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Analog Devices Inc. LT3804EFE#TRPBF
- Part No.:
- LT3804EFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Supply Controllers, Monitors
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3804EFE#TRPBF.pdf
- Description:
- IC SECONDARY SIDE CTRLR 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,956
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Product details
Overview
LT3804EFE#TRPBF from Analog Devices (formerly Linear Technology) is a dual-output synchronous secondary-side DC/DC controller with integrated optocoupler driver for isolated power supplies. It regulates two independent outputs - one via optocoupler feedback (e.g., 3.3V/15A), the other via voltage-mode PWM (e.g., 1.8V/15A) - using true differential remote sensing, programmable current limit, and up to 800kHz switching frequency. Designed for high-efficiency forward converters with synchronous rectification.
For engineers reviewing the LT3804EFE#TRPBF datasheet, LT3804EFE#TRPBF pinout, LT3804EFE#TRPBF application, or LT3804EFE#TRPBF equivalent, key selection considerations include its dual-output regulation architecture, 0.6V reference voltage per output, 28-lead TSSOP thermally enhanced package with exposed pad, and support for leading-edge modulation with trailing-edge synchronization in isolated topologies.
Technical Context
The LT3804EFE#TRPBF implements a hybrid control scheme: VA1/OA1 with optocoupler feedback governs the primary output, while VA2 drives a voltage-mode PWM for the secondary output with leading-edge modulation synchronized to the transformer secondary falling edge. It supports discontinuous conduction mode via BGS pin control and uses separate GNDS1/GNDS2 pins for true Kelvin sensing on both outputs.
Its oscillator is set by CSET (500pF typical for 200kHz), with synchronization range up to 800kHz depending on CSET value. Gate drivers deliver ±1A peak current with 25ns rise/fall time (1nF load), and GBIAS provides an internally regulated 8V supply for bootstrapping TGATE.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Count | Dual independent outputs: main (optocoupler-regulated) + auxiliary (PWM-regulated) |
| Reference Voltage | 0.6V per output (VREF1/VREF2), referenced to dedicated GNDS1/GNDS2 pins for true remote sensing |
| Switching Frequency | Up to 800kHz (synchronized); programmable via CSET capacitor (e.g., 500pF → 200kHz) |
| Current Limit Threshold | 50mV across CL1P–CL1N and CL2P–CL2N for both outputs |
| Soft-Start Current | 10µA per SS1/SS2 pin, enabling controlled ramp-up with external capacitor |
| Power Good Logic | PGOOD asserts high only when both PGIN1 and PGIN2 are within ±10% of VREF1/VREF2 (90–110%) |
| Operating Temp Range | –40°C to 125°C junction temperature (LT3804E grade) |
Pinout & Package
LT3804EFE#TRPBF is housed in a thermally enhanced 28-lead plastic TSSOP package with exposed signal-ground pad (Pin 29), requiring PCB connection for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CL1P / CL1N | CA1 current sense inputs | 50mV threshold sets first-output current limit; CL1N connects to output ground side of sense resistor |
| ILCOMP1 | CA1 compensation node | Pull-down node for optocoupler-driven current limiting; stabilizes loop with external capacitor |
| VFB1 / GNDS1 | Main output feedback network | VFB1 accepts resistor divider; GNDS1 is dedicated remote ground reference for <±100mV accuracy |
| VAOUT1 / OPTO | Optocoupler driver interface | VAOUT1 drives OA1 amplifier; OPTO sources up to 10mA to bias optocoupler LED |
| CL2P / CL2N / ILCOMP2 | CA2 current sense & compensation | 50mV threshold for second output; ILCOMP2 pulled low during current limit to regulate VAOUT2 |
| VFB2 / GNDS2 | Auxiliary output feedback network | Independent 0.6V reference at VFB2; GNDS2 enables true Kelvin sensing for second output |
| BGS | Discontinuous mode enable | Open = auto DCM at light load; grounded = forced CCM (except during soft-start) |
| SS1 / SS2 | Soft-start timing inputs | 10µA current charges external capacitor; ramp time = (C × 0.6V)/10µA |
| PGIN1 / PGIN2 | Power good monitor inputs | Compare against VREF1/VREF2; require resistor dividers tied to GNDS1/GNDS2 |
| PGOOD | Combined power-good indicator | Open-drain output; requires external pull-up; asserts only when both outputs are in regulation |
| TGATE / BGATE | Synchronous N-MOSFET drivers | TGATE: bootstrapped high-side drive (6–7.5V swing); BGATE: low-side drive (5–7.5V swing) |
| GBIAS | Internal 8V regulator output | Supplies gate drivers; requires ≥2µF low-ESR bypass capacitor to PGND |
| CSET | Oscillator frequency setting | Capacitor to ground sets free-running frequency; determines sync range upper bound |
| SYNC | Falling-edge synchronization input | Triggers new cycle on transformer secondary falling edge; threshold = 2.5V |
Key Features
| Feature | Design Value |
|---|---|
| True differential remote sensing | Dedicated GNDS1/GNDS2 pins eliminate PCB trace IR drop error; enables ±0.5% output regulation accuracy |
| Integrated optocoupler driver | OA1 amplifier with 6× gain and 10mA sourcing capability eliminates external transistor stage |
| Programmable dual soft-start | Independent SS1/SS2 pins allow staggered ramp-up of outputs to manage inrush and sequencing |
| Automatic frequency synchronization | SYNC pin locks switching to transformer secondary falling edge, eliminating beat frequencies in multi-rail systems |
| Discontinuous conduction mode control | BGS pin enables light-load efficiency boost by disabling BGATE when inductor current falls below 8mV threshold |
| High-speed gate drivers | ±1A peak drive with 25ns (1nF) rise/fall ensures minimal switching loss in high-frequency synchronous rectifiers |
Applications
| 48V Input Isolated DC/DC Converters | Multiple Output Power Supplies |
|---|---|
|
Use Scenario: Telecom and industrial 48V intermediate bus powering mixed-voltage loads (e.g., 3.3V FPGA core, 1.8V memory). IC Role / Device Role / Timing Role: Secondary-side dual-output controller managing both regulation loops and synchronous rectifier timing. Use Value: Eliminates need for multiple secondary windings or post-regulators, reducing transformer size and improving cross-regulation. |
Use Scenario: Server motherboard VRMs requiring tightly regulated 12V, 5V, 3.3V, and 1.8V rails from a single isolation boundary. IC Role / Device Role / Timing Role: Regulates main output via optocoupler feedback and auxiliary output via internal PWM with precise duty-cycle control. Use Value: Achieves ±0.5% output accuracy per rail using dedicated remote-sense grounds, minimizing inter-rail coupling errors. |
| Offline Converters | DC/DC Power Modules |
|
Use Scenario: AC/DC front-end with isolated DC bus feeding downstream DC/DC stages in medical or industrial equipment. IC Role / Device Role / Timing Role: Secondary-side controller providing feedback to primary-side IC (e.g., LT3781) while independently regulating auxiliary output. Use Value: Enables compact, high-density offline designs with >90% system efficiency via synchronous rectification and DCM optimization. |
Use Scenario: Half-brick or quarter-brick isolated modules delivering dual outputs (e.g., 3.3V/15A + 1.8V/15A) with full protection and monitoring. IC Role / Device Role / Timing Role: Core secondary-side regulation engine with integrated PGOOD, current limit, and soft-start sequencing. Use Value: Reduces external component count by integrating optocoupler driver, dual error amplifiers, and gate drivers in one 28-pin TSSOP. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output secondary-side controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3803-5 | Single-output synchronous controller; no optocoupler driver or second-output PWM; fixed 5V output option | Lacks dual-output regulation capability; suitable only for main-output-only isolated supplies | Select LTC3803-5 only when auxiliary output regulation is handled externally or not required |
| UCC28911 | Primary-side flyback controller with integrated HV start-up; no secondary-side sensing or synchronous drive | Eliminates optocoupler but sacrifices tight cross-regulation and synchronous rectification benefits | Choose UCC28911 for cost-sensitive, lower-power (<15W) flyback designs where ±5% regulation suffices |
Compared with LTC3803-5 and UCC28911, LT3804EFE#TRPBF uniquely delivers simultaneous optocoupler-based main-output control and autonomous auxiliary-output PWM regulation in a single IC - enabling high-efficiency, tightly regulated dual-rail isolated supplies without external controllers or discrete drivers.
Availability
LT3804EFE#TRPBF is available at Aetrix Electronics and suitable for 48V telecom power systems, multi-output server VRMs, offline industrial PSUs, and compact DC/DC power modules requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LT3804EFE#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 acquired Linear Technology in 2017 and maintains its precision analog and power management portfolio. Linear pioneered high-performance switching regulators with advanced control architectures and robust thermal packaging.
The LT3804 product line was designed specifically for high-efficiency, multi-output isolated DC/DC converters - targeting applications demanding tight cross-regulation, synchronous rectification, and simplified secondary-side design without sacrificing accuracy or reliability.
FAQ
What is the function of the BGS pin on the LT3804EFE#TRPBF?
The BGS (Bottom Gate Switching) pin on the LT3804EFE#TRPBF controls discontinuous conduction mode (DCM) operation for the second output. When left open, CA2 monitors inductor current and disables BGATE when the sense voltage drops below 8mV - preventing reverse current and improving light-load efficiency. Grounding BGS forces continuous conduction mode (CCM) except during soft-start. This behavior is confirmed in the Applications Information section of the LT3804EFE#TRPBF datasheet and validated in Figure 2's operating description.
How does the LT3804EFE#TRPBF achieve true differential remote sensing?
The LT3804EFE#TRPBF achieves true differential remote sensing through dedicated GNDS1 and GNDS2 pins, each serving as the local ground reference for VFB1 and VFB2 respectively. These pins must be connected directly to the load-side ground points of their respective outputs - not to the common PCB ground - to eliminate voltage drop errors from PCB traces. The datasheet specifies that GNDS1/GNDS2 must remain within ±100mV of system ground for proper operation, and disconnecting either shuts down the LT3804EFE#TRPBF.
Can the LT3804EFE#TRPBF regulate outputs with different voltage levels simultaneously?
Yes, the LT3804EFE#TRPBF is explicitly designed to regulate two independent output voltages simultaneously - for example, 3.3V and 1.8V - using separate feedback networks. VFB1 and VFB2 each reference a 0.6V internal bandgap, allowing output programming via resistor dividers: VOUT1 = 0.6 × (1 + R13/R14), VOUT2 = 0.6 × (1 + R3/R4). The design example on page 11 confirms concurrent 3.3V/15A and 1.8V/15A regulation using this method in an actual LT3804EFE#TRPBF application.
What is the maximum switching frequency supported by the LT3804EFE#TRPBF?
The LT3804EFE#TRPBF supports a maximum switching frequency of 800kHz when synchronized, as specified in the "Final Electrical Specifications" table. This upper limit depends on the CSET capacitor value: with CSET = 200pF, the sync range is 575–800kHz. In free-running mode (no SYNC signal), the max frequency is 570kHz (CSET = 200pF). The 800kHz figure is measured and guaranteed over temperature for the LT3804E grade, per the Electrical Characteristics table on page 3.
Does the LT3804EFE#TRPBF include built-in protection features?
Yes, the LT3804EFE#TRPBF integrates multiple protection functions: programmable current limiting on both outputs (50mV threshold), power-good monitoring with 200µs delay on out-of-regulation detection, soft-start sequencing for controlled turn-on, and automatic shutdown if GNDS1 or GNDS2 is disconnected. The datasheet confirms these in the Features list, Electrical Characteristics (e.g., PGOOD delay time), and Applications Information sections - all verified for the LT3804EFE#TRPBF part number.
LT3804EFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Programmable:
- Not Verified
- Applications:
- Secondary-Side Controller
- Voltage - Input:
- -
- Voltage - Supply:
- 8V ~ 25V
- Current - Supply:
- 9 mA
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TSSOP-EP
LT3804EFE#TRPBF FAQ
1.How can I place an order for LT3804EFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3804EFE#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 LT3804EFE#TRPBF reliable?
The price and inventory of LT3804EFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3804EFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3804EFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3804EFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3804EFE#TRPBF?
LT3804EFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3804EFE#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 LT3804EFE#TRPBF?
For technical support, including LT3804EFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3804EFE#TRPBF requirements.
6.How does Aetrix verify that LT3804EFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3804EFE#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 LT3804EFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3804EFE#TRPBF?
All LT3804EFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3804EFE#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 LT3804EFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3804EFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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