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Analog Devices Inc. LT3688IFE#TRPBF
- Part No.:
- LT3688IFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3688IFE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 800MA DL 24TSSOP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LT3688IFE#TRPBF from Analog Devices (formerly 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, and maintains <25mVP-P output ripple in Burst Mode® at 115μA quiescent current - ideal for automotive ECU and high-reliability μProcessor power sequencing.
For engineers reviewing the LT3688IFE#TRPBF datasheet, LT3688IFE#TRPBF pinout, LT3688IFE#TRPBF application, or LT3688IFE#TRPBF equivalent, key selection criteria include its dual-channel 800mA capability, 350kHz–2.2MHz synchronizable 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 LT3688IFE#TRPBF implements constant-frequency current-mode control per channel, with independent soft-start (RUN/SS1/SS2), internal slope compensation, and valley-current limiting (1.2A typical) triggered by DA1/DA2 pins. Its dual-reset architecture monitors each FB pin independently for 10% undervoltage detection, asserting open-drain RST1/RST2 after user-programmed CPOR1/CPOR2 timeout.
The integrated window watchdog uses WDI edge timing to enforce both upper (tWDU) and lower (tWDL) boundaries set by CWDT capacitance; violation pulls WDO low for 1/8×tWDU. CONFIG pin logic selects startup sequencing (coincident, cascaded, or gated), while BIAS pin operation reduces VIN quiescent current when supplied ≥3V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.8V to 36V - supports wide automotive battery transients and industrial DC rails without external pre-regulation. |
| Output Current per Channel | 800mA - sufficient to power dual-core microcontrollers, FPGAs I/O banks, or sensor signal chains directly. |
| Feedback Voltage Accuracy | 0.790V to 0.814V (±2%) - enables precise 5V/3.3V/1.8V regulation with minimal output error across temperature. |
| Burst Mode® Quiescent Current | 115μA at 12VIN → 3.3V/5V - extends battery life in always-on systems while holding output ripple below 25mVP-P. |
| Switching Frequency Range | 350kHz to 2.2MHz - adjustable via RT resistor; higher frequencies allow smaller 4.7μH inductors and compact 22μF ceramic output caps. |
| Reset Threshold Accuracy | 90% of FB voltage (±2%) - ensures reliable μP reset assertion without false triggering during brown-out recovery. |
| Watchdog Window Timing | tWDU = 20ms / tWDL = 1.25ms (CWDT = 1000pF) - provides robust fault detection for safety-critical firmware execution monitoring. |
Pinout & Package
LT3688IFE#TRPBF is housed in a thermally enhanced 24-pin plastic TSSOP (FE package) with exposed pad (Pin 25) electrically and thermally connected to GND. The package has θJA = 38°C/W and requires PCB ground plane connection for thermal reliability.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1, FB2 | Output voltage feedback inputs | Regulated to 0.800V ±2%; connect resistor dividers to set 5V/3.3V outputs with <1% tolerance. |
| RUN/SS1, RUN/SS2 | Soft-start timing inputs | Capacitor-to-GND sets ramp time; internal discharge ensures controlled startup and fault recovery. |
| RST1, RST2 | Open-drain reset outputs | Assert low when respective VOUT drops 10% below target; timeout programmed by CPOR1/CPOR2. |
| WDI, WDO, WDE | Watchdog interface pins | WDI accepts μP pulses; WDO asserts low on timing violation; WDE disables watchdog when >1V. |
| BST1, BST2 | Bootstrap drive supplies | Charge pump nodes enabling full NPN switch saturation; require 0.22μF ceramic caps to SW. |
| DA1, DA2 | Catch diode anode sense | Monitor external Schottky diode current; disable switching if valley current exceeds 1.2A during fault. |
| CONFIG | Startup sequencing mode select | Tie to VIN/GND/floating to configure coincident, cascaded, or gated channel enable and reset behavior. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent 800mA regulators | Enables single-chip power for dual-rail systems (e.g., 5V core + 3.3V I/O) without cross-talk or shared thermal stress. |
| Programmable power-on reset timers | CPOR1/CPOR2 capacitors set reset hold-off (e.g., 23.5ms typical); eliminates need for external RC reset generators. |
| Window watchdog timer | Detects both stuck and runaway firmware via tWDU/tWDL boundaries - more robust than simple timeout watchdogs. |
| Burst Mode® operation | Maintains 115μA IQ and <25mVP-P ripple at light load - critical for battery-backed automotive telematics and IoT edge nodes. |
| Synchronizable 350kHz–2.2MHz switching | RT resistor or external clock on SYNC pin avoids EMI peaks; supports spread-spectrum compatibility in dense layouts. |
Applications
| Automotive Engine Control Unit (ECU) | Industrial PLC Power Module |
|---|---|
Use Scenario: Powering dual-rail microcontroller (5V core, 3.3V peripherals) and CAN transceiver in under-hood ECU with 12V battery input subject to load dump. IC Role / Device Role / Timing Role: Dual buck regulator provides isolated 5V/3.3V rails; RST1/RST2 ensure synchronized μP reset on cold crank; watchdog monitors firmware execution. Use Value: Single-package solution replaces discrete regulators + reset IC + watchdog, reducing BOM count and PCB area by 40%. |
Use Scenario: Generating stable 5V and 3.3V for FPGA configuration, analog I/O, and communication interfaces in DIN-rail mounted PLC with 24VDC input. IC Role / Device Role / Timing Role: Regulator supplies FPGA core/I/O banks; programmable POR timers coordinate power-up sequence; watchdog prevents lockup during field updates. Use Value: Tight ±2% FB accuracy and 10% reset threshold ensure reliable operation across –40°C to 125°C ambient without derating. |
| Medical Diagnostic Imaging Sensor Hub | Ruggedized Edge AI Gateway |
Use Scenario: Powering low-noise ADC front-end (3.3V) and high-speed digital processing unit (5V) in portable ultrasound probe with Li-ion battery input. IC Role / Device Role / Timing Role: Dual buck delivers clean, low-ripple supplies; Burst Mode® extends battery runtime; RST1/RST2 guarantee safe boot after battery insertion. Use Value: <25mVP-P ripple in Burst Mode® preserves SNR in 16-bit ADC paths without requiring additional LDO post-regulation. |
Use Scenario: Supplying vision processor SoC (5V) and wireless module (3.3V) in outdoor-mounted AI gateway exposed to solar heating and voltage surges. IC Role / Device Role / Timing Role: Handles 36V transients; thermal shutdown protects during sustained 85°C ambient; watchdog recovers frozen inference engines. Use Value: Exposed-pad TSSOP achieves 38°C/W θJA, enabling 800mA/channel operation at 125°C junction without heatsink. |
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 |
|---|---|---|---|
| LT3689IFE#TRPBF | Same pinout, identical features, but rated for –40°C to 150°C (H-grade); 150°C max junction vs. 125°C for LT3688IFE#TRPBF. | Required for under-hood automotive applications exceeding 125°C ambient or where extended thermal margin is mandated. | Select LT3689IFE#TRPBF only when operating junction temperature must exceed 125°C; otherwise LT3688IFE#TRPBF is cost-optimized. |
| TPS65270QPWPRQ1 | Dual 1.2A/1.2A buck; no integrated watchdog or POR timers; requires external reset IC (e.g., TPS3808) and separate watchdog circuit. | Suitable for cost-sensitive industrial designs where supervisory functions are implemented discretely or omitted. | Choose TPS65270QPWPRQ1 when higher current (1.2A) is needed and external supervision is acceptable; avoid if space-constrained or system-level safety certification (e.g., ISO 26262) mandates integrated watchdog. |
Compared with LT3689IFE#TRPBF, the LT3688IFE#TRPBF offers identical functionality at lower cost and standard temperature grade, while TPS65270QPWPRQ1 trades integrated supervision for higher current and lower price - making LT3688IFE#TRPBF optimal for space-constrained, safety-aware automotive and industrial applications needing all three functions in one package.
Availability
LT3688IFE#TRPBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial PLCs, and high-reliability μProcessor systems requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3688IFE#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving automotive, industrial, communications, and healthcare markets.
The LT3688IFE#TRPBF belongs to Linear's µModule®-adjacent high-integration power management family, designed specifically for space-constrained, safety-critical applications demanding combined regulation, reset, and watchdog functionality in a single IC.
FAQ
What is the maximum input voltage rating for the LT3688IFE#TRPBF?
The LT3688IFE#TRPBF has an absolute maximum input voltage of 36V on the VIN pin, with guaranteed operation from 3.8V to 36V. This allows direct connection to 24V industrial rails and 12V automotive batteries including load-dump transients up to 36V, provided thermal limits are observed in the 24-pin TSSOP package.
How do I configure the power-on reset timeout for LT3688IFE#TRPBF?
The LT3688IFE#TRPBF uses external capacitors on CPOR1 (Pin 23) and CPOR2 (Pin 21) to set independent reset timeout periods. With CPOR = 4700pF, tRST is 23.5ms typical; scaling follows linear proportionality (e.g., 9400pF yields ~47ms). The capacitor must be placed between CPORx and GND with low-ESR ceramic construction.
Does the LT3688IFE#TRPBF support synchronization to an external clock?
Yes, the LT3688IFE#TRPBF supports external clock synchronization via the SYNC pin (Pin 2). A logic-level square wave with ≥150ns pulse width can be applied to synchronize switching frequency to an external source, reducing EMI in multi-regulator systems. When unused, SYNC must be tied to GND - floating is not allowed.
What is the purpose of the CONFIG pin on the LT3688IFE#TRPBF?
The CONFIG pin (Pin 10) selects startup sequencing and reset behavior: tied to VIN enables cascaded startup (Channel 2 starts after FB1 reaches 0.72V); tied to GND enforces simultaneous release of RST1/RST2 after both FB pins rise; floating configures coincident channel enable. This eliminates external logic for complex power-up sequences.
Can the LT3688IFE#TRPBF operate without an external catch diode?
No - the LT3688IFE#TRPBF requires external Schottky catch diodes connected to DA1/DA2 pins. These diodes provide the freewheeling path during switch off-time and are monitored for overcurrent (1.2A limit). Omitting them causes immediate failure due to lack of inductor current path and loss of valley-current limiting protection.
LT3688IFE#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
LT3688IFE#TRPBF FAQ
1.How can I place an order for LT3688IFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3688IFE#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 LT3688IFE#TRPBF reliable?
The price and inventory of LT3688IFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3688IFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3688IFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3688IFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3688IFE#TRPBF?
LT3688IFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3688IFE#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 LT3688IFE#TRPBF?
For technical support, including LT3688IFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3688IFE#TRPBF requirements.
6.How does Aetrix verify that LT3688IFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3688IFE#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 LT3688IFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3688IFE#TRPBF?
All LT3688IFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3688IFE#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 LT3688IFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3688IFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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