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Analog Devices Inc. LT3694IFE#TRPBF
- Part No.:
- LT3694IFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Voltage Regulators - Linear + Switching
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3694IFE#TRPBF.pdf
- Description:
- IC REG TRIPLE BUCK/LNR 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,221
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Product details
Overview
LT3694IFE#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic 36V, 2.6A step-down DC/DC converter with dual LDO regulator controllers in a 20-lead TSSOP package. It delivers three regulated outputs (buck + two LDOs), supports 4V–36V input, features adjustable 250kHz–2.5MHz switching frequency, and includes independent track/soft-start inputs for power supply sequencing in industrial power systems.
For engineers reviewing the LT3694IFE#TRPBF datasheet, LT3694IFE#TRPBF pinout, LT3694IFE#TRPBF application, or LT3694IFE#TRPBF equivalent, this page provides verified technical context, confirmed pin functions, real-world application mappings, and validated alternative options for multi-rail power management designs requiring high-voltage tolerance and precise sequencing.
Technical Context
The LT3694IFE#TRPBF integrates a constant-frequency current-mode buck regulator with internal 2.6A bipolar NPN switch and two independent LDO controller channels using external NPN pass transistors. Its VC1 error amplifier output controls peak switch current with 0.75V reference threshold and 2V clamp, enabling stable loop compensation.
It implements overvoltage shutdown at 38V (surviving 70V transients), programmable EN/UVLO thresholds (1.20V typical turn-on), and PGOOD monitoring across all three FB pins with 90% regulation window. The SYNC pin accepts external clocks up to 2.5MHz (LT3694 variant), while the FE package excludes CLKOUT functionality present in LT3694-1.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 36V continuous; survives 70V non-repetitive transients - enables direct use with 24V industrial rails and unregulated wall adapters. |
| Switching Regulator Output | Up to 2.6A at VOUT ≥ 0.75V - supports high-current digital loads like FPGAs or microcontrollers without external MOSFETs. |
| Switching Frequency Range | 250kHz to 2.5MHz via RT resistor - allows optimization between small ceramic capacitor size (high-f) and efficiency (low-f). |
| Feedback Reference Voltage | 750mV ±15mV over temperature - ensures accurate output regulation across –40°C to 125°C junction range. |
| LDO Controller Current Limit | Programmable via external sense resistors on LIM2/LIM3 pins - provides foldback protection for external NPN pass transistors. |
| Power Good Threshold | 90% of nominal FB voltage - asserts PGOOD only when all three regulators (buck + two LDOs) are within regulation tolerance. |
| Thermal Shutdown | Active above 165°C junction temperature - protects device during sustained overload or poor PCB thermal design. |
Pinout & Package
LT3694IFE#TRPBF uses a 20-lead plastic TSSOP package with exposed pad (Pin 21 = GND). Thermal resistance θJA = 38°C/W. Exposed pad must be soldered to PCB ground for electrical integrity and thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Main input power supply | Supplies internal switch, bias circuitry, and startup logic; bypass locally with ≥4.7µF X7R ceramic capacitor. |
| EN/UVLO (Pin 2) | Enable and undervoltage lockout input | Shuts down device below 0.35V; initiates soft-start at 1.20V typical; configurable as precision UVLO with resistor divider from VIN. |
| SYNC (Pin 3) | External clock synchronization input | Accepts 0.25–2.5MHz TTL/CMOS clock; forces LT3694IFE#TRPBF to synchronize switching to external source - no CLKOUT function. |
| PGOOD (Pin 4) | Open-collector power-good indicator | Pulls low if any FB pin drops below 90% of target - enables system-level power sequencing and fault detection. |
| RT (Pin 5) | Frequency setting resistor connection | Connects to ground to set fSW = 49.8/(RT + 8.8) MHz; RT = 40.2kΩ yields 1MHz typical - critical for EMI and component sizing. |
| TRK/SS1–3 (Pins 5,6,17) | Tracking/soft-start control inputs | Override 0.75V FB reference when <0.75V - enables ratiometric start-up or controlled ramp-up of each output independently. |
| FB1–3 (Pins 18,7,16) | Negative feedback inputs | Regulate respective outputs to min(0.75V, TRK/SSx); require resistor dividers with ≤10kΩ Thevenin impedance to minimize bias error. |
| DRV2/DRV3 (Pins 8,15) | LDO base drive outputs | Supply up to 6V/15mA base current to external NPN transistors - eliminates need for discrete driver stages. |
| LIM2/LIM3 (Pins 9,14) | LDO current limit sense inputs | Monitor voltage across external sense resistors tied to BIAS - implement foldback current limiting for LDO pass devices. |
| BST (Pin 21) | Bootstrap drive voltage node | Requires external capacitor to generate >VIN voltage - ensures full saturation of internal bipolar switch for low VCESAT operation. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent LDO controllers | Each with dedicated TRK/SS, FB, DRV, and LIM pins - enables fully decoupled sequencing and current limiting for mixed-signal subsystems. |
| Overvoltage transient protection | Shuts down at 38V input, withstands 70V/1s transients - eliminates need for external TVS diodes in 24V industrial environments. |
| Three-output power management | Single IC generates buck + two LDO rails (e.g., 3.3V/1.7A, 2.5V/450mA, 1.8V/450mA) - reduces BOM count and board area vs discrete solutions. |
| Current-mode control architecture | Provides inherent cycle-by-cycle current limiting and improved transient response vs voltage-mode converters - stabilizes under dynamic load steps. |
| Thermally enhanced TSSOP package | 20-lead exposed-pad TSSOP with θJA = 38°C/W - supports 2.6A continuous operation without forced air in compact industrial layouts. |
Applications
| Industrial PLC I/O Modules | DSL/Cable Modem Power Supplies |
|---|---|
|
Use Scenario: Powering isolated analog input/output circuits, communication interfaces, and microcontroller cores in DIN-rail mounted controllers. IC Role / Device Role / Timing Role: Primary triple-output PMIC delivering 3.3V for MCU, 2.5V for ADC/DAC, and 1.8V for FPGA I/O banks with synchronized soft-start. Use Value: Eliminates need for three separate regulators and external sequencing ICs; overvoltage protection handles 24V rail transients per IEC 61000-4-4. |
Use Scenario: Generating clean, sequenced rails for QAM demodulators, Ethernet PHYs, and DOCSIS-compliant processors in broadband gateways. IC Role / Device Role / Timing Role: Buck regulator supplies main 3.3V domain; LDO controllers condition 1.8V and 2.5V low-noise analog rails with independent tracking. Use Value: 10Hz–100kHz LDO output noise < 20µVRMS meets DSL spectral mask requirements; PGOOD enables firmware-controlled boot validation. |
| Distributed Power Regulation | Wall Transformer-Based Systems |
|
Use Scenario: Local regulation at point-of-load in factory automation nodes with long 24V distribution lines and variable loading. IC Role / Device Role / Timing Role: Step-down converter regulates from 24V bus; LDOs provide stable auxiliary voltages immune to upstream line drop and ripple. Use Value: Wide 4V–36V input accommodates voltage sag under load; LDO controllers maintain regulation even if buck output dips due to line impedance. |
Use Scenario: Compact AC/DC adapter replacement powering embedded Linux systems, routers, or VoIP phones with multiple voltage domains. IC Role / Device Role / Timing Role: Accepts unregulated 9–36V DC from off-line rectifier; generates tightly regulated, low-ripple outputs with minimal external components. Use Value: High 2.6A buck current and ceramic-capacitor compatibility reduce solution size by >40% vs legacy controllers requiring electrolytics. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar triple-output power management applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EFE#PBF | Single 3.5A buck regulator only; no integrated LDO controllers - requires external linear regulators for auxiliary rails. | Lacks native dual-LDO control, tracking, and PGOOD aggregation - increases component count and sequencing complexity. | Select when only high-current buck output is needed and LDOs can be implemented discretely with tighter noise specs. |
| TPS546B24RVFT | 6V–18V input, 12A buck with PMBus interface; no LDO controllers - digital control but narrower voltage range and no analog sequencing support. | Requires external DACs or supervisors for multi-rail sequencing; lacks analog TRK/SS pins and overvoltage survival capability. | Choose for digitally managed server or telecom systems where telemetry and remote configuration outweigh analog simplicity. |
Compared with LTC3631EFE#PBF and TPS546B24RVFT, the LT3694IFE#TRPBF uniquely integrates buck + dual LDO controllers with analog tracking, 36V input tolerance, and 70V transient survival in one TSSOP package - making it optimal for cost-sensitive, high-reliability industrial power designs requiring minimal external components.
Availability
LT3694IFE#TRPBF is available at Aetrix Electronics and suitable for industrial PLCs, DSL modems, distributed power nodes, and wall transformer-based embedded systems requiring stable component supply across extended temperature ranges.
Supply support for LT3694IFE#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 full product support, datasheets, and application engineering for legacy Linear parts including the LT3694 family.
The LT3694 product line was designed for high-voltage, multi-rail industrial power management - emphasizing robustness against transients, analog sequencing flexibility, and integration of switching + linear regulation in single packages.
FAQ
What is the maximum continuous output current of the LT3694IFE#TRPBF buck regulator?
The LT3694IFE#TRPBF buck regulator supports up to 2.6A continuous output current at its main switching output. This rating assumes proper thermal design with the exposed pad soldered to PCB ground and ambient temperature ≤85°C. Peak switch current limit is 3.5A minimum at low duty cycles, decreasing linearly to 2.8A at 80% duty cycle per datasheet specifications.
Does the LT3694IFE#TRPBF support clock synchronization, and how is it implemented?
Yes, the LT3694IFE#TRPBF supports clock synchronization via its SYNC pin (Pin 3), which accepts external TTL/CMOS clock signals from 0.25MHz to 2.5MHz. Unlike the LT3694-1 variant, it does not provide CLKOUT functionality. To synchronize, connect the external clock to SYNC and set the RT resistor to program a free-running frequency at least 20% below the sync frequency.
How does the LT3694IFE#TRPBF handle input overvoltage conditions?
The LT3694IFE#TRPBF includes built-in overvoltage shutdown that disables regulation when VIN exceeds 38V (typical), protecting internal circuitry. It is rated to survive non-repetitive 70V transients for up to 1 second - a key differentiator for industrial applications with inductive load switching or poor input filtering.
Can the LT3694IFE#TRPBF generate three independent output voltages, and how are they configured?
Yes, the LT3694IFE#TRPBF generates three independent regulated outputs: one buck (via SW/FB1) and two LDOs (via DRV2/FB2/LIM2 and DRV3/FB3/LIM3). Each output is configured using external resistor dividers on FB pins and optional TRK/SS pins for tracking or soft-start. The datasheet confirms simultaneous operation with independent feedback loops and current limiting.
What package type and thermal characteristics apply to the LT3694IFE#TRPBF?
The LT3694IFE#TRPBF uses a 20-lead plastic TSSOP package with exposed thermal pad (Pin 21 = GND). Its junction-to-ambient thermal resistance is θJA = 38°C/W when mounted on a standard 2-layer PCB with 2 in² copper pour. The exposed pad must be soldered to a grounded PCB plane to ensure both electrical stability and thermal performance.
LT3694IFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Topology:
- Step-Down (Buck) (1), Linear (LDO) (2)
- Number of Outputs:
- 3
- Frequency - Switching:
- 250kHz ~ 2.5MHz
- Voltage/Current - Output 1:
- 0.75V ~ 16V, 2.6A
- Voltage/Current - Output 2:
- Controller
- Voltage/Current - Output 3:
- Controller
- w/LED Driver:
- No
- w/Supervisor:
- No
- w/Sequencer:
- Yes
- Voltage - Supply:
- 4V ~ 36V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP-EP
LT3694IFE#TRPBF FAQ
1.How can I place an order for LT3694IFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3694IFE#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 LT3694IFE#TRPBF reliable?
The price and inventory of LT3694IFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3694IFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3694IFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3694IFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3694IFE#TRPBF?
LT3694IFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3694IFE#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 LT3694IFE#TRPBF?
For technical support, including LT3694IFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3694IFE#TRPBF requirements.
6.How does Aetrix verify that LT3694IFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3694IFE#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 LT3694IFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3694IFE#TRPBF?
All LT3694IFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3694IFE#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 LT3694IFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3694IFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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