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Analog Devices Inc. LTC3521EFE#TRPBF
- Part No.:
- LTC3521EFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LTC3521EFE#TRPBF.pdf
- Description:
- IC REG BUCK BST ADJ TRPL 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,211
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Product details
Overview
LTC3521EFE#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 thermally enhanced 20-pin TSSOP package. It operates from 1.8V to 5.5V input, delivers regulated outputs of 1.2V, 1.8V, and 3.3V, and supports pin-selectable Burst Mode® operation for ultra-low quiescent current - ideal for battery-powered handheld medical instruments and GPS receivers.
For engineers reviewing the LTC3521EFE#TRPBF datasheet, LTC3521EFE#TRPBF pinout, LTC3521EFE#TRPBF application, or LTC3521EFE#TRPBF equivalent, key selection considerations include its 1.1MHz fixed-frequency PWM/Burst Mode dual-control logic, independent PGOOD indicators per rail, integrated soft-start and thermal protection, and compatibility with standard 0.6V feedback reference architecture across all three regulators.
Technical Context
The LTC3521EFE#TRPBF implements a proprietary 4-switch buck-boost topology enabling seamless regulation above, below, or equal to input voltage without mode discontinuities. Its buck-boost converter uses voltage-mode control with internal compensation, while both buck channels employ current-mode control with slope compensation and 100% duty-cycle capability for extended battery runtime.
All three converters share a synchronized 1.1MHz oscillator, support independent enable/shutdown via SHDN1–SHDN3, and feature open-drain PGOOD outputs with –9% regulation threshold and 2% hysteresis. The device integrates PMOS/NMOS power switches with RDS(ON) values of 0.11Ω/0.085Ω (buck-boost) and 0.205Ω/0.17Ω (buck), plus average and peak current limiting with reverse-current protection on the buck-boost output.
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 USB-powered systems without external LDO pre-regulation. |
| Buck-Boost Output | 1.8V to 5.25V at up to 1A - enables VOUT1 to track battery voltage across full discharge curve while maintaining stable system rail. |
| Dual Buck Outputs | 0.6V to VIN at up to 600mA each - supports core logic (1.2V), I/O (1.8V), and analog subsystems (3.3V) with independent feedback and shutdown. |
| Quiescent Current | 30µA total in Burst Mode - extends battery life in always-on monitoring applications like portable ECG devices. |
| Shutdown Current | <2µA - ensures negligible drain during deep sleep states in handheld terminals and barcode scanners. |
| Switching Frequency | 1.1MHz typical - allows use of compact 4.7µH inductors and ceramic capacitors, minimizing PCB area in space-constrained PDAs. |
| Feedback Reference | 0.6V ±1.5% - enables precise output setting using standard resistor dividers; compatible with existing 0.6V-feedback PMIC designs. |
Pinout & Package
The LTC3521EFE#TRPBF is housed in a 20-lead plastic TSSOP package (FE grade, –40°C to 125°C junction temperature), featuring exposed thermal pad connected internally to PGND1A for enhanced heat dissipation in high-density layouts.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| FB3 (Pin 1) | Buck Converter 3 Feedback Input | Connects to resistor divider from VOUT3 (e.g., 1.2V rail); sets output via 0.6V reference - enables accurate low-voltage core supply regulation. |
| SHDN2 (Pin 3) | Buck Converter 2 Enable Control | Logic-high (>1.4V) enables SW2 output; logic-low (<0.4V) disables converter - allows dynamic power gating of peripheral subsystems. |
| PGOOD2 (Pin 5) | Buck Converter 2 Power Good Flag | Open-drain output pulls low if VOUT2 deviates >9% from target or during overtemperature/UVLO - provides fault signaling to host microcontroller. |
| VIN (Pin 7) | Internal Bias Supply Input | Powers internal circuitry (bandgap, oscillators, logic); must be tied to PVIN1/PVIN2 and bypassed with ≥4.7µF ceramic capacitor - ensures stable startup and sequencing. |
| PWM (Pin 9) | Global Mode Select Input | Low = Burst Mode (30µA IQ) for light loads; High = forced 1.1MHz PWM for low-noise, high-transient performance - simplifies system-level power policy control. |
| PGND2 (Pin 18) | High-Current Ground Return | Common return path for both buck converters' synchronous rectifiers - requires wide, low-inductance PCB trace to minimize ground bounce and EMI. |
Key Features
| Feature | Design Value |
|---|---|
| Triple integrated DC/DC conversion | Eliminates need for three discrete regulators and associated external components - reduces BOM count by >15 parts and saves >25mm² PCB area. |
| Independent PGOOD outputs | Three open-drain flags (PGOOD1/2/3) allow sequenced power-up verification and real-time rail monitoring without external supervisors. |
| 100% duty-cycle buck operation | Enables VOUT2/VOUT3 to track input down to dropout - extends usable battery capacity in handheld PCs operating near end-of-discharge. |
| Thermal and overcurrent protection | Integrated overtemperature shutdown and cycle-by-cycle current limiting prevent damage during sustained overload or poor heatsinking conditions. |
| Internal soft-start (800µs) | Prevents inrush current and output overshoot during power-up - eliminates need for external soft-start timing components in medical instrument designs. |
Applications
| Barcode Readers | Medical Instruments |
|---|---|
Use Scenario: Portable laser barcode scanners powered by single-cell Li-ion batteries requiring multiple clean, low-noise rails for MCU, imager, and laser driver. IC Role / Device Role / Timing Role: LTC3521EFE#TRPBF serves as primary power source, generating 3.3V (MCU/I/O), 1.8V (imager interface), and 1.2V (core logic) from 2.4V–4.2V input. Use Value: Burst Mode operation maintains <30µA system standby current; 1.1MHz switching avoids audible noise in laser modulation circuits. |
Use Scenario: Battery-operated portable ECG monitors needing reliable, low-quiescent-power regulation for analog front-end, digital processing, and display backlight. IC Role / Device Role / Timing Role: LTC3521EFE#TRPBF delivers isolated, low-noise 3.3V (AFE), 1.8V (microcontroller), and 1.2V (ADC/DAC core) with independent shutdown control per subsystem. Use Value: Integrated soft-start prevents signal corruption during power-on; PGOOD flags enable firmware-controlled power sequencing and fault recovery. |
| Handheld Terminals | GPS Receivers |
Use Scenario: Ruggedized industrial handhelds with RF, touchscreen, and cellular connectivity demanding robust, thermally efficient multi-rail power. IC Role / Device Role / Timing Role: LTC3521EFE#TRPBF supplies 3.3V (RF transceiver), 1.8V (touch controller), and 1.2V (application processor) while managing thermal load via exposed TSSOP pad. Use Value: Thermal shutdown protection prevents field failures under high ambient temperatures; 100% duty-cycle operation preserves runtime during low-battery operation. |
Use Scenario: Compact GNSS modules requiring ultra-low IQ power for cold-start acquisition and continuous tracking in battery-limited wearables. IC Role / Device Role / Timing Role: LTC3521EFE#TRPBF powers GPS baseband (1.2V), RF frontend (3.3V), and memory interface (1.8V) with synchronized 1.1MHz clocks to reduce beat-frequency interference. Use Value: 2µA shutdown current minimizes battery drain during sleep; Burst Mode enables sub-100µA active tracking current in urban canyon environments. |
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 |
|---|---|---|---|
| MAX8646ETJ+T | Single 1.2A buck + dual 600mA bucks; no buck-boost channel; 2.7–5.5V input; 2.2MHz switching. | Lacks input-voltage-flexible VOUT1 rail - unsuitable where output must exceed or fall below battery voltage. | Select only when all required rails are step-down and higher-frequency operation is prioritized over input range flexibility. |
| TPS65217CRSLR | Quad buck (3×1A + 1×2A) + LDOs; 2.7–5.5V input; integrated fuel gauge and RTC; QFN-48 package. | Higher integration but larger footprint and fixed 2.7V min input - incompatible with deep-discharge Li-ion or coin-cell operation. | Choose when system requires battery monitoring and real-time clock, and board space permits larger package. |
Compared with MAX8646ETJ+T and TPS65217CRSLR, the LTC3521EFE#TRPBF uniquely combines buck-boost flexibility with dual buck outputs in a compact TSSOP, making it optimal for space-constrained, wide-input-range portable devices where rail independence and ultra-low IQ are critical.
Availability
LTC3521EFE#TRPBF is available at Aetrix Electronics and suitable for barcode readers, portable medical instruments, handheld terminals, GPS receivers, and PDAs requiring stable component supply across extended production lifecycles.
Supply support for LTC3521EFE#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 and maintains its legacy of high-performance analog and power management ICs with rigorous reliability testing and automotive-grade process controls.
The LTC3521 product line was designed specifically for portable, battery-powered systems requiring multiple tightly regulated rails with minimal quiescent power - targeting handheld computing, instrumentation, and location-based electronics.
FAQ
What is the maximum output current capability of the LTC3521EFE#TRPBF's buck-boost converter?
The LTC3521EFE#TRPBF buck-boost converter delivers up to 1A continuous output current under typical conditions (VIN = 3.6V, VOUT1 = 3.3V). Its average current limit is specified at 1.65A to 2.1A, with peak current limiting at ~165% of that value for short-circuit protection. Performance depends on input voltage, output voltage, inductor selection, and thermal management - the 20-pin TSSOP package supports this rating with proper PCB copper area and airflow.
Does the LTC3521EFE#TRPBF support independent enable/disable of each converter?
Yes, the LTC3521EFE#TRPBF provides three dedicated shutdown pins: SHDN1 controls the buck-boost converter (SW1A/SW1B), SHDN2 controls buck converter 2 (SW2), and SHDN3 controls buck converter 3 (SW3). Each pin accepts standard logic levels (≥1.4V to enable, ≤0.4V to disable), allowing granular power sequencing and subsystem-level power gating without affecting other rails.
How does the PWM pin affect operation modes across all three converters in the LTC3521EFE#TRPBF?
The PWM pin on the LTC3521EFE#TRPBF globally selects between two operating modes: when pulled low, all three converters enter Burst Mode® (30µA total IQ), with buck converters auto-transitioning to PWM at higher loads; when pulled high, all remain in fixed 1.1MHz PWM mode regardless of load - ensuring consistent switching frequency and low-noise performance for sensitive analog circuits.
What is the function of the PGOOD pins on the LTC3521EFE#TRPBF, and how are they implemented?
The LTC3521EFE#TRPBF features three open-drain PGOOD pins (PGOOD1, PGOOD2, PGOOD3), each monitoring its respective output rail. They pull low if output voltage falls >9% below regulation, or during overtemperature shutdown, UVLO, or corresponding SHDN pin assertion. Each includes 60µs deglitching to reject transient noise, and requires an external pull-up resistor to indicate valid regulation status to system controllers.
Can the LTC3521EFE#TRPBF operate with input voltages below 2.4V, such as from partially discharged Li-ion cells?
Yes, the LTC3521EFE#TRPBF supports input voltages as low as 1.8V, making it compatible with deeply discharged single-cell Li-ion batteries (down to ~2.0V) and other low-voltage sources. Its buck-boost architecture maintains regulation even when VIN drops below VOUT1, and its buck converters sustain 100% duty cycle to maximize usable battery energy - critical for long-duration portable medical and handheld applications.
LTC3521EFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width) 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:
- 20-TSSOP-EP
LTC3521EFE#TRPBF FAQ
1.How can I place an order for LTC3521EFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3521EFE#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 LTC3521EFE#TRPBF reliable?
The price and inventory of LTC3521EFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3521EFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3521EFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3521EFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3521EFE#TRPBF?
LTC3521EFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3521EFE#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 LTC3521EFE#TRPBF?
For technical support, including LTC3521EFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3521EFE#TRPBF requirements.
6.How does Aetrix verify that LTC3521EFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3521EFE#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 LTC3521EFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3521EFE#TRPBF?
All LTC3521EFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3521EFE#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 LTC3521EFE#TRPBF part is unused and in its original packaging.
Return procedure for LTC3521EFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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