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Analog Devices Inc. LTC3900IS8#PBF
- Part No.:
- LTC3900IS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Gate Drivers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC3900IS8#PBF.pdf
- Description:
- IC GATE DRVR LOW-SIDE 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:647
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Product details
Overview
LTC3900IS8#PBF from Analog Devices (formerly Linear Technology) is a secondary-side N-channel synchronous rectifier driver for isolated forward converters, featuring programmable timeout protection, reverse inductor current detection, pulse transformer synchronization, 4.5V–11V VCC supply range, and 15ns rise/fall times at 5V with 4700pF load - deployed in 48V telecom power supplies and high-voltage distributed step-down systems.
For engineers reviewing the LTC3900IS8#PBF datasheet, LTC3900IS8#PBF pinout, LTC3900IS8#PBF application, or LTC3900IS8#PBF equivalent, key selection criteria include its dual-gate drive timing accuracy, differential current sense threshold (10.5mV), SYNC input hysteresis (±0.2V), UVLO threshold (4.1V), and SO-8 thermal performance (θJA = 130°C/W) in isolated DC/DC designs.
Technical Context
The LTC3900IS8#PBF implements edge-sensitive dual-driver logic synchronized via external pulse transformer signals: negative SYNC slew forces FG high/CG low; positive slew forces FG low/CG high. Its internal timer resets on every negative SYNC transition and disables both drivers if timeout (programmed by RTMR/CTMR) elapses without valid polarity alternation.
Current sensing uses a differential comparator (CS+/CS–) active 250ns after CG goes high, with 10.5mV threshold and +0.33%/°C TC matching MOSFET RDS(ON) drift. A 0.5×VCC clamp on TIMER pin prevents excessive charge buildup during SYNC loss, while CS+ includes an 11V Zener clamp for drain-voltage transient protection.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Supply Range | 4.5V to 11V - supports bias from peak-rectified secondary windings across wide input voltage rails (36–72V primary) |
| Current Sense Threshold | 10.5mV - set to match RDS(ON) temperature coefficient and prevent false trip during light-load discontinuous conduction |
| SYNC Input Thresholds | ±1.4V with ±0.2V hysteresis - ensures robust edge detection despite pulse transformer amplitude variation or noise |
| Rise/Fall Time | 15ns at VCC = 5V, CL = 4700pF - enables fast MOSFET switching for high-efficiency operation up to ~1MHz |
| UVLO Threshold | 4.1V rising, 3.6V falling - prevents erratic gate drive during startup or brownout while avoiding chattering near threshold |
| Driver Output Resistance | 0.9Ω pull-up / 0.9Ω pull-down (typ.) - delivers >1A peak current to drive large N-channel MOSFET gates with minimal delay |
| Timeout Programmability | Configurable via RTMR/CTMR network - independent of VCC, enabling precise alignment with primary-side switching period |
Pinout & Package
Package: 8-Lead Plastic Small Outline (SO-8), –40°C to 125°C operating junction temperature, θJA = 130°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CS+ (Pin 1) | Differential current sense input (+) | Connected via series resistor to catch MOSFET drain; clamped to 11V for overvoltage protection during power transfer |
| CS– (Pin 2) | Differential current sense input (–) | Connected to catch MOSFET source; forms Kelvin sense path to detect reverse inductor current flow |
| CG (Pin 3) | Catch MOSFET gate driver output | Drives gate of Q4 during catch phase; disabled when CS+ exceeds CS– by >10.5mV or timeout occurs |
| VCC (Pin 4) | Main supply input | Powers internal logic and drivers; requires local 4.7µF ceramic bypass to GND for stable high-frequency operation |
| FG (Pin 5) | Forward MOSFET gate driver output | Drives gate of Q3 during forward conduction phase; synchronized to negative SYNC edge |
| GND (Pin 6) | Power ground reference | Return path for VCC bypass capacitor and internal circuitry; must be low-inductance connection to minimize noise coupling |
| TIMER (Pin 7) | Programmable timeout input | Accepts RC network (RTMR/CTMR); reset by internal 200ns pulse on each negative SYNC edge |
| SYNC (Pin 8) | Synchronization input | Edge-triggered interface accepting ±12V pulses; dual comparators (S+/S–) detect polarity for alternating FG/CG sequencing |
Key Features
| Feature | Design Value |
|---|---|
| Pulse transformer synchronization | Enables galvanic isolation between primary controller and secondary-side drivers without optocouplers or digital isolators |
| Reverse inductor current protection | Shuts off CG within nanoseconds when sensed current reverses - prevents MOSFET avalanche during power-down or Burst Mode® |
| Programmable timeout function | Disables both drivers if SYNC signal stalls or repeats same polarity - avoids sustained single-MOSFET conduction and thermal runaway |
| Temperature-compensated current sense | 10.5mV threshold with +0.33%/°C TC matches MOSFET RDS(ON) drift, maintaining consistent reverse-current trip point across –40°C to 125°C |
| Wide VCC operating range | 4.5V–11V support allows direct biasing from transformer secondaries or auxiliary windings without LDO regulation |
Applications
| 48V Telecom Power Supplies | Industrial Control System PSUs |
|---|---|
Use Scenario: Isolated 48V input to 3.3V/40A output in telecom shelf power modules requiring >90% efficiency and strict thermal management. IC Role / Device Role / Timing Role: Secondary-side synchronous rectifier driver coordinating Q3/Q4 switching via pulse-transformer-coupled SYNC signal from LT1952 primary controller. Use Value: Replaces Schottky diodes to reduce conduction losses by >50%, enabling higher power density and lower heatsink requirements in confined chassis space. |
Use Scenario: High-reliability 36–72V input power conversion for PLC I/O modules operating in harsh factory environments with wide ambient temperature swings. IC Role / Device Role / Timing Role: Dual-NMOS gate driver enforcing strict alternating conduction sequence and disabling outputs during undervoltage or SYNC fault conditions. Use Value: Prevents MOSFET destruction during brownout or controller lockup via UVLO (4.1V) and timeout-based driver disable - critical for functional safety compliance. |
| High-Voltage Distributed Power | Automotive & Heavy Equipment PSUs |
Use Scenario: 72V battery-fed distributed power architecture supplying multiple isolated 12V/24V rails to sensors and actuators in electric vehicle charging infrastructure. IC Role / Device Role / Timing Role: Synchronous rectifier controller interfacing with primary-side LT1952 via pulse transformer T2, managing forward/catch phases with <150ns propagation delay. Use Value: Achieves 95% efficiency at full load (VIN=72V, VOUT=3.3V) per Figure 10, reducing system-level heat generation and improving battery runtime. |
Use Scenario: Onboard charger auxiliary power supply in commercial EVs where EMI immunity and startup reliability under cold-cranking (down to 6V battery) are mandatory. IC Role / Device Role / Timing Role: Gate driver with integrated reverse-current protection and programmable timeout - eliminates need for external current-sense amplifiers or watchdog ICs. Use Value: Enables safe startup even when VCC ramps slowly: body diodes conduct until VCC reaches 4.1V, then seamless transition to synchronous rectification without voltage overshoot. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous rectifier driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM5113SD/NOPB | Single-channel high-side driver with bootstrap supply; no built-in current sense or timeout logic | Requires external comparators, timers, and level-shifting for isolated forward topologies | Choose when designing custom control schemes with discrete protection circuits and tighter layout control |
| UCC27211D | Dual N-channel driver with 4A peak current but no integrated SYNC decoding, current sense, or UVLO hysteresis | Needs companion ICs for polarity detection, reverse-current monitoring, and fault shutdown | Prefer for non-isolated or half-bridge applications where full forward-converter protection is implemented externally |
Compared with LM5113SD/NOPB and UCC27211D, the LTC3900IS8#PBF integrates all forward-converter-specific functions - SYNC polarity decoding, differential current sense with TC compensation, programmable timeout, and UVLO - eliminating 3–5 external components and reducing PCB area by >30% in isolated designs.
Availability
LTC3900IS8#PBF is available at Aetrix Electronics and suitable for 48V telecom power supplies, industrial control system PSUs, and high-voltage distributed power converters requiring stable component supply, long-term lifecycle support, and guaranteed -40°C to 125°C operation.
Supply support for LTC3900IS8#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 the LTC portfolio.
The LTC3900IS8#PBF belongs to Linear's precision power management IC family, designed specifically for high-efficiency isolated DC/DC conversion where secondary-side intelligence replaces passive rectification without adding complexity or cost.
FAQ
What is the primary function of the LTC3900IS8#PBF in a forward converter?
The LTC3900IS8#PBF serves as a secondary-side synchronous rectifier driver that replaces Schottky diodes with N-channel MOSFETs (Q3 and Q4) in isolated forward converters. It accepts synchronization signals via pulse transformer, drives both forward and catch MOSFETs with precise timing, and incorporates protection features including reverse inductor current detection and programmable timeout - all integrated into the LTC3900IS8#PBF.
How does the LTC3900IS8#PBF protect against reverse inductor current?
The LTC3900IS8#PBF monitors the voltage across the catch MOSFET's drain-source terminals using its differential CS+/CS– inputs. If inductor current reverses and causes CS+ to exceed CS– by more than 10.5mV, the LTC3900IS8#PBF immediately pulls CG low to turn off the catch MOSFET - preventing avalanche failure. This comparator activates only 250ns after CG goes high to avoid switching transients.
Can the LTC3900IS8#PBF operate with different primary-side controllers?
Yes - the LTC3900IS8#PBF interfaces with any primary-side controller capable of generating bipolar SYNC pulses (±1.4V threshold, ±12V absolute max), such as LT1952, LT3782, or custom ASICs. Its edge-sensitive SYNC input and polarity-detection logic allow interoperability across multiple controller families without protocol translation, as confirmed in the LTC3900IS8#PBF datasheet Figures 2 and 7.
What is the purpose of the TIMER pin on the LTC3900IS8#PBF?
The TIMER pin on the LTC3900IS8#PBF accepts an external RC network (RTMR/CTMR) to program a timeout period. The LTC3900IS8#PBF resets this timer on every negative SYNC edge; if SYNC stops or repeats polarity incorrectly, the timer expires and both FG and CG outputs are forced low - protecting external MOSFETs from uncontrolled conduction. Timeout is VCC-independent due to internal 0.2×VCC threshold scaling.
Does the LTC3900IS8#PBF require external components for basic operation?
Yes - the LTC3900IS8#PBF requires external components for core functionality: a 4.7µF ceramic capacitor on VCC-GND, RC network (RTMR/CTMR) on TIMER, series resistors (RCS1/RCS2/RCS3) on CS+, and pulse transformer interface on SYNC. These are not optional; they enable UVLO bypass, timeout programming, reverse-current sensing, and isolation-coupled synchronization - all essential to LTC3900IS8#PBF operation.
LTC3900IS8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Programmable:
- Not Verified
- Driven Configuration:
- Low-Side
- Channel Type:
- Synchronous
- Number of Drivers:
- 2
- Gate Type:
- N-Channel MOSFET
- Voltage - Supply:
- 4.5V ~ 11V
- Logic Voltage - VIL, VIH:
- -
- Current - Peak Output (Source, Sink):
- 2A, 2A
- Input Type:
- Inverting, Non-Inverting
- High Side Voltage - Max (Bootstrap):
- -
- Rise / Fall Time (Typ):
- 15ns, 15ns
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LTC3900IS8#PBF FAQ
1.How can I place an order for LTC3900IS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3900IS8#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 LTC3900IS8#PBF reliable?
The price and inventory of LTC3900IS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3900IS8#PBF is usually 5 days.
3.What payment methods are accepted for LTC3900IS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3900IS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3900IS8#PBF?
LTC3900IS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3900IS8#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 LTC3900IS8#PBF?
For technical support, including LTC3900IS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3900IS8#PBF requirements.
6.How does Aetrix verify that LTC3900IS8#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3900IS8#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 LTC3900IS8#PBF meets industry standards.
7.What is the process for return or replacement of LTC3900IS8#PBF?
All LTC3900IS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3900IS8#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 LTC3900IS8#PBF part is unused and in its original packaging.
Return procedure for LTC3900IS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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