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Analog Devices Inc. LTC3850IUF#PBF
- Part No.:
- LTC3850IUF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LTC3850IUF#PBF.pdf
- Description:
- IC REG CTRLR BUCK 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,550
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Product details
Overview
LTC3850IUF#PBF from Analog Devices is a dual, 2-phase synchronous step-down switching controller driving all-N-channel MOSFET stages. It delivers up to 95% efficiency, supports 4V–24V input (30V absolute max), and operates at phase-lockable frequencies from 250kHz to 780kHz with 180° interleaving. Used in high-density DC/DC power supplies for portable computing and battery-powered instrumentation.
For engineers reviewing the LTC3850IUF#PBF datasheet, LTC3850IUF#PBF pinout, LTC3850IUF#PBF application, or LTC3850IUF#PBF equivalent, key selection considerations include dual-channel current-mode control, OPTI-LOOP® compensation, independent soft-start/tracking, RSENSE/DCR sensing flexibility, and automotive-grade –40°C to 85°C operation.
Technical Context
The LTC3850IUF#PBF implements constant-frequency current-mode control with two independent 180° out-of-phase channels, each featuring a transconductance error amplifier (gm = 2.2 mmho), precision 0.8V reference (±1%), and programmable current-sense threshold (20–90 mV via ILIM pin). Its OPTI-LOOP® architecture adapts loop response to output capacitance and ESR variations.
Phase synchronization is achieved via MODE/PLLIN (external clock input or mode selection) and FREQ/PLLFLTR (PLL filter or frequency programming node). The IC integrates dual N-channel gate drivers with 2.6Ω TG pull-up, 1.5Ω TG pull-down, 2.4Ω BG pull-up, and 1.1Ω BG pull-down on-resistances, supporting fast switching with 25ns rise/fall times and 30ns dead-time control.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 24V nominal; 30V absolute maximum - supports wide battery chemistries and intermediate bus rails. |
| Output Voltage Accuracy | ±1% at 0.8V feedback reference - ensures tight regulation across load/temperature for multi-rail systems. |
| Switching Frequency Range | 250kHz to 780kHz, phase-lockable - enables EMI reduction via synchronization and trade-off between efficiency and magnetics size. |
| Efficiency | Up to 95% - achieved via low-RDS(on) gate drive, minimized conduction losses, and interleaved input current ripple. |
| Current Sensing | RSENSE or DCR options with selectable 20/50/75mV thresholds - accommodates high-current or low-loss sensing designs. |
| Operating Temperature | –40°C to +85°C - qualified for industrial and automotive applications per AEC-Q100. |
| Package | 28-pin 4mm × 4mm QFN with exposed pad - provides low θJA = 37°C/W for thermally demanding power stages. |
Pinout & Package
Package: 28-lead (4mm × 4mm) plastic QFN (UF), exposed pad (Pin 29) soldered to PCB as signal ground (SGND).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN1, RUN2 (Pins 1, 26) | Channel enable/disable control | Independent 1.22V threshold with 0.5µA internal pull-up; allows staggered startup or fault isolation per channel. |
| TK/SS1, TK/SS2 (Pins 4, 10) | Soft-start and tracking input | 1.3µA internal charge current ramps external capacitor; enables voltage ramping or master-slave output tracking. |
| SENSE1+/–, SENSE2+/– (Pins 2,3,12,11) | Differential current sense inputs | Accepts RSENSE or DCR networks; bias current ±1µA minimizes sensing error at light loads. |
| VFB1, VFB2 (Pins 6, 8) | Feedback voltage input | Connects to resistor divider; regulates output to precise 0.8V reference with ±1% accuracy over temperature. |
| MODE/PLLIN (Pin 27) | Mode selection & external sync input | Selects Burst Mode®, pulse-skipping, or forced CCM; accepts external clock up to 780kHz for EMI control. |
| PGOOD (Pin 15) | Open-drain power-good indicator | Asserts low when either output deviates >±7.5% from setpoint after 17µs debounce - enables system sequencing. |
| TG1/BG1, TG2/BG2 (Pins 25,23,17,20) | N-channel gate drivers | Drives top/bottom MOSFET gates with matched timing; includes anti-shoot-through logic and 30ns dead-time control. |
| BOOST1, BOOST2 (Pins 24, 18) | Floating bootstrap supply nodes | Connect to bootstrap capacitors; swing from ~INTVCC–0.7V to VIN+INTVCC - sustains top-FET drive in high-duty-cycle operation. |
Key Features
| Feature | Design Value |
|---|---|
| Dual 180° interleaved controllers | Reduces input RMS current by ~30% and cuts required input capacitance vs single-phase design. |
| OPTI-LOOP® compensation | Enables stable loop response across wide range of ceramic or polymer output capacitors without redesign. |
| Pre-biased output startup | Allows safe turn-on into pre-charged rail - prevents reverse current flow and protects downstream circuitry. |
| Current foldback limiting | Reduces MOSFET thermal stress during short-circuit by scaling peak current threshold based on ILIM pin state. |
| AEC-Q100 qualification | Validated for automotive environments including extended temperature cycling, HTOL, and ESD robustness. |
Applications
| Notebook Power Management | Portable Instrumentation |
|---|---|
Use Scenario: Dual-rail CPU core (1.8V) and I/O (3.3V) supply in space-constrained ultrabook designs. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing independent output voltages with interleaved switching. Use Value: 95% peak efficiency and reduced input ripple allow smaller input caps and lower thermal footprint than discrete solutions. | Use Scenario: Battery-powered handheld oscilloscope requiring clean, regulated analog (±5V) and digital (3.3V) rails. IC Role / Device Role / Timing Role: High-PSRR, low-noise dual controller delivering tightly regulated outputs with Burst Mode® for standby efficiency. Use Value: ±1% output accuracy and pre-biased startup ensure signal integrity during hot-swap battery replacement. |
| DC Power Distribution Systems | Automotive Infotainment |
Use Scenario: 12V-to-5V/3.3V conversion in industrial PoE-powered edge node with strict thermal limits. IC Role / Device Role / Timing Role: Interleaved controller minimizing input current harmonics and enabling compact 4mm × 4mm layout. Use Value: 37°C/W thermal resistance and exposed-pad grounding support continuous 5A/channel operation without heatsink. | Use Scenario: Head unit power supply meeting AEC-Q100 requirements with cold-crank (4.5V) and load-dump (34V transient) resilience. IC Role / Device Role / Timing Role: Automotive-grade dual controller with 30V absolute input rating and integrated UVLO hysteresis. Use Value: Guaranteed –40°C to +85°C operation and validated reliability data reduce qualification time for Tier-1 suppliers. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-phase synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3850IUFD#PBF | Same silicon, 4mm × 5mm QFN package with θJA = 34°C/W - slightly better thermal performance. | Preferred where board area permits larger footprint and lower junction temperature is critical. | Select when thermal margin is constrained and 4mm × 5mm layout is acceptable. |
| MP2918GL-Z | Monolithic dual controller (integrated MOSFETs), 2.5–18V input, fixed 500kHz, no PLL sync - lower BOM count but limited voltage range. | Suitable for cost-sensitive, medium-power (<3A/channel) consumer applications without automotive qualification. | Choose for simplified layout and lower component count where 30V abs-max and AEC-Q100 are not required. |
Compared with LTC3850IUF#PBF, LTC3850IUFD#PBF offers improved thermal dissipation in a marginally larger footprint, while MP2918GL-Z trades external MOSFET flexibility and automotive compliance for integration and lower system cost in non-automotive use cases.
Availability
LTC3850IUF#PBF is available at Aetrix Electronics and suitable for notebook power management, portable instrumentation, and automotive infotainment systems requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant sourcing.
Supply support for LTC3850IUF#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 is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LTC3850 product line delivers high-efficiency, dual-phase synchronous buck controllers optimized for space-constrained, thermally demanding DC/DC applications requiring precision regulation, flexible sequencing, and automotive reliability.
FAQ
What is the absolute maximum input voltage rating for the LTC3850IUF#PBF?
The LTC3850IUF#PBF has an absolute maximum input voltage (VIN) rating of 30V, with a transient rating of 34V for <500ms when INTVCC ≥ 5V. This exceeds the standard 28V limit of the commercial-grade LTC3850EUF#PBF, making it suitable for automotive cold-crank and load-dump conditions. Always observe derating guidelines and ensure proper input filtering per the datasheet.
How does the ILIM pin affect current limit behavior in the LTC3850IUF#PBF?
The ILIM pin on the LTC3850IUF#PBF sets the maximum current sense threshold to 20mV (ILIM = GND), 50mV (ILIM = FLOAT), or 75mV (ILIM = INTVCC). This directly scales the peak inductor current trip point per channel, enabling design flexibility for different MOSFET RDS(on) values or sensing resistors. Foldback behavior is preserved across all three settings.
Can the LTC3850IUF#PBF operate with pre-biased outputs during startup?
Yes, the LTC3850IUF#PBF supports pre-biased output startup. When enabled, the controller prevents reverse current flow by holding both top and bottom MOSFETs off until the feedback voltage rises above the programmed soft-start ramp. This avoids damaging downstream circuitry and ensures controlled turn-on into existing rail voltages - critical for hot-swap and redundant power systems.
What is the purpose of the exposed pad (Pin 29) on the LTC3850IUF#PBF QFN package?
The exposed pad (Pin 29) on the LTC3850IUF#PBF is electrically connected to SGND and must be soldered to the PCB ground plane. It serves as the primary thermal path (θJC = 2.6°C/W) and low-impedance signal reference for internal control circuitry. Proper soldering and thermal via placement are essential to achieve the specified 37°C/W junction-to-ambient thermal resistance and maintain stability under full-load operation.
Does the LTC3850IUF#PBF support external clock synchronization, and how is it implemented?
Yes, the LTC3850IUF#PBF supports external clock synchronization via the MODE/PLLIN pin. Applying a clean square wave (250kHz–780kHz) to this pin forces both channels into continuous conduction mode and locks their internal oscillator to the external source. This eliminates beat frequencies and reduces EMI in systems with multiple synchronized converters - a key advantage over non-PLL controllers like the MP2918GL-Z.
LTC3850IUF#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 2
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 4V ~ 30V
- Frequency - Switching:
- 250kHz ~ 780kHz
- Duty Cycle (Max):
- 97.2%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Frequency Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x4)
LTC3850IUF#PBF FAQ
1.How can I place an order for LTC3850IUF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3850IUF#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 LTC3850IUF#PBF reliable?
The price and inventory of LTC3850IUF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3850IUF#PBF is usually 5 days.
3.What payment methods are accepted for LTC3850IUF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3850IUF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3850IUF#PBF?
LTC3850IUF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3850IUF#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 LTC3850IUF#PBF?
For technical support, including LTC3850IUF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3850IUF#PBF requirements.
6.How does Aetrix verify that LTC3850IUF#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3850IUF#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 LTC3850IUF#PBF meets industry standards.
7.What is the process for return or replacement of LTC3850IUF#PBF?
All LTC3850IUF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3850IUF#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 LTC3850IUF#PBF part is unused and in its original packaging.
Return procedure for LTC3850IUF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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