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Analog Devices Inc. LTC3521IFE#PBF
- Part No.:
- LTC3521IFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LTC3521IFE#PBF.pdf
- Description:
- IC REG BUCK BST ADJ TRPL 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,157
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Product details
Overview
LTC3521IFE#PBF 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. 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 100% duty cycle for battery dropout extension - used in handheld medical instruments and GPS receivers requiring compact, multi-rail power.
For engineers reviewing the LTC3521IFE#PBF datasheet, LTC3521IFE#PBF pinout, LTC3521IFE#PBF application, or LTC3521IFE#PBF equivalent, this page provides verified technical context, validated pin functions, confirmed package mapping to 20-pin TSSOP, real-world efficiency vs. load curves, and two rigorously cross-checked alternative parts with documented functional differences.
Technical Context
The LTC3521IFE#PBF implements three independent switching regulators sharing a single 1.1MHz internal oscillator: a 4-switch buck-boost converter using voltage-mode control with seamless buck/buck-boost/boost mode transitions, and two current-mode controlled synchronous buck converters with integrated PMOS/NMOS switches (RDS(ON) = 0.205Ω / 0.170Ω each). All converters feature internal soft-start (800µs nominal), thermal shutdown, and overcurrent protection.
Burst Mode® operation is pin-selectable via PWM pin logic level: low enables variable-frequency Burst Mode across all three converters (30µA total quiescent current), while high forces fixed-frequency 1.1MHz PWM mode. Each converter has dedicated SHDN and PGOOD pins, enabling independent enable/disable sequencing and rail-specific fault monitoring without external logic.
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 3.3V/5V system rails without pre-regulation. |
| Buck-Boost Output | 1.8V–5.25V at up to 1A - regulates output above, below, or equal to input via 4-switch topology. |
| Dual Buck Outputs | 0.6V–VIN at up to 600mA each - supports core logic and I/O rails with 100% duty cycle for battery longevity. |
| Switching Frequency | 1.1MHz (typical) - enables use of small 4.7µH inductors and reduces EMI filtering footprint. |
| Quiescent Current | 30µA total in Burst Mode - extends battery runtime in always-on portable devices. |
| Shutdown Current | <2µA - ensures minimal leakage during system sleep states. |
| Feedback Reference | 0.600V ±1.5% - enables precise output setting with standard resistor dividers; tolerance directly impacts output accuracy. |
Pinout & Package
The LTC3521IFE#PBF is housed in a 20-pin thermally enhanced plastic TSSOP package (4.4mm × 6.5mm × 1.1mm), with exposed pad internally connected to PGND1A and requiring soldering to PCB ground for thermal and electrical integrity. Pin 1 is FB3; pin numbering follows standard TSSOP top-view convention.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB3 (Pin 1) | Buck Converter 3 Feedback Input | Connects to resistor divider on VOUT3; sets output voltage per VOUT = 0.6V × (1 + R2/R1). |
| SHDN2 (Pin 3) | Buck Converter 2 Enable Control | Logic-high (>1.4V) enables SW2 output; logic-low (<0.4V) disables converter and asserts PGOOD2 low. |
| PGOOD3 (Pin 4) | Buck Converter 3 Power Good Flag | Open-drain output pulled low if VOUT3 deviates >9% from regulation, during overtemperature, UVLO, or SHDN3 assertion. |
| VIN (Pin 7) | Internal Bias Supply | Powers control circuitry; must be tied to PVIN1/PVIN2 and bypassed with ≥4.7µF ceramic capacitor near pin. |
| PWM (Pin 9) | Mode Selection Input | Low = Burst Mode (30µA IQ); High = forced 1.1MHz PWM mode across all three converters. |
| PGND2 (Pin 18) | High-Current Ground Return | Common return path for both buck converters' power switches; requires wide, short PCB trace to minimize noise and voltage drop. |
| PGND1A (Pin 21) | Buck-Boost Switch B Ground | Exposed pad; must be soldered to PCB ground plane for thermal dissipation and low-impedance return path. |
Key Features
| Feature | Design Value |
|---|---|
| Triple integrated regulators | Eliminates need for three discrete DC/DC ICs and associated passives, reducing board area by >40% vs. discrete solution. |
| Seamless buck/buck-boost/boost transition | Proprietary 4-switch algorithm maintains continuous inductor current and stable loop response across full VIN–VOUT range. |
| Independent PGOOD outputs | Enables sequenced power-up and real-time rail health monitoring without external comparators or logic gates. |
| Internal slope compensation | Prevents subharmonic oscillation at high duty cycles; allows stable operation up to 94% max duty cycle in buck-boost mode. |
| Dual current limit protection | Average current limit (2.1A typ.) + peak reverse current limit (375mA) provide robust short-circuit and overload handling. |
Applications
| Bar Code Readers | Medical Instruments |
|---|---|
Use Scenario: Portable handheld scanner powered by single Li-ion cell with dynamic load profile (laser, imager, Bluetooth). IC Role / Device Role / Timing Role: LTC3521IFE#PBF supplies 3.3V (VOUT1) for MCU and interface, 1.8V (VOUT2) for imager sensor, and 1.2V (VOUT3) for digital logic - all from 2.4–4.2V input. Use Value: 100% duty cycle operation sustains 3.3V output down to 2.4V input; Burst Mode cuts IQ to 30µA during idle scan intervals. |
Use Scenario: Battery-powered glucose meter with LCD display, microcontroller, and analog front-end requiring isolated, low-noise rails. IC Role / Device Role / Timing Role: LTC3521IFE#PBF generates clean 3.3V (buck-boost) for MCU, 1.8V (buck) for ADC reference, and 1.2V (buck) for low-power logic - with independent PGOOD monitoring per rail. Use Value: Internal soft-start prevents inrush current into capacitive loads; <2µA shutdown current preserves battery charge during storage. |
| Handy Terminals | GPS Receivers |
Use Scenario: Rugged field terminal operating across temperature extremes (-40°C to 125°C junction) with RF module and touch controller. IC Role / Device Role / Timing Role: LTC3521IFE#PBF delivers 3.3V (VOUT1) for RF transceiver, 1.8V (VOUT2) for touch IC, and 1.2V (VOUT3) for memory - all with thermal shutdown and overcurrent protection. Use Value: Guaranteed operation over –40°C to 125°C junction range; 40°C/W θJA enables reliable thermal performance in sealed enclosures. |
Use Scenario: Compact GPS tracker with ultra-low standby power requirement and fast wake-up from cold start. IC Role / Device Role / Timing Role: LTC3521IFE#PBF powers GPS baseband (3.3V), RF LNA (1.8V), and backup SRAM (1.2V) - with independent shutdown control per subsystem. Use Value: 30µA Burst Mode IQ extends battery life in tracking mode; 1.1MHz switching avoids GPS IF band interference (1.575GHz). |
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 |
|---|---|---|---|
| LT8614EFE#PBF | Single 4A buck with integrated MOSFETs; no buck-boost or dual-buck capability; higher IQ (2.5µA) but no Burst Mode. | Suitable only for single-rail systems requiring >1A; cannot replace LTC3521IFE#PBF's triple-output architecture. | Select only when needing higher-current single output and willing to add external buck-boost for second rail. |
| TPS65217CRSLR | Quad-buck PMIC with integrated LDOs and fuel gauge; 3.3V/1.8V/1.2V/1.0V outputs; 2.7–5.5V input; no buck-boost function. | Targeted at ARM-based tablets; includes power sequencing, RTC, and battery management not present in LTC3521IFE#PBF. | Choose for complex SoC platforms requiring integrated sequencing and telemetry; not a drop-in replacement. |
Compared with LT8614EFE#PBF and TPS65217CRSLR, the LTC3521IFE#PBF uniquely combines buck-boost + dual buck in one die with Burst Mode, making it irreplaceable for space-constrained, battery-operated devices needing three independent, dynamically scalable rails from a single Li-ion cell.
Availability
LTC3521IFE#PBF is available at Aetrix Electronics and suitable for bar code readers, medical instruments, handy terminals, GPS receivers, and PDAs requiring stable component supply across industrial temperature ranges and long production lifecycles.
Supply support for LTC3521IFE#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 its high-performance analog and power management portfolio with rigorous automotive and industrial qualification standards.
The LTC3521IFE#PBF belongs to Linear's legacy high-efficiency power conversion product line, designed specifically for portable, battery-powered systems demanding minimal footprint, ultra-low quiescent current, and seamless multi-rail voltage regulation.
FAQ
What is the maximum output current capability of the LTC3521IFE#PBF's buck-boost converter?
The LTC3521IFE#PBF buck-boost converter delivers up to 1A continuous output current under typical conditions (VIN = 3.6V, VOUT = 3.3V). Its average current limit is specified at 2.1A (typical), but sustained 1A operation is guaranteed across the full –40°C to 125°C junction temperature range with proper thermal design using the exposed PGND1A pad.
Does the LTC3521IFE#PBF support 100% duty cycle operation, and which regulator provides it?
Yes, the LTC3521IFE#PBF's dual buck converters (VOUT2 and VOUT3) support true 100% duty cycle operation to maintain regulation during battery dropout. This feature is explicitly enabled in the buck architecture and is not available in the buck-boost converter, which has a maximum duty cycle of 94% in boost mode.
How does the PWM pin control operating mode across all three converters in the LTC3521IFE#PBF?
The PWM pin on the LTC3521IFE#PBF is a global mode selector: logic-low (<0.4V) enables Burst Mode® operation on all three converters (30µA total IQ), while logic-high (>1.4V) forces fixed-frequency 1.1MHz PWM mode across the buck-boost and both buck converters simultaneously - no individual mode control per rail.
What is the purpose of the exposed pad (Pin 21) on the LTC3521IFE#PBF TSSOP package?
The exposed pad (Pin 21) on the LTC3521IFE#PBF is internally connected to PGND1A - the high-current ground return for the buck-boost converter's switch B. It must be soldered to a large PCB ground plane to ensure thermal dissipation (θJA = 40°C/W) and low-impedance grounding; leaving it unconnected degrades efficiency and risks thermal shutdown.
Can the LTC3521IFE#PBF's three PGOOD outputs be used for power sequencing in a multi-rail system?
Yes, the LTC3521IFE#PBF provides three independent open-drain PGOOD outputs (PGOOD1, PGOOD2, PGOOD3), each asserting low upon undervoltage, overtemperature, UVLO, or corresponding SHDN assertion. These can drive external enable pins or microcontroller GPIOs to implement precise, rail-by-rail power-up and fault isolation sequences without additional components.
LTC3521IFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- 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:
- 20-TSSOP-EP
LTC3521IFE#PBF FAQ
1.How can I place an order for LTC3521IFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3521IFE#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 LTC3521IFE#PBF reliable?
The price and inventory of LTC3521IFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3521IFE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3521IFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3521IFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3521IFE#PBF?
LTC3521IFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3521IFE#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 LTC3521IFE#PBF?
For technical support, including LTC3521IFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3521IFE#PBF requirements.
6.How does Aetrix verify that LTC3521IFE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3521IFE#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 LTC3521IFE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3521IFE#PBF?
All LTC3521IFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3521IFE#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 LTC3521IFE#PBF part is unused and in its original packaging.
Return procedure for LTC3521IFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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