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Analog Devices Inc. LTC1698IGN#TRPBF
- Part No.:
- LTC1698IGN#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Supply Controllers, Monitors
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC1698IGN#TRPBF.pdf
- Description:
- IC SECONDARY SIDE CTRLR 16SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,556
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Product details
Overview
LTC1698IGN#TRPBF from Analog Devices (formerly Linear Technology) is a precision secondary-side synchronous rectifier controller for isolated forward converters, designed to pair with the LT3781 primary-side controller. It drives dual external N-channel MOSFETs, delivers ±0.8% output voltage accuracy, supports 50–400 kHz synchronization frequency, and integrates a 3.3V/10mA auxiliary supply - used in telecom 48V DC/DC systems requiring high-efficiency secondary-side regulation.
For engineers reviewing the LTC1698IGN#TRPBF datasheet, LTC1698IGN#TRPBF pinout, LTC1698IGN#TRPBF application, or LTC1698IGN#TRPBF equivalent, key selection criteria include its pulse-transformer-synchronized dual gate drive, optocoupler feedback driver with 5 V/V gain, ±5% margin-adjustable output, and -25 mV current limit threshold referenced to ISNSGND.
Technical Context
The LTC1698IGN#TRPBF implements a secondary-side error amplifier (1.233 V reference, 90 dB open-loop gain, 2 MHz bandwidth) that regulates VFB via an external resistor divider and feeds back through an inverting optocoupler driver (5 V/V DC gain, 1 MHz bandwidth). Its current limit amplifier senses average secondary current via an external sense resistor, comparing the differential voltage across ISNS–ISNSGND to a -25 mV threshold with 3.5 millimho transconductance.
Synchronization is achieved via a bipolar SYNC input (-14 V to +14 V range) that directly controls FG and CG drivers with <90 ns propagation delay; loss of SYNC triggers an adaptive disable timeout (10–20 µs) proportional to fSYNC, ensuring both drivers go low within one switching cycle to prevent negative output transients.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Accuracy | ±0.8% over temperature and line - enables tight regulation in telecom power supplies without post-regulation. |
| Synchronization Frequency Range | 50 kHz to 400 kHz - supports flexible primary-side clocking while maintaining stable secondary timing alignment. |
| Current Sense Threshold | -25 mV (ISNS – ISNSGND) - sets precise average-current limit for secondary-side overcurrent protection. |
| Auxiliary Supply | 3.3 V ±3.5%, 10 mA max - powers external logic or bias circuitry without requiring separate LDO. |
| Optocoupler Driver Gain | 5 V/V DC gain - provides robust closed-loop feedback signal transmission across isolation barrier. |
| Power Good Threshold | VFB < 94% nominal for >1 ms pulls PWRGD low - delivers reliable system-level power status indication. |
| MARGIN Adjustment Range | ±5% output voltage shift - allows fine-tuning via simple 0 V or 3.3 V connection to MARGIN pin. |
Pinout & Package
Package: 16-lead plastic SSOP (GN), 5.3 mm × 6.2 mm, 0.65 mm pitch, moisture sensitivity level 1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VDD (1) | Primary power input | Accepts 6–12.6 V; powers gate drivers, VAUX, and opto driver; requires 4.7 µF bypass capacitor. |
| CG (2) | Catch gate driver output | Drives N-MOSFET source-to-PGND; swings rail-to-rail between VDD and PGND during catch phase. |
| PGND (3) | Power ground return | Low-impedance return path for gate drivers and current sense resistor; must tie directly to GND at chip. |
| GND (4) | Signal and logic ground | Reference for internal analog circuitry; layout separation from PGND critical for noise immunity. |
| OPTODRV (5) | Optocoupler driver output | Inverting driver with 10 mA sink/source capability; pulls high during OVP or overcurrent faults. |
| VCOMP (6) | Error amplifier output | Compensated node for feedback loop stability; connects to VFB via RC network for pole-zero placement. |
| MARGIN (7) | Voltage adjustment current input | 16.5 kΩ internal resistor; sourcing/sinking 100 µA shifts VFB by ±5% for programmable output setpoint. |
| VFB (8) | Feedback voltage input | Servo point regulated to 1.233 V bandgap reference; determines output voltage via external resistor divider. |
| OVPIN (9) | Overvoltage comparator input | High-impedance input referenced to 1.233 V; triggers immediate OPTODRV high on overvoltage event. |
| PWRGD (10) | Open-drain power-good flag | Pulls low if VFB drops below 94% for >1 ms; floats high if stable for >2 ms - used for system enable sequencing. |
| ISNSGND (11) | Current sense ground reference | Connects to positive side of external sense resistor; defines zero-reference for ISNS measurement. |
| ISNS (12) | Current sense input | Accepts negative voltage proportional to load current; differential input with -25 mV trip threshold. |
| ICOMP (13) | Current limit amplifier output | Compensation node for current loop; can float if only fault shutdown (not regulation) is required. |
| VAUX (14) | Auxiliary 3.3 V supply | Stable 3.3 V output with internal current limiting; requires ≥0.1 µF ceramic bypass capacitor. |
| SYNC (15) | Synchronization input | Bipolar input (-14 V to +14 V); negative slew activates FG, positive slew activates CG; 75 ns min pulse width. |
| FG (16) | Forward gate driver output | Drives N-MOSFET source-to-PGND; active during forward conduction phase; rail-to-rail swing. |
Key Features
| Feature | Design Value |
|---|---|
| Dual N-channel MOSFET drivers | Independent FG and CG outputs with rail-to-rail swing and <90 ns SYNC-to-output delay ensure precise timing control of forward/catch phases. |
| Pulse transformer synchronization | SYNC input accepts bipolar pulses up to ±14 V and adapts to 50–400 kHz frequencies, enabling robust isolation-coupled timing without PLL complexity. |
| Optocoupler feedback driver | 5 V/V inverting gain with 1 MHz bandwidth and short-circuit protection delivers stable, noise-immune feedback across isolation boundary. |
| Programmable current limit | -25 mV ISNS–ISNSGND threshold with 3.5 millimho transconductance enables accurate average-current limiting without external op-amps. |
| ±5% output voltage margining | MARGIN pin accepts 0 V or 3.3 V to shift regulated output by ±5% - simplifies factory calibration and dynamic voltage scaling. |
| Auxiliary 3.3 V logic supply | Integrated LDO delivers 3.3 V ±3.5% at up to 10 mA with internal current limiting - eliminates need for external bias rail in space-constrained designs. |
Applications
| 48V Input Isolated DC/DC Converters | Isolated Telecommunication Power Systems |
|---|---|
Use Scenario: Step-down conversion from 48 V telecom battery bus to 3.3 V or 5 V for line cards and baseband processors. IC Role / Device Role / Timing Role: Secondary-side synchronous rectifier controller coordinating with LT3781 to replace Schottky diodes and reduce conduction losses. Use Value: Achieves >92% efficiency at full load by eliminating diode forward drop, reducing thermal stress and enabling smaller heatsinks. | Use Scenario: Redundant -48 V DC power distribution in central office equipment with strict ripple and transient response requirements. IC Role / Device Role / Timing Role: Isolated feedback controller providing optocoupler-driven voltage regulation and PWRGD signaling to upstream supervisors. Use Value: ±0.8% output accuracy and 2 ms PWRGD assertion time ensure compliance with GR-1089-CORE immunity and safety standards. |
| Distributed Power Step-Down Converters | Industrial Control Systems |
Use Scenario: Local 12 V or 24 V intermediate bus conversion to 1.2 V–3.3 V for FPGAs and microcontrollers in modular PLC backplanes. IC Role / Device Role / Timing Role: Secondary-side regulator enforcing tight voltage tolerance and fast transient recovery via dual-MOSFET synchronous rectification. Use Value: 50–400 kHz sync range accommodates variable-frequency primary controllers, improving EMI spread-spectrum compatibility. | Use Scenario: Isolated 24 V AC/DC front-end powering I/O modules with functional safety monitoring and brownout detection. IC Role / Device Role / Timing Role: Fault-aware power manager providing OVPIN-triggered shutdown, PWRGD status, and auxiliary 3.3 V for digital isolators. Use Value: Integrated OVP comparator with 5 µs response and 10 mV hysteresis prevents damage during input surge events per IEC 61000-4-5. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar secondary-side synchronous rectifier controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC2897A | Requires external optocoupler biasing; no integrated VAUX; lower current limit accuracy (±10%). | Designed for flyback/forward topologies with primary-side sensing; lacks dedicated ISNS/ISNSGND differential inputs. | Choose UCC2897A only when primary-side sensing suffices and auxiliary 3.3 V is provided externally. |
| MAX17597 | No pulse-transformer SYNC interface; uses digital communication (I²C) for configuration; no MARGIN pin. | Targets high-density industrial SMPS with programmable parameters; not optimized for telecom isolation barrier constraints. | Select MAX17597 where digital configurability and footprint reduction outweigh need for analog sync simplicity and margining. |
Compared with UCC2897A and MAX17597, the LTC1698IGN#TRPBF uniquely combines pulse-transformer synchronization, integrated 3.3 V auxiliary supply, ±5% analog margining, and differential current sense - making it optimal for cost-sensitive, high-reliability telecom forward converters where analog simplicity and isolation integrity are paramount.
Availability
LTC1698IGN#TRPBF is available at Aetrix Electronics and suitable for 48V telecom power systems, isolated industrial DC/DC modules, and distributed power step-down converters requiring stable component supply, long-term lifecycle support, and guaranteed parametric performance over –40°C to +85°C.
Supply support for LTC1698IGN#TRPBF 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) is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, serving industrial, automotive, communications, and healthcare markets.
The LTC1698IGN#TRPBF belongs to ADI's legacy Linear Technology power management portfolio, specifically engineered for isolated synchronous forward converter architectures - emphasizing secondary-side regulation fidelity, robust isolation interface design, and integration of housekeeping functions (VAUX, PWRGD, OVP) into a single SSOP package.
FAQ
What is the operating temperature range for the LTC1698IGN#TRPBF?
The LTC1698IGN#TRPBF is rated for operation from –40°C to +85°C (industrial grade). Its electrical specifications - including ±0.8% output voltage accuracy, -25 mV current limit threshold, and 3.3 V VAUX output - are guaranteed across this full range. The device features internal thermal shutdown and operates reliably under continuous load conditions within these limits.
How does the LTC1698IGN#TRPBF synchronize with the LT3781 primary controller?
The LTC1698IGN#TRPBF synchronizes with the LT3781 using a small pulse transformer connected to the SYNC pin (Pin 15). A negative slew on SYNC forces FG high and CG low; a positive slew resets FG and pulls CG high. The SYNC input accepts ±14 V signals, supports 50–400 kHz frequencies, and includes an adaptive disable timeout that shuts down both drivers if SYNC is lost for >10 µs.
Can the LTC1698IGN#TRPBF be used without the LT3781 primary controller?
While the LTC1698IGN#TRPBF is optimized for use with the LT3781, it can operate with other primary controllers that provide compatible bipolar SYNC pulses (±14 V, 50–400 kHz, ≥75 ns width). However, full functionality - including seamless optocoupler feedback closure and synchronized start-up - is validated only with the LT3781. Independent use requires careful validation of timing margins and fault response.
What is the purpose of the MARGIN pin on the LTC1698IGN#TRPBF?
The MARGIN pin (Pin 7) on the LTC1698IGN#TRPBF enables ±5% linear adjustment of the regulated output voltage. Internally connected to a 16.5 kΩ resistor biased at 1.65 V, applying 3.3 V sources 100 µA and raises VFB by 5%; applying 0 V sinks 100 µA and lowers VFB by 5%. This allows factory calibration or dynamic voltage scaling without modifying the feedback resistor network.
Does the LTC1698IGN#TRPBF require external compensation components?
Yes, the LTC1698IGN#TRPBF requires external compensation: an RC network between VFB (Pin 8) and VCOMP (Pin 6) stabilizes the voltage feedback loop, and another RC network from ICOMP (Pin 13) to VOUT compensates the current limit loop. Typical values are selected based on output capacitance, inductance, and desired crossover frequency - guidance is provided in Figure 12 of the datasheet for a 3.3 V/15 A design.
LTC1698IGN#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Programmable:
- Not Verified
- Applications:
- Secondary-Side Controller, Synchronous Rectifier
- Voltage - Input:
- -
- Voltage - Supply:
- 6V ~ 12.6V
- Current - Supply:
- 1.8 mA
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SSOP
LTC1698IGN#TRPBF FAQ
1.How can I place an order for LTC1698IGN#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1698IGN#TRPBF 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 LTC1698IGN#TRPBF reliable?
The price and inventory of LTC1698IGN#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1698IGN#TRPBF is usually 5 days.
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LTC1698IGN#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1698IGN#TRPBF 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 LTC1698IGN#TRPBF?
For technical support, including LTC1698IGN#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1698IGN#TRPBF requirements.
6.How does Aetrix verify that LTC1698IGN#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC1698IGN#TRPBF 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 LTC1698IGN#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC1698IGN#TRPBF?
All LTC1698IGN#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1698IGN#TRPBF, 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 LTC1698IGN#TRPBF part is unused and in its original packaging.
Return procedure for LTC1698IGN#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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