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Analog Devices Inc. LTC3728LXCUH#PBF
- Part No.:
- LTC3728LXCUH#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3728LXCUH#PBF.pdf
- Description:
- IC REG CTRLR BUCK 32QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,340
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Product details
Overview
LTC3728LXCUH#PBF from Analog Devices (formerly Linear Technology) is a dual-phase, constant-frequency current-mode synchronous step-down controller driving two independent N-channel MOSFET stages with 180° phase offset. It operates from 4.5V to 28V input, delivers ±1% output voltage accuracy at 0.8V reference, supports up to 550kHz switching, and integrates 5V/3.3V auxiliary regulators - used in high-density notebook DC/DC power rails.
For engineers reviewing the LTC3728LXCUH#PBF datasheet, LTC3728LXCUH#PBF pinout, LTC3728LXCUH#PBF application, or LTC3728LXCUH#PBF equivalent, key selection criteria include dual-phase interleaving for reduced input ripple, OPTI-LOOP compensation adaptability across ceramic output capacitors, FCB-selectable operating modes (Burst Mode®, constant-frequency, forced continuous), and integrated overvoltage/short-circuit protection with latchoff.
Technical Context
The LTC3728LXCUH#PBF implements a dual-channel, current-mode control architecture with independent error amplifiers (ITH1/ITH2), differential current sense inputs (SENSE1±/SENSE2±), and phase-locked oscillator enabling synchronization across channels and to external clocks via PLLIN. Each channel features dedicated RUN/SS pins for soft-start ramping and timed short-circuit shutdown.
It integrates a 5V INTVCC LDO and 3.3V linear regulator (3.3VOUT), supports EXTVCC switchover above 4.7V, and includes PGOOD open-drain output asserting when either VOSENSE1 or VOSENSE2 deviates >±7.5% from setpoint. Output overvoltage protection latches bottom MOSFET until recovery.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 28V (30V absolute max); supports Li-ion, Li-poly, and 12V/24V industrial rails. |
| Switching Frequency | 250kHz–550kHz adjustable via PLLFLTR voltage; phase-lockable to external clock on PLLIN. |
| Output Voltage Accuracy | ±1% over temperature (0°C to 85°C); 0.8V reference enables precise 1.2V, 1.8V, 3.3V, or 5V regulation. |
| Current Sense Threshold | 62mV to 88mV (typ. 75mV); sets peak inductor current limit with RSENSE = 0.01Ω → 7.5A per phase. |
| Shutdown Quiescent Current | 20µA; enables ultra-low-power standby in battery-operated systems. |
| PGOOD Window | ±7.5% of set output voltage; provides system-level power sequencing and fault indication. |
| Operating Temperature | 0°C to +85°C (commercial grade); validated for notebook and telecom ambient conditions. |
Pinout & Package
Package: 32-lead (5mm × 5mm) plastic QFN (UH), exposed pad soldered to SGND. Thermal resistance θJA = 34°C/W.
| 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 drive outputs | Floating high-side drivers (INTVCC – 0.5V swing); require external bootstrap diode and capacitor. |
| BG1/BG2 | Bottom-gate drive outputs | Ground-referenced low-side drivers (0V to INTVCC); directly drive synchronous N-MOSFET sources. |
| SW1/SW2 | Switch node connections | Connect to inductor high-side terminals; voltage swings from GND to VIN during operation. |
| VOSENSE1/VOSENSE2 | Feedback voltage inputs | Remote sensing inputs for each channel; referenced to 0.8V internal precision bandgap. |
| SENSE1±/SENSE2± | Differential current sense inputs | Measure voltage drop across RSENSE to regulate peak inductor current per phase. |
| RUN/SS1/RUN/SS2 | Soft-start & fault timer inputs | Capacitor-based ramp controls startup current; also triggers timed latchoff during sustained overcurrent. |
| FCB | Mode select input | Selects Burst Mode® (0.8V < VFCB < VINTVCC–2V), constant-frequency (VFCB = INTVCC), or forced PWM (VFCB < 0.8V). |
| PGOOD | Open-drain status output | Pulled low if either VOSENSE deviates >±7.5%; requires external pull-up to ≤7V. |
| 3.3VOUT | Integrated linear regulator | Provides 10mA DC / 50mA peak 3.3V supply for biasing logic or auxiliary circuits. |
| INTVCC | Internal 5V LDO output | Power source for control logic and gate drivers; decoupled with ≥4.7µF tantalum/low-ESR cap. |
| EXTVCC | External VCC switchover input | Enables bypass of internal LDO when >4.7V applied; reduces power loss in high-current designs. |
| PLLIN/PLLFLTR | Phase-lock interface | PLLIN accepts external sync clock; PLLFLTR sets frequency via DC voltage (0–2.4V = 260–550kHz). |
| SGND / Exposed Pad | Small-signal ground | Must be routed separately from PGND; exposed pad is SGND and must be soldered to PCB ground plane. |
Key Features
| Feature | Design Value |
|---|---|
| 180° interleaved dual-phase operation | Halves input ripple current vs single-phase, reducing required CIN by ~70% and EMI filtering cost. |
| OPTI-LOOP® compensation | Enables stable loop response across wide range of ceramic output capacitance (10µF–1000µF) and ESR. |
| Three selectable operating modes | Burst Mode® (high efficiency at light load), constant-frequency (low noise), forced PWM (reverse current support). |
| Integrated 3.3V linear regulator | Eliminates need for external 3.3V LDO in dual-rail systems; supplies 10mA with <2% load regulation. |
| Output overvoltage protection | Latches bottom MOSFET on during >+7.5% overvoltage event, preventing damage to downstream loads. |
| Programmable short-circuit latchoff | Uses RUN/SS capacitor time constant to disable channel after sustained low-VOUT condition; defeatable with pull-up. |
Applications
| High-Density Notebook Power Rails | Telecom Intermediate Bus Converters |
|---|---|
|
Use Scenario: Dual-output 5V/3.3V or 1.2V/1.8V power for CPU core, I/O, and memory subsystems in space-constrained notebooks. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing two independent regulated rails with interleaved timing to minimize input ripple. Use Value: Reduces total input capacitance by 50–70% versus single-phase solutions while maintaining <1% output voltage deviation under dynamic load steps. |
Use Scenario: High-efficiency 48V-to-12V intermediate bus conversion in telecom line cards requiring tight thermal management. IC Role / Device Role / Timing Role: Dual-phase controller operating at 500kHz with phase synchronization to system clock, minimizing conducted EMI in dense backplane environments. Use Value: Achieves >92% peak efficiency at 20A output with 180° phase shift, lowering RMS input current stress on bulk capacitors and PCB traces. |
| Portable Instrumentation Power | Battery-Powered Digital Signal Processors |
|
Use Scenario: Low-noise, dual-rail power for precision ADCs, DACs, and op-amps in handheld test equipment. IC Role / Device Role / Timing Role: Controller delivering clean 3.3V analog and 1.8V digital rails using Burst Mode® at light load and constant-frequency during active sampling. Use Value: Maintains <20mVpp output ripple in Burst Mode® and enables <20µA shutdown IQ to extend battery life between measurements. |
Use Scenario: Efficient 2-cell Li-ion (6V–8.4V) to 1.2V/3.3V conversion for DSPs in portable audio or edge AI devices. IC Role / Device Role / Timing Role: Dual-phase buck controller with dropout detection and 99% duty cycle capability to sustain output as battery discharges. Use Value: Delivers full rated current down to 6V input without derating; integrated 3.3VOUT powers auxiliary logic, eliminating discrete LDO. |
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 |
|---|---|---|---|
| LTC3728LCUH#PBF | Same pinout and functionality but rated for 0°C to 85°C (LTC3728LXCUH#PBF is identical except marking; both share same electrical specs and UH package). | No functional difference; LTC3728LCUH#PBF is standard commercial variant; LTC3728LXCUH#PBF is identical part with X-marking denoting specific wafer lot/test bin. | Select LTC3728LXCUH#PBF when traceability to Linear's X-series qualification or documented production lot history is required. |
| MP2918GL-Z | Single-chip dual-phase controller with integrated MOSFET drivers only; lacks 3.3VOUT regulator, EXTVCC switchover, and PLL sync capability. | Suitable for cost-sensitive, lower-feature applications where auxiliary rail generation and clock synchronization are not needed. | Choose MP2918GL-Z only if design does not require 3.3VOUT, PLLIN sync, or EXTVCC efficiency optimization - otherwise LTC3728LXCUH#PBF offers broader feature coverage. |
Compared with LTC3728LCUH#PBF, LTC3728LXCUH#PBF provides identical performance and packaging with enhanced traceability; versus MP2918GL-Z, it adds critical features including integrated 3.3V bias rail, PLL synchronization, and EXTVCC switchover - enabling higher system integration and tighter EMI control in demanding applications.
Availability
LTC3728LXCUH#PBF is available at Aetrix Electronics and suitable for notebook computing, telecom infrastructure, and portable instrumentation requiring stable component supply, long-term lifecycle assurance, and guaranteed commercial-temperature performance.
Supply support for LTC3728LXCUH#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 acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for all Linear-branded power ICs.
The LTC3728LXCUH#PBF belongs to Linear's high-performance synchronous buck controller family, designed specifically for high-efficiency, dual-rail, multi-phase DC/DC conversion in space- and thermally-constrained portable and telecom systems.
FAQ
What is the operating temperature range for the LTC3728LXCUH#PBF?
The LTC3728LXCUH#PBF is specified for 0°C to +85°C ambient operation. This commercial-grade rating aligns with typical notebook and telecom equipment thermal profiles. The device uses the UH (5mm × 5mm QFN) package with θJA = 34°C/W, enabling reliable operation without forced airflow when properly heatsinked via the exposed SGND pad. Full electrical specifications are guaranteed across this range.
How does the FCB pin configure operating modes on the LTC3728LXCUH#PBF?
The FCB pin on the LTC3728LXCUH#PBF selects among three distinct modes: pulling FCB below 0.8V forces continuous PWM operation; applying 0.8V < VFCB < VINTVCC–2V enables Burst Mode® for high light-load efficiency; tying FCB to INTVCC disables Burst Mode® and enables constant-frequency discontinuous conduction mode. Each mode alters gate drive behavior and current flow direction, directly impacting efficiency, noise, and reverse-current capability.
Does the LTC3728LXCUH#PBF support external clock synchronization?
Yes, the LTC3728LXCUH#PBF supports full external clock synchronization via the PLLIN pin. Its internal phase-locked loop locks the rising edge of TG1 to the rising edge of an external clock applied to PLLIN. The PLLFLTR pin serves as both the phase detector output and DC frequency control input - varying its voltage from 0V to 2.4V adjusts the oscillator frequency from 260kHz to 550kHz, enabling precise alignment with system clocks or noise-sensitive frequency bands.
What protection features are integrated into the LTC3728LXCUH#PBF?
The LTC3728LXCUH#PBF integrates multiple hardware-based protections: output overvoltage protection (latches BG on if VOSENSE exceeds +7.5%), foldback current limiting during short-circuit conditions, programmable short-circuit latchoff using RUN/SS capacitor timing, undervoltage lockout (UVLO trips at ~3.75V), and thermal shutdown. All operate independently per channel and require no external components - ensuring robustness in unattended or mission-critical power systems.
Can the LTC3728LXCUH#PBF generate both 5V and 3.3V rails simultaneously?
Yes, the LTC3728LXCUH#PBF is explicitly designed for dual-rail generation: its two independent synchronous buck controllers can be configured for separate outputs (e.g., 5V/3.3V or 1.2V/1.8V), while the integrated 3.3VOUT linear regulator provides a third, low-noise auxiliary rail. The 3.3VOUT pin delivers up to 10mA DC and 50mA peak current, eliminating the need for an external 3.3V LDO in many compact designs - confirmed in Figure 1 and Applications section of the datasheet.
LTC3728LXCUH#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)
LTC3728LXCUH#PBF FAQ
1.How can I place an order for LTC3728LXCUH#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3728LXCUH#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 LTC3728LXCUH#PBF reliable?
The price and inventory of LTC3728LXCUH#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3728LXCUH#PBF is usually 5 days.
3.What payment methods are accepted for LTC3728LXCUH#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3728LXCUH#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3728LXCUH#PBF?
LTC3728LXCUH#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3728LXCUH#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 LTC3728LXCUH#PBF?
For technical support, including LTC3728LXCUH#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3728LXCUH#PBF requirements.
6.How does Aetrix verify that LTC3728LXCUH#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3728LXCUH#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 LTC3728LXCUH#PBF meets industry standards.
7.What is the process for return or replacement of LTC3728LXCUH#PBF?
All LTC3728LXCUH#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3728LXCUH#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 LTC3728LXCUH#PBF part is unused and in its original packaging.
Return procedure for LTC3728LXCUH#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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