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Analog Devices Inc. LTC3726IGN#PBF
- Part No.:
- LTC3726IGN#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Supply Controllers, Monitors
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3726IGN#PBF.pdf
- Description:
- IC SECONDARY SIDE CTRLR 16SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,629
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Product details
Overview
LTC3726IGN#PBF from Analog Devices (formerly Linear Technology) is a secondary-side synchronous forward controller IC designed for isolated DC/DC power conversion. It delivers ±1% output voltage accuracy, supports 100kHz–500kHz PLL-synchronized switching, and enables self-starting operation without external bias regulators in telecom 36V–72V to 3.3V/20A forward converters.
For engineers reviewing the LTC3726IGN#PBF datasheet, LTC3726IGN#PBF pinout, LTC3726IGN#PBF application, or LTC3726IGN#PBF equivalent, key selection criteria include its proprietary gate-drive encoding across isolation barriers, current-mode control with adaptive shoot-through prevention, OPTI-LOOP® compensation, and 16-lead SSOP package compatibility with high-density telecommunication power designs.
Technical Context
The LTC3726IGN#PBF implements constant-frequency current-mode control with internal 0.6V reference and transconductance error amplifier (gm = 2.75 mS). Its PLL-based oscillator accepts external sync signals from 75kHz to 500kHz and supports frequency setting via resistor on FS/SYNC pin.
It features dual current sensing modes (RSENSE or CT), programmable slope compensation via SLP pin, and integrated overvoltage protection that activates the synchronous MOSFET when FB exceeds 117% of 0.6V. The MODE pin configures maximum duty cycle (50% or 75%) and selects between encoded PWM (for use with LTC3705/LTC3725) or standard PWM outputs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Accuracy | ±1% - ensures tight regulation under line/load/temperature variation for telecom and server rails |
| Switching Frequency Range | 100kHz–500kHz PLL-synchronized - enables EMI reduction and multi-phase synchronization |
| Feedback Reference Voltage | 0.600V ±6mV - stable internal reference for precision voltage loop design |
| Current Sense Threshold | 78mV (RSENSE mode) or 1.28V (CT mode) - supports low-loss shunt or transformer-based sensing |
| UVLO Threshold | 4.60V ±0.08V - prevents erratic startup below valid VCC operating range (5V–10V) |
| Operating Temperature | –40°C to +85°C - qualified for industrial and telecom ambient conditions |
| Supply Current | 4.2mA at 200kHz - defines bias power requirement for secondary-side control circuitry |
Pinout & Package
The LTC3726IGN#PBF is housed in a narrow 16-lead plastic SSOP package (GN package) with 0.65mm lead pitch and exposed pad thermal enhancement.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SG (Pin 1) | Synchronous MOSFET gate driver output | Drives low-side synchronous rectifier; includes adaptive shoot-through prevention via SW pin monitoring |
| FG (Pin 2) | Forward MOSFET gate driver output | Drives high-side forward switch; complements SG in synchronous forward topology |
| MODE (Pin 3) | Duty cycle and encoding mode select | Configures max duty cycle (50%/75%) and enables/disables proprietary pulse transformer encoding |
| FB/PHASE (Pin 4) | Inverting error amp input / phase selector | Serves as voltage feedback node in master mode; sets phase angle (0°–180°) in PolyPhase slave mode |
| ITH (Pin 5) | Error amplifier output | Carries compensated control signal to PWM comparator; connects to compensation network to GND |
| RUN/SS (Pin 6) | Soft-start and shutdown control | Capacitor-to-ground sets ramp time; <0.45V forces full shutdown; used for fault propagation in multi-phase systems |
| SLP (Pin 7) | Slope compensation programming | Resistor-to-ground selects one of five slope values; doubles above 50% duty cycle for stability |
| GND (Pin 8) | Signal ground reference | Reference for analog circuitry; separate from PGND to minimize noise coupling |
| FS/SYNC (Pin 9) | Oscillator frequency set and PLL sync input | Resistor-to-ground sets fOSC = 4×RFS – 200kΩ; >2V clock input enables PLL lock from 75–500kHz |
| IS– (Pin 10) | Negative current sense input | Connects to shunt low side or CT secondary; tied to VCC for CT mode to scale gain and raise trip threshold |
| IS+ (Pin 11) | Positive current sense input | Connects to shunt high side or CT secondary; differential input with 16× gain reduction in CT mode |
| SW (Pin 12) | Synchronous MOSFET drain monitor | Enables leading-edge blanking and adaptive turn-on timing to prevent shoot-through |
| PGND (Pin 13) | Power ground for gate drivers | Low-impedance return path for FG/SG/PT+/- drivers; must be connected near power FETs |
| PT+ / PT– (Pins 14,15) | Pulse transformer encoded outputs | Complementary 50% duty-cycle encoded signals carrying PWM + bias power across single transformer |
| VCC (Pin 16) | Main supply input | 5V–10V operating range powers all control and driver circuitry; includes UVLO and 700µA shutdown current |
Key Features
| Feature | Design Value |
|---|---|
| Secondary-side control architecture | Enables fast transient response by closing voltage loop directly on output side, eliminating primary-side delay and transformer leakage effects |
| Self-starting bias generation | Eliminates need for dedicated auxiliary bias supply-operates from peak-charged capacitor during startup, enabling seamless handoff from LTC3705/LTC3725 open-loop soft-start |
| Proprietary gate drive encoding | Combines PWM signals and DC bias power into single pulse transformer interface-reduces isolation components and avoids optocoupler latency |
| OPTI-LOOP® compensation | Reduces external compensation components and simplifies loop stability design while maintaining wide bandwidth and phase margin |
| Adaptive shoot-through prevention | Monitors SW pin voltage to precisely time SG turn-on after FG turn-off-prevents cross-conduction without fixed dead-time programming |
Applications
| Telecom 48V Isolated Power | Internet Server VRM |
|---|---|
Use Scenario: 36V–72V input telecom rectifier supplying 3.3V/20A to line cards in NEBS-compliant chassis. IC Role / Device Role / Timing Role: Secondary-side controller managing synchronous rectification, current sharing, and fast load-step response in isolated forward converter. Use Value: ±1% output accuracy and 500kHz PLL sync enable compliance with GR-1089 EMI limits and support dynamic CPU core scaling. | Use Scenario: Distributed 12V intermediate bus stepping down to 3.3V for ASICs and memory in rack-mounted servers. IC Role / Device Role / Timing Role: Master controller in PolyPhase configuration coordinating multiple LTC3726IGN#PBF units for interleaved current sharing. Use Value: Slave-mode phase shifting (0°/60°/90°/120°/180°) reduces input/output ripple and improves thermal distribution across PCB. |
| Automotive Heavy Equipment | Distributed Step-Down Converter |
Use Scenario: 24V/48V battery-fed forward converter powering 3.3V control logic in off-highway vehicle ECUs. IC Role / Device Role / Timing Role: Isolated secondary-side regulator with OVP crowbar protection safeguarding sensitive microcontrollers from bus transients. Use Value: Overvoltage protection triggers synchronous MOSFET turn-on within 100ns to clamp output at safe level during load dump events. | Use Scenario: Modular power system where multiple isolated 3.3V outputs are derived from common 48V backplane. IC Role / Device Role / Timing Role: Standalone forward controller (MODE pin = 100kΩ to GND) driving discrete MOSFETs without LTC3705/LTC3725. Use Value: Standard PWM outputs (PT+, PT–) allow direct gate drive of high-side/lower-side FETs-eliminating need for companion ICs in cost-sensitive designs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar secondary-side forward controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3725IGN#PBF | Primary-side gate driver and controller; requires external secondary-side controller; no built-in OPTI-LOOP | Used on primary side only; cannot replace LTC3726IGN#PBF's secondary-side voltage regulation function | Select LTC3725IGN#PBF only when designing primary-side control with separate secondary feedback path |
| UCC2897APW | Secondary-side forward controller with 50kHz–1MHz range; no integrated PLL sync; uses external compensation | Lacks pulse-transformer encoding and self-starting architecture; requires optocoupler or digital isolator for primary communication | Choose UCC2897APW for higher-frequency (>500kHz) or non-Linear-compatible designs where isolation interface flexibility is prioritized |
Compared with LTC3725IGN#PBF and UCC2897APW, the LTC3726IGN#PBF uniquely integrates secondary-side voltage regulation, self-starting bias, and encoded pulse-transformer communication-enabling simpler, lower-latency isolated power with fewer BOM components and no optocouplers.
Availability
LTC3726IGN#PBF is available at Aetrix Electronics and suitable for telecom infrastructure, internet server VRMs, and automotive heavy equipment requiring stable component supply, long-term lifecycle support, and guaranteed -40°C to +85°C operation.
Supply support for LTC3726IGN#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 qualification for all former Linear parts including the LTC3726 series.
The LTC3726IGN#PBF belongs to Linear's high-efficiency isolated power controller family, engineered specifically for secondary-side synchronous forward topologies in telecom, datacom, and industrial systems demanding fast transient response and simplified isolation interfaces.
FAQ
What is the function of the MODE pin on the LTC3726IGN#PBF?
The MODE pin on the LTC3726IGN#PBF configures both maximum duty cycle (50% or 75%) and gate drive encoding mode. When tied to GND or VCC, it enables encoded PWM for use with LTC3705/LTC3725. With resistors (100kΩ or 200kΩ to GND), it disables encoding and outputs standard PWM signals at PT+ and PT–-allowing standalone operation without companion ICs. This dual functionality makes the LTC3726IGN#PBF adaptable across 1-switch and 2-switch forward topologies.
How does the LTC3726IGN#PBF achieve self-starting without an external bias supply?
The LTC3726IGN#PBF achieves self-starting by deriving initial bias from a peak-charged capacitor connected to VCC, which charges faster than the main output during startup. Once operational, it assumes control from the primary-side LTC3705/LTC3725 by synchronizing its soft-start ramp to the rising output voltage. This eliminates the need for a separate auxiliary bias regulator and enables seamless handoff-ensuring monotonic output rise and robust startup even under light-load or high-input-voltage conditions in the LTC3726IGN#PBF design.
Can the LTC3726IGN#PBF be used in PolyPhase configurations?
Yes, the LTC3726IGN#PBF supports PolyPhase operation via its FB/PHASE pin. When configured as a slave (FB/PHASE >2V), it disables local ITH control and accepts current-sharing commands from a master LTC3726IGN#PBF. Phase angles of 0°, 60°, 90°, 120°, or 180° are selected by tying FB/PHASE to VCC or specific resistor dividers. This allows interleaved operation across multiple LTC3726IGN#PBF units-reducing input/output ripple, improving thermal distribution, and increasing effective switching frequency without raising EMI.
What protection features does the LTC3726IGN#PBF include?
The LTC3726IGN#PBF includes overvoltage protection (OVP) that triggers when FB exceeds 117% of 0.6V (0.7V), turning on the synchronous MOSFET to crowbar the output. It also provides undervoltage lockout (UVLO) at 4.60V ±0.08V, adaptive leading-edge blanking for clean current sensing, and hiccup-mode short-circuit protection using the RUN/SS pin to coordinate fault response across multiple phases. These protections are fully integrated and require no external components-enhancing reliability in mission-critical telecom and industrial applications using the LTC3726IGN#PBF.
Does the LTC3726IGN#PBF support synchronization with external clock sources?
Yes, the LTC3726IGN#PBF supports PLL-based synchronization via its FS/SYNC pin. Applying a >2V clock signal (75kHz–500kHz) to this pin locks the internal oscillator to the external reference with minimal jitter. Multiple LTC3726IGN#PBF units can be synchronized by connecting the PT+ output of one device to the FS/SYNC pin of others-ensuring identical frequency and phase alignment. This capability is essential for EMI reduction, current sharing, and noise-sensitive applications where deterministic timing is required in systems using the LTC3726IGN#PBF.
LTC3726IGN#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Programmable:
- Not Verified
- Applications:
- Secondary-Side Controller
- Voltage - Input:
- -
- Voltage - Supply:
- 5V ~ 10V
- Current - Supply:
- 4.2 mA
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SSOP
LTC3726IGN#PBF FAQ
1.How can I place an order for LTC3726IGN#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3726IGN#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 LTC3726IGN#PBF reliable?
The price and inventory of LTC3726IGN#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3726IGN#PBF is usually 5 days.
3.What payment methods are accepted for LTC3726IGN#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3726IGN#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3726IGN#PBF?
LTC3726IGN#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3726IGN#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 LTC3726IGN#PBF?
For technical support, including LTC3726IGN#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3726IGN#PBF requirements.
6.How does Aetrix verify that LTC3726IGN#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3726IGN#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 LTC3726IGN#PBF meets industry standards.
7.What is the process for return or replacement of LTC3726IGN#PBF?
All LTC3726IGN#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3726IGN#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 LTC3726IGN#PBF part is unused and in its original packaging.
Return procedure for LTC3726IGN#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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