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Analog Devices Inc. LT3694IFE-1#TRPBF
- Part No.:
- LT3694IFE-1#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Voltage Regulators - Linear + Switching
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3694IFE-1#TRPBF.pdf
- Description:
- IC REG TRIPLE BUCK/LNR 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,459
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Product details
Overview
LT3694IFE-1#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 PGOOD, TRK/SS, and CLKOUT for power sequencing and synchronization. It is used in DSL modems and distributed power systems requiring compact triple-output regulation.
For engineers reviewing the LT3694IFE-1#TRPBF datasheet, LT3694IFE-1#TRPBF pinout, LT3694IFE-1#TRPBF application, or LT3694IFE-1#TRPBF equivalent, key selection considerations include its 2.6A buck switch current limit, dual LDO controller architecture with external NPN pass transistors, CLKOUT functionality (distinguishing it from LT3694), thermal shutdown, overvoltage protection up to 70V transients, and compatibility with ceramic output capacitors and small inductors.
Technical Context
The LT3694IFE-1#TRPBF integrates a constant-frequency current-mode buck regulator with two independent LDO controllers, each using external NPN transistors and programmable current limiting via LIM2/LIM3 pins. Its internal error amplifier regulates FB pins to 0.75V (or tracks TRK/SS voltage if lower), enabling precise soft-start and supply sequencing.
Unlike the base LT3694, the -1 variant replaces SYNC with CLKOUT - a digital clock output that allows other switching regulators to synchronize to its internal oscillator. This eliminates need for external clock sources in multi-rail systems while maintaining full control over switching frequency via RT resistor or internal oscillator.
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 industrial rails. |
| Buck Output Current | Up to 2.6A with internal bipolar switch - eliminates need for external MOSFET in mid-power applications. |
| Switching Frequency | Adjustable 250kHz–2.5MHz via RT resistor; supports external sync only on LT3694 (not LT3694-1) - enables optimization of size vs. efficiency. |
| Feedback Reference | 0.75V ±15mV across all three FB pins - ensures tight output voltage accuracy and simplifies resistor divider design. |
| LDO Controller Type | Dual NPN-based linear regulator controllers with foldback current limit - supports high-current, low-noise post-regulation with external pass devices. |
| CLKOUT Function | Digital clock output (1.6–2.6V VOH, 0.3V VOL at 50µA) - enables deterministic timing coordination across multiple DC/DC stages without external clock generator. |
| Thermal Protection | Internal thermal shutdown with automatic recovery - prevents latch-up during overload or poor heatsinking conditions. |
Pinout & Package
LT3694IFE-1#TRPBF is housed in a thermally enhanced 20-lead plastic TSSOP package (JEDEC MO-153) with exposed pad (Pin 21) soldered to PCB ground for thermal and electrical integrity. θJA = 38°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Main input power supply | Supplies internal switch, reference, and startup circuitry; must be locally bypassed with ≥4.7µF ceramic capacitor. |
| EN/UVLO (Pin 2) | Enable and undervoltage lockout input | Shuts down device below 0.5V (typ); enables at >1.2V (typ); supports resistor-divider UVLO configuration. |
| CLKOUT (Pin 3) | Digital clock output | Provides synchronized clock signal (same frequency as internal oscillator) to coordinate other regulators - unique to LT3694-1 variants. |
| PGOOD (Pin 4) | Open-collector power-good indicator | Pulls low when any FB pin drops below 90% of nominal - enables system-level power sequencing and fault detection. |
| RT (Pin 4) | Frequency-setting resistor connection | Sets switching frequency by drawing 0.75V reference current; formula: fSW = 49.8/(RT + 8.8) MHz (RT in kΩ). |
| TRK/SS1–3 (Pins 5,6,17) | Tracking/soft-start inputs | Override 0.75V reference when <0.75V - enables ratiometric start-up, voltage tracking, or controlled soft-start via capacitor ramp. |
| FB1–3 (Pins 18,7,16) | Negative feedback inputs | Each regulates corresponding output to lesser of 0.75V or TRK/SS voltage - supports independent or coordinated regulation. |
| DRV2/DRV3 (Pins 8,15) | LDO base drive outputs | Provide up to 6V base drive for external NPN pass transistors - enables high-current LDO operation with low VCE(sat) transistors. |
| LIM2/LIM3 (Pins 9,14) | LDO current limit sense inputs | Monitor voltage across external sense resistors connected to BIAS - implement foldback current limiting for LDO pass devices. |
| BIAS (Pin 20) | Internal bias supply input | Must be ≥3V (typically tied to VOUT1); supplies internal regulator and LDO base current - reduces VIN dissipation and improves efficiency. |
| BST (Pin 21) | Bootstrap supply for internal switch | Requires external capacitor between BST and SW - generates boosted gate drive to fully saturate internal bipolar switch. |
| DA (Pin 22) | Diode current sense input | Detects catch diode conduction to prevent excessive inductor current during overload or short-circuit - enhances fault robustness. |
| SW (Pins 23,24) | Switch node output | Connects to inductor and Schottky catch diode - carries high di/dt switching current; requires tight layout and Kelvin connection. |
Key Features
| Feature | Design Value |
|---|---|
| Triple-output architecture (1 buck + 2 LDO controllers) | Reduces bill-of-materials and board space in multi-rail systems such as DSL modems and industrial controllers. |
| CLKOUT instead of SYNC (LT3694-1 variant) | Enables master-slave synchronization without external clock source - simplifies timing design in multi-converter power trees. |
| Independent TRK/SS and PGOOD per regulator | Supports flexible power-up/down sequencing and real-time fault monitoring across all three outputs. |
| Overvoltage shutdown (38V trip, 70V transient survival) | Protects downstream circuitry from line surges and hot-swap events - critical for automotive and industrial environments. |
| Current-mode control with slope compensation | Ensures stable operation across wide duty-cycle range and input/output combinations - eliminates need for external compensation. |
| Thermally enhanced TSSOP with exposed pad | Enables 2.6A continuous operation at ambient temperatures up to 85°C without forced airflow - suitable for dense industrial layouts. |
Applications
| DSL/Cable Modem Power | Industrial Distributed Power |
|---|---|
|
Use Scenario: Powering FPGA I/O banks, PHY interfaces, and microcontroller cores in broadband access equipment. IC Role / Device Role / Timing Role: Primary triple-output PMIC delivering 3.3V/1.7A (buck), 2.5V/450mA and 1.8V/450mA (LDOs) with synchronized startup. Use Value: Eliminates need for discrete LDOs and sequencing ICs; CLKOUT ensures jitter-free timing alignment between data path and control logic. |
Use Scenario: Regulating auxiliary rails in programmable logic controllers (PLCs) and sensor interface modules. IC Role / Device Role / Timing Role: Centralized power manager providing isolated, sequenced 5V, 3.3V, and 1.2V supplies from 24V industrial bus. Use Value: Withstands 70V transients on 24V rail; TRK/SS inputs enable safe cold-start sequencing; PGOOD confirms all rails before system boot. |
| Wall Transformer Regulation | Automotive Infotainment Core Supply |
|
Use Scenario: Converting unregulated 9–24V AC/DC adapter output into clean, low-noise 3.3V and 1.8V for embedded processors. IC Role / Device Role / Timing Role: Buck-LDO hybrid regulator minimizing EMI and output ripple while supporting variable input from low-quality adapters. Use Value: Ceramic-capacitor compatible design reduces footprint and cost; overvoltage shutdown protects against adapter failure modes. |
Use Scenario: Generating core voltages for infotainment SoCs in vehicles with 12V battery input subject to load dump. IC Role / Device Role / Timing Role: High-input-voltage PMIC delivering 1.1V/2A (buck), 3.3V/500mA and 5V/300mA (LDOs) with automotive-grade thermal margin. Use Value: Survives 70V load-dump transients; thermal shutdown prevents thermal runaway under hood-high ambient conditions. |
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 |
|---|---|---|---|
| LT3694IFE#TRPBF | Lacks CLKOUT; has SYNC pin instead - cannot act as clock master but can synchronize to external source. | Suitable where centralized clock distribution is not required and external sync is available. | Select LT3694IFE#TRPBF only if system already provides a stable clock source and no master timing role is needed. |
| LT8614EFE#TRPBF | Single 4A buck with integrated MOSFETs; no LDO controllers - requires external LDOs for auxiliary rails. | Better efficiency above 1MHz; smaller solution size for buck-only designs; no native triple-output capability. | Choose LT8614EFE#TRPBF when highest efficiency (>95%) and minimal footprint are prioritized over integrated LDO control. |
Compared with LT3694IFE#TRPBF, the LT3694IFE-1#TRPBF adds system-level timing control via CLKOUT but sacrifices SYNC flexibility; versus LT8614EFE#TRPBF, it trades peak efficiency for integrated LDO management and transient-hardened input stage - making it optimal for cost-sensitive, multi-rail industrial designs needing robustness and simplicity.
Availability
LT3694IFE-1#TRPBF is available at Aetrix Electronics and suitable for DSL modems, industrial PLCs, and automotive infotainment systems requiring stable component supply, long-term lifecycle support, and guaranteed performance across –40°C to 125°C junction temperature.
Supply support for LT3694IFE-1#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3694/LT3694-1 product line was designed for compact, robust multi-rail power conversion in space-constrained systems requiring high input voltage tolerance, precise sequencing, and low EMI - especially where ceramic capacitors and small magnetics are preferred.
FAQ
What is the key functional difference between LT3694IFE-1#TRPBF and LT3694IFE#TRPBF?
The LT3694IFE-1#TRPBF replaces the SYNC input pin with a CLKOUT pin, enabling it to serve as a clock master for synchronizing other switching regulators. In contrast, the LT3694IFE#TRPBF uses SYNC to accept an external clock signal but cannot generate one. This makes LT3694IFE-1#TRPBF ideal for systems requiring deterministic timing coordination without external clock generators, while LT3694IFE#TRPBF suits designs with existing clock infrastructure.
Does LT3694IFE-1#TRPBF support adjustable output voltages for all three regulators?
Yes, LT3694IFE-1#TRPBF supports adjustable outputs for all three rails. The buck output is set via resistor divider on FB1; the two LDO outputs are configured using external NPN pass transistors and feedback dividers on FB2/FB3. All three FB pins regulate to 0.75V (±15mV), allowing precise voltage programming - for example, 3.3V (FB1), 2.5V (FB2), and 1.8V (FB3) - with independent TRK/SS control for sequencing.
What is the maximum supported switching frequency for LT3694IFE-1#TRPBF, and how is it set?
The LT3694IFE-1#TRPBF supports switching frequencies from 250kHz to 2.5MHz, set exclusively by an external resistor (RT) connected from Pin 4 to ground. The relationship is fSW = 49.8/(RT + 8.8) MHz (RT in kΩ). For example, a 40.2kΩ resistor yields ~1.0MHz. Unlike the LT3694, the LT3694-1 variant does not support external clock synchronization - its CLKOUT pin is output-only.
How does the overvoltage protection work on LT3694IFE-1#TRPBF?
The LT3694IFE-1#TRPBF includes overvoltage shutdown that trips at ~38V (typical) on the VIN pin, disabling the internal switch to protect downstream components. It is rated to survive non-repetitive 70V transients for up to 1 second - critical for applications powered from unregulated wall transformers or automotive batteries. This protection operates independently of EN/UVLO and remains active even during shutdown.
Can LT3694IFE-1#TRPBF drive external MOSFETs instead of bipolar switches for the LDO sections?
No - the LT3694IFE-1#TRPBF's DRV2 and DRV3 pins are specifically designed to drive the base of external NPN transistors (not MOSFET gates). They provide up to 6V base drive and rely on BIAS pin current for sourcing. Using MOSFETs would require level-shifting, gate-drive buffering, and loss of built-in foldback current limiting - which is implemented via LIM2/LIM3 sensing of emitter current in NPN configurations.
LT3694IFE-1#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-1#TRPBF FAQ
1.How can I place an order for LT3694IFE-1#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3694IFE-1#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-1#TRPBF reliable?
The price and inventory of LT3694IFE-1#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-1#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3694IFE-1#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3694IFE-1#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3694IFE-1#TRPBF?
LT3694IFE-1#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3694IFE-1#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-1#TRPBF?
For technical support, including LT3694IFE-1#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3694IFE-1#TRPBF requirements.
6.How does Aetrix verify that LT3694IFE-1#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3694IFE-1#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-1#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3694IFE-1#TRPBF?
All LT3694IFE-1#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3694IFE-1#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-1#TRPBF part is unused and in its original packaging.
Return procedure for LT3694IFE-1#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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