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Analog Devices Inc. LT3694EFE#TRPBF
- Part No.:
- LT3694EFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Voltage Regulators - Linear + Switching
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3694EFE#TRPBF.pdf
- Description:
- IC REG TRIPLE BUCK/LNR 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,409
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Product details
Overview
LT3694EFE#TRPBF from Analog Devices (formerly Linear Technology) is a 36V, 2.6A monolithic buck regulator with dual LDO 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 integrates track/soft-start for power sequencing in industrial power supplies.
For engineers reviewing the LT3694EFE#TRPBF datasheet, LT3694EFE#TRPBF pinout, LT3694EFE#TRPBF application, or LT3694EFE#TRPBF equivalent, key selection considerations include its triple-output architecture, 0.75V feedback reference, overvoltage shutdown up to 70V transients, thermal shutdown, and compatibility with external NPN pass transistors for LDOs.
Technical Context
The LT3694EFE#TRPBF implements constant-frequency current-mode control for the main buck stage, using VC1 error amplifier output to regulate peak switch current. Its dual LDO controllers operate independently with programmable current limit via external sense resistors on LIM2/LIM3 pins and base drive on DRV2/DRV3 pins.
It supports power supply sequencing via three TRK/SS pins (each with 3–4µA pull-up and 35–70mV start threshold), provides PGOOD monitoring across all three FB pins (90% VFB threshold), and includes BST boost circuitry requiring external capacitor for internal NPN switch saturation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 36V continuous; survives 70V non-repetitive transients - enables use with lead-acid batteries, wall adapters, and unregulated DC rails. |
| Buck Output Current | Up to 2.6A - sufficient for primary system rail in DSL modems or industrial I/O modules. |
| Feedback Reference | 750mV ±15mV - sets precise output voltage with resistor divider; supports VOUT(MIN) = 0.75V. |
| Switching Frequency | 250kHz to 2.5MHz (RT-programmable) - allows optimization of size (high fSW) vs. efficiency (low fSW). |
| Overvoltage Shutdown | 38V typical trip point - protects internal circuitry during load dump or surge events. |
| EN/UVLO Threshold | 1.20V typical turn-on; 500mV bias-on - enables precise undervoltage lockout with resistor divider from VIN. |
| Thermal Shutdown | Activates above 165°C junction - prevents permanent damage during overload or poor heatsinking. |
Pinout & Package
LT3694EFE#TRPBF uses a thermally enhanced 20-lead plastic TSSOP package with exposed pad (Pin 21) soldered to PCB ground for thermal and electrical integrity (θJA = 38°C/W). Pin functions are validated per Linear Technology datasheet 36941fb.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Main power input | Supplies internal switch, reference, and startup circuits; requires local ceramic bypass (4.7–22µF). |
| EN/UVLO (Pin 2) | Enable & undervoltage detection | Shuts down device below 0.35V; enables at >1.20V; supports resistor-divider UVLO configuration. |
| SYNC (Pin 3) | Frequency sync input | Accepts external clock (0.25–2.5MHz, TTL/CMOS); unused must be grounded - LT3694 variant only. |
| PGOOD (Pin 4) | Power-good open-collector output | Pulls low if any FB pin drops below 90% of nominal - enables system-level power sequencing and fault reporting. |
| RT (Pin 5) | Frequency programming | Sets switching frequency via resistor to GND (e.g., 40.2kΩ → 1MHz); 0.75V applied across RT. |
| TRK/SS1–3 (Pins 5,6,17) | Tracking/soft-start inputs | Override 0.75V reference when <0.75V; enable ratiometric start-up or soft-start with capacitor to GND. |
| FB1–3 (Pins 18,7,16) | Feedback inputs | Regulate respective outputs to min(0.75V, TRK/SSx); require resistor dividers with ≤10kΩ Thevenin impedance. |
| DRV2/DRV3 (Pins 8,15) | LDO base drive outputs | Supply up to 6V/15mA to external NPN pass transistors - BIAS pin must be ≥1.8V above LDO output. |
| LIM2/LIM3 (Pins 9,14) | LDO current limit sense | Monitor voltage across external sense resistor connected to BIAS; set foldback current limit (e.g., 60mV = 1A with 60mΩ). |
| BST (Pin 21) | Bootstrap supply | Drives internal NPN switch; requires external capacitor between BST and SW for voltage boost above VIN. |
| DA (Pin 22) | Diode current sense | Detects catch diode conduction to prevent excessive inductor current during overload or short-circuit. |
| SW (Pins 23,24) | Switch node | Connects to inductor and Schottky catch diode; high dv/dt node requiring careful layout and grounding. |
| GND (Pin 21 Exposed Pad) | Power/signal ground | Exposed thermal pad must be soldered to large PCB ground plane - critical for thermal performance and noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| Triple-output regulation | One 2.6A buck + two independent LDO controllers - reduces component count in multi-rail systems like industrial PLCs. |
| Programmable switching frequency | 250kHz–2.5MHz via single RT resistor - enables compact designs with ceramic capacitors and small inductors. |
| Independent track/soft-start | Three dedicated TRK/SS pins with 3–4µA pull-up - simplifies controlled power-up sequencing for microcontrollers and FPGAs. |
| Overvoltage transient protection | 70V absolute max input; 38V overvoltage shutdown - ensures robustness in automotive or factory-floor environments. |
| Integrated PGOOD monitoring | Single open-drain output asserting low if any of three FB voltages falls below 90% - eliminates need for external supervisors. |
Applications
| Industrial Power Distribution | DSL/Cable Modem Power |
|---|---|
Use Scenario: Providing isolated 3.3V, 2.5V, and 1.8V rails from a 12V or 24V backplane in programmable logic controllers. IC Role / Device Role / Timing Role: Primary triple-output PMIC managing main processor, I/O, and memory rails with coordinated soft-start. Use Value: Reduces bill-of-materials by integrating buck + dual LDO controllers; TRK/SS pins ensure safe power-up order without external sequencers. | Use Scenario: Generating stable 3.3V (PHY), 2.5V (analog front-end), and 1.8V (DSP core) from a 48V PoE-derived 12V supply in broadband gateways. IC Role / Device Role / Timing Role: Central power management IC delivering tightly regulated, low-noise outputs with fast transient response. Use Value: 0.75V reference and current-mode control deliver <1% output deviation under dynamic load steps; PGOOD enables firmware-initiated reset on rail failure. |
| Wall Transformer Regulation | Distributed Power Systems |
Use Scenario: Replacing linear regulators in AC/DC adapter secondary-side regulation for consumer electronics with wide-input legacy supplies. IC Role / Device Role / Timing Role: High-efficiency buck-LDO hybrid replacing inefficient discrete solutions while maintaining low EMI. Use Value: 4V–36V input range accommodates aging wall adapters with sagging output; 2.6A buck handles peak loads without thermal derating. | Use Scenario: Local regulation in distributed architectures where 5V or 12V bus powers multiple subsystems with differing voltage requirements. IC Role / Device Role / Timing Role: Point-of-load regulator providing clean, sequenced power to sensor nodes, communication modules, and actuators. Use Value: Dual LDO controllers support custom current-limited outputs (e.g., 450mA @ 2.5V, 450mA @ 1.8V) with independent tracking - avoids overdesigning pass devices. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar triple-output buck+LDO regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3694-1EFE#TRPBF | Replaces SYNC pin with CLKOUT pin; identical buck/LDO specs and pinout. | Required when synchronizing other DC/DC converters to LT3694's clock - not drop-in compatible for SYNC-driven systems. | Select LT3694-1EFE#TRPBF only if master clock output is needed; otherwise LT3694EFE#TRPBF is preferred for slave synchronization. |
| LT3573EFE#TRPBF | Single 2.5A buck + one LDO controller; no TRK/SS or PGOOD; 32V max input. | Lacks dual LDOs and sequencing capability - suitable only for simpler two-rail systems without strict startup ordering. | Choose LT3694EFE#TRPBF when three independent, trackable outputs and system-level fault reporting are required. |
Compared with LT3694-1EFE#TRPBF, the LT3694EFE#TRPBF provides synchronization input instead of clock output - making it ideal for systems where timing is externally controlled. Versus LT3573EFE#TRPBF, it adds a second LDO channel, TRK/SS sequencing, and PGOOD, enabling more complex power architectures without additional ICs.
Availability
LT3694EFE#TRPBF is available at Aetrix Electronics and suitable for industrial power distribution, DSL/cable modem power, and wall transformer regulation requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LT3694EFE#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LT3694 product line was designed for compact, high-reliability triple-output power conversion in space-constrained industrial and communications equipment - emphasizing wide input range, robust protection, and flexible sequencing.
FAQ
What is the maximum input voltage rating for LT3694EFE#TRPBF?
The LT3694EFE#TRPBF has an absolute maximum input voltage rating of 70V for non-repetitive 1-second transients, with continuous operation limited to 36V. Its overvoltage shutdown activates at approximately 38V to protect internal circuitry - a key feature for automotive and industrial environments with load-dump risks.
Does LT3694EFE#TRPBF support external clock synchronization?
Yes, the LT3694EFE#TRPBF supports external clock synchronization via its SYNC pin (Pin 3), accepting TTL/CMOS logic-level signals from 0.25MHz to 2.5MHz. The RT resistor must be configured for a frequency at least 20% below the sync source to ensure reliable locking - confirmed in the 36941fb datasheet Figure 1 and Electrical Characteristics table.
How does the PGOOD function work on LT3694EFE#TRPBF?
The PGOOD pin (Pin 4) is an open-collector output that pulls low when the voltage on any of the three FB pins falls below 90% of its nominal regulated value. This provides system-level fault detection across all three outputs - for example, if the 1.8V LDO output droops due to overload, PGOOD asserts low to trigger host processor reset or alert logic.
Can LT3694EFE#TRPBF drive external NPN transistors for the LDOs?
Yes, the LT3694EFE#TRPBF includes dedicated DRV2 and DRV3 pins (Pins 8 and 15) that provide up to 6V and 15mA of base drive for external NPN pass transistors. The LIM2 and LIM3 pins (Pins 9 and 14) allow current limiting via external sense resistors connected to the BIAS pin - fully documented in the Pin Functions section of the LT3694/LT3694-1 datasheet.
What package type and thermal characteristics apply to LT3694EFE#TRPBF?
The LT3694EFE#TRPBF uses a 20-lead plastic TSSOP package with exposed thermal pad (Pin 21), specified for θJA = 38°C/W. The exposed pad must be soldered to a PCB ground plane for both thermal dissipation and signal integrity - a requirement explicitly stated in the datasheet's FE Package drawing and Absolute Maximum Ratings notes.
LT3694EFE#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
LT3694EFE#TRPBF FAQ
1.How can I place an order for LT3694EFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3694EFE#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 LT3694EFE#TRPBF reliable?
The price and inventory of LT3694EFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3694EFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3694EFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3694EFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3694EFE#TRPBF?
LT3694EFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3694EFE#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 LT3694EFE#TRPBF?
For technical support, including LT3694EFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3694EFE#TRPBF requirements.
6.How does Aetrix verify that LT3694EFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3694EFE#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 LT3694EFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3694EFE#TRPBF?
All LT3694EFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3694EFE#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 LT3694EFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3694EFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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