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Analog Devices Inc. LT3688EFE#TRPBF
- Part No.:
- LT3688EFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3688EFE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 800MA DL 24TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,007
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Product details
Overview
LT3688EFE#TRPBF from Analog Devices (acquired Linear Technology) is a dual monolithic step-down switching regulator IC with integrated 800mA power switches, two programmable power-on reset timers, and a window watchdog timer. It operates from 3.8V to 36V input, delivers adjustable 5V/3.3V outputs in Burst Mode with <25mVP-P ripple, and maintains 115μA quiescent current at 12VIN. It serves as a compact, high-reliability power and supervisory solution for automotive ECU and industrial μProcessor systems.
For engineers reviewing the LT3688EFE#TRPBF datasheet, LT3688EFE#TRPBF pinout, LT3688EFE#TRPBF application, or LT3688EFE#TRPBF equivalent, key selection considerations include its dual-output synchronous buck architecture, 350kHz–2.2MHz adjustable switching frequency, ±2% FB voltage accuracy, programmable POR/watchdog timing via external capacitors, and thermal performance in the 24-pin TSSOP package with exposed pad.
Technical Context
The LT3688EFE#TRPBF implements constant-frequency current-mode control with internal slope compensation and soft-start via RUN/SS pins. Its dual regulators operate independently with separate feedback (FB1/FB2), soft-start (RUN/SS1/RUN/SS2), and reset (RST1/RST2) paths, enabling staggered or coincident startup based on CONFIG pin state.
It integrates a window watchdog timer with programmable upper/lower boundaries (tWDU/tWDL) and timeout (tWDTO) via CWDT capacitor, plus two independent POR timers set by CPOR1/CPOR2. Reset assertion occurs when output falls 10% below regulation (90% VFB threshold), with glitch-immune comparator design ensuring reliable microprocessor supervision.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.8V to 36V - supports wide-range industrial and automotive battery inputs without pre-regulation. |
| Output Current per Channel | 800mA - sufficient to power dual-core microcontrollers or FPGA I/O banks directly. |
| Switching Frequency Range | 350kHz to 2.2MHz - adjustable via RT resistor; enables optimization of inductor size vs. efficiency tradeoff. |
| Quiescent Current (Burst Mode) | 115μA at 12VIN → 3.3V/5V - enables ultra-low-power standby in always-on systems. |
| Feedback Voltage Accuracy | ±2% over –40°C to 125°C - ensures stable output regulation across automotive temperature range. |
| Reset Threshold Accuracy | ±2% (90% of VFB) - guarantees precise power-good detection without false triggering. |
| Watchdog Window Accuracy | ±15% (tWDU, tWDL) - provides deterministic fault-detection timing for safety-critical firmware monitoring. |
Pinout & Package
The LT3688EFE#TRPBF is housed in a thermally enhanced 24-pin plastic TSSOP package (FE) with exposed pad (Pin 25) electrically and thermally connected to GND. The package has θJA = 38°C/W and requires PCB-level thermal vias under the exposed pad for reliable operation at full load.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1 / FB2 | Output voltage sense input | Regulates VOUT1/VOUT2 to 0.800V reference; connects to resistor divider for precise output programming. |
| RUN/SS1 / RUN/SS2 | Soft-start timing control | Capacitor-to-GND sets soft-start duration; internal pull-down ensures controlled ramp-up and fault recovery. |
| RST1 / RST2 | Open-drain reset output | Active-low, weak-pull-up-to-BIAS; asserts when respective VOUT drops below 90% VFB; timing set by CPOR1/CPOR2. |
| WDI / WDO / WDE | Watchdog interface | WDI accepts microprocessor pulse train; WDO pulses low on watchdog violation; WDE enables/disables timer. |
| CONFIG | Startup and supervision mode selector | Three-state logic (VIN/GND/floating) configures POR sequencing, channel enable order, and watchdog activation conditions. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent buck regulators | Enables single-chip power for dual-rail systems (e.g., 5V core + 3.3V I/O), eliminating need for discrete second converter. |
| Programmable window watchdog timer | Prevents runaway code execution by detecting both too-frequent and too-infrequent WDI edges - critical for ASIL-B/C applications. |
| Two configurable power-on reset timers | Allows staggered or synchronized startup of subsystems; CPOR1/CPOR2 capacitors provide ±15% timing accuracy over temperature. |
| Burst Mode operation | Maintains <25mVP-P output ripple at light loads while drawing only 115μA from VIN - extends battery life in intermittent-use devices. |
| BIAS pin for efficiency optimization | When connected to regulated output (>3V), reduces VIN quiescent current and supplies BST charging path - improves full-load efficiency by ~2%. |
Applications
| Automotive Engine Control Unit (ECU) | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering 32-bit MCU, CAN transceiver, and analog sensor front-end in under-hood environment. IC Role / Device Role / Timing Role: Dual-output DC/DC regulator + system supervisor; provides 5V for MCU core and 3.3V for peripherals, with POR and watchdog enforcing boot integrity. Use Value: Single-chip solution meets AEC-Q100 Grade 1 (–40°C to 125°C) requirements; 36V max input handles load-dump transients; exposed-pad TSSOP ensures thermal reliability at 85°C ambient. | Use Scenario: Supplying isolated field I/O circuits and ARM-based controller in factory automation cabinet. IC Role / Device Role / Timing Role: Primary power manager and watchdog supervisor; generates clean 5V/3.3V rails and monitors controller health during cyclic operation. Use Value: Programmable CPOR1/CPOR2 allows coordinated reset of I/O ASICs and processor; WDI/WDO interface supports SIL-2 functional safety diagnostics per IEC 61508. |
| High-Reliability Medical Data Logger | Ruggedized Edge Gateway |
Use Scenario: Battery-backed data acquisition node logging sensor data in remote locations. IC Role / Device Role / Timing Role: Low-quiescent-power dual regulator with POR and watchdog; manages Li-ion battery discharge profile and ensures firmware restart on brownout. Use Value: 115μA Burst Mode IQ extends battery life >6 months; tRST programmability (21–26ms typical) matches microcontroller reset timing specs; RST1/RST2 support redundant reset signaling. | Use Scenario: Outdoor wireless gateway powering LTE modem, Ethernet PHY, and security MCU. IC Role / Device Role / Timing Role: Central power and supervision IC; delivers 5V to modem and 3.3V to MCU/PHY, while monitoring firmware liveness via WDI pulses. Use Value: 350kHz–2.2MHz fSW allows use of small 4.7μH inductors; CWDT capacitor sets 20ms watchdog window matching modem heartbeat interval; CONFIG pin enables fail-safe startup sequence. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output buck regulator with supervisory functions applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3689EFE#TRPBF | Same pinout and feature set, but rated for –40°C to 150°C junction (H-grade); higher max TJ and tighter thermal derating. | Suitable for under-hood automotive applications requiring extended temperature operation beyond 125°C ambient. | Select LT3689EFE#TRPBF when operating junction temperature exceeds 125°C or AEC-Q100 Grade 0 qualification is required. |
| TPS65270PWP | Dual 1.2A buck with integrated LDOs and sequencer; no watchdog timer; fixed 500kHz/1MHz fSW; different pinout and control interface. | Targeted at cost-sensitive consumer electronics; lacks programmable POR/watchdog, limiting suitability for safety-critical systems. | Choose TPS65270PWP only for non-safety applications where watchdog supervision is unnecessary and higher output current is needed. |
Compared with LT3689EFE#TRPBF, the LT3688EFE#TRPBF offers identical functionality at lower thermal rating, reducing BOM cost where 125°C operation suffices; versus TPS65270PWP, it trades higher integration for essential supervisory features-making it the only choice when watchdog-enforced firmware reliability is mandatory.
Availability
LT3688EFE#TRPBF is available at Aetrix Electronics and suitable for automotive engine control units, industrial PLC I/O modules, and high-reliability medical data loggers requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3688EFE#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, formed through the acquisition of Linear Technology in 2017.
The LT3688 belongs to ADI's Power by Linear™ family of high-voltage monolithic DC/DC converters, designed specifically for demanding automotive, industrial, and medical applications requiring robust power conversion combined with intelligent system supervision.
FAQ
What is the maximum input voltage supported by the LT3688EFE#TRPBF?
The LT3688EFE#TRPBF supports a maximum continuous input voltage of 36V, as specified in its Absolute Maximum Ratings. This enables direct connection to 24V industrial buses and 12V automotive systems with load-dump protection. Operation above 36V risks permanent damage. The device also features an accurate 3.8V minimum UVLO threshold to prevent startup under insufficient input conditions.
How do I configure the power-on reset timeout for each channel of the LT3688EFE#TRPBF?
Each channel's power-on reset timeout is set independently using external capacitors: CPOR1 (Pin 23) controls RST1 assertion time, and CPOR2 (Pin 21) controls RST2. For example, a 4700pF capacitor yields a typical tRST of 23.5ms. The relationship is linear - doubling capacitance doubles timeout. The LT3688EFE#TRPBF datasheet provides a graph (Figure G28) showing tRST vs. CPOR from 1pF to 100nF.
Can the LT3688EFE#TRPBF operate in Burst Mode at full load?
No, the LT3688EFE#TRPBF automatically exits Burst Mode above ~10–20mA load and enters continuous conduction mode (CCM) to maintain regulation and efficiency. Burst Mode is active only at light loads, where it reduces input quiescent current to 115μA while keeping output ripple below 25mVP-P. At full 800mA load, the device operates in fixed-frequency PWM mode with typical efficiency >85% at 12VIN → 3.3V.
What is the function of the CONFIG pin on the LT3688EFE#TRPBF?
The CONFIG pin (Pin 10) selects one of three startup and supervision modes: tied to VIN enables independent RST behavior and delayed Channel 2 startup; tied to GND forces both RST outputs to remain asserted until both outputs reach regulation; left floating enables simultaneous startup and RST1-triggered watchdog activation. This pin directly determines sequencing logic and fault-handling behavior without requiring external firmware control.
Does the LT3688EFE#TRPBF require external catch diodes?
Yes, the LT3688EFE#TRPBF requires external Schottky catch diodes connected between DA1/SW1 and DA2/SW2. The DA pins monitor diode current and disable switching if valley current exceeds 1.2A - protecting against short-circuit faults. Recommended diodes include B140HB (1A, 40V) or equivalents with low forward voltage (<0.45V) and fast recovery (<10ns) to minimize losses and ensure stability.
LT3688EFE#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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-TSSOP
LT3688EFE#TRPBF FAQ
1.How can I place an order for LT3688EFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3688EFE#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 LT3688EFE#TRPBF reliable?
The price and inventory of LT3688EFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3688EFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3688EFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3688EFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3688EFE#TRPBF?
LT3688EFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3688EFE#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 LT3688EFE#TRPBF?
For technical support, including LT3688EFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3688EFE#TRPBF requirements.
6.How does Aetrix verify that LT3688EFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3688EFE#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 LT3688EFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3688EFE#TRPBF?
All LT3688EFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3688EFE#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 LT3688EFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3688EFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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