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Analog Devices Inc. LTC3521EUF#TRPBF
- Part No.:
- LTC3521EUF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LTC3521EUF#TRPBF.pdf
- Description:
- IC REG BUCK BOOST ADJ TRPL 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,621
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Product details
Overview
LTC3521EUF#TRPBF from Analog Devices (formerly Linear Technology) is a triple-output monolithic DC/DC converter integrating one 1A buck-boost and two 600mA synchronous buck regulators in a single 24-pin 4mm × 4mm QFN package. It operates from 1.8V to 5.5V input, delivers regulated outputs at 1.8–5.25V (buck-boost) and 0.6–VIN (buck), and supports pin-selectable Burst Mode® for ultra-low quiescent current (30µA total). It is used in battery-powered handheld instruments requiring compact multi-rail power.
For engineers reviewing the LTC3521EUF#TRPBF datasheet, LTC3521EUF#TRPBF pinout, LTC3521EUF#TRPBF application, or LTC3521EUF#TRPBF equivalent, key selection criteria include its triple-converter integration, 1.1MHz fixed-frequency PWM/Burst Mode operation, independent PGOOD indicators, thermal/overcurrent protection, and compatibility with Li-ion input (2.4V–4.2V) in space-constrained portable systems.
Technical Context
The LTC3521EUF#TRPBF implements three independent switching regulators sharing a single 1.1MHz oscillator: a 4-switch buck-boost core using proprietary mode-transition logic (buck → buck-boost → boost) without output discontinuity, and two current-mode controlled synchronous buck stages with internal PMOS/NMOS switches (RDS(ON) = 0.205Ω / 0.170Ω each) and 100% duty-cycle dropout capability.
Each regulator features integrated soft-start (800µs nominal), voltage-mode error amplifiers with internal compensation, and dedicated open-drain PGOOD outputs with –9% regulation threshold and 2% hysteresis. Shutdown draws <2µA, and Burst Mode reduces total quiescent current to 30µA while maintaining regulation across all three outputs.
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 industrial rails without external LDO pre-regulation. |
| Buck-Boost Output | 1.8V to 5.25V @ 1A - regulates above, below, or equal to input; enables single-rail battery backup for 3.3V/5V systems. |
| Dual Buck Outputs | 0.6V to VIN @ 600mA each - supports low-voltage digital cores (e.g., 1.2V, 1.8V) with 100% duty cycle for maximum battery runtime. |
| Switching Frequency | 0.85MHz to 1.35MHz (typ. 1.1MHz) - enables small external inductors (e.g., 4.7µH) and ceramic capacitors while maintaining >90% efficiency. |
| Quiescent Current | 30µA in Burst Mode - extends shelf life and standby time in always-on medical/handheld devices. |
| Protection Features | <2µA shutdown, thermal shutdown, per-converter current limit (1.65A avg / 375mA reverse for buck-boost; 1.05A for bucks), and UVLO - ensures robust operation under fault conditions without external circuitry. |
| Package | 24-pin 4mm × 4mm QFN with exposed PGND1A pad - provides low thermal resistance (θJA = 37°C/W) and high-current grounding for all three power stages. |
Pinout & Package
The LTC3521EUF#TRPBF is housed in a 24-pin, 4mm × 4mm plastic QFN package with an exposed thermal pad (Pin 25 = PGND1A) that must be soldered to PCB ground. Pin count and layout match the UF package variant; NC pins are present at Pins 13 and 19.
| 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 - enables precise 1.8–5.25V programming with <±0.5% initial accuracy. |
| SW1A/SW1B (Pins 15/14) | Buck-boost switch nodes | Drive external inductor legs; support 4-switch topology - require low-inductance layout to minimize EMI and switching losses. |
| VOUT1 (Pin 16) | Buck-boost output node | High-current output terminal - must connect directly to low-ESR ceramic capacitor (≥22µF) with short ground return path. |
| PGND1A (Pin 25) | Buck-boost switch B ground | Exposed thermal pad tied internally to PGND1A - mandatory solder connection to PCB ground plane for thermal management and noise control. |
| PWM (Pin 7) | Mode select logic input | Low = Burst Mode (30µA IQ); High = forced 1.1MHz PWM - enables dynamic efficiency/runtime trade-off without firmware changes. |
| PGOOD1/2/3 (Pins 4/5/6) | Open-drain power-good flags | Assert low if output out-of-regulation (–9%), OT, UVLO, or SHDN asserted - allows system-level sequencing and fault monitoring. |
Key Features
| Feature | Design Value |
|---|---|
| Triple integrated converters | Eliminates need for three discrete regulators - reduces BOM count, PCB area, and design validation effort in multi-rail portable systems. |
| Proprietary 4-switch buck-boost algorithm | Enables seamless transition between buck/boost modes with continuous inductor current - avoids output glitches during input voltage sag (e.g., battery discharge). |
| Independent soft-start (800µs) | Prevents inrush current and output overshoot across all three rails - critical for powering mixed-signal SoCs with strict voltage ramp requirements. |
| Internal compensation | Removes need for external compensation components - simplifies layout and ensures stable operation with wide-range ceramic output capacitors (10–100µF). |
| Per-converter shutdown control | SHDN1/SHDN2/SHDN3 enable independent enable/disable of each regulator - supports dynamic power gating for subsystem-level energy optimization. |
Applications
| Bar Code Readers | Medical Instruments |
|---|---|
Use Scenario: Portable laser or imager-based scanners powered by single-cell Li-ion batteries with tight size constraints and intermittent high-current decode bursts. IC Role / Device Role / Timing Role: LTC3521EUF#TRPBF supplies 3.3V (logic), 1.8V (imager), and 5V (laser driver) simultaneously from 2.4–4.2V input, enabling full functionality without external regulators. Use Value: 30µA Burst Mode IQ extends idle time between scans; 1.1MHz switching allows use of tiny 4.7µH inductors; integrated PGOOD signals ensure clean power-up sequencing. | Use Scenario: Handheld diagnostic devices (e.g., pulse oximeters, glucose meters) requiring isolated analog rails, low-noise digital supplies, and long battery life. IC Role / Device Role / Timing Role: LTC3521EUF#TRPBF generates precision 1.2V (ADC/DAC core), 1.8V (microcontroller I/O), and 3.3V (RF transceiver) from a single Li-ion cell with independent regulation and fault reporting. Use Value: <2µA shutdown minimizes battery drain during storage; thermal protection prevents overheating in sealed enclosures; 0.6V feedback reference enables accurate low-voltage outputs. |
| Handy Terminals | GPS Receivers |
Use Scenario: Ruggedized field terminals running Linux/RTOS with LCD, cellular modem, and SD card - demanding multiple voltage domains and reliable cold-start performance. IC Role / Device Role / Timing Role: LTC3521EUF#TRPBF delivers 3.3V (CPU), 1.8V (memory), and adjustable buck-boost rail (e.g., 5V for USB host) from 2.7–4.5V input, supporting wide battery voltage range. Use Value: 100% duty cycle operation maintains 3.3V output down to 3.3V input - extends usable battery capacity; 24-pin QFN fits dense layouts with minimal thermal derating. | Use Scenario: Compact GPS modules in asset trackers or wearables where RF sensitivity demands ultra-low-noise power and minimal quiescent draw. IC Role / Device Role / Timing Role: LTC3521EUF#TRPBF powers GPS baseband (1.2V), RF front-end (3.3V), and optional flash memory (1.8V) while suppressing switching noise via Burst Mode during satellite acquisition. Use Value: Synchronized 1.1MHz clocks prevent beat frequencies; internal compensation ensures stable loop response with low-ESR MLCCs; PGOOD flags validate rail readiness before RF activation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar multi-output DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX20403ATPA+T | Triple buck only (no buck-boost); 2.5V–5.5V input; 0.4V–5.5V outputs; 3A/2A/2A rating; 2.2MHz switching. | Suitable for systems with stable input >2.5V and no need for output > input; higher current but less flexible VIN/VOUT relationship. | Select when higher output current and faster transient response are required, and input never drops below 2.5V. |
| TPS65218D0RSLR | Power management IC with dual buck + single boost + LDOs + fuel gauge; 2.7V–5.5V input; fixed 3.3V/1.8V/1.5V/1.2V outputs; integrated battery charging. | Targeted at AM335x/AM437x processors; includes PMIC-specific features (RTC, reset, thermal monitor) not present in LTC3521EUF#TRPBF. | Select for TI Sitara-based designs requiring full-featured PMIC with battery management, not standalone triple-converter flexibility. |
Compared with MAX20403ATPA+T and TPS65218D0RSLR, the LTC3521EUF#TRPBF uniquely combines buck-boost + dual buck in one chip with true 1.8V start-up and sub-µA shutdown - making it optimal for ultra-low-power, wide-input portable systems where output voltage must exceed input (e.g., 5V from dying Li-ion).
Availability
LTC3521EUF#TRPBF is available at Aetrix Electronics and suitable for bar code readers, medical instruments, handy terminals, GPS receivers, and PDAs requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LTC3521EUF#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.
The LTC3521EUF#TRPBF belongs to Linear's µPower DC/DC converter family, designed specifically for space- and power-constrained portable electronics requiring high integration, ultra-low quiescent current, and robust multi-rail power delivery.
FAQ
What is the minimum input voltage required for the LTC3521EUF#TRPBF to start switching?
The LTC3521EUF#TRPBF has a guaranteed operating input voltage range of 1.8V to 5.5V. It achieves reliable startup and regulation down to 1.8V - enabling direct operation from partially discharged single-cell Li-ion batteries (down to ~2.4V typical, with margin). Below 1.8V, undervoltage lockout disables all converters to protect internal circuitry.
Does the LTC3521EUF#TRPBF support independent enable/disable of each converter?
Yes. The LTC3521EUF#TRPBF provides three dedicated shutdown pins: SHDN1 controls the buck-boost converter (Pin 10), SHDN2 controls Buck 2 (Pin 3), and SHDN3 controls Buck 3 (Pin 11). Each accepts standard logic levels (VIH ≥ 1.4V, VIL ≤ 0.4V) and must not be left floating - enabling precise power sequencing and subsystem-level power gating.
What is the purpose of the exposed pad (Pin 25) on the LTC3521EUF#TRPBF QFN package?
The exposed pad (Pin 25) on the LTC3521EUF#TRPBF is internally connected to PGND1A - the high-current ground return for the buck-boost switch B. It must be soldered to a solid PCB ground plane to ensure proper thermal dissipation (θJA = 37°C/W) and low-impedance return path, preventing voltage spikes, EMI, and thermal shutdown during 1A buck-boost operation.
How does Burst Mode® operation affect output voltage ripple on the LTC3521EUF#TRPBF?
In Burst Mode®, the LTC3521EUF#TRPBF reduces switching frequency dynamically at light loads to achieve 30µA total quiescent current, resulting in higher peak-to-peak output voltage ripple (typically 20–30mVPP) compared to fixed-frequency PWM mode (<10mVPP). This trade-off is intentional for ultra-low-power standby; ripple remains within specification and is suppressed by standard 10–22µF ceramic output capacitors.
Can the LTC3521EUF#TRPBF generate an output voltage higher than its input voltage?
Yes. The buck-boost converter section of the LTC3521EUF#TRPBF is a true 4-switch topology capable of regulating output voltages from 1.8V to 5.25V regardless of input - including boosting (e.g., 5V output from 3.3V input) and buck-boost (e.g., 3.3V from 2.7V input). This is enabled by its proprietary seamless mode-transition algorithm, which avoids discontinuities in inductor current or regulation.
LTC3521EUF#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)
LTC3521EUF#TRPBF FAQ
1.How can I place an order for LTC3521EUF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3521EUF#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 LTC3521EUF#TRPBF reliable?
The price and inventory of LTC3521EUF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3521EUF#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3521EUF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3521EUF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3521EUF#TRPBF?
LTC3521EUF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3521EUF#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 LTC3521EUF#TRPBF?
For technical support, including LTC3521EUF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3521EUF#TRPBF requirements.
6.How does Aetrix verify that LTC3521EUF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3521EUF#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 LTC3521EUF#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3521EUF#TRPBF?
All LTC3521EUF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3521EUF#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 LTC3521EUF#TRPBF part is unused and in its original packaging.
Return procedure for LTC3521EUF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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