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Analog Devices Inc. LTC3728LEUH#PBF
- Part No.:
- LTC3728LEUH#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3728LEUH#PBF.pdf
- Description:
- IC REG CTRLR BUCK 32QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,246
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Product details
Overview
LTC3728LEUH#PBF from Analog Devices (formerly Linear Technology) is a dual-channel, 180° out-of-phase, synchronous step-down controller IC designed for high-efficiency, low-noise DC/DC conversion in space-constrained systems. It drives all-N-channel MOSFET stages, supports phase-lockable switching frequencies up to 550 kHz, delivers ±1% output voltage accuracy at 0.8 V reference, operates from 4.5 V to 28 V input, and features integrated 5 V and 3.3 V auxiliary regulators - used in notebook computers and telecom power rails.
For engineers reviewing the LTC3728LEUH#PBF datasheet, LTC3728LEUH#PBF pinout, LTC3728LEUH#PBF application, or LTC3728LEUH#PBF equivalent, key selection criteria include dual-phase current-mode control, OPTI-LOOP™ compensation for wide output capacitor/ESR tolerance, FCB-selectable operating modes (Burst Mode®, constant-frequency, forced continuous), and robust protection including output overvoltage latch, foldback current limiting, and short-circuit shutdown with defeat option.
Technical Context
The LTC3728LEUH#PBF implements a constant-frequency, current-mode architecture with two independent control loops sharing a common 0.8 V precision reference and synchronized 180° out-of-phase operation to reduce input ripple and EMI. Each channel uses an error amplifier (ITH pin) driving a peak-current comparator referenced to sensed voltage across RSENSE, with transconductance gm = 1.3 mmho and gain-bandwidth product of 3 MHz.
Phase synchronization is achieved via PLLIN/PLLFLTR pins enabling external clock locking or DC-voltage-controlled frequency tuning from 260 kHz to 550 kHz. The IC integrates dual gate drivers (TG/BG) with <100 ns transition times, internal 5 V LDO (INTVCC), 3.3 V linear regulator (10 mA), and open-drain PGOOD indicating both outputs within ±7.5% of setpoint.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5 V to 28 V - supports full battery chemistries (Li-ion, LiFePO₄, 12 V lead-acid) and industrial DC rails without external pre-regulation. |
| Switching Frequency | 260 kHz to 550 kHz - adjustable via PLLFLTR pin or external sync on PLLIN; enables EMI optimization and inductor size reduction. |
| Feedback Reference Voltage | 0.792 V to 0.812 V (–40°C to 85°C) - ±1% accuracy ensures tight regulation for microprocessor core and I/O rails. |
| Output Overvoltage Protection | Latches bottom MOSFET until VOSENSE returns to normal - prevents damage to downstream logic during transient overshoots >7.5%. |
| Shutdown Quiescent Current | 20 µA - enables ultra-low-power standby in battery-operated portable instruments and palmtop devices. |
| Operating Temperature Range | –40°C to +85°C - qualified for industrial and extended-temperature embedded applications including telecom systems. |
| Package | 32-lead 5 mm × 5 mm QFN (UH) with exposed thermal pad - provides low θJA = 34°C/W for high-power density designs. |
Pinout & Package
Package: 32-lead (5 mm × 5 mm) plastic QFN (UH) with exposed SGND pad soldered to PCB for thermal and signal integrity. Pin 33 is the exposed pad, electrically connected to SGND.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main power supply input | Accepts 4.5 V–28 V; bypassed to SGND; powers INTVCC LDO and internal circuitry. |
| TG1, TG2 | Top N-MOSFET gate drivers | Floating drivers with swing = INTVCC – 0.5 V superimposed on SW node; drive high-side switches. |
| BG1, BG2 | Bottom N-MOSFET gate drivers | Ground-referenced drivers (0 V to INTVCC); enable synchronous rectification for >95% efficiency. |
| SENSE1+, SENSE1− SENSE2+, SENSE2− |
Differential current sense inputs | Measure voltage across RSENSE to regulate peak inductor current; tolerate common-mode up to 1.1×INTVCC. |
| VOSENSE1, VOSENSE2 | Output voltage feedback inputs | Connect to resistive divider; compared to 0.8 V reference; trigger PGOOD when deviation exceeds ±7.5%. |
| RUN/SS1, RUN/SS2 | Soft-start and short-circuit timer inputs | Capacitor-based ramp controls startup current; falling below 1.0 V shuts down respective channel; enables timed latchoff. |
| FCB | Forced continuous/burst mode select | Pull <0.8 V for PWM mode; 0.8–(INTVCC–2) V for Burst Mode®; tie to INTVCC for constant-frequency operation. |
| PGOOD | Open-drain power-good indicator | Active-low signal asserting only when both VOSENSE1 and VOSENSE2 are within ±7.5% of target. |
| 3.3VOUT | Integrated linear regulator output | Delivers 10 mA DC (50 mA peak); powers bias circuits or low-noise analog subsystems without external LDO. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP™ compensation | Enables stable loop response across wide range of ceramic output capacitors (10 µF–1000 µF) and ESR (0.5 mΩ–50 mΩ), eliminating need for manual compensation redesign. |
| 180° dual-phase interleaving | Reduces RMS input capacitor current by ~30% and cuts peak-to-peak input ripple amplitude by ~50%, allowing smaller, lower-cost bulk capacitance. |
| Three selectable operating modes | Burst Mode® (high light-load efficiency), constant-frequency (low noise), or forced continuous (PWM) - selected via single FCB pin without external logic. |
| Integrated 3.3 V linear regulator | Provides clean, low-noise bias for ADC references, sensors, or level-shifters - eliminates discrete LDO and saves board area. |
| Output overvoltage latch protection | Immediately disables top MOSFET and asserts bottom MOSFET to clamp VOUT during fault, preventing damage to sensitive downstream loads like FPGAs or memory. |
Applications
| Notebook Power Rails | Telecom DC Distribution |
|---|---|
|
Use Scenario: Dual-output power supply for CPU core (5 V/5 A) and I/O (3.3 V/5 A) in ultraportable notebooks with strict thermal and EMI constraints. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing interleaved switching, phase synchronization, and coordinated soft-start sequencing. Use Value: 180° phase shift reduces input ripple current by 70%, enabling use of smaller 22 µF ceramic input caps instead of larger electrolytics - saving >30 mm² PCB area. |
Use Scenario: Primary 48 V-to-12 V and 5 V conversion stage in telecom line cards requiring high reliability and low standby power. IC Role / Device Role / Timing Role: Dual-channel controller delivering regulated intermediate bus voltages with PGOOD coordination and overvoltage fault containment. Use Value: Integrated 3.3 V LDO powers monitoring ICs and EEPROMs; 20 µA shutdown IQ extends system uptime during maintenance mode. |
| Portable Test Instruments | Battery-Powered Digital Systems |
|
Use Scenario: Precision dual-rail supply (±5 V equivalents via isolated secondaries) in handheld oscilloscopes and multimeters with battery backup. IC Role / Device Role / Timing Role: High-accuracy (±1%) voltage controller with programmable soft-start and foldback current limiting to protect Li-ion cells during load faults. Use Value: Foldback current limiting reduces MOSFET dissipation during short-circuit events - maintains safe junction temperature without thermal shutdown. |
Use Scenario: Main DC/DC converter in ruggedized PDAs and handheld terminals powered by 2-cell Li-ion (6–8.4 V) with variable load profiles. IC Role / Device Role / Timing Role: Adaptive efficiency controller selecting Burst Mode® at light load (<50 mA) and constant-frequency above 500 mA via FCB pin. Use Value: Achieves >85% efficiency at 10 mA load (Burst Mode®) and >92% at full 5 A load - extending battery runtime by 22% vs fixed-frequency alternatives. |
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 |
|---|---|---|---|
| MP8770GQ-Z | Single-channel controller; no integrated 3.3 V LDO; requires external VREF; max fSW = 2 MHz; no PLL sync. | Suitable for cost-sensitive, non-interleaved designs where phase cancellation is not required. | Select when needing higher switching frequency (>1 MHz) and lower BOM count, but accept loss of dual-phase noise reduction and auxiliary rail integration. |
| LTC3855EUH#PBF | Dual-phase controller with same UH package; wider VIN (4.5–38 V); includes PMBus interface; no 3.3 V LDO; higher IQ (40 µA). | Targeted at industrial servers and PoE-powered equipment requiring digital telemetry and extended input range. | Choose when digital monitoring, fault logging, or 36 V input support is mandatory - but expect higher cost and complexity than LTC3728LEUH#PBF. |
Compared with MP8770GQ-Z and LTC3855EUH#PBF, the LTC3728LEUH#PBF uniquely combines dual-phase interleaving, integrated 3.3 V LDO, sub-20 µA shutdown IQ, and Burst Mode® efficiency - making it optimal for compact, battery-sensitive, dual-rail portable systems where analog simplicity and thermal headroom are critical.
Availability
LTC3728LEUH#PBF is available at Aetrix Electronics and suitable for notebook computers, telecom systems, and portable instruments requiring stable component supply, long-term lifecycle support, and guaranteed industrial temperature grade (–40°C to +85°C).
Supply support for LTC3728LEUH#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 its high-performance analog and power management portfolio with rigorous automotive and industrial qualification standards.
The LTC3728L/LTC3728LX product line was engineered for high-density, low-noise dual-output DC/DC conversion in portable computing and communications infrastructure - emphasizing phase interleaving, adaptive efficiency modes, and integrated auxiliary regulation.
FAQ
What is the maximum supported switching frequency for the LTC3728LEUH#PBF?
The LTC3728LEUH#PBF supports a phase-lockable switching frequency range of 260 kHz to 550 kHz, set via the PLLFLTR pin voltage (0 V to 2.4 V) or synchronized externally through PLLIN. At VPLLFLTR ≥ 2.4 V, the nominal maximum is 550 kHz - confirmed in Electrical Characteristics Table (fHIGH = 550 kHz). This limit ensures stable gate driver timing and current-sense accuracy across the –40°C to +85°C operating range.
Does the LTC3728LEUH#PBF support true dual-phase interleaving with 180° phase offset?
Yes, the LTC3728LEUH#PBF natively implements 180° out-of-phase operation between its two controller channels. This is intrinsic to its architecture - verified in the Functional Diagram (Figure 2), Typical Application (Figure 1), and Operation section - and reduces input capacitor RMS current and conducted EMI without requiring external phase-shift circuitry or master-slave configuration.
How does the FCB pin affect operating mode selection in the LTC3728LEUH#PBF?
The FCB pin selects among three distinct modes: pulling FCB < 0.8 V forces continuous PWM operation; holding FCB between 0.8 V and (INTVCC – 2 V) enables Burst Mode® for high light-load efficiency; tying FCB to INTVCC disables Burst Mode® and enables constant-frequency discontinuous conduction mode. These thresholds and behaviors are specified in the Electrical Characteristics table (VFCB, VBINHIBIT) and Operation section.
What protection features are built into the LTC3728LEUH#PBF?
The LTC3728LEUH#PBF includes output overvoltage latch (OV comparator clamping top MOSFET), foldback current limiting during output shorts, timed short-circuit shutdown via RUN/SS discharge, undervoltage lockout (UVLO = 3.5 V), and thermal shutdown (TJMAX = 125°C). All are documented in Absolute Maximum Ratings, Electrical Characteristics, and Operation sections - with no external components required for basic fault coverage.
Is the 3.3VOUT pin on the LTC3728LEUH#PBF regulated and load-capable?
Yes, the 3.3VOUT pin is a fully regulated linear output delivering 3.2 V to 3.45 V (±2.3%) at up to 10 mA DC with 50 mA peak capability. Its line regulation is 0.05–0.2% over 6–30 V input, and load regulation is 0.5–2% across 0–10 mA - specified in Electrical Characteristics (V3.3OUT, V3.3IL, V3.3VL) and used to power auxiliary circuitry without external regulators.
LTC3728LEUH#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:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-QFN (5x5)
LTC3728LEUH#PBF FAQ
1.How can I place an order for LTC3728LEUH#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3728LEUH#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 LTC3728LEUH#PBF reliable?
The price and inventory of LTC3728LEUH#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3728LEUH#PBF is usually 5 days.
3.What payment methods are accepted for LTC3728LEUH#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3728LEUH#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3728LEUH#PBF?
LTC3728LEUH#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3728LEUH#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 LTC3728LEUH#PBF?
For technical support, including LTC3728LEUH#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3728LEUH#PBF requirements.
6.How does Aetrix verify that LTC3728LEUH#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3728LEUH#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 LTC3728LEUH#PBF meets industry standards.
7.What is the process for return or replacement of LTC3728LEUH#PBF?
All LTC3728LEUH#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3728LEUH#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 LTC3728LEUH#PBF part is unused and in its original packaging.
Return procedure for LTC3728LEUH#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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