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Analog Devices Inc. LT3688EFE#PBF
- Part No.:
- LT3688EFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3688EFE#PBF.pdf
- Description:
- IC REG BUCK ADJ 800MA DL 24TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,988
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Product details
Overview
LT3688EFE#PBF from Analog Devices (formerly Linear Technology) is a dual monolithic step-down switching regulator IC with integrated 800mA power switches, programmable power-on reset timers, and a window watchdog timer. It operates from 3.8V to 36V input, delivers two independent regulated outputs (e.g., 5V/800mA and 3.3V/800mA), and maintains <25mVP-P output ripple in Burst Mode at 115μA quiescent current - ideal for automotive ECU and industrial μProcessor supervisory power systems.
For engineers reviewing the LT3688EFE#PBF datasheet, LT3688EFE#PBF pinout, LT3688EFE#PBF application, or LT3688EFE#PBF equivalent, key selection criteria include its dual-output adjustable-frequency (350kHz–2.2MHz) PWM architecture, ±2% FB voltage accuracy, 10% reset threshold hysteresis, and thermally enhanced 24-pin TSSOP package with exposed GND pad.
Technical Context
The LT3688EFE#PBF implements constant-frequency current-mode control with internal slope compensation and dual independent soft-start (RUN/SS1/RUN/SS2) for sequenced or coincident startup. Its oscillator frequency is resistor-programmable via RT pin (350kHz–2.2MHz), and it supports external synchronization via SYNC pin with ≥150ns pulse width tolerance.
Power-on reset is implemented using two independent comparators monitoring FB1/FB2 against 90% of 0.800V reference, with timeout periods set by CPOR1/CPOR2 capacitors (e.g., 23.5ms typical at 4700pF). The window watchdog timer uses CWDT capacitor to define upper (tWDU) and lower (tWDL) boundaries (e.g., 20ms/1.25ms typical at 1000pF), detecting both too-frequent and too-infrequent WDI edges.
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, FPGAs, or sensor interfaces directly. |
| Feedback Reference Voltage | 0.800V ±1.25% - enables precise output regulation with standard resistor dividers (e.g., 5V = 0.8V × (R1/R2 + 1)). |
| Burst Mode Quiescent Current | 115μA at 12VIN → 3.3V/5V - extends battery life in always-on systems while maintaining <25mVP-P ripple. |
| Reset Threshold Accuracy | 90% of VFB ±2% - ensures reliable μP reset assertion without false triggering during line transients. |
| Watchdog Window Timing | tWDU = 20ms / tWDL = 1.25ms (typ. at CWDT = 1000pF) - provides robust fault detection for safety-critical firmware execution. |
| Switching Frequency Range | 350kHz to 2.2MHz - allows optimization of inductor size (e.g., 4.7μH at 1MHz) vs. efficiency (peak >90% at 500kHz). |
Pinout & Package
LT3688EFE#PBF is housed in a thermally enhanced 24-lead plastic TSSOP package (FE) with exposed GND pad (Pin 25), θJA = 38°C/W. The exposed pad must be electrically and thermally connected to PCB ground plane for reliable operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN/UVLO (Pin 3) | Enable / Undervoltage Lockout Input | Pull below 0.3V to shut down; 1.25V threshold enables accurate UVLO for input brownout protection. |
| FB1, FB2 (Pins 4, 15) | Feedback Inputs | Regulated to 0.800V - connect resistor dividers to set output voltages (e.g., 5V, 3.3V, 1.8V). |
| RUN/SS1, RUN/SS2 (Pins 5, 14) | Soft-Start Control | Capacitor-to-GND sets soft-start time; internal discharge ensures controlled startup sequencing. |
| RST1, RST2 (Pins 17, 16) | Open-Drain Reset Outputs | Assert low when respective VOUT drops 10% below target; timing set by CPOR1/CPOR2 capacitors. |
| WDI, WDO, WDE (Pins 20, 18, 19) | Watchdog Interface | WDI accepts μP watchdog pulses; WDO asserts low on timeout; WDE disables timer when >1V. |
| CWDT, CPOR1, CPOR2 (Pins 24, 23, 21) | Timing Capacitor Inputs | Set watchdog window (CWDT) and power-on reset delays (CPOR1/CPOR2) with standard ceramic capacitors. |
| VIN (Pin 9), BIAS (Pin 22) | Power Inputs | VIN supplies main circuitry and switches; BIAS >3V reduces IQ and powers BST charge path. |
| BST1, BST2 (Pins 6, 13) | Bootstrap Drivers | Drive internal NPN switches; require 0.22μF ceramic capacitors to SW for full saturation and low VCE(SAT). |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent 800mA buck regulators | Enables compact dual-rail power for SoCs or split-domain logic without external MOSFETs or controllers. |
| Programmable window watchdog timer | Prevents runaway code by detecting both stuck and excessively fast WDI pulses - critical for ASIL-B/C systems. |
| Two independently programmable POR timers | Supports flexible power sequencing (e.g., core before I/O) or simultaneous startup via CONFIG pin strapping. |
| Adjustable 350kHz–2.2MHz switching frequency | Allows trade-off between small magnetics (high-freq) and high efficiency (low-freq) across diverse input/output conditions. |
| Low-noise Burst Mode operation | Maintains <25mVP-P ripple at light loads while drawing only 115μA - eliminates need for LDO post-regulation in standby. |
| Thermally enhanced TSSOP with exposed pad | θJA = 38°C/W enables 1.5W+ continuous dissipation at 70°C ambient - suitable for convection-cooled industrial enclosures. |
Applications
| Automotive Engine Control Unit (ECU) | Industrial PLC Power Management |
|---|---|
|
Use Scenario: Powers MCU, CAN transceiver, and analog sensors in under-hood engine control modules exposed to 12V/24V battery fluctuations and -40°C to 125°C ambient. IC Role / Device Role / Timing Role: Dual-buck regulator + POR + watchdog - provides clean 5V/3.3V rails, ensures deterministic MCU boot after cold crank, and monitors firmware execution. Use Value: Eliminates discrete supervisor IC and dual DC/DC converters; meets AEC-Q100 Grade 1 temp range with no derating up to 125°C junction. |
Use Scenario: Supplies field-programmable gate array (FPGA), I/O isolators, and real-time Ethernet PHY in modular industrial controllers operating continuously at 60°C ambient. IC Role / Device Role / Timing Role: Dual-output PMIC with sequenced startup - delivers 1.2V core and 3.3V I/O rails with controlled ramp rates and independent reset assertion. Use Value: Reduces BOM count by 4 components (2 buck controllers + 2 supervisors); simplifies layout with single-exposed-pad thermal solution. |
| High-Reliability Medical Data Acquisition | Ruggedized IoT Edge Gateway |
|
Use Scenario: Powers precision ADCs, low-noise amplifiers, and ARM Cortex-M7 processor in portable diagnostic equipment requiring long battery life and fail-safe operation. IC Role / Device Role / Timing Role: Low-IQ dual regulator with watchdog - maintains 3.3V/5V rails during sleep modes and triggers system reset on firmware hang. Use Value: Achieves 115μA quiescent current in Burst Mode, extending battery runtime; watchdog window prevents silent data corruption. |
Use Scenario: Supplies LTE modem, secure element, and environmental sensors in outdoor cellular gateways subjected to wide temperature swings and intermittent solar charging. IC Role / Device Role / Timing Role: Wide-input buck regulator with UVLO and POR - handles 9V–36V solar/battery input, guarantees clean boot after brownout recovery. Use Value: Integrated 3.8V UVLO and 10% reset hysteresis prevent oscillatory resets during marginal input conditions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output supervisory regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3688EUF#PBF | Same die in 4mm × 4mm QFN (UF) package; θJA = 37°C/W; identical electrical specs and pinout mapping. | Preferred for space-constrained designs requiring lower profile and better thermal performance on dense PCBs. | Select LT3688EUF#PBF when board area or thermal resistance is prioritized over TSSOP reworkability. |
| LT3579EFE#PBF | Dual 1.5A buck with fixed 5V/3.3V outputs, no watchdog, single POR timer, 3.3V–40V input, 20-pin TSSOP. | Suitable for cost-sensitive applications needing higher current but lacking firmware supervision requirements. | Choose LT3579EFE#PBF only if watchdog and dual POR are unnecessary and 1.5A per channel is required. |
Compared with LT3688EUF#PBF, the LT3688EFE#PBF offers identical functionality in a more serviceable TSSOP package with slightly higher thermal resistance; compared with LT3579EFE#PBF, it trades higher current for integrated safety features essential in certified embedded systems.
Availability
LT3688EFE#PBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial programmable logic controllers, and high-reliability μProcessor systems requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3688EFE#PBF 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 and maintains full product support, datasheets, and application engineering for legacy Linear parts including the LT3688 series.
The LT3688 belongs to Linear's high-voltage monolithic buck regulator family, designed specifically for automotive and industrial applications demanding integrated power, reset, and watchdog supervision in a single package.
FAQ
What is the maximum input voltage rating for the LT3688EFE#PBF?
The LT3688EFE#PBF has an absolute maximum VIN rating of 36V and operates continuously from 3.8V to 36V. This wide range supports 12V and 24V automotive battery systems, including cold-crank transients, without external clamping or pre-regulation circuits.
How does the LT3688EFE#PBF implement power-on reset functionality?
The LT3688EFE#PBF uses two independent comparators monitoring FB1 and FB2 pins. When either output falls 10% below its regulated value (i.e., below 90% of 0.800V), the corresponding RST pin pulls low. After the output recovers, a reset timeout period - set by an external capacitor on CPOR1 or CPOR2 - elapses before RST releases high.
Can the LT3688EFE#PBF operate in Burst Mode at full load?
No - Burst Mode operation is automatically engaged only at light loads (typically <10–20mA per channel) to minimize quiescent current to 115μA. At full 800mA load, the LT3688EFE#PBF operates in continuous PWM mode with constant switching frequency set by the RT resistor.
What is the purpose of the CONFIG pin on the LT3688EFE#PBF?
The CONFIG pin on the LT3688EFE#PBF selects one of three startup and supervision modes: tied to VIN (channel 2 starts after FB1 reaches 0.72V), tied to GND (both RST pins held low until both FB pins rise above 0.72V), or floating (coincident startup with independent RST behavior). This enables flexible sequencing for complex μProcessor systems.
Does the LT3688EFE#PBF require external catch diodes?
Yes - the LT3688EFE#PBF requires external Schottky catch diodes (e.g., B140HB) connected from DA1/DA2 to SW1/SW2. These diodes provide the freewheeling path during switch off-time and are monitored by internal comparators for overcurrent protection (1.2A limit).
LT3688EFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- 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#PBF FAQ
1.How can I place an order for LT3688EFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3688EFE#PBF 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#PBF reliable?
The price and inventory of LT3688EFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3688EFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3688EFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3688EFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3688EFE#PBF?
LT3688EFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3688EFE#PBF 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#PBF?
For technical support, including LT3688EFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3688EFE#PBF requirements.
6.How does Aetrix verify that LT3688EFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3688EFE#PBF 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#PBF meets industry standards.
7.What is the process for return or replacement of LT3688EFE#PBF?
All LT3688EFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3688EFE#PBF, 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#PBF part is unused and in its original packaging.
Return procedure for LT3688EFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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