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Analog Devices Inc. LTC3850EUF#PBF
- Part No.:
- LTC3850EUF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LTC3850EUF#PBF.pdf
- Description:
- IC REG CTRLR BUCK 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:394
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Product details
Overview
LTC3850EUF#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, provides ±1% 0.8V reference accuracy, and operates at phase-lockable frequencies from 250kHz to 780kHz - enabling high-density DC/DC conversion in portable computing and battery-powered instrumentation.
For engineers reviewing the LTC3850EUF#PBF datasheet, LTC3850EUF#PBF pinout, LTC3850EUF#PBF application, or LTC3850EUF#PBF equivalent, key selection considerations include dual-phase current-mode control, RSENSE/DCR sensing flexibility, OPTI-LOOP® compensation for wide output capacitor/ESR tolerance, independent soft-start/tracking (TK/SS), and Burst Mode® operation for ultra-low quiescent current.
Technical Context
The LTC3850EUF#PBF implements constant-frequency current-mode control with two independent 180° out-of-phase channels, each featuring an error amplifier, transconductance gm = 2.2 mmho, and ITH-controlled peak current limiting. Its architecture includes integrated anti-shoot-through logic, slope compensation, and dropout detection to maintain bootstrap capacitor recharge during low-VIN operation.
It supports three light-load operating modes via MODE/PLLIN: Burst Mode® (1.3µA typical shutdown current), pulse-skipping, or forced continuous conduction - with mode selection directly affecting output ripple, audio noise, and efficiency below 10% load. The IC uses separate RUN1/RUN2 pins for per-channel enable/disable and TK/SS pins for independent voltage ramping or tracking.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 24V (28V absolute max); covers common Li-ion, Li-poly, and intermediate bus rails without external regulators. |
| Output Voltage Accuracy | ±1% at 0.8V feedback reference; ensures tight regulation across temperature and line/load variations. |
| Switching Frequency | 250kHz to 780kHz, adjustable via FREQ/PLLFLTR pin; enables optimization of size vs. efficiency trade-offs. |
| Current Sense Threshold | Configurable 20mV/40mV/60mV via ILIM pin; allows precise overcurrent protection scaling for RSENSE or DCR sensing. |
| Quiescent Current | 850µA typical in normal mode; drops to 30µA in shutdown - critical for battery runtime in always-on systems. |
| Gate Driver Strength | TG/BG pull-up/down resistances: 2.6Ω/1.5Ω (TG), 2.4Ω/1.1Ω (BG); supports fast switching of high-Qg MOSFETs up to 5A per channel. |
| Thermal Performance | θJA = 37°C/W (4mm × 4mm QFN); enables >5A/channel operation with minimal heatsinking in compact layouts. |
Pinout & Package
Package: 28-lead (4mm × 4mm) plastic QFN with exposed pad (Pin 29 = SGND/PGND), RoHS-compliant, –40°C to +85°C operating range.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN1, RUN2 | Per-channel enable inputs | Logic-high (>1.22V) enables channel; internal 0.5µA pull-up allows simple RC soft-start; <1.1V forces shutdown. |
| TK/SS1, TK/SS2 | Soft-start & tracking inputs | Internal 1.3µA current charges external capacitor; linear ramp from 0V to 0.8V controls VOUT rise time or enables supply tracking. |
| SENSE1+/–, SENSE2+/– | Differential current sense inputs | Accepts Kelvin-connected RSENSE or DCR network; ±1µA bias current minimizes measurement error. |
| VFB1, VFB2 | Feedback inputs | High-impedance (–50nA typical) nodes for remote sensing; referenced to precise 0.8V internal bandgap. |
| TG1, TG2 / BG1, BG2 | Top/bottom gate drivers | Drive N-MOSFET gates with 25ns transition times; integrated anti-shoot-through prevents cross-conduction. |
| BOOST1, BOOST2 | Floating bootstrap supplies | Connect to bootstrap capacitors; swing from ~INTVCC–0.7V to VIN+INTVCC, enabling high-side N-MOSFET drive. |
| MODE/PLLIN | Mode select & sync input | Ground = forced CCM; INTVCC = pulse-skip; floating = Burst Mode®; external clock = PLL synchronization. |
| PGOOD | Open-drain power-good indicator | Pulls low if either VOUT deviates >±7.5% from setpoint after 17µs debounce; supports system sequencing. |
Key Features
| Feature | Design Value |
|---|---|
| Dual 180° phased control | Reduces input RMS current by ~30%, cutting required bulk capacitance and lowering EMI on shared input rails. |
| OPTI-LOOP® compensation | Allows stable loop response across 10× variation in output capacitor ESR and capacitance - eliminates re-tuning for BOM changes. |
| Pre-biased output startup | Supports hot-swap and rail-stacking applications where output voltage is non-zero at power-on; avoids reverse current flow. |
| Independent current foldback | Each channel limits peak inductor current based on ILIM setting - protects MOSFETs during short-circuit without affecting other channel. |
| EXTVCC support | Enables bypassing internal 5V LDO by supplying INTVCC from a secondary converter output - improves overall system efficiency. |
Applications
| Notebook CPU Core Power | Portable Test Instrumentation |
|---|---|
Use Scenario: Dual-rail core voltage (e.g., 1.8V/1.2V) for Intel/AMD mobile processors with dynamic load steps up to 5A/µs. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller providing tightly regulated, low-noise, fast-transient power with phase interleaving. Use Value: 180° phasing cuts input ripple current by 50%, reducing bulk cap count and PCB area; Burst Mode® extends battery life during idle states. |
Use Scenario: Multi-rail power for handheld oscilloscopes or spectrum analyzers requiring isolated 3.3V, 2.5V, and 1.8V analog/digital supplies. IC Role / Device Role / Timing Role: Dual-channel controller generating independent, tracked outputs with programmable soft-start and power-good sequencing. Use Value: Independent TK/SS pins enable precise voltage ramp alignment; ±1% reference ensures ADC/DAC reference stability across temperature. |
| Battery-Powered Medical Sensors | Industrial DC Distribution Systems |
Use Scenario: Long-life wearable ECG or glucose monitors powered by single-cell Li-ion (3.0–4.2V) requiring ultra-low IQ and clean 1.8V/3.3V rails. IC Role / Device Role / Timing Role: High-efficiency dual buck controller operating in Burst Mode® to minimize standby power while maintaining fast wake-up response. Use Value: 30µA shutdown current and 1.3µA TK/SS charge current extend battery life beyond 1 year; pre-biased startup supports hot-plug battery replacement. |
Use Scenario: Distributed 12V-to-3.3V/2.5V conversion in factory automation controllers with strict EMC and thermal constraints. IC Role / Device Role / Timing Role: Dual-phase controller driving discrete MOSFETs for high-current, high-reliability local regulation near FPGA or SoC loads. Use Value: RSENSE/DCR sensing flexibility accommodates cost-optimized or precision current monitoring; 780kHz max frequency enables small magnetics. |
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 |
|---|---|---|---|
| LTC3850EUFD#PBF | Same die, 4mm × 5mm QFN package with θJA = 34°C/W (vs. 37°C/W for UF); identical pinout except exposed pad layout. | Preferred for higher-power designs (>6A/channel) requiring lower thermal resistance and larger PCB copper area for heat spreading. | Select when thermal margin is constrained and board space allows larger footprint; no schematic or layout change needed beyond pad expansion. |
| LTC3850IGN#PBF | Same functionality, but in narrow SSOP-28 package (θJA = 95°C/W); rated for –40°C to +85°C industrial temp range (same as E-grade). | Suitable for legacy SSOP-based designs or space-constrained boards where QFN reflow is not available. | Choose only when mechanical compatibility with existing SSOP footprints is mandatory; expect higher thermal rise at full load. |
Compared with LTC3850EUF#PBF, the EUFD variant offers better thermal performance in a slightly larger footprint, while the IGN version trades thermal efficiency for through-hole or reflow-compatible packaging - neither is pin-compatible with the UF package due to differing land patterns and exposed pad geometry.
Availability
LTC3850EUF#PBF is available at Aetrix Electronics and suitable for notebook computing, portable instrumentation, and battery-operated medical devices requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for LTC3850EUF#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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LTC3850EUF#PBF belongs to Analog Devices' Power by Linear™ controller family, designed specifically for high-efficiency, multi-phase DC/DC conversion in space- and power-constrained portable and embedded systems.
FAQ
What is the maximum input voltage rating for the LTC3850EUF#PBF?
The LTC3850EUF#PBF has an absolute maximum input voltage (VIN) rating of 28V. Its recommended operating range is 4V to 24V, covering standard Li-ion battery packs and intermediate bus voltages. Exceeding 28V risks permanent damage per Absolute Maximum Ratings. The LTC3850I variant supports up to 30V, but the E-grade LTC3850EUF#PBF must remain within 28V.
Does the LTC3850EUF#PBF support pre-biased output startup?
Yes, the LTC3850EUF#PBF supports pre-biased output startup. When the output voltage is non-zero at enable, the controller prevents reverse current flow by disabling bottom-FET turn-on until the inductor current reaches zero. This behavior is inherent to its current-mode architecture and is confirmed in the Applications Information section of the datasheet for LTC3850EUF#PBF.
How does the ILIM pin configure current limit thresholds on the LTC3850EUF#PBF?
The ILIM pin on the LTC3850EUF#PBF sets the maximum current sense threshold for both channels: tying ILIM to SGND selects 20mV, floating selects 40mV, and connecting to INTVCC selects 60mV. These values are specified in the Electrical Characteristics table and directly scale the overcurrent protection point for RSENSE or DCR sensing networks used with LTC3850EUF#PBF.
Can the LTC3850EUF#PBF synchronize to an external clock?
Yes, the LTC3850EUF#PBF can synchronize to an external clock via the MODE/PLLIN pin. When an external clock signal is applied to MODE/PLLIN, the internal oscillator locks to it using the integrated phase-locked loop (PLL). The FREQ/PLLFLTR pin serves as the PLL loop filter node, and synchronization is functional across the full 250kHz–780kHz range supported by LTC3850EUF#PBF.
What is the purpose of the exposed pad (Pin 29) on the LTC3850EUF#PBF QFN package?
The exposed pad (Pin 29) on the LTC3850EUF#PBF is electrically connected to SGND and must be soldered to a PCB thermal pad tied to PGND. It serves as the primary signal ground return path for internal circuitry and significantly reduces θJA to 37°C/W. Leaving it unconnected degrades thermal performance and may cause instability or premature failure of LTC3850EUF#PBF.
LTC3850EUF#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 ~ 24V
- 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)
LTC3850EUF#PBF FAQ
1.How can I place an order for LTC3850EUF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3850EUF#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 LTC3850EUF#PBF reliable?
The price and inventory of LTC3850EUF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3850EUF#PBF is usually 5 days.
3.What payment methods are accepted for LTC3850EUF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3850EUF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3850EUF#PBF?
LTC3850EUF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3850EUF#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 LTC3850EUF#PBF?
For technical support, including LTC3850EUF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3850EUF#PBF requirements.
6.How does Aetrix verify that LTC3850EUF#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3850EUF#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 LTC3850EUF#PBF meets industry standards.
7.What is the process for return or replacement of LTC3850EUF#PBF?
All LTC3850EUF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3850EUF#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 LTC3850EUF#PBF part is unused and in its original packaging.
Return procedure for LTC3850EUF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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