Auxiliary Regulators | Eliminates need for external bias supplies - 3.3VOUT delivers 10mA with <2% load regulation. |
| Robust Fault Protection | Includes output overvoltage latching, foldback current limiting, and configurable short-circuit latchoff with disable option. |
Applications
| Notebook Power Systems | Telecom DC-DC Conversion |
|---|---|
Use Scenario: Dual-output core/VDDQ supply for Intel/AMD mobile processors requiring tightly regulated 1.0V/1.2V and 3.3V/5V rails. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing independent current-mode loops with phase interleaving and PGOOD sequencing. Use Value: Reduces input capacitor count by 50% and improves transient response via OPTI-LOOP™, meeting strict ±1% CPU voltage tolerance. | Use Scenario: Distributed 5V/3.3V power for line card ASICs and FPGA I/O banks in 48V intermediate bus telecom systems. IC Role / Device Role / Timing Role: High-efficiency dual controller converting 48V intermediate bus to point-of-load voltages with synchronized switching to minimize EMI. Use Value: 550kHz max frequency enables compact magnetics; phase-locking allows coherent noise cancellation across multiple boards. |
| Portable Instrumentation | Battery-Powered Digital Devices |
Use Scenario: Precision analog front-end and digital subsystem power in handheld test equipment with Li-ion battery input (3.0–4.2V nominal). IC Role / Device Role / Timing Role: Dual buck controller operating in Burst Mode® at light loads to extend battery life, with seamless transition to constant-frequency mode under full load. Use Value: 20µA shutdown current and 99% duty cycle dropout operation maximize runtime and maintain regulation down to battery end-of-discharge. | Use Scenario: Dual-rail power for ARM-based embedded systems with separate core (1.1V) and I/O (3.3V) requirements, powered from 2-cell LiPo (6–8.4V). IC Role / Device Role / Timing Role: Synchronous step-down controller delivering high efficiency (>92% at 3A) across full load range using N-MOSFETs and adaptive mode selection. Use Value: Integrated 3.3VOUT regulator powers USB PHY or display interface, eliminating discrete LDO and reducing BOM count. |
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#PBF | Same functionality and pinout; extended temperature range (–40°C to +85°C) vs. LTC3728LCUH#PBF's 0°C to +85°C. | Suitable for industrial or automotive environments where ambient temperature exceeds 0°C minimum. | Select when operating in cold-temperature environments; otherwise LTC3728LCUH#PBF is cost-optimized for commercial use. |
| LTC3728LXCUH#PBF | Includes enhanced phase-jitter performance and tighter oscillator tolerance (±1% vs. ±3% typical); identical pinout and electrical specs. | Preferred for noise-sensitive RF or high-speed serial link power where clock jitter impacts signal integrity. | Choose when phase synchronization stability is critical; otherwise LTC3728LCUH#PBF meets standard timing requirements. |
Compared with LTC3728LEUH#PBF and LTC3728LXCUH#PBF, the LTC3728LCUH#PBF offers the lowest-cost path for commercial-temperature dual-phase buck control with full feature parity - differing only in temp grade and oscillator spec, not architecture or pin compatibility.
Availability
LTC3728LCUH#PBF is available at Aetrix Electronics and suitable for notebook power systems, telecom DC-DC conversion, and portable instrumentation requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LTC3728LCUH#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, datasheets, and application engineering for legacy Linear parts including the LTC3728 family.
The LTC3728L/LTC3728LX product line was designed specifically for high-efficiency, dual-phase synchronous buck conversion in space-constrained portable and telecom applications - emphasizing thermal performance, light-load efficiency, and robust fault handling.
FAQ
What is the maximum switching frequency supported by the LTC3728LCUH#PBF?
The LTC3728LCUH#PBF supports a maximum switching frequency of 550kHz, achievable when the PLLFLTR pin voltage is ≥2.4V. This frequency is phase-lockable to an external clock via the PLLIN pin, and the device maintains stable operation across its full 250kHz–550kHz range with minimal jitter. The LTC3728LCUH#PBF achieves this while maintaining tight output regulation and efficient thermal dissipation in its 5mm × 5mm QFN package.
How does the LTC3728LCUH#PBF implement output overvoltage protection?
The LTC3728LCUH#PBF uses an internal overvoltage comparator that monitors VOSENSE1 and VOSENSE2 against a threshold of ±7.5% of the nominal output voltage. When triggered, it immediately disables the top MOSFET and latches the bottom MOSFET ON until the output recovers. This action clamps the output and prevents damage to downstream components. The LTC3728LCUH#PBF integrates this protection without external components, ensuring fast response and reliable fault containment.
Can the LTC3728LCUH#PBF operate with a single output configuration?
Yes, the LTC3728LCUH#PBF can be configured for single-output operation by tying both VOSENSE pins to the same feedback divider and disabling one channel via its RUN/SS pin. Its dual independent control loops allow flexible implementation - either as two fully isolated outputs or as a single high-current output using paralleled phases. The LTC3728LCUH#PBF retains all protection features and mode selection capabilities in either configuration.
What is the purpose of the FCB pin on the LTC3728LCUH#PBF?
The FCB (Forced Continuous/Burst Mode) pin on the LTC3728LCUH#PBF selects among three operating modes: Burst Mode® (FCB = 0.8–VINTVCC–2V), constant-frequency (FCB = INTVCC), or forced continuous PWM (FCB = GND). It also enables secondary-winding regulation by forcing both channels into synchronous operation. The LTC3728LCUH#PBF uses this pin to optimize efficiency across load conditions without changing external components.
Does the LTC3728LCUH#PBF require external bootstrap diodes?
Yes, the LTC3728LCUH#PBF requires external Schottky diodes between BOOST1/BOOST2 and INTVCC to recharge the bootstrap capacitors during each switching cycle. These diodes must have low forward voltage (<0.4V) and fast recovery to ensure reliable top-gate drive under high-duty-cycle or dropout conditions. The LTC3728LCUH#PBF datasheet specifies typical part numbers and layout guidelines to prevent bootstrap failure and gate drive collapse.
LTC3728LCUH#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 32-WFQFN Exposed Pad
- 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 ~ 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:
- 0°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-QFN (5x5)
LTC3728LCUH#PBF FAQ
1.How can I place an order for LTC3728LCUH#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3728LCUH#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 LTC3728LCUH#PBF reliable?
The price and inventory of LTC3728LCUH#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3728LCUH#PBF is usually 5 days.
3.What payment methods are accepted for LTC3728LCUH#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3728LCUH#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3728LCUH#PBF?
LTC3728LCUH#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3728LCUH#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 LTC3728LCUH#PBF?
For technical support, including LTC3728LCUH#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3728LCUH#PBF requirements.
6.How does Aetrix verify that LTC3728LCUH#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3728LCUH#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 LTC3728LCUH#PBF meets industry standards.
7.What is the process for return or replacement of LTC3728LCUH#PBF?
All LTC3728LCUH#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3728LCUH#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 LTC3728LCUH#PBF part is unused and in its original packaging.
Return procedure for LTC3728LCUH#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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