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Analog Devices Inc. LTC3520EUF#PBF
- Part No.:
- LTC3520EUF#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LTC3520EUF#PBF.pdf
- Description:
- IC REG BUCK BOOST ADJ DL 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,933
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Product details
Overview
LTC3520EUF#PBF from Analog Devices (formerly Linear Technology) is a dual-output synchronous DC/DC converter integrating a 1A buck-boost and 600mA buck regulator in a single 24-lead 4mm × 4mm QFN package. It supports input voltages from 2.2V to 5.5V, delivers regulated outputs of 2.2V–5.25V (buck-boost) and 0.8V–VIN (buck), and features programmable switching frequency (100kHz–2MHz), <1μA shutdown current, and integrated uncommitted gain block for LDO control or battery-good indication - used in portable media players and GPS receivers.
For engineers reviewing the LTC3520EUF#PBF datasheet, LTC3520EUF#PBF pinout, LTC3520EUF#PBF application, or LTC3520EUF#PBF equivalent, key selection considerations include dual-converter integration, Burst Mode® operation for ultra-low quiescent current (55μA typ. in Burst Mode for both converters), thermal/overcurrent protection, pin-selectable PWM/Burst mode per converter, and compatibility with lithium-ion battery inputs (2.7V–4.2V).
Technical Context
The LTC3520EUF#PBF implements two independent, internally synchronized switching regulators: a four-switch buck-boost using voltage-mode control with seamless buck/buck-boost/boost transitions, and a current-mode synchronous buck with internal PMOS/NMOS switches (0.32Ω/0.18Ω typical RDS(ON)). Both share a programmable oscillator and soft-start circuitry, with separate shutdown (SD1/SD2), mode control (PWM1/PWM2), and feedback (FB1/FB2) pins.
Its uncommitted gain block operates as a rail-to-rail comparator (AIN threshold: 0.786V typ.) or transconductance amplifier (80dB open-loop gain, 45μA quiescent), configurable for battery monitoring or external PNP-based LDO regulation. Overtemperature shutdown activates at 125°C junction temperature, and absolute maximum ratings include 6V on all power pins with –0.3V to 6V tolerance on signal pins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.2V to 5.5V - supports single-cell Li-ion (2.7V–4.2V) and USB-powered systems without external pre-regulation. |
| Buck-Boost Output Range | 2.2V to 5.25V at up to 1A (VOUT = 3.3V, VIN ≥ 3V) - enables output above, below, or equal to input for flexible rail generation. |
| Buck Output Range | 0.8V to VIN at up to 600mA - provides efficient low-voltage core supply with 100% duty-cycle dropout capability. |
| Switching Frequency | Programmable 100kHz to 2MHz via RT pin resistor - allows optimization of efficiency vs. size (e.g., smaller inductors at higher frequencies). |
| Quiescent Current (Burst Mode) | 55μA total for both converters - extends battery life in standby or low-duty-cycle portable applications. |
| Shutdown Current | <1μA - meets stringent off-state leakage requirements for always-on subsystems. |
| Package | 24-lead 4mm × 4mm QFN, 0.75mm profile, exposed pad (Pin 25) - enables high-density layout with low thermal resistance (θJA = 37°C/W). |
Pinout & Package
24-lead (4mm × 4mm) plastic QFN package with exposed thermal pad (Pin 25 = GND). Requires soldering of exposed pad to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SVIN (1) | Small-signal power supply | Powers internal analog circuitry; must be tied to PVIN1/PVIN2/PVIN3 and bypassed with ≥0.1μF ceramic capacitor. |
| AOUT (2) | Uncommitted amplifier output | Drives external PNP base for LDO or serves as open-collector comparator output for battery-good indication. |
| AIN (3) | Non-inverting input of gain block | Sets LDO reference or battery threshold (0.786V typ.); bias current ≤50nA enables high-impedance divider networks. |
| RT (4) | Oscillator frequency programming | Resistor to ground sets switching frequency (e.g., 54.9kΩ → 1MHz); critical for EMI and inductor sizing. |
| PWM1 (5) | Buck-boost mode control | High = fixed-frequency PWM; Low = variable-frequency Burst Mode (reduced light-load noise/efficiency trade-off). |
| SD1 (6) | Buck-boost enable/disable | Active-low shutdown; >1.4V = enabled, <0.4V = disabled - prevents unintended startup during power sequencing. |
| SD2 (7) | Buck enable/disable | Independent active-low control; allows selective powering of buck rail without affecting buck-boost output. |
| SD3 (8) | Gain block enable/disable | Enables/disables AOUT/AIN functionality - essential for dynamic battery monitoring or LDO activation. |
| PVIN2 (9) | Buck high-current input | Carries buck converter input current; requires ≥22μF local ceramic bypass to minimize voltage droop and EMI. |
| SW2 (10) | Buck switch node | Connects to buck inductor; high dv/dt node requiring short, low-inductance PCB routing to reduce ringing. |
| PGND2 (11) | Buck power ground | Return path for buck NMOS switch; must be wide, low-impedance trace connected directly to exposed pad. |
| PWM2 (12) | Buck mode control | Configurable for forced PWM, resistor-programmed Burst entry threshold, or forced Burst - enables precise ripple/noise control. |
| SS2 (13) | Buck soft-start capacitor | External capacitor sets soft-start duration (tSS ≈ 0.15·CSS in ms); prevents inrush current into output capacitors. |
| FB2 (14) | Buck feedback input | 0.790V nominal reference; resistor divider from VOUT2 sets output voltage with ±1.9% tolerance over temp. |
| VC1 (15) | Buck-boost error amp output | Compensation node for FB1 loop; requires external RC network for stability across capacitor ESR/load ranges. |
| SGND (16) | Small-signal ground | Analog reference for FB/AIN/SS pins; must be isolated from PGND traces until joined at single point near exposed pad. |
| SS1 (17) | Buck-boost soft-start capacitor | Same function as SS2 but for buck-boost rail; ensures monotonic startup under varying input/output conditions. |
| FB1 (18) | Buck-boost feedback input | 0.782V nominal reference; sets VOUT1 with ±1.6% tolerance; compatible with standard resistor-divider design practices. |
| VOUT1 (19) | Buck-boost output | Delivers regulated output; requires low-ESR ceramic capacitor (e.g., 47μF) placed adjacent to pin with short ground return. |
| SW1B (20) | Buck-boost switch node B | One terminal of buck-boost inductor; works with SW1A to implement four-switch topology for seamless mode transitions. |
| PGND1 (21) | Buck-boost power ground | Return for buck-boost NMOS devices; shares exposed pad with PGND2 but must be routed separately to avoid coupling. |
| SW1A (22) | Buck-boost switch node A | Second buck-boost switch node; complements SW1B to enable bidirectional energy transfer in boost/buck-boost modes. |
| PVIN1 (23), PVIN3 (24) | Buck-boost high-current inputs | Parallel paths for buck-boost input current; each requires ≥22μF ceramic bypass and direct connection to SVIN/PVIN2. |
| Exposed Pad (25) | Thermal & electrical ground | Mandatory GND connection; soldering ensures thermal dissipation (TJMAX = 125°C) and low-noise reference for analog blocks. |
Key Features
| Feature | Design Value |
|---|---|
| Dual synchronous converters in one QFN | Eliminates discrete buck + buck-boost solutions, reducing board area by >40% and component count by ≥12 (inductors, MOSFETs, passives). |
| Pin-selectable Burst Mode® per converter | Enables independent optimization: buck in Burst for ultra-low IQ, buck-boost in PWM for low-noise RF supply - no firmware or external logic required. |
| Four-switch buck-boost with seamless mode transition | Prevents output glitches and inductor current discontinuity when VIN crosses VOUT, improving system reliability in battery-voltage-tracking applications. |
| Uncommitted gain block (AIN/AOUT) | Replaces external comparator or op-amp for battery-good detection or low-noise LDO - saves 2–3 passives and simplifies BOM. |
| Integrated thermal and overcurrent protection | Automatic shutdown at 125°C junction temperature and cycle-by-cycle current limiting prevent damage during overload or poor heatsinking. |
| 100% duty-cycle buck operation | Maintains regulation down to VIN = VOUT + ILOAD·RDS(ON), extending usable battery range in portable devices. |
Applications
| Portable Media Players | Digital Cameras |
|---|---|
Use Scenario: Powering DSP, display backlight, and image sensor from single Li-ion cell with varying voltage (4.2V → 3.0V). IC Role / Device Role / Timing Role: LTC3520EUF#PBF generates stable 3.3V (buck-boost) for logic and 1.8V (buck) for sensor core, while its gain block monitors battery voltage for low-battery warning. Use Value: Seamless buck-boost mode transition avoids brownouts during battery discharge; 55μA Burst Mode quiescent current extends playback time by >15% versus discrete solutions. |
Use Scenario: Supplying CMOS image sensor (1.2V), ISP (1.8V), and flash LED driver (3.3V) from compact 3.7V battery pack. IC Role / Device Role / Timing Role: LTC3520EUF#PBF delivers regulated rails with independent shutdown control (SD1/SD2) to sequence sensor power-up and disable unused subsystems during standby. Use Value: Dual-converter integration reduces PCB footprint by 28mm²; programmable 1MHz switching frequency minimizes EMI coupling into analog image path. |
| Handheld PCs / PDAs | GPS Receivers |
Use Scenario: Supporting ARM processor core (1.2V), memory interface (3.3V), and RF front-end (2.8V) in space-constrained handheld device. IC Role / Device Role / Timing Role: LTC3520EUF#PBF's buck-boost outputs 2.8V for RF section while buck supplies 1.2V core; RT pin allows frequency tuning to avoid GSM band interference. Use Value: 0.75mm QFN package enables placement under processor; <1μA shutdown current preserves RTC/sleep state during extended off periods. |
Use Scenario: Providing clean 3.3V for GPS baseband IC and 1.8V for RF LNA from coin-cell or Li-ion source in asset tracker. IC Role / Device Role / Timing Role: LTC3520EUF#PBF uses Burst Mode on both converters during GPS cold-start idle phases, while gain block triggers wake-up on battery voltage drop below 3.2V. Use Value: 55μA combined quiescent current enables >3-year battery life in periodic-reporting trackers; integrated protection eliminates need for external OVP/OCP components. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS63020DSJR | Single-inductor buck-boost only (no separate buck channel); 96% peak efficiency vs. LTC3520EUF#PBF's 95%; 2.5V–5.5V input; 1.2A output. | Lacks independent buck rail and uncommitted gain block - cannot replicate three-rail (3.3V/1.8V/LDO) capability or battery monitoring without added components. | Select when only one regulated output is needed and board space is more constrained than feature count. |
| MAX17504ATP+T | Two independent buck controllers (no integrated FETs); requires external MOSFETs, inductors, and compensation; 4.5V–36V input; 2A/channel. | Supports higher input voltage and current but adds ≥10 passive components per channel; no integrated gain block or Burst Mode optimization. | Select for industrial/high-voltage applications where LTC3520EUF#PBF's 5.5V max input is insufficient. |
Compared with TPS63020DSJR and MAX17504ATP+T, the LTC3520EUF#PBF uniquely integrates dual synchronous converters plus an analog gain block in one QFN - enabling three regulated outputs (buck-boost, buck, LDO) with minimal external components, making it optimal for space- and battery-life-constrained portable electronics.
Availability
LTC3520EUF#PBF is available at Aetrix Electronics and suitable for portable media players, digital cameras, and GPS receivers requiring stable component supply with guaranteed long-term availability and full temperature-grade support (–40°C to 85°C).
Supply support for LTC3520EUF#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 precision analog and power management portfolio with rigorous qualification and longevity commitment.
The LTC3520EUF#PBF belongs to Linear's high-efficiency dual-converter family designed specifically for battery-powered portable electronics needing multiple regulated rails, ultra-low quiescent current, and seamless voltage-mode operation across input voltage variations.
FAQ
What is the operating temperature range for the LTC3520EUF#PBF?
The LTC3520EUF#PBF is specified for operation from –40°C to +85°C ambient temperature. Its internal overtemperature protection activates at 125°C junction temperature, and the device is qualified to maintain performance across this full range with guaranteed specifications including feedback voltage accuracy, current limit, and switching frequency stability.
Can the LTC3520EUF#PBF generate three independent output voltages?
Yes - the LTC3520EUF#PBF can generate three regulated outputs: (1) buck-boost output (2.2V–5.25V), (2) buck output (0.8V–VIN), and (3) a third voltage via its uncommitted gain block configured with an external PNP transistor as an LDO. This configuration enables low-noise, adjustable auxiliary rails without additional ICs.
How does Burst Mode® operation affect output voltage ripple on the LTC3520EUF#PBF?
Burst Mode® operation on the LTC3520EUF#PBF increases output voltage ripple compared to PWM mode due to intermittent switching. Ripple magnitude depends on RBURST value, input/output voltage, inductor size, and output capacitance. Increasing RBURST or output capacitance reduces ripple, but may delay Burst Mode entry; typical ripple is 20–50mVPP under light load.
What is the purpose of the exposed pad (Pin 25) on the LTC3520EUF#PBF?
The exposed pad (Pin 25) on the LTC3520EUF#PBF is electrically and thermally connected to GND. It must be soldered to a PCB copper pour tied to system ground to ensure proper thermal dissipation (θJA = 37°C/W) and low-impedance reference for analog circuits. Failure to solder it degrades thermal performance and may cause instability or premature thermal shutdown.
Does the LTC3520EUF#PBF support 100% duty-cycle operation on the buck converter?
Yes - the LTC3520EUF#PBF buck converter supports true 100% duty-cycle operation, allowing VOUT2 to track VIN minus resistive losses (RDS(ON) × ILOAD) when input voltage drops near or below the regulated output. This extends usable battery life in portable applications by maintaining regulation down to ~2.5V input for a 2.8V output.
LTC3520EUF#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-WFQFN 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:
- 2
- Voltage - Input (Min):
- 2.2V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 5.5V
- Current - Output:
- 600mA, 1A
- Frequency - Switching:
- 100kHz ~ 2MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-QFN (4x4)
LTC3520EUF#PBF FAQ
1.How can I place an order for LTC3520EUF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3520EUF#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 LTC3520EUF#PBF reliable?
The price and inventory of LTC3520EUF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3520EUF#PBF is usually 5 days.
3.What payment methods are accepted for LTC3520EUF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3520EUF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3520EUF#PBF?
LTC3520EUF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3520EUF#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 LTC3520EUF#PBF?
For technical support, including LTC3520EUF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3520EUF#PBF requirements.
6.How does Aetrix verify that LTC3520EUF#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3520EUF#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 LTC3520EUF#PBF meets industry standards.
7.What is the process for return or replacement of LTC3520EUF#PBF?
All LTC3520EUF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3520EUF#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 LTC3520EUF#PBF part is unused and in its original packaging.
Return procedure for LTC3520EUF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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