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Analog Devices Inc. LT3688HFE#TRPBF
- Part No.:
- LT3688HFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3688HFE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 800MA DL 24TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,099
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Product details
Overview
LT3688HFE#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, operating from 3.8V to 36V input, delivering two independent 800mA outputs at adjustable voltages (e.g., 5V/3.3V), and featuring programmable 350kHz–2.2MHz switching frequency, <25mVP-P output ripple in Burst Mode®, and 115μA quiescent current - used in automotive ECU power sequencing and high-reliability μProcessor supervision.
For engineers reviewing the LT3688HFE#TRPBF datasheet, LT3688HFE#TRPBF pinout, LT3688HFE#TRPBF application, or LT3688HFE#TRPBF equivalent, key selection criteria include its dual-output thermal robustness (150°C max junction), adjustable POR/watchdog timing via external capacitors, and TSSOP-24 package with exposed pad for low-θJA (38°C/W).
Technical Context
The LT3688HFE#TRPBF implements constant-frequency current-mode PWM control per channel, with independent soft-start (via RUN/SS pins), internal slope compensation, and VC-clamped current limiting. Its dual oscillator architecture supports master/slave synchronization via SYNC pin and enables precise duty-cycle management up to 90%.
Power-supervision logic includes two independent POR comparators (90% VFB threshold, ±2% accuracy), open-drain RST outputs with 2.5μA weak pull-up to BIAS, and a windowed watchdog timer (tWDL/tWDU set by CWDT capacitor) that detects both too-frequent and too-infrequent WDI edges - all guaranteed over –40°C to 150°C junction temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.8V to 36V - supports wide automotive battery transients and industrial 24V rails without external pre-regulation. |
| Output Current (per channel) | 800mA - sufficient to power dual-core microcontrollers, FPGAs, or sensor subsystems directly. |
| Switching Frequency Range | 350kHz to 2.2MHz - adjustable via RT resistor; enables optimization of inductor size vs. efficiency (e.g., 500kHz typical for 12V→5V/3.3V). |
| Burst Mode® Quiescent Current | 115μA at 12VIN - maintains high light-load efficiency while holding output ripple below 25mVP-P. |
| Reset Threshold Accuracy | ±2% (88%–92% of FB voltage) - ensures reliable μP reset assertion without false triggering under line/load transients. |
| Watchdog Window Timing | tWDL = 0.8–1.6ms / tWDU = 18–22ms (CWDT = 1000pF) - provides configurable fault detection window for real-time software execution monitoring. |
| Junction Temperature Range | –40°C to +150°C - qualified for under-hood automotive applications and high-ambient industrial environments. |
Pinout & Package
LT3688HFE#TRPBF is housed in a thermally enhanced 24-pin plastic TSSOP (FE package) with exposed pad (Pin 25), rated θJA = 38°C/W. The exposed pad must be electrically and thermally connected to PCB ground plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN/UVLO (Pin 3) | Enable / Undervoltage Lockout Input | Shuts down IC when pulled <0.3V; 1.25V threshold enables accurate UVLO (e.g., disable below 6V battery). |
| VIN (Pin 9) | Main Power Input | Supplies internal circuitry and power switches; requires local 4.7μF ceramic bypass. |
| FB1 / FB2 (Pins 4, 15) | Feedback Inputs | Regulated to 0.800V ±1%; sets output voltage via resistor divider (e.g., 5V: R1=523kΩ, R2=100kΩ). |
| RUN/SS1 / RUN/SS2 (Pins 5, 14) | Soft-Start Control | Capacitor-to-GND sets startup ramp time; internal discharge ensures controlled re-start after fault. |
| RST1 / RST2 (Pins 17, 16) | Open-Drain Reset Outputs | Pull low if respective VOUT drops >10% below regulation; timeout set by CPOR1/CPOR2 capacitors. |
| WDI / WDO / WDE (Pins 20, 18, 19) | Watchdog Interface | WDI accepts μP pulses; WDO asserts low on watchdog timeout; WDE disables timer when >1V. |
| CWDT / CPOR1 / CPOR2 (Pins 24, 23, 21) | Timing Capacitor Inputs | Set watchdog window (CWDT) and POR delays (CPOR1/CPOR2); e.g., 4700pF → 23.5ms tRST. |
| BIAS (Pin 22) | Bias Supply Input | Reduces VIN quiescent current when supplied ≥3V (e.g., from regulated 5V output); powers BST charging path. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent 800mA regulators | Enables compact dual-rail power for SoC + peripheral subsystems without discrete DC/DC converters. |
| Programmable window watchdog timer | Prevents runaway code by detecting both stuck and excessively fast WDI transitions - critical for ASIL-B systems. |
| Two independently programmable POR timers | Allows staggered or coincident power-up sequencing (via CONFIG pin states) for complex μP/FPGA boot order control. |
| Low-ripple Burst Mode® operation | Maintains <25mVP-P output noise at light loads while achieving 115μA IQ, extending battery life in always-on modules. |
| Thermally robust H-grade qualification | Guaranteed operation to +150°C junction temperature - suitable for engine control units and industrial motor drives. |
Applications
| Automotive Engine Control Unit (ECU) | Industrial PLC Power Module |
|---|---|
Use Scenario: Supplies 5V for MCU core and 3.3V for CAN transceiver and sensors in under-hood ECU with 12V/24V battery input and load dump transients. IC Role / Device Role / Timing Role: Dual buck regulator + POR supervisor + watchdog - manages power sequencing, monitors MCU health, and asserts reset on undervoltage or software hang. Use Value: Eliminates need for separate supervisor IC and reduces BOM count by integrating reset/watchdog with power conversion. |
Use Scenario: Powers FPGA, I/O drivers, and communication interfaces in DIN-rail mounted PLC with 24V DC input and extended temperature requirements. IC Role / Device Role / Timing Role: Dual-output DC/DC converter with programmable POR delay and windowed watchdog - ensures deterministic startup and runtime fault detection. Use Value: Guarantees safe restart after brownout and prevents field failures due to firmware lockup in unattended operation. |
| High-Reliability Medical Imaging Subsystem | Aerospace Data Acquisition Node |
Use Scenario: Generates stable 5V/3.3V rails for ADCs, DACs, and FPGA in portable ultrasound equipment requiring low-noise, low-power operation. IC Role / Device Role / Timing Role: Low-ripple dual regulator with Burst Mode® and precise POR - delivers clean analog supply while minimizing standby power. Use Value: Achieves <25mVP-P ripple at 10mA load, enabling 16-bit ADC performance without additional LDO post-regulation. |
Use Scenario: Provides fault-tolerant power and supervision for radiation-hardened microcontroller in satellite telemetry unit operating across –40°C to +85°C ambient. IC Role / Device Role / Timing Role: Dual buck with 150°C-rated H-grade silicon and open-drain RST/WDO - meets MIL-STD-810G thermal cycling and latch-up immunity needs. Use Value: Enables single-chip power + supervision solution qualified for space-qualified thermal profiles without derating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output buck regulator with supervision applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3649EMSE#PBF | Single 2A output, no integrated watchdog; supports higher VIN (60V), wider frequency range (100kHz–3MHz). | Lacks dual independent outputs and POR/watchdog - requires external supervisor for equivalent functionality. | Select when higher current per rail or extended input voltage is prioritized over integration density. |
| TPS65217CRSLR | PMIC with 3 buck + 2 LDO + fuel gauge; fixed 5V/3.3V outputs; no programmable watchdog window. | Integrated battery management but lacks adjustable POR timing and windowed watchdog - less flexible for custom μP supervision. | Choose for portable battery-powered systems needing fuel gauging and fixed-rail simplicity over programmability. |
Compared with LTC3649EMSE#PBF and TPS65217CRSLR, LT3688HFE#TRPBF uniquely combines dual 800mA buck regulation, independent programmable POR, and windowed watchdog in a single H-grade TSSOP package - offering superior integration for automotive and industrial μP supervision where timing precision and thermal ruggedness are critical.
Availability
LT3688HFE#TRPBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial PLCs, and high-reliability medical imaging systems requiring stable component supply with guaranteed 150°C operation and long-term lifecycle support.
Supply support for LT3688HFE#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 semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3688HFE#TRPBF belongs to ADI's Power by Linear™ family of high-voltage monolithic DC/DC regulators, designed specifically for demanding automotive, industrial, and aerospace applications requiring integrated power and system supervision.
FAQ
What is the maximum junction temperature rating for LT3688HFE#TRPBF?
The LT3688HFE#TRPBF is an H-grade device with a guaranteed operating junction temperature range of –40°C to +150°C. This rating is validated per the manufacturer's datasheet and makes LT3688HFE#TRPBF suitable for under-hood automotive applications and high-ambient industrial environments where standard E- or I-grade parts would require derating.
How does the CONFIG pin affect power-on reset behavior in LT3688HFE#TRPBF?
The CONFIG pin on LT3688HFE#TRPBF selects among three startup modes: tied to VIN enables independent RST assertion per channel; tied to GND forces both RST outputs to remain low until both FB pins exceed 0.72V; floating configures coincident channel startup with RST1-triggered watchdog enable. This flexibility allows LT3688HFE#TRPBF to support diverse μP boot sequences without external logic.
Can LT3688HFE#TRPBF operate with a 24V input and generate 3.3V/5V outputs simultaneously?
Yes - LT3688HFE#TRPBF supports input voltages up to 36V and can simultaneously deliver 3.3V and 5V at up to 800mA each. With proper layout (including 4.7μF VIN bypass, 22μF output caps, and 12μH/18μH inductors), LT3688HFE#TRPBF achieves >85% efficiency at full load from 24V input, as confirmed in the typical application circuit (TA01a) and efficiency graphs (G01–G03).
What external components define the watchdog timeout period for LT3688HFE#TRPBF?
The watchdog upper and lower window boundaries (tWDU, tWDL) and timeout period (tWDTO) of LT3688HFE#TRPBF are set solely by the capacitor connected between CWDT (Pin 24) and GND. For example, a 1000pF capacitor yields tWDU = 20ms (typ), tWDL = 1.25ms (typ), and tWDTO = 2.5ms - values verified across the full –40°C to +150°C temperature range.
Does LT3688HFE#TRPBF require an external catch diode, and what are the specifications?
Yes - LT3688HFE#TRPBF requires external Schottky catch diodes connected to DA1/DA2 pins. The datasheet specifies B140HB (40V, 1A) as the typical part; diode forward voltage must be ≤0.5V at rated current to maintain efficiency, and reverse leakage must be minimized (<2μA at 0V BIAS) to avoid increased no-load current at high temperature - a key design consideration for LT3688HFE#TRPBF in battery-critical applications.
LT3688HFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-TSSOP (0.173", 4.40mm Width) 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 ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-TSSOP
LT3688HFE#TRPBF FAQ
1.How can I place an order for LT3688HFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3688HFE#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 LT3688HFE#TRPBF reliable?
The price and inventory of LT3688HFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3688HFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3688HFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3688HFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3688HFE#TRPBF?
LT3688HFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3688HFE#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 LT3688HFE#TRPBF?
For technical support, including LT3688HFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3688HFE#TRPBF requirements.
6.How does Aetrix verify that LT3688HFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3688HFE#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 LT3688HFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3688HFE#TRPBF?
All LT3688HFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3688HFE#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 LT3688HFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3688HFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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