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Analog Devices Inc. LTC3858IUH-2#PBF
- Part No.:
- LTC3858IUH-2#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3858IUH-2#PBF.pdf
- Description:
- IC REG CTRLR BUCK 32QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,015
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Product details
Overview
LTC3858IUH-2#PBF from Analog Devices (formerly Linear Technology) is a dual-phase, synchronous step-down DC/DC controller IC designed for high-efficiency intermediate bus conversion. It delivers two independent output rails (e.g., 8.5V/3.3V), supports 4V–38V input, achieves 99% duty cycle in dropout, and operates with 170μA quiescent current (one channel active) - enabling long battery life in portable industrial and automotive power systems.
For engineers reviewing the LTC3858IUH-2#PBF datasheet, LTC3858IUH-2#PBF pinout, LTC3858IUH-2#PBF application, or LTC3858IUH-2#PBF equivalent, key selection criteria include out-of-phase dual-channel operation to reduce input ripple, OPTI-LOOP® compensation for wide capacitor ESR tolerance, programmable 50kHz–900kHz switching frequency, and selectable light-load modes (Burst Mode®, pulse-skipping, forced continuous).
Technical Context
The LTC3858IUH-2#PBF implements a constant-frequency current-mode architecture with two independent 180° out-of-phase controllers, minimizing input capacitance requirements and supply-induced noise. Its dual error amplifiers drive ITH pins to regulate peak inductor current via RSENSE or DCR sensing, while the OPTI-LOOP® network adapts loop response across diverse output capacitor types and ESR values.
This variant disables overvoltage crowbar protection and short-circuit latchoff versus the base LTC3858, enabling cleaner fault recovery in distributed power systems. It features independent RUN/SS/PGOOD pins per channel, phase-lockable synchronization (75kHz–850kHz), and internal LDOs powered from VIN or EXTVCC (4.7V switchover threshold) to optimize gate drive efficiency.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4V to 38V - supports 12V/24V automotive batteries and 5V–36V intermediate bus architectures without external pre-regulation. |
| VOUT Range | 0.8V to 24V - enables generation of logic rails (1.2V, 1.8V, 3.3V), analog supplies (5V, 12V), and higher-voltage bias rails. |
| IQ (One Channel Active) | 170μA typical - extends runtime in always-on battery-powered devices such as telematics modules and portable test equipment. |
| Switching Frequency | Programmable 50kHz–900kHz (via FREQ pin resistor) or syncable 75kHz–850kHz (via PLLIN/MODE) - balances size, efficiency, and EMI in space-constrained designs. |
| Duty Cycle Max | 99% - sustains regulation during deep input voltage sag (e.g., cold-crank automotive transients down to ~4.5V at 12V nominal). |
| Current Sensing | RSENSE or DCR - eliminates sense resistor losses in high-current applications; supports accurate current limiting and phase balancing. |
| Package | 32-lead 5mm × 5mm QFN with exposed thermal pad (Pin 33 = SGND) - provides low θJA = 34°C/W for thermally demanding 5A+ per phase designs. |
Pinout & Package
32-lead (5mm × 5mm) plastic QFN package with exposed thermal pad (Pin 33 = SGND), rated for –40°C to +125°C junction temperature. Exposed pad must be soldered to PCB ground plane for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SENSE1– / SENSE2– (1, 9) | Differential current sense (–) input | Reference node for DCR/RSENSE current sensing; supplies current when > INTVCC – 0.5V to enable accurate zero-current detection. |
| FREQ (2) | Oscillator frequency control | Resistor-to-GND sets 50kHz–900kHz fixed frequency; tied to GND/INTVCC selects 350kHz/535kHz default. |
| PHASMD (3) | Phase relationship selector | Configures TG2/CLKOUT phase offset vs TG1: 180°/60° (GND), 240°/120° (INTVCC), or 180°/90° (floating). |
| CLKOUT (4) | Synchronization clock output | Drives daisy-chained controllers; swing = INTVCC to GND; enables PolyPhase™ multi-phase expansion. |
| PLLIN/MODE (5) | Sync input / light-load mode select | Accepts external clock (75kHz–850kHz); GND = Burst Mode®, INTVCC = forced continuous, 1.2V–(INTVCC–1.3V) = pulse-skipping. |
| SGND (6, 33) | Small-signal ground reference | Common analog ground for feedback, error amp, and sensing; must be isolated from PGND to avoid noise coupling. |
| RUN1 / RUN2 (7, 8) | Independent channel enable | <1.26V disables respective controller; both <0.7V enters 8μA shutdown - enables dynamic rail sequencing and power gating. |
| BOOST1 / BOOST2 (17, 24) | Top MOSFET bootstrap supply | Floats above SW nodes; powers floating gate drivers; requires external Schottky diode + ceramic cap per phase. |
| TG1 / TG2 (15, 26) | Top N-MOSFET gate driver output | Swings from SW node + (INTVCC – 0.5V); drives high-side FET gates in synchronous buck topology. |
| SW1 / SW2 (16, 25) | Switch node connection | Connects to inductor center taps; carries high di/dt switching currents - requires tight layout and Kelvin routing. |
| BG1 / BG2 (18, 23) | Bottom N-MOSFET gate driver output | Swings from GND to INTVCC; drives synchronous rectifier FETs with 1.1Ω pull-down resistance for fast turn-off. |
| PGND (21) | Power ground return | Return path for bottom FET sources and input capacitor negative terminals - must connect directly to CIN– and MOSFET source pads. |
| VIN (22) | Main input supply | Primary power input (4V–38V); powers internal VIN LDO for INTVCC when EXTVCC is inactive or <4.7V. |
| EXTVCC (20) | External INTVCC supply input | Enables bypass of VIN LDO when >4.7V; allows efficient sourcing of INTVCC from regulated output rails (e.g., 5V or 8.5V). |
| INTVCC (19) | Internal LDO output | 5.1V ±3% regulated supply for gate drivers and control circuitry; requires ≥4.7μF ceramic decoupling to PGND. |
| VFB1 / VFB2 (11, 31) | Output voltage feedback input | Compares resistive divider output to 0.800V reference; regulates VOUT with ±10% PGOOD window and 0.01% load regulation. |
| ITH1 / ITH2 (12, 30) | Error amplifier output / current limit control | Directly sets peak inductor current trip point; voltage range 0.425V–2V determines operating mode (sleep, burst, continuous). |
| SS1 / SS2 (13, 29) | Soft-start / tracking input | Internal 1μA pull-up charges external capacitor for linear ramp; also accepts resistor divider for supply tracking during startup. |
| PGOOD1 / PGOOD2 (14, 27) | Open-drain power-good indicator | Asserts low when VFB deviates >±10% from target; includes 2.5% hysteresis and 25μs fault reporting delay. |
| ILIM (28) | Current limit threshold select | Three-level sense voltage setting: GND = 22mV, FLOAT = 43mV, INTVCC = 64mV - enables scalable current limiting across load ranges. |
Key Features
| Feature | Design Value |
|---|---|
| Out-of-phase dual controllers | Reduces RMS input ripple current by up to 70%, cutting required input capacitance and easing EMI filter design. |
| OPTI-LOOP® compensation | Allows stable loop response across 10× variation in output capacitor ESR and 100× variation in capacitance - simplifies BOM consolidation. |
| Selectably optimized light-load efficiency | Burst Mode® (170μA IQ), pulse-skipping, or forced continuous operation - preserves efficiency across 1000:1 load range without compromising transient response. |
| Independent soft-start and tracking | Per-channel SS pins support staggered rail sequencing or precise voltage tracking (e.g., 3.3V following 5V) to prevent back-powering or latch-up. |
| No current foldback at startup | Prevents MOSFET thermal stress during output short-circuit conditions by maintaining full current limit until steady-state fault detection. |
| Robust thermal management | Exposed pad (Pin 33) tied to SGND provides low thermal resistance (θJA = 34°C/W) - sustains 5A+ per phase operation in compact layouts. |
Applications
| Automotive Infotainment Power Supply | Industrial PLC I/O Module |
|---|---|
Use Scenario: Dual-rail power for SoC (1.2V core), DDR memory (1.35V), and interface logic (3.3V) in head-unit ECUs under 12V battery input with cold-crank immunity. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing independent 1.2V/3.3V outputs with out-of-phase switching to suppress conducted EMI on shared 12V bus. Use Value: 99% duty cycle maintains regulation during 4.5V cold-crank events; 170μA IQ extends backup power hold-up time for safe system shutdown. |
Use Scenario: Distributed 24V-to-5V/3.3V conversion for sensor signal conditioning, isolation, and microcontroller supply in DIN-rail mounted PLCs. IC Role / Device Role / Timing Role: High-voltage input controller generating isolated auxiliary rails using transformer-coupled secondary side sensing and OPTI-LOOP® stability across temperature. Use Value: 4V–38V input range accommodates 24V industrial bus fluctuations; RSENSE/DCR flexibility supports cost-optimized inductor selection. |
| Battery-Powered Test Equipment | Telecom Remote Radio Unit (RRU) |
Use Scenario: Portable oscilloscope or multimeter requiring ultra-low standby power, clean analog rails (±5V, 3.3V), and fast wake-up from sleep mode. IC Role / Device Role / Timing Role: Dual-channel controller with independent RUN pin control enabling selective rail shutdown and rapid reactivation of measurement circuits. Use Value: 8μA shutdown current extends shelf life; Burst Mode® ensures <10mV output ripple at 100μA loads without audible coil whine. |
Use Scenario: Base station RRU converting -48V telecom supply to 12V PA bias and 3.3V digital control rails in outdoor enclosures with wide ambient temperature swings. IC Role / Device Role / Timing Role: High-reliability dual controller with –40°C to +125°C rating, EXTVCC capability (to derive INTVCC from 12V rail), and robust current limit programming via ILIM pin. Use Value: EXTVCC switchover improves overall system efficiency by 2–3% versus VIN-powered gate drive; 125°C junction rating ensures operation in sealed, unventilated housings. |
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 |
|---|---|---|---|
| MP8772GQ-Z (Monolithic Power Systems) | Integrated dual buck converter (MOSFETs onboard); 4.5V–18V input; fixed 500kHz fSW; no phase synchronization or EXTVCC. | Lower component count but limited input range and no polyphase expansion - suitable for space-constrained, lower-power (<3A) applications. | Choose MP8772GQ-Z when board area is critical and input voltage is stable ≤18V; avoid for automotive cold-crank or telecom -48V-derived supplies. |
| LTC3892IUH-2#PBF (Analog Devices) | Pin-compatible upgrade with wider 4.5V–60V input, integrated boost for gate drive, and improved current sense accuracy (±0.5% vs ±1.5%). | Supports higher-voltage industrial and telecom inputs; enhanced light-load efficiency and faster transient response due to improved error amp bandwidth. | Choose LTC3892IUH-2#PBF for new designs requiring >38V input or tighter current regulation; existing LTC3858IUH-2#PBF layouts require no changes. |
Compared with MP8772GQ-Z, LTC3858IUH-2#PBF offers broader input range and flexible synchronization but requires external MOSFETs; versus LTC3892IUH-2#PBF, it lacks 60V capability and precision current sensing but remains optimal for cost-sensitive 12V/24V systems where its 170μA IQ and proven reliability are decisive.
Availability
LTC3858IUH-2#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial PLC I/O modules, and battery-powered test equipment requiring stable component supply, extended temperature operation, and long-term lifecycle support.
Supply support for LTC3858IUH-2#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LTC3858 product line was engineered for high-efficiency, dual-output DC/DC conversion in harsh environments - emphasizing low quiescent current, wide input range, and robust fault handling for automotive and industrial power systems.
FAQ
What is the maximum input voltage rating for the LTC3858IUH-2#PBF?
The LTC3858IUH-2#PBF has an absolute maximum input supply voltage (VIN) of 40V, with a recommended operating range of 4V to 38V. This makes it suitable for 24V industrial buses and 12V automotive systems including cold-crank transients. Exceeding 40V risks permanent damage per Absolute Maximum Ratings.
Does the LTC3858IUH-2#PBF support synchronization to an external clock source?
Yes, the LTC3858IUH-2#PBF supports external clock synchronization via the PLLIN/MODE pin (Pin 5). When an external clock signal (75kHz–850kHz) is applied, the internal phase-locked loop aligns the rising edge of TG1 with the external clock's rising edge - enabling deterministic timing across multiple phases or ICs in dense power systems.
How does the LTC3858IUH-2#PBF achieve ultra-low quiescent current in battery applications?
The LTC3858IUH-2#PBF achieves 170μA quiescent current (one channel active) through integrated sleep-mode circuitry triggered when ITH drops below 0.425V. In this state, most internal blocks power down while maintaining regulation via output capacitance - extending runtime in always-on portable devices like handheld meters and telematics units.
Can the LTC3858IUH-2#PBF operate with only one output enabled?
Yes, the LTC3858IUH-2#PBF supports independent channel control: pulling RUN1 low disables Channel 1 while Channel 2 remains fully operational, and vice versa. Both RUN pins must be pulled below 0.7V to enter full 8μA shutdown - enabling dynamic rail management and power sequencing in multi-rail systems.
What is the purpose of the ILIM pin on the LTC3858IUH-2#PBF?
The ILIM pin (Pin 28) selects one of three maximum current sense thresholds - 22mV (ILIM = GND), 43mV (ILIM = FLOAT), or 64mV (ILIM = INTVCC) - for both current comparators. This allows designers to scale overcurrent protection across different MOSFET RDS(on) values or sense resistor sizes without changing feedback networks.
LTC3858IUH-2#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 32-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%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Frequency Control, Phase Control, Power Good, Soft Start
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-QFN (5x5)
LTC3858IUH-2#PBF FAQ
1.How can I place an order for LTC3858IUH-2#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3858IUH-2#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 LTC3858IUH-2#PBF reliable?
The price and inventory of LTC3858IUH-2#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3858IUH-2#PBF is usually 5 days.
3.What payment methods are accepted for LTC3858IUH-2#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3858IUH-2#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3858IUH-2#PBF?
LTC3858IUH-2#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3858IUH-2#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 LTC3858IUH-2#PBF?
For technical support, including LTC3858IUH-2#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3858IUH-2#PBF requirements.
6.How does Aetrix verify that LTC3858IUH-2#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3858IUH-2#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 LTC3858IUH-2#PBF meets industry standards.
7.What is the process for return or replacement of LTC3858IUH-2#PBF?
All LTC3858IUH-2#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3858IUH-2#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 LTC3858IUH-2#PBF part is unused and in its original packaging.
Return procedure for LTC3858IUH-2#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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