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Analog Devices Inc. LTC3521IUF#TRPBF
- Part No.:
- LTC3521IUF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LTC3521IUF#TRPBF.pdf
- Description:
- IC REG BUCK BOOST ADJ TRPL 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,535
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Product details
Overview
LTC3521IUF#TRPBF from Analog Devices (formerly Linear Technology) is a triple-output monolithic power management IC integrating one 1A buck-boost DC/DC converter and two independent 600mA synchronous buck DC/DC converters in a single 24-pin 4mm × 4mm QFN package. It operates from 1.8V to 5.5V input, delivers regulated outputs of 1.8–5.25V (buck-boost) and 0.6–VIN (dual buck), and supports Burst Mode® operation with 30µA total quiescent current - ideal for battery-powered handheld medical instruments and GPS receivers.
For engineers reviewing the LTC3521IUF#TRPBF datasheet, LTC3521IUF#TRPBF pinout, LTC3521IUF#TRPBF application, or LTC3521IUF#TRPBF equivalent, key selection considerations include its 1.1MHz fixed-frequency PWM/Burst Mode dual-control logic, integrated soft-start and compensation, independent PGOOD indicators, thermal/overcurrent protection, and verified 4mm × 4mm QFN footprint compatibility with industrial-grade temperature range (–40°C to 125°C).
Technical Context
The LTC3521IUF#TRPBF implements a proprietary 4-switch buck-boost topology enabling seamless mode transitions (buck → buck-boost → boost) without inductor current discontinuity or loop instability. Its voltage-mode controlled buck-boost stage uses internal slope-compensated error amplification and dual current limiting (2.1A average, 375mA reverse), while the two current-mode buck stages feature 100% duty-cycle dropout support and synchronized 1.1MHz switching.
All three converters share a single oscillator, support independent enable/shutdown via SHDN1–SHDN3, and use dedicated feedback pins (FB1/FB2/FB3) with 0.6V reference and ±3% PGOOD thresholds. The device integrates high-side PMOS (0.11Ω buck-boost, 0.205Ω buck) and low-side NMOS (0.085Ω buck-boost, 0.17Ω buck) switches with thermal shutdown and <2µA shutdown current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 1.8V to 5.5V - supports single-cell Li-ion (2.4V–4.2V) and wide-input portable systems without external regulators. |
| Buck-Boost Output | 1.8V to 5.25V at up to 1A - enables VOUT > VIN, VOUT < VIN, or VOUT ≈ VIN operation from one rail. |
| Dual Buck Outputs | 0.6V to VIN at up to 600mA each - supports core/logic rails with 100% duty cycle for maximum battery runtime. |
| Switching Frequency | 1.1MHz (typical) - minimizes external inductor/capacitor size; fixed-frequency PWM mode eliminates EMI variability. |
| Quiescent Current | 30µA total in Burst Mode - extends battery life in always-on, low-duty-cycle applications like barcode scanners. |
| Shutdown Current | <2µA - ensures negligible drain during system sleep or storage. |
| Feedback Reference | 0.6V ±2% - enables precise output programming with standard resistor dividers; stable over –40°C to 125°C. |
| Package | 24-pin 4mm × 4mm QFN with exposed PGND1A pad - provides low thermal resistance (θJA = 37°C/W) and robust ground return for high-current paths. |
Pinout & Package
Package: 24-lead plastic QFN (4mm × 4mm, 0.5mm pitch), thermally enhanced with exposed PGND1A pad (Pin 25) requiring PCB solder connection to ground plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1 (Pin 8) | Buck-boost feedback input | Connects to resistor divider on VOUT1; sets output via 0.6V reference; determines regulation accuracy and loop stability. |
| SW1A/SW1B (Pins 15/14) | Buck-boost switch nodes | Drive external inductor; require low-inductance layout; SW1A connects to PVIN1, SW1B to PGND1A/PGND1B. |
| VOUT1 (Pin 16) | Buck-boost output node | High-current output; must be decoupled with low-ESR ceramic capacitor placed adjacent to IC and grounded to PGND1A. |
| SHDN1 (Pin 10) | Buck-boost enable control | Logic-high (>1.4V) enables buck-boost; logic-low (<0.4V) disables it with <2µA shutdown current. |
| PGOOD1 (Pin 6) | Buck-boost power-good indicator | Open-drain flag pulls low if VOUT1 deviates >9%, during overtemperature, UVLO, or SHDN1 assertion. |
| PVIN1/PVIN2 (Pins 11/22) | High-current input supplies | Carry peak switch currents; require local 4.7µF (PVIN1) and 10µF (PVIN2) ceramic bypass caps with short ground returns. |
| PGND1A/PGND1B (Pins 21/12) | High-current ground terminals | Separate ground returns for buck-boost switches A/B and C/D; must connect to low-impedance PCB ground plane. |
| PWM (Pin 7) | Mode select input | Low = Burst Mode (30µA IQ, variable frequency); High = forced 1.1MHz PWM for low-noise operation. |
Key Features
| Feature | Design Value |
|---|---|
| Triple integrated converters | Eliminates need for three discrete regulators - reduces BOM count, PCB area, and design validation effort. |
| Seamless 4-switch buck-boost algorithm | Enables continuous conduction across buck/buck-boost/boost modes - avoids output glitches and loop re-tuning. |
| Independent PGOOD outputs | Three open-drain flags (PGOOD1/2/3) allow system-level power sequencing and fault isolation without external monitoring ICs. |
| Internal soft-start and compensation | 800µs soft-start prevents inrush; fully compensated loops accept wide capacitor ranges - accelerates design-in. |
| Thermal + overcurrent protection | Junction shutdown at 125°C; per-converter current limits (2.1A avg, 375mA reverse, 1.05A buck) prevent damage under fault conditions. |
| 100% duty-cycle buck operation | Maintains regulation down to VIN ≈ VOUT - maximizes usable battery voltage range in portable devices. |
Applications
| Handheld Medical Instruments | GPS Receivers |
|---|---|
|
Use Scenario: Portable blood glucose meters and pulse oximeters powered by single Li-ion cells with strict low-power standby requirements. IC Role / Device Role / Timing Role: LTC3521IUF#TRPBF provides three regulated rails (3.3V analog, 1.8V digital, 1.2V sensor core) from 2.4–4.2V battery input. Use Value: 30µA Burst Mode IQ extends battery life beyond 1 week in sleep mode; independent PGOOD signals enable safe power-up sequencing. |
Use Scenario: Compact GNSS modules requiring simultaneous 3.3V RF, 1.8V baseband, and 1.2V processor supply with minimal EMI. IC Role / Device Role / Timing Role: LTC3521IUF#TRPBF delivers clean, synchronized 1.1MHz outputs - avoiding beat frequencies between converters. Use Value: Fixed-frequency PWM mode suppresses switching noise near GPS L1 band (1.575GHz); 4mm × 4mm QFN fits tight RF shield envelopes. |
| Barcode Scanners | Industrial Handheld Terminals |
|
Use Scenario: Rugged laser scanners operating from rechargeable batteries with frequent high-pulse laser loads. IC Role / Device Role / Timing Role: LTC3521IUF#TRPBF powers laser driver (3.3V), microcontroller (1.8V), and imager (1.2V) with fast load-step response. Use Value: Current-mode buck stages recover from 10mA→400mA steps in <100µs; 100% duty cycle maintains VOUT during battery sag. |
Use Scenario: Warehouse terminals exposed to wide ambient temperatures (–20°C to 70°C) and requiring long-term supply continuity. IC Role / Device Role / Timing Role: LTC3521IUF#TRPBF serves as main PMIC across all operating conditions with guaranteed –40°C to 125°C junction rating. Use Value: Thermal shutdown and overcurrent protection ensure reliability in unventilated enclosures; QFN package withstands mechanical shock. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar multi-rail DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX20073ATP+T | Single 3A buck with integrated FETs; no buck-boost or dual-buck capability; requires external LDOs for auxiliary rails. | Suitable only when primary rail dominates power budget and secondary rails are low-current (≤100mA). | Select MAX20073ATP+T only if system needs higher single-rail current and can tolerate added complexity for auxiliary regulation. |
| TPS65218D0RSLR | Power-management IC with 4 buck converters (up to 1.8A), but no buck-boost; includes integrated RTC, reset, and battery charger. | Better suited for AM335x/AM437x-based embedded processors requiring full PMIC functionality beyond DC/DC conversion. | Choose TPS65218D0RSLR when processor-specific integration (charger, PMIC sequencer) outweighs need for buck-boost flexibility. |
Compared with MAX20073ATP+T and TPS65218D0RSLR, the LTC3521IUF#TRPBF uniquely combines buck-boost + dual buck in one chip with verified 1.1MHz synchronization, making it optimal for space-constrained, battery-fed systems needing flexible input-to-output voltage relationships without external components.
Availability
LTC3521IUF#TRPBF is available at Aetrix Electronics and suitable for handheld medical instruments, GPS receivers, barcode scanners, and industrial handheld terminals requiring stable component supply across extended temperature operation and long product lifecycles.
Supply support for LTC3521IUF#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 (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors with emphasis on precision, reliability, and energy efficiency.
The LTC3521IUF#TRPBF belongs to Linear's Power Management IC family, designed specifically for compact, multi-rail battery-powered systems where integration, low IQ, and seamless voltage conversion are critical.
FAQ
What is the operating temperature range for the LTC3521IUF#TRPBF?
The LTC3521IUF#TRPBF is rated for –40°C to 125°C junction temperature. This industrial-grade specification ensures reliable operation in handheld medical devices, GPS units, and ruggedized terminals exposed to wide ambient conditions. The 24-pin QFN package features an exposed thermal pad (PGND1A) that must be soldered to the PCB ground plane to maintain thermal performance at full load.
Does the LTC3521IUF#TRPBF support 100% duty cycle operation?
Yes, the dual buck converters in the LTC3521IUF#TRPBF support true 100% duty cycle operation, allowing VOUT to track VIN minus small resistive drops - essential for maximizing battery runtime in portable equipment. This behavior is enabled automatically during dropout conditions and does not require external circuitry or mode configuration.
How does Burst Mode® operation work on the LTC3521IUF#TRPBF?
When the PWM pin is pulled low, the LTC3521IUF#TRPBF enters Burst Mode®, reducing total quiescent current to 30µA. In this mode, the buck converters transition dynamically between burst pulses and full PWM cycles based on load; the buck-boost converter operates at variable frequency with reduced max load (~50mA). Holding PWM high forces all three converters into fixed 1.1MHz PWM mode.
What protection features are built into the LTC3521IUF#TRPBF?
The LTC3521IUF#TRPBF includes overtemperature shutdown (125°C junction), per-converter current limiting (2.1A avg for buck-boost, 1.05A for each buck), reverse current limiting (375mA on buck-boost), undervoltage lockout, and <2µA shutdown current. Each PGOOD pin also asserts low during faults - providing hardware-level system monitoring without software intervention.
Can the LTC3521IUF#TRPBF generate an output voltage higher than its input?
Yes - the buck-boost converter in the LTC3521IUF#TRPBF uses a 4-switch topology with proprietary mode-switching logic to regulate VOUT1 from 1.8V to 5.25V regardless of input voltage. When VIN < VOUT, it operates in boost mode; when VIN > VOUT, in buck mode; and seamlessly transitions through buck-boost - all while maintaining continuous inductor current and stable loop response.
LTC3521IUF#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down, Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck, Buck-Boost
- Output Type:
- Adjustable
- Number of Outputs:
- 3
- Voltage - Input (Min):
- 1.8V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- 0.6V
- Voltage - Output (Max):
- 5.5V
- Current - Output:
- 600mA, 1A
- Frequency - Switching:
- 1.1MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-QFN (4x4)
LTC3521IUF#TRPBF FAQ
1.How can I place an order for LTC3521IUF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3521IUF#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 LTC3521IUF#TRPBF reliable?
The price and inventory of LTC3521IUF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3521IUF#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3521IUF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3521IUF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3521IUF#TRPBF?
LTC3521IUF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3521IUF#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 LTC3521IUF#TRPBF?
For technical support, including LTC3521IUF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3521IUF#TRPBF requirements.
6.How does Aetrix verify that LTC3521IUF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3521IUF#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 LTC3521IUF#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3521IUF#TRPBF?
All LTC3521IUF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3521IUF#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 LTC3521IUF#TRPBF part is unused and in its original packaging.
Return procedure for LTC3521IUF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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