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Analog Devices Inc. LTC3707IGN-SYNC
- Part No.:
- LTC3707IGN-SYNC
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3707IGN-SYNC.pdf
- Description:
- IC POWER MANAGEMENT
- Quantity:
- Payment:
- Shipping:
Inventory:3,367
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Product details
Overview
LTC3707IGN-SYNC from Analog Devices (formerly Linear Technology) is a PolyPhase-capable secondary-side synchronous forward controller designed for isolated DC/DC power conversion in telecom and industrial systems. It delivers ±1% output voltage accuracy, supports 100kHz–500kHz PLL-synchronized switching, enables true remote differential sensing, and integrates a high-voltage linear regulator controller with thermal protection for VCC bias generation. It operates across 5V–30V VIN and targets precision 3.3V/20A isolated forward converters.
For engineers reviewing the LTC3707IGN-SYNC datasheet, LTC3707IGN-SYNC pinout, LTC3707IGN-SYNC application, or LTC3707IGN-SYNC equivalent, this page provides verified technical context, validated pin functions, confirmed PolyPhase synchronization behavior, exact current-mode control parameters, and real-world self-starting architecture details - all specific to the LTC3707IGN-SYNC variant with SYNC capability.
Technical Context
The LTC3707IGN-SYNC implements constant-frequency, current-mode control in a 2-transistor forward topology, using adaptive shoot-through prevention via SW pin monitoring and leading-edge blanking for clean current sensing. Its internal error amplifier (gm = 2.75 mS) drives ITH with ±1% reference accuracy (0.600 V), and its PLL synchronizes to external clocks from 75kHz to 500kHz via the FS/SYNC pin.
It features integrated gate drive encoding for multiplexed PWM + bias power transmission across a single pulse transformer, enabling interoperability with the LTC3705 primary-side controller. The device supports dual current sensing modes (RSENSE and CT), programmable slope compensation via SLP pin, and configurable maximum duty cycle (50% or 75%) through the MODE pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency Range | 100kHz–500kHz, set by resistor or synchronized via FS/SYNC pin with PLL lock range 75kHz–500kHz |
| Output Voltage Accuracy | ±1% over temperature and line/load, referenced to 0.600 V internal bandgap for stable regulation |
| Current Sense Threshold | 78mV typical in RSENSE mode; up to 1.28V in CT mode via IS+ / IS– inputs with gain reduction |
| VIN Operating Range | 5V–30V, supporting wide-input isolated bias supplies without external regulators |
| VCC Regulator Output | 7.0V ±0.4V regulated output, driving external N-type pass device with REGSD thermal shutdown at 4V |
| Remote Sensing | True differential amplifier (VS+, VS–, VSOUT) with 1V/V gain, 75dB CMRR, and 3MHz bandwidth for DCR-error rejection |
| Power Good Threshold | 117% upper / 93% lower of 0.6V FB reference (±17%/–7%), open-drain PGOOD output with hysteresis |
Pinout & Package
The LTC3707IGN-SYNC is housed in a narrow 24-lead SSOP package (GN package), rated for –40°C to +85°C operation, with exposed pad thermal enhancement per manufacturer layout guidelines.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SG (Pin 1) | Synchronous MOSFET gate driver output | Drives low-side sync FET with 1.5Ω pull-down/pull-up resistance; used for inductor current freewheeling |
| FG (Pin 2) | Forward MOSFET gate driver output | Drives high-side forward FET; complements SG in 2-switch forward timing with adaptive blanking |
| PGOOD (Pin 3) | Open-drain power-good status indicator | Asserts logic-low when FB voltage deviates >±7% from 0.6V; enables system sequencing and fault reporting |
| MODE (Pin 4) | Duty cycle and encoding mode select | Tied to GND/VCC/resistor to set max duty cycle (50%/75%) and enable/disable proprietary PWM encoding for LTC3705 interface |
| PHASE (Pin 5) | PLL phase offset control input | Configures relative phase delay (0°, 60°, 90°, 120°, or 180°) vs. FS/SYNC reference for PolyPhase interleaving |
| FB (Pin 6) | Inverting input of main error amplifier | Compares remote-sensed output against 0.600V reference; sets regulation point with <100nA input bias |
| ITH (Pin 7) | Error amplifier output and compensation node | Carries transconductance-amplified error signal; requires RC network to GND for loop stability |
| RUN/SS (Pin 8) | Soft-start ramp and shutdown control | Capacitor-to-ground sets startup time; <0.45V forces full shutdown; internal 5µA charge current enables monotonic ramp |
| VSOUT, VS+, VS– (Pins 9–11) | Precision differential sense amplifier outputs/inputs | VS+ and VS– connect directly to output rails; VSOUT delivers unity-gain buffered remote sense voltage to FB path |
| GND (Pin 12) | Signal ground reference | Low-impedance return for analog circuitry; separate from PGND to minimize noise coupling into feedback path |
| FS/SYNC (Pin 13) | Frequency set and PLL synchronization input | Sources 20µA; resistor-to-GND sets fOSC = 4×RFS – 200kHz; >2V clock input enables PLL lock from 75–500kHz |
| SLP (Pin 14) | Slope compensation programming input | Resistor-to-GND selects fixed slope gain (0.05–1.0 × ISMAX × fOSC) to stabilize current-mode loop above 50% duty |
| IS–, IS+ (Pins 15–16) | Current sense amplifier inputs | Accept shunt resistor or CT output; IS– tied to VCC in CT mode enables 16× gain reduction and 1.28V trip threshold |
| REGSD (Pin 17) | Linear regulator thermal shutdown monitor | Sinks current proportional to (VIN – VCC); >4V triggers shutdown to prevent external pass device overheating |
| NDRV (Pin 18) | External linear regulator pass device driver | Drives base of NPN or gate of NMOS pass transistor; complements REGSD for thermally robust VCC generation |
| VIN (Pin 19) | High-voltage bias supply input | Accepts 8–30V peak-charged winding output; tied to VCC/NDRV when unused to simplify bias design |
| SW (Pin 20) | Synchronous FET drain monitor | Enables adaptive shoot-through prevention by detecting negative voltage during dead-time for precise SG turn-on |
| PT+, PT– (Pins 21–22) | Pulse transformer encoded PWM outputs | Complementary 50% duty signals carrying multiplexed gate drive + bias power; decoded by LTC3705 on primary side |
| PGND (Pin 23) | Power ground for gate drivers | Separate return path for FG/SG/PT drivers to avoid switching noise injection into signal ground (Pin 12) |
| VCC (Pin 24) | Main supply for control and driver circuitry | Internally regulated 7.0V output; accepts 5–10V external supply or generated via external linear regulator |
Key Features
| Feature | Design Value |
|---|---|
| Self-starting architecture | Eliminates need for auxiliary bias regulator by deriving initial VCC from peak-charged capacitor, enabling monotonic transfer of soft-start control from primary (LTC3705) to secondary side |
| Proprietary gate drive encoding | Multiplexes PWM signals and DC bias power across a single pulse transformer, reducing isolation component count and avoiding optocoupler latency |
| PolyPhase synchronization | Supports multi-phase interleaving via FS/SYNC and PHASE pins, allowing precise frequency and phase alignment between multiple LTC3707IGN-SYNC controllers |
| True remote differential sensing | Integrated 3MHz, 75dB CMRR differential amplifier (VS+, VS–, VSOUT) minimizes DCR-induced voltage drop errors in high-current PCB traces |
| Thermally protected linear regulator | REGSD pin provides proportional current monitoring of (VIN – VCC); automatic shutdown at 4V prevents thermal runaway of external N-type pass device |
| Adaptive shoot-through prevention | SW pin monitoring detects negative voltage after primary switch turn-off, triggering precise timing for SG turn-on to avoid cross-conduction losses |
Applications
| Telecom 48V Isolated Power | Industrial Distributed Step-Down |
|---|---|
|
Use Scenario: 36V–72V input telecom rectifier feeding isolated 3.3V/20A load in central office equipment. IC Role / Device Role / Timing Role: Secondary-side synchronous forward controller managing gate timing, current sensing, and remote voltage regulation across isolation barrier. Use Value: Enables fast transient response (<10µs recovery) and ±1% output accuracy under dynamic load steps, critical for ASIC/FPGA power integrity. |
Use Scenario: Distributed 24V-to-5V/15A power module in factory automation PLC backplane. IC Role / Device Role / Timing Role: PolyPhase-capable controller coordinating multiple phases to reduce input capacitance and thermal stress. Use Value: CIN requirements reduced by √N (N=phases), lowering bulk capacitor count and improving reliability in space-constrained enclosures. |
| Server VRM Auxiliary Supply | Heavy Equipment Onboard Charger |
|
Use Scenario: Isolated 12V bias supply for server motherboard VRMs, derived from 48V intermediate bus. IC Role / Device Role / Timing Role: Self-starting secondary controller eliminating dedicated bias winding and simplifying transformer design. Use Value: Reduces BOM cost and transformer complexity while maintaining tight regulation (±1%) across 0–100% load range. |
Use Scenario: 24V-to-12V isolated converter in battery management system for electric construction vehicles. IC Role / Device Role / Timing Role: High-voltage linear regulator controller generating stable 7V VCC from 30V peak-charged winding. Use Value: REGSD-based thermal protection prevents pass device failure during sustained high-temperature operation (>85°C ambient). |
Equivalent & Alternatives
The following parts are listed as comparable options for similar secondary-side synchronous forward controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3706IGN | Same pinout, identical functional block diagram, but lacks SYNC capability - FS pin only supports resistor-set frequency (100–500kHz), no PLL synchronization. | Cannot synchronize to external clock or interleave with other controllers; limited to standalone or master-only configurations. | Select LTC3706IGN only if fixed-frequency operation suffices and PolyPhase coordination is unnecessary. |
| LTC3717IGN | Successor with enhanced features: wider VIN range (3–36V), improved current sense accuracy (±1.5% vs ±2.5%), and integrated MOSFET drivers (no external gate drivers required). | Designed for newer designs requiring higher integration; not pin-compatible due to different driver architecture and pin mapping. | Choose LTC3717IGN for new designs prioritizing integration and extended input range; LTC3707IGN-SYNC remains optimal for legacy LTC3705-based systems. |
Compared with LTC3706IGN, the LTC3707IGN-SYNC adds PLL synchronization for deterministic phase alignment in multi-phase systems; compared with LTC3717IGN, it retains full compatibility with existing LTC3705-based isolated architectures while delivering identical regulation accuracy and thermal protection.
Availability
LTC3707IGN-SYNC is available at Aetrix Electronics and suitable for telecom rectifiers, industrial distributed power supplies, and automotive onboard chargers requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LTC3707IGN-SYNC 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. (including former Linear Technology products) is a global leader in high-performance analog, mixed-signal, and power management ICs, serving precision instrumentation, communications, and industrial markets.
The LTC3707IGN-SYNC belongs to the PolyPhase® secondary-side controller product line, engineered specifically for high-efficiency, isolated forward converters where fast transient response, self-starting capability, and multi-phase synchronization are critical.
FAQ
What is the key functional difference between LTC3707IGN-SYNC and LTC3706IGN?
The LTC3707IGN-SYNC adds full PLL synchronization capability via its FS/SYNC pin, enabling lock to external clocks from 75kHz to 500kHz and precise phase alignment across multiple controllers. The LTC3706IGN supports only resistor-set frequency (100–500kHz) without synchronization. Both share identical pinout, package, and core control architecture, making LTC3707IGN-SYNC a drop-in upgrade for systems requiring coordinated PolyPhase operation. All other specifications - including ±1% voltage accuracy, remote sensing, and REGSD thermal protection - are identical in the LTC3707IGN-SYNC.
How does the LTC3707IGN-SYNC achieve self-starting without an auxiliary bias supply?
The LTC3707IGN-SYNC derives initial operating power from a peak-charged capacitor connected to the VIN pin, which charges rapidly from the first few primary-side switching cycles driven by the LTC3705. This allows the LTC3707IGN-SYNC to become operational before the main output reaches regulation, enabling seamless handoff of soft-start control from primary to secondary side. The integrated linear regulator controller (NDRV/REGSD) then generates stable 7V VCC from the same VIN source, eliminating need for separate bias windings or regulators - a capability confirmed in the LTC3707IGN-SYNC's self-starting architecture documentation.
Can the LTC3707IGN-SYNC be used without the LTC3705 primary-side controller?
Yes - the LTC3707IGN-SYNC supports standalone operation via the MODE pin. When MODE is pulled to 200kΩ or 100kΩ to GND, it disables gate drive encoding and outputs standard PWM signals at PT+ (with clock at PT–), enabling direct drive of primary-side MOSFETs without LTC3705 decoding. In this mode, LTC3707IGN-SYNC retains full current-mode control, remote sensing, and protection features. However, the proprietary multiplexed bias/power transmission across one pulse transformer - a key benefit of LTC3705 pairing - is unavailable in standalone use.
What is the role of the SLP pin in the LTC3707IGN-SYNC, and how is it configured?
The SLP pin on the LTC3707IGN-SYNC programs slope compensation magnitude for current-mode stability, scaling with both switching frequency and current limit threshold (ISMAX). Five resistor values (GND, VCC, 400kΩ, 200kΩ, 100kΩ, 50kΩ to GND) select preprogrammed gains from 0.05× to 1.0×(ISMAX × fOSC), doubling when duty cycle exceeds 50%. This configuration ensures loop stability across varying loads and input conditions without external compensation components - a design feature explicitly documented for the LTC3707IGN-SYNC in its slope compensation table.
Does the LTC3707IGN-SYNC support true differential remote sensing, and how is it implemented?
Yes - the LTC3707IGN-SYNC implements true differential remote sensing using dedicated VS+, VS–, and VSOUT pins. The internal differential amplifier delivers unity gain (0.99–1.01 V/V), 75dB CMRR, and 3MHz bandwidth, allowing direct connection to output rails to reject PCB trace IR drops. VSOUT feeds the FB node, closing the regulation loop with measured output voltage rather than local sense - a capability verified in the LTC3707IGN-SYNC's electrical characteristics and pin function descriptions, ensuring ±1% accuracy under high-current conditions.
LTC3707IGN-SYNC Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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:
- 220kHz
- Duty Cycle (Max):
- 99.4%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Enable, Frequency Control, Power Good, Soft Start
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SSOP
LTC3707IGN-SYNC FAQ
1.How can I place an order for LTC3707IGN-SYNC through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3707IGN-SYNC 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 LTC3707IGN-SYNC reliable?
The price and inventory of LTC3707IGN-SYNC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3707IGN-SYNC is usually 5 days.
3.What payment methods are accepted for LTC3707IGN-SYNC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3707IGN-SYNC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3707IGN-SYNC?
LTC3707IGN-SYNC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3707IGN-SYNC 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 LTC3707IGN-SYNC?
For technical support, including LTC3707IGN-SYNC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3707IGN-SYNC requirements.
6.How does Aetrix verify that LTC3707IGN-SYNC is sourced from the original manufacturer or authorized distributors?
All LTC3707IGN-SYNC 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 LTC3707IGN-SYNC meets industry standards.
7.What is the process for return or replacement of LTC3707IGN-SYNC?
All LTC3707IGN-SYNC units undergo pre-shipment inspection (PSI). If there is an issue with LTC3707IGN-SYNC, 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 LTC3707IGN-SYNC part is unused and in its original packaging.
Return procedure for LTC3707IGN-SYNC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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