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Analog Devices Inc. LT3688IFE#PBF
- Part No.:
- LT3688IFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3688IFE#PBF.pdf
- Description:
- IC REG BUCK ADJ 800MA DL 24TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,329
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Product details
Overview
LT3688IFE#PBF 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 LT3688IFE#PBF datasheet, LT3688IFE#PBF pinout, LT3688IFE#PBF application, or LT3688IFE#PBF equivalent, key selection criteria include dual-output timing coordination, external capacitor-programmable POR/watchdog timeouts, thermal performance of the 24-pin TSSOP package with exposed pad, and compatibility with BIAS-assisted efficiency optimization in industrial and automotive power systems.
Technical Context
The LT3688IFE#PBF implements constant-frequency current-mode 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 extension up to 90% for low-input operation.
Power-supervisory 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 validated across –40°C to +125°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 unregulated rails without pre-regulation. |
| Output Current (per channel) | 800mA - sufficient to power dual-core microcontrollers, FPGA I/O banks, or sensor signal chains directly. |
| Switching Frequency | 350kHz to 2.2MHz (RT-programmable) - enables tradeoff between small magnetics (high-f) and EMI/efficiency (low-f). |
| Burst Mode® Quiescent Current | 115μA at 12VIN → 3.3V/5V - maintains regulation with ultra-low standby power for always-on systems. |
| Reset Threshold Accuracy | ±2% (90% of 0.800V FB reference) - ensures reliable μP reset assertion without false triggering under line/load variation. |
| Watchdog Window Range | tWDL = 0.8–1.6ms / tWDU = 18–22ms (CWDT = 1000pF) - provides configurable fault-detection timing margins for diverse firmware execution profiles. |
| Thermal Resistance θJA | 38°C/W (TSSOP-24 with exposed pad) - requires PCB thermal vias to ground plane for sustained 800mA operation at 125°C ambient. |
Pinout & Package
LT3688IFE#PBF uses a 24-pin plastic TSSOP package (FE) with exposed thermal pad (Pin 25 = GND). The package is RoHS-compliant, lead-free, and rated for –40°C to +125°C operating junction temperature.
| 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 for input rail monitoring. |
| FB1, FB2 (Pins 4, 15) | Feedback Inputs | Regulate outputs to 0.800V reference; support resistor-divider programming of VOUT (e.g., 5V, 3.3V). |
| RUN/SS1, RUN/SS2 (Pins 5, 14) | Soft-Start Timing Inputs | Capacitor-to-GND sets startup ramp time; internal discharge ensures controlled re-start after fault. |
| RST1, RST2 (Pins 17, 16) | Open-Drain Reset Outputs | Assert low when respective VOUT drops <90% of target; timeout set by CPOR1/CPOR2 capacitors. |
| WDI, WDO, WDE (Pins 20, 18, 19) | Watchdog Interface | WDI accepts μP pulse train; WDO pulses low on timing violation; WDE disables watchdog when >1V. |
| CWDT, CPOR1, CPOR2 (Pins 24, 23, 21) | Timing Capacitor Inputs | Single capacitor per pin programs watchdog window bounds (CWDT) or POR delay (CPOR1/CPOR2). |
| VIN (Pin 9), BIAS (Pin 22) | Power Inputs | VIN supplies main switch and bias circuitry; BIAS >3V reduces VIN quiescent current and powers BST charge path. |
| BST1, BST2 (Pins 6, 13) | Bootstrap Drivers | Drive internal NPN switches; require 0.22μF ceramic caps from BST 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 systems without external controllers or discrete FETs. |
| Programmable windowed watchdog timer | Prevents runaway code by detecting both stuck and excessively fast WDI toggling - critical for ASIL-B/C safety-critical firmware. |
| Two independently adjustable power-on reset timers | Allows staggered or coincident startup sequencing (via CONFIG pin states) for complex μP/FPGA boot dependencies. |
| Burst Mode® with <25mVP-P ripple | Maintains tight output regulation at light loads (e.g., sleep mode) while minimizing standby power in battery-backed systems. |
| BIAS-assisted efficiency mode | Reduces total input quiescent current by sourcing bias power from regulated output, improving system-level efficiency above 3V. |
Applications
| Automotive Engine Control Unit (ECU) | Industrial PLC Power Module |
|---|---|
Use Scenario: Powers MCU core (3.3V) and CAN transceiver (5V) from 12V battery with cold-crank tolerance down to 3.8V. IC Role / Device Role / Timing Role: Dual-buck regulator + POR supervisor ensures deterministic boot sequence and resets MCU if either rail sags during cranking. Use Value: Eliminates need for separate reset IC and discrete DC/DC converters, reducing BOM count and board area by 40% vs discrete solution. |
Use Scenario: Supplies 5V logic and 3.3V I/O for modular I/O cards in DIN-rail mounted PLC chassis with 24V DC input. IC Role / Device Role / Timing Role: Provides isolated, sequenced power with watchdog monitoring of main controller firmware execution. Use Value: Configurable CPOR/CWDT capacitors enable field-adjustable reset and watchdog timing without firmware update or hardware change. |
| High-Reliability Medical Data Logger | Ruggedized IoT Edge Gateway |
Use Scenario: Powers ARM Cortex-M7 processor and SD card interface from 9–36V wide-input supply in portable diagnostic equipment. IC Role / Device Role / Timing Role: Dual regulator delivers clean, low-noise rails; watchdog guards against firmware lockup during long-term unattended operation. Use Value: 115μA Burst Mode current extends battery life in backup operation; -40°C to +125°C rating ensures reliability in sterilization cycles. |
Use Scenario: Supplies 3.3V wireless SoC and 5V cellular modem in outdoor gateway exposed to automotive-grade temperature cycling. IC Role / Device Role / Timing Role: Coordinates power-up of modem before radio initialization; POR timers prevent premature firmware execution. Use Value: Exposed-pad TSSOP package achieves 38°C/W θJA, enabling full 800mA load at 70°C ambient without derating. |
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 |
|---|---|---|---|
| LT3689IFE#PBF | Same pinout, but adds third 800mA buck channel and extra RST/WDO pins; higher quiescent current (130μA). | Required when three independent regulated rails and triple supervision are needed - e.g., multi-core processors with dedicated I/O domain. | Select LT3689IFE#PBF only if third output is required; otherwise LT3688IFE#PBF offers lower cost and identical dual-rail performance. |
| TPS65270PWP | TI dual 1.2A buck with integrated LDOs; no watchdog/POR timers; fixed 500kHz/1MHz freq; no BIAS efficiency mode. | Suitable for non-safety-critical consumer applications where supervision is handled externally or omitted. | Choose TPS65270PWP for cost-sensitive, non-safety designs lacking watchdog requirements; avoid where POR timing coordination or low-IQ is mandatory. |
Compared with LT3689IFE#PBF, LT3688IFE#PBF saves board space and cost in dual-rail systems, while offering superior low-power supervision; versus TPS65270PWP, it delivers essential watchdog/POR functionality and 15% lower quiescent current, making it the only choice for automotive and industrial safety-aware designs.
Availability
LT3688IFE#PBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial PLC power modules, and high-reliability medical data loggers requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3688IFE#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, serving industrial, automotive, communications, and healthcare markets.
The LT3688IFE#PBF belongs to ADI's Power by Linear™ family of highly integrated DC/DC regulators with embedded system supervision - designed specifically for space-constrained, safety-critical applications demanding coordinated power sequencing and real-time fault detection.
FAQ
What is the maximum input voltage supported by the LT3688IFE#PBF?
The LT3688IFE#PBF supports a continuous input voltage range of 3.8V to 36V, with absolute maximum ratings up to 36V on VIN, EN/UVLO, and CONFIG pins. Operation at 36V is validated across the full –40°C to +125°C junction temperature range, making LT3688IFE#PBF suitable for automotive battery systems including load-dump conditions.
How do I configure independent power-on reset timing for each output using the LT3688IFE#PBF?
Independent POR timing is set using external capacitors on CPOR1 (Pin 23) and CPOR2 (Pin 21): tRST ≈ 5 × CPOR (in ms/nF). For example, 4.7nF yields ~23.5ms timeout. The CONFIG pin state determines whether RST1/RST2 operate independently (CONFIG = VIN or floating) or jointly (CONFIG = GND), as defined in the LT3688IFE#PBF datasheet Section 8.
Does the LT3688IFE#PBF require external catch diodes, and what are the specifications?
Yes, LT3688IFE#PBF requires external Schottky catch diodes connected to DA1/DA2 pins. Recommended devices include B140HB (IF = 1A, VF ≈ 400mV @ 0.8A) or equivalents with ≤500mV forward voltage and ≥1.2A surge rating. Diode reverse leakage must be minimized to avoid increased no-load current, especially at high temperature.
Can the LT3688IFE#PBF synchronize its switching frequency to an external clock source?
Yes, the LT3688IFE#PBF supports external synchronization via the SYNC pin (Pin 2). A logic-level square wave (≥150ns min pulse width, 0.4V–1.3V threshold) can override the internal RT-set oscillator. When unused, SYNC must be tied to GND - floating is not allowed. Synchronization eliminates beat frequencies in multi-regulator systems and aids EMI compliance.
What thermal design considerations apply to the LT3688IFE#PBF in its TSSOP-24 package?
The LT3688IFE#PBF TSSOP-24 package has θJA = 38°C/W when mounted with the exposed pad (Pin 25) soldered to a 4-layer PCB's internal ground plane using ≥6 thermal vias. To sustain 800mA per channel at 125°C ambient, keep power dissipation below 1.3W; use BIAS supply >3V to reduce VIN current and associated losses. Thermal shutdown activates at TJ >160°C.
LT3688IFE#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
LT3688IFE#PBF FAQ
1.How can I place an order for LT3688IFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3688IFE#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 LT3688IFE#PBF reliable?
The price and inventory of LT3688IFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3688IFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3688IFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3688IFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3688IFE#PBF?
LT3688IFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3688IFE#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 LT3688IFE#PBF?
For technical support, including LT3688IFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3688IFE#PBF requirements.
6.How does Aetrix verify that LT3688IFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3688IFE#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 LT3688IFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3688IFE#PBF?
All LT3688IFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3688IFE#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 LT3688IFE#PBF part is unused and in its original packaging.
Return procedure for LT3688IFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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