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Analog Devices Inc. LT3688IUF#TRPBF
- Part No.:
- LT3688IUF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LT3688IUF#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 800MA DL 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,143
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Product details
Overview
LT3688IUF#TRPBF from Analog Devices (formerly Linear Technology) is a dual monolithic step-down switching regulator IC with integrated power-on reset (POR) and watchdog timer functions, designed for high-reliability microprocessor supervision in harsh environments. It delivers two independent 800mA outputs (5V and 3.3V typical), operates from 3.8V to 36V input, features adjustable 350kHz–2.2MHz switching frequency, and maintains <25mVP-P output ripple in Burst Mode® with 115μA quiescent current.
For engineers reviewing the LT3688IUF#TRPBF datasheet, LT3688IUF#TRPBF pinout, LT3688IUF#TRPBF application, or LT3688IUF#TRPBF equivalent, key selection criteria include dual-output sequencing control via CONFIG pin, independently programmable POR timeout (via CPOR1/CPOR2), windowed watchdog timing (via CWDT), and thermal performance in the 4mm × 4mm QFN-24 package with exposed pad.
Technical Context
The LT3688IUF#TRPBF implements constant-frequency current-mode PWM control per channel, with internal NPN power switches, slope compensation, and VC-clamped current limiting. Its dual-regulator architecture supports independent soft-start (RUN/SS1/RUN/SS2), feedback regulation to 0.800V (±1.4% over temperature), and programmable undervoltage lockout (EN/UVLO threshold = 1.25V ±0.1V).
Supervisory functions are hardware-based: RST1/RST2 assert low when respective FB voltage drops below 90% of 0.800V; watchdog monitors WDI edge timing against user-set tWDU (18–22ms) and tWDL (0.8–1.6ms) boundaries; both POR and watchdog timeouts are capacitor-programmed with guaranteed accuracy over –40°C to 125°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.8V to 36V - supports wide industrial and automotive battery-fed systems without pre-regulation. |
| Output Current (per channel) | 800mA - sufficient to power dual-core microcontrollers, FPGAs, or sensor subsystems directly. |
| Feedback Reference Voltage | 0.800V ±1.4% - enables precise output setting with standard 1% resistors; line regulation 0.002%/V ensures stability across input range. |
| Burst Mode® Quiescent Current | 115μA at 12VIN → 3.3V/5V - extends battery life in always-on monitoring applications while holding ripple <25mVP-P. |
| Switching Frequency Range | 350kHz to 2.2MHz - selectable via RT resistor; higher frequencies allow smaller magnetics (e.g., 4.7μH at 1MHz), lower frequencies improve efficiency at high VIN/VOUT ratios. |
| Reset Threshold Accuracy | 90% of FB voltage (±2%) - guarantees reliable microprocessor reset initiation without false triggering under load transients. |
| Watchdog Window Tolerance | tWDU = 20ms ±10%, tWDL = 1.25ms ±35% at CWDT = 1000pF - provides deterministic fault detection for safety-critical firmware execution. |
Pinout & Package
The LT3688IUF#TRPBF is housed in a thermally enhanced 24-pin 4mm × 4mm plastic QFN package with exposed pad (Pin 25 = GND), θJA = 37°C/W. The exposed pad must be soldered to PCB ground plane for electrical integrity and thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1 / FB2 | Output voltage sense inputs | Regulate respective outputs to 0.800V; connect to resistor divider taps - determines VOUT1/VOUT2 precision and stability. |
| RUN/SS1 / RUN/SS2 | Soft-start timing inputs | Capacitor-to-GND sets startup ramp time; internal discharge logic prevents premature enable during power-up sequencing. |
| RST1 / RST2 | Open-drain reset outputs | Assert low when corresponding FB falls below 90% of 0.800V; weak 2.5μA pull-up to BIAS - external 100kΩ pull-up recommended for faster rise. |
| WDI / WDO / WDE | Watchdog interface | WDI accepts microprocessor pulse train; WDO pulses low on timing violation; WDE disables watchdog when >1V - enables flexible firmware supervision modes. |
| CPOR1 / CPOR2 / CWDT | Capacitor-programmed timing | CPOR1/CPOR2 set POR delay (e.g., 23.5ms @ 4700pF); CWDT sets watchdog window bounds - eliminates need for external timers or MCU GPIO overhead. |
| VIN / BIAS / BST1 / BST2 | Power delivery network | VIN supplies main switch and bias circuitry; BIAS reduces input IQ when ≥3V; BST pins drive internal NPN switches via external boost capacitors - enables high-efficiency operation up to 36V. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent regulators with sequencing control | CONFIG pin selects three startup modes: staggered (Ch2 after Ch1 OK), simultaneous, or coordinated POR - ensures deterministic power-up for multi-rail SoCs. |
| Capacitor-programmable supervisory timers | CPOR1/CPOR2 and CWDT accept standard ceramic capacitors (e.g., 4700pF for 23.5ms POR) - eliminates trimming resistors and improves production yield vs. RC-based solutions. |
| Burst Mode® with ultra-low IQ | 115μA input quiescent current at light load preserves battery runtime in remote sensors or always-on controllers without sacrificing transient response. |
| Robust fault protection | DA pin current limit (1.2A typ), overtemperature shutdown, and glitch-immune reset comparators prevent latch-up or damage during short-circuit or thermal overload events. |
| Thermally optimized QFN package | 4mm × 4mm footprint with exposed GND pad achieves θJA = 37°C/W - supports 800mA continuous output in compact industrial PCB layouts without heatsinks. |
Applications
| Automotive ECU Power Management | Industrial PLC I/O Module |
|---|---|
|
Use Scenario: Powering dual-rail microcontroller (e.g., ARM Cortex-M7 + CAN transceiver) in engine control unit with 12V/24V battery input and transient spikes up to 36V. IC Role / Device Role / Timing Role: Primary DC/DC converter providing regulated 5V (MCU core) and 3.3V (peripherals), with POR ensuring clean boot after cold crank, and watchdog verifying firmware liveness. Use Value: Eliminates discrete reset IC and separate DC/DC stages; single-chip solution withstands automotive load dump (ISO 7637-2) and meets AEC-Q100 Grade I temp range (–40°C to 125°C). |
Use Scenario: Powering isolated analog front-end (AFE), digital I/O bank, and real-time controller in modular programmable logic controller rack. IC Role / Device Role / Timing Role: Dual-output regulator delivering stable 5V (logic) and 3.3V (ADC reference), with independent POR timers validating each rail before enabling fieldbus communication. Use Value: Reduces BOM count by replacing two buck converters + two supervisors; capacitor-programmed timing simplifies certification for IEC 61000-4 immunity testing. |
| High-Reliability Medical Sensor Hub | Ruggedized IoT Edge Gateway |
|
Use Scenario: Supplying low-noise power to MEMS accelerometers, ECG amplifiers, and BLE radio in portable diagnostic device operating from Li-ion battery. IC Role / Device Role / Timing Role: Efficient dual-buck regulator with Burst Mode® minimizing standby power, and watchdog monitoring host MCU to prevent silent firmware hangs during data acquisition. Use Value: Achieves >90% efficiency at 100mA load and <25mVP-P ripple critical for analog signal integrity; integrated supervision meets IEC 62304 Class B software safety requirements. |
Use Scenario: Powering cellular modem (LTE-M), secure element, and environmental sensors in outdoor smart meter with wide ambient temperature range. IC Role / Device Role / Timing Role: Main power IC providing 3.3V/5V rails, with CONFIG pin configured for simultaneous startup and CWDT-tuned watchdog detecting modem firmware stalls. Use Value: Enables extended battery life (115μA IQ) and field-upgrade-safe operation; QFN package resists vibration and thermal cycling in uncontrolled environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output supervisor-regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX20090ATPA/VY+ | Single 2.2MHz buck + integrated watchdog/POR; no dual-output capability; requires external LDO for second rail. | Suitable for space-constrained designs needing only one regulated output plus supervision; lacks independent sequencing control. | Select when BOM simplicity outweighs need for dual native outputs - adds external 3.3V LDO but saves board area vs. dual-buck IC. |
| TPS6521905RGER | Dual 1.2A buck + PMIC features (LDOs, GPIOs); fixed 5V/3.3V outputs; no programmable watchdog window or POR timeout. | Targeted at TI ecosystem designs requiring integrated power management for Sitara processors; less flexible timing configuration. | Choose for TI-based AM335x/AM437x platforms where fixed outputs and companion LDOs simplify system design - sacrifices programmability for integration. |
Compared with MAX20090ATPA/VY+ and TPS6521905RGER, the LT3688IUF#TRPBF uniquely combines dual 800mA adjustable-output regulation, capacitor-programmable POR/watchdog timing, and robust 36V operation - making it optimal for custom industrial and automotive power architectures requiring deterministic sequencing and field-programmable supervision.
Availability
LT3688IUF#TRPBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial programmable logic controllers, and high-reliability medical sensor hubs requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3688IUF#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. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, serving industrial, automotive, communications, and healthcare markets with precision power, sensing, and timing solutions.
The LT3688IUF#TRPBF belongs to ADI's Power by Linear™ portfolio of high-voltage monolithic DC/DC regulators, engineered specifically for demanding applications requiring integrated power conversion and microprocessor supervision in harsh environments.
FAQ
What is the maximum input voltage rating for the LT3688IUF#TRPBF?
The LT3688IUF#TRPBF has an absolute maximum input voltage rating of 36V on the VIN pin, with guaranteed operation from 3.8V to 36V. This allows direct connection to 24V industrial buses or automotive batteries without external pre-regulation, provided minimum on-time and duty cycle constraints are respected at high VIN/VOUT ratios.
How does the CONFIG pin affect startup behavior of the LT3688IUF#TRPBF?
The CONFIG pin on the LT3688IUF#TRPBF selects among three distinct power-up sequences: tied to VIN enables staggered startup (Channel 2 begins only after FB1 rises above 0.72V), tied to GND enforces coordinated POR (both RST pins remain low until both FB voltages stabilize), and floating configures simultaneous startup with independent reset assertion - all modes are validated across the full –40°C to 125°C range.
Can the LT3688IUF#TRPBF operate in Burst Mode® at full temperature range?
Yes, the LT3688IUF#TRPBF maintains Burst Mode® operation with 115μA typical input quiescent current across its full specified junction temperature range of –40°C to 125°C. This performance is guaranteed by design and correlation, not just characterized at 25°C, ensuring consistent low-power behavior in automotive under-hood or industrial cabinet environments.
What is the purpose of the DA1 and DA2 pins on the LT3688IUF#TRPBF?
The DA1 and DA2 pins on the LT3688IUF#TRPBF monitor catch diode current to protect against short-circuit faults. When diode current exceeds 1.2A (typical), the LT3688IUF#TRPBF disables switching until current falls below threshold - this valley-current limiting ensures survivability during sustained output shorts without external current-sense components.
Is the LT3688IUF#TRPBF pin-compatible with other packages in the LT3688 family?
No, the LT3688IUF#TRPBF uses a 24-pin 4mm × 4mm QFN package (UF), while the TSSOP variant (e.g., LT3688IFE#TRPBF) uses a 24-lead plastic TSSOP (FE) with different pin assignments and thermal characteristics. Although both share identical functionality and electrical specifications, PCB layout and thermal management must be redesigned when switching between UF and FE packages.
LT3688IUF#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 2
- Voltage - Input (Min):
- 3.8V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 36V
- Current - Output:
- 800mA
- Frequency - Switching:
- 500kHz ~ 2.1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-QFN (4x4)
LT3688IUF#TRPBF FAQ
1.How can I place an order for LT3688IUF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3688IUF#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 LT3688IUF#TRPBF reliable?
The price and inventory of LT3688IUF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3688IUF#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3688IUF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3688IUF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3688IUF#TRPBF?
LT3688IUF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3688IUF#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 LT3688IUF#TRPBF?
For technical support, including LT3688IUF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3688IUF#TRPBF requirements.
6.How does Aetrix verify that LT3688IUF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3688IUF#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 LT3688IUF#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3688IUF#TRPBF?
All LT3688IUF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3688IUF#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 LT3688IUF#TRPBF part is unused and in its original packaging.
Return procedure for LT3688IUF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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