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Analog Devices Inc. LTC3858IUFD-1#PBF
- Part No.:
- LTC3858IUFD-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LTC3858IUFD-1#PBF.pdf
- Description:
- IC REG CTRLR BUCK 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,098
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Product details
Overview
LTC3858IUFD-1#PBF from Analog Devices (formerly Linear Technology) is a dual-phase, synchronous step-down DC/DC controller IC driving two independent N-channel MOSFET stages. It delivers 3.3V/5A and 8.5V/3.5A outputs from a 4V–38V input, features 170μA no-load quiescent current, 0.8V reference accuracy, and out-of-phase operation to reduce input ripple. It is used in battery-powered digital systems requiring high-efficiency dual-rail power conversion.
For engineers reviewing the LTC3858IUFD-1#PBF datasheet, LTC3858IUFD-1#PBF pinout, LTC3858IUFD-1#PBF application, or LTC3858IUFD-1#PBF equivalent, key selection considerations include its dual-channel phase control, RSENSE/DCR current sensing flexibility, OPTI-LOOP® compensation, programmable 50kHz–900kHz switching frequency, and latchoff protection during short-circuit conditions.
Technical Context
The LTC3858IUFD-1#PBF implements a constant-frequency current-mode architecture with two independent 180° out-of-phase controllers, minimizing input capacitor ESR losses and supply-induced noise. Each channel uses an error amplifier (EA) comparing VFB to a precision 0.800V reference, with ITH voltage modulating peak inductor current via differential current sense inputs (SENSE±).
It supports three light-load operating modes-Burst Mode®, pulse-skipping, and forced continuous-selected via the PLLIN/MODE pin. Internal LDOs power gate drivers from VIN or EXTVCC (≥4.7V), and the device integrates dedicated soft-start (SS1/SS2), power-good (PGOOD1), overvoltage protection, and short-circuit latchoff with arming/latch thresholds at 2.0V/1.5V on SS pins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports wide intermediate bus and battery chemistries including 12V, 24V, and 36V systems. |
| Quiescent Current (One Channel On) | 170μA - extends runtime in battery-operated devices without compromising regulation. |
| Feedback Reference Voltage | 0.800V ±12mV (–40°C to 125°C) - enables precise output voltage setting with minimal drift across temperature. |
| Switching Frequency Range | 50kHz to 900kHz (programmable) - allows optimization of size, efficiency, and EMI for diverse PCB layouts. |
| Output Phase Relationship | 180° out-of-phase - cuts required input capacitance by ~50% and reduces RMS input ripple current. |
| Current Sense Interface | RSENSE or DCR - supports low-loss inductor-based sensing or high-accuracy shunt-based current monitoring. |
| Shutdown Current | 8μA - ensures ultra-low standby power when both RUN pins are pulled below 0.7V. |
Pinout & Package
Package: 28-lead (4mm × 5mm) plastic QFN with exposed pad (Pin 29 = SGND). Thermal resistance θJA = 43°C/W. Exposed pad must be soldered to PCB for rated thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SENSE1+, SENSE2+ | Differential current sense (+) input | Connects to DCR network or RSENSE top node; sets current limit threshold with SENSE– and ITH voltage. |
| SENSE1–, SENSE2– | Differential current sense (–) input | Reference point for current comparator; supplies bias current above INTVCC – 0.5V. |
| FREQ | VCO frequency programming | Resistor-to-GND sets 50kHz–900kHz; GND = 350kHz, INTVCC = 535kHz. |
| PLLIN/MODE | Sync input / light-load mode select | GND = Burst Mode®, INTVCC = forced continuous, 1.2V–(INTVCC–1.3V) = pulse-skipping. |
| RUN1, RUN2 | Channel enable/disable control | <1.26V disables respective channel; <0.7V shuts down entire IC with 8μA IQ. |
| SS1, SS2 | Soft-start and latchoff timer | Internal 1μA pull-up ramps voltage; >2.0V arms latchoff; falling below 1.5V triggers shutdown. |
| VFB1, VFB2 | Feedback input | Compares output divider voltage to 0.800V reference; PGOOD1 asserts when within ±10%. |
| TG1, TG2 / BG1, BG2 | Top/bottom gate drivers | TG swing = INTVCC–0.5V referenced to SW; BG swing = 0V to INTVCC; 1.1–2.5Ω on-resistance. |
| BOOST1, BOOST2 | Bootstrap supply | Provides floating bias for TG drivers; swing = INTVCC to (VIN + INTVCC); requires external diode + capacitor. |
| SW1, SW2 | Switch node | Connects to inductor center tap; handles full switching waveform and dV/dt stress. |
| PGOOD1 | Power-good indicator | Open-drain output active low when VFB1 deviates >±10% from regulation; 25μs fault delay. |
| ITH1, ITH2 | Error amplifier output | Controls peak current limit; voltage range 0.425V–1.2V defines current trip point per channel. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Enables stable loop response across wide COUT/ESR variations without manual compensation redesign. |
| Out-of-Phase Dual Control | Reduces input RMS ripple current by up to 30%, allowing smaller bulk capacitors and lower EMI. |
| Adjustable Light-Load Operation | Selectable Burst Mode®, pulse-skipping, or forced continuous via single PLLIN/MODE pin. |
| Short-Circuit Latchoff Protection | Independent per-channel latchoff triggered after programmable timeout using SS pin capacitor. |
| Low-Dropout Capability | 99.4% max duty cycle enables operation with VIN as low as VOUT + 0.2V under light loads. |
| EXTVCC Power Option | Accepts external 4.7V–14V supply to bypass VIN LDO, improving system efficiency when powering from regulated rail. |
Applications
| Automotive Infotainment Power | Industrial PLC Dual-Rail Supply |
|---|---|
Use Scenario: Powering SoC, DDR memory, and display interface in automotive head units with 12V battery input. IC Role / Device Role / Timing Role: Dual-phase controller generating isolated 3.3V (SoC core) and 8.5V (display backlight) rails with tight cross-regulation. Use Value: Out-of-phase operation minimizes input ripple on shared 12V bus, reducing need for large bulk capacitors and easing EMC compliance. |
Use Scenario: Providing 3.3V logic and 8.5V analog sensor excitation in modular industrial PLC backplanes. IC Role / Device Role / Timing Role: Dual independent controllers with separate RUN/SS pins enabling staggered startup and fault isolation between subsystems. Use Value: Short-circuit latchoff per channel prevents cascading failure; 170μA IQ extends uptime in battery-backed control modules. |
| Battery-Powered Test Equipment | Distributed Telecom DC System |
Use Scenario: Portable oscilloscope or spectrum analyzer requiring clean, low-noise dual-rail power from Li-ion pack (8.4V–12.6V). IC Role / Device Role / Timing Role: High-efficiency dual buck controller with Burst Mode® operation to sustain >10-hour runtime at microamp idle currents. Use Value: 8μA shutdown IQ and 170μA light-load IQ directly extend battery life without sacrificing transient response. |
Use Scenario: Intermediate bus converter in 48V telecom shelf supplying local 3.3V/8.5V rails to multiple line cards. IC Role / Device Role / Timing Role: Dual-phase controller accepting wide 4V–38V input, supporting hot-swap and brownout resilience in distributed power architecture. Use Value: Wide VIN range and 38V absolute max rating tolerate transients; phase-lockable frequency enables synchronization with shelf-level clock. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-phase synchronous step-down controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3858EUFD-1#PBF | Same silicon, –40°C to 85°C temp grade (vs. –40°C to 125°C for LTC3858IUFD-1#PBF) | Suitable for commercial/industrial ambient environments without extended junction temperature requirements | Select when full automotive-grade thermal margin is not required and cost sensitivity favors E-grade. |
| MP2918GL-Z | Single-chip dual-phase controller with integrated MOSFET drivers but no EXTVCC option or latchoff protection | Lacks independent short-circuit latchoff per channel and programmable light-load modes beyond basic PSM | Choose for space-constrained designs where integration outweighs need for robust fault management and flexible efficiency tuning. |
Compared with LTC3858EUFD-1#PBF, the LTC3858IUFD-1#PBF offers guaranteed operation to 125°C junction temperature and tighter parametric specs over full range; versus MP2918GL-Z, it provides superior fault handling, wider frequency programming, and EXTVCC support for higher overall system efficiency.
Availability
LTC3858IUFD-1#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial PLC power supplies, and battery-powered test equipment requiring stable component supply with guaranteed long-term availability and traceable sourcing.
Supply support for LTC3858IUFD-1#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 full product support, documentation, and manufacturing continuity for all Linear power management ICs.
The LTC3858-1 belongs to Linear's high-performance dual-phase controller family, designed specifically for efficient, low-quiescent-current dual-rail DC/DC conversion in battery-powered and thermally constrained systems.
FAQ
What is the maximum junction temperature specification for the LTC3858IUFD-1#PBF?
The LTC3858IUFD-1#PBF is rated for operation from –40°C to 125°C junction temperature. Its 28-lead QFN package has θJA = 43°C/W, so maximum ambient temperature depends on power dissipation and PCB layout. The exposed pad (Pin 29) must be soldered to SGND for thermal performance compliance. Derating curves in the official datasheet confirm full parameter guarantees across this range.
Does the LTC3858IUFD-1#PBF support synchronization to an external clock source?
Yes, the LTC3858IUFD-1#PBF supports external synchronization via the PLLIN/MODE pin. When an external clock signal is applied, the internal phase-locked loop aligns the rising edge of TG1 with the external clock's rising edge. This enables noise-sensitive systems to avoid beat frequencies and simplifies EMI filtering by locking switching noise to a known frequency.
How does the short-circuit latchoff function work on the LTC3858IUFD-1#PBF?
The LTC3858IUFD-1#PBF implements independent latchoff per channel using the SS1/SS2 pins. Once the SS voltage exceeds 2.0V (arming threshold), a 9μA discharge current pulls SS down if VFB falls below 70% of regulation. If SS drops below 1.5V, the channel latches off until VIN or RUN is recycled. This protects MOSFETs and magnetics during sustained overloads without relying on current foldback alone.
Can the LTC3858IUFD-1#PBF operate with only one output enabled?
Yes, the LTC3858IUFD-1#PBF supports independent channel control. Pulling RUN1 low disables Channel 1 while Channel 2 remains fully operational, and vice versa. Quiescent current drops to 170μA (one channel active) or 8μA (both RUN pins <0.7V). Both channels retain full functionality-including soft-start, PGOOD, and current limiting-when individually enabled.
What is the purpose of the EXTVCC pin on the LTC3858IUFD-1#PBF?
The EXTVCC pin on the LTC3858IUFD-1#PBF accepts an external 4.7V–14V supply to power the internal INTVCC LDO, bypassing the VIN-based regulator. This improves overall system efficiency when powering INTVCC from a clean, pre-regulated rail (e.g., one of the LTC3858IUFD-1#PBF's own outputs), reducing heat generation and input current draw from the main supply.
LTC3858IUFD-1#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 ~ 38V
- Frequency - Switching:
- 105kHz ~ 835kHz, 350kHz ~ 535kHz
- Duty Cycle (Max):
- 99.4%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Enable, Frequency Control, Power Good, Soft Start
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LTC3858IUFD-1#PBF FAQ
1.How can I place an order for LTC3858IUFD-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3858IUFD-1#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 LTC3858IUFD-1#PBF reliable?
The price and inventory of LTC3858IUFD-1#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3858IUFD-1#PBF is usually 5 days.
3.What payment methods are accepted for LTC3858IUFD-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3858IUFD-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3858IUFD-1#PBF?
LTC3858IUFD-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3858IUFD-1#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 LTC3858IUFD-1#PBF?
For technical support, including LTC3858IUFD-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3858IUFD-1#PBF requirements.
6.How does Aetrix verify that LTC3858IUFD-1#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3858IUFD-1#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 LTC3858IUFD-1#PBF meets industry standards.
7.What is the process for return or replacement of LTC3858IUFD-1#PBF?
All LTC3858IUFD-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3858IUFD-1#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 LTC3858IUFD-1#PBF part is unused and in its original packaging.
Return procedure for LTC3858IUFD-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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