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Analog Devices Inc. LTC3857IUH#TRPBF
- Part No.:
- LTC3857IUH#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3857IUH#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 32QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,280
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Product details
Overview
LTC3857IUH#TRPBF from Analog Devices (formerly Linear Technology) is a dual-phase, synchronous step-down DC/DC controller IC driving two independent N-channel MOSFET stages for high-efficiency power conversion. It delivers 5A at 3.3V and 3.5A at 8.5V with 50μA quiescent current (one channel active), 4V–38V input range, and 0.8V–24V programmable output voltage - ideal for battery-powered digital systems requiring ultra-low standby power and tight voltage regulation.
For engineers reviewing the LTC3857IUH#TRPBF datasheet, LTC3857IUH#TRPBF pinout, LTC3857IUH#TRPBF application, or LTC3857IUH#TRPBF equivalent, key selection criteria include dual-channel out-of-phase operation to reduce input ripple, OPTI-LOOP® compensation minimizing output capacitance, selectable light-load modes (Burst Mode®, pulse-skipping, or forced CCM), and precise 0.8V ±1.5% feedback reference across –40°C to 125°C.
Technical Context
The LTC3857IUH#TRPBF implements a constant-frequency current-mode architecture with two independent controllers operating 180° out of phase, reducing input capacitor RMS current and system noise. Each channel features a transconductance error amplifier (gm = 2 mmho), programmable current limit via ILIM pin (22/43/64 mV thresholds), and precision 0.8V reference with ±0.1% load regulation over temperature.
It integrates dual gate drivers (TG/BG) with 2.5Ω pull-up / 1.5Ω pull-down on top-side and 2.4Ω/1.1Ω on bottom-side drivers, 95ns minimum on-time, and internal LDOs enabling INTVCC generation from VIN (4.85–5.35V) or EXTVCC (4.5–4.9V switchover). Phase-lockable frequency spans 75kHz–850kHz, with fixed-frequency programming from 50kHz–900kHz using FREQ pin resistor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports wide industrial bus voltages and multi-cell Li-ion, lead-acid, or automotive batteries. |
| Quiescent Current (Sleep Mode) | 50μA (one channel active) - extends runtime in always-on battery systems without compromising startup responsiveness. |
| Feedback Reference Voltage | 0.800V ±1.5% (–40°C to 125°C) - enables accurate output regulation across full automotive temperature range. |
| Output Voltage Range | 0.8V ≤ VOUT ≤ 24V - configurable for dual-rail supplies (e.g., 3.3V + 8.5V) using external resistive dividers on VFB1/VFB2. |
| Phase-Lockable Frequency | 75kHz to 850kHz - allows synchronization to external clock or noise-sensitive system timing domains. |
| Current Sense Threshold | Selectable 22/43/64 mV via ILIM pin - sets peak current limit without external resistor changes, simplifying design for varying MOSFET RDS(on). |
| Duty Cycle Max | 99.4% - supports ultra-low dropout operation down to VIN – VOUT ≈ 0.3V, critical for high-input, low-output applications. |
Pinout & Package
Package: 32-lead (5mm × 5mm) plastic QFN with exposed thermal pad (Pin 33 = SGND), rated for –40°C to 125°C junction temperature (θJA = 34°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SENSE1– / SENSE2– (Pins 1, 9) | Differential current sense (–) input | Supplies bias current when > INTVCC – 0.5V; enables DCR or RSENSE sensing with ±1μA input bias. |
| FREQ (Pin 2) | VCO frequency control | Resistor-to-GND sets 50–900kHz; GND = 350kHz, INTVCC = 535kHz - defines switching frequency without external clock. |
| PLLIN/MODE (Pin 5) | Sync input / light-load mode select | GND = Burst Mode®, INTVCC = forced CCM, 1.2–3.8V = pulse-skipping - determines efficiency vs. noise trade-off at light loads. |
| TG1/TG2 (Pins 26, 15) | Top N-MOS gate drive outputs | Floats with SW node; 2.5Ω pull-up / 1.5Ω pull-down drives high-side MOSFETs with 25ns rise/fall time (3300pF load). |
| PGOOD1/PGOOD2 (Pins 27, 14) | Open-drain power-good indicators | Assert low when VFB deviates >±10% from 0.8V - provides sequenced enable signals for downstream rails or system monitoring. |
| TRACK/SS1/SS2 (Pins 29, 13) | Soft-start and tracking control | Internal 1μA pull-up charges external capacitor; voltage ramp controls output slew rate or enables supply tracking during startup. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by optimizing loop stability with ceramic capacitors - reduces BOM cost and board area. |
| Out-of-Phase Dual Control | 180° phase shift between channels cuts input ripple current by ~70%, allowing smaller input bulk capacitors and lower EMI. |
| Low Dropout Operation | 99.4% max duty cycle enables regulation with VIN as low as VOUT + 0.3V - essential for high-voltage input, low-VOUT applications. |
| Programmable Light-Load Mode | Three selectable modes (Burst, pulse-skipping, forced CCM) let designers optimize efficiency, output ripple, and transient response per rail. |
| Independent Soft-Start/Tracking | Dedicated TRACK/SS pins per channel allow staggered startup or precise voltage sequencing - prevents back-powering or latch-up in multi-rail systems. |
Applications
| Automotive Infotainment Power Supply | Industrial IoT Sensor Hub |
|---|---|
Use Scenario: Dual-rail power for SoC (3.3V core) and display interface (8.5V backlight) in vehicle head units with cold-crank tolerance. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing independent voltage rails with phase interleaving and PGOOD sequencing. Use Value: 50μA sleep IQ maintains CAN wake capability; 4V–38V input handles 12V/24V systems and load-dump transients up to 40V. |
Use Scenario: Battery-backed wireless sensor node requiring long shelf life and fast wake-up from deep sleep. IC Role / Device Role / Timing Role: Primary power controller delivering regulated 3.3V and 8.5V from Li-SOCl₂ or Li-Po cells with ultra-low quiescent draw. Use Value: 50μA one-channel sleep current extends 10-year battery life; Burst Mode® maintains <15mV output ripple at μA loads. |
| Medical Portable Diagnostic Device | Telecom Remote Radio Unit (RRU) |
Use Scenario: Compact handheld ultrasound unit needing isolated, low-noise 3.3V logic and 8.5V analog front-end supplies. IC Role / Device Role / Timing Role: Dual-channel controller with OPTI-LOOP® and out-of-phase operation to suppress switching noise coupling into sensitive analog circuitry. Use Value: 0.8V ±1.5% reference ensures ADC/DAC accuracy; 75kHz–850kHz sync range avoids interference with RF or sampling clocks. |
Use Scenario: Outdoor small-cell base station powered from 48V PoE or solar/battery hybrid with strict thermal limits. IC Role / Device Role / Timing Role: High-efficiency dual-buck controller converting 48V intermediate bus to 3.3V FPGA core and 8.5V RF PA bias rails. Use Value: 99.4% duty cycle supports 48V→3.3V conversion without external pre-regulator; EXTVCC input enables self-bias from 8.5V rail for higher efficiency. |
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 |
|---|---|---|---|
| MP2918GL-Z | Fixed 600kHz frequency; no PLL sync; 3.3V–36V input; 45μA IQ (single channel); no EXTVCC option | Suitable for cost-sensitive, non-synchronized designs where phase interleaving and wide frequency tuning aren't required | Choose MP2918GL-Z when fixed frequency and simpler layout outweigh need for burst-mode optimization or external clock sync. |
| ISL81601FRZ-T7A | 60V max input; dual-phase with 0°/180°/270° phase options; 40μA IQ; integrated MOSFET drivers only (no external FET support) | Targeted at higher-input industrial systems requiring 60V rating and integrated driver simplicity, but lacks RSENSE/DCR flexibility | Choose ISL81601FRZ-T7A for 60V-rated designs where integrated drivers reduce component count, accepting loss of discrete FET control. |
Compared with MP2918GL-Z and ISL81601FRZ-T7A, the LTC3857IUH#TRPBF uniquely combines ultra-low 50μA sleep IQ, full 75kHz–850kHz PLL sync range, EXTVCC biasing, and independent TRACK/SS control - making it optimal for thermally constrained, battery-critical, or noise-sensitive dual-rail systems.
Availability
LTC3857IUH#TRPBF is available at Aetrix Electronics and suitable for automotive infotainment power supplies, industrial IoT sensor hubs, and medical portable diagnostic devices requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC3857IUH#TRPBF 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 aerospace, automotive, industrial, and communications markets.
The LTC3857IUH#TRPBF belongs to Linear's high-efficiency DC/DC controller product line, designed specifically for dual-output, low-IQ, wide-input industrial and automotive power systems demanding precision regulation, thermal resilience, and flexible light-load operation.
FAQ
What is the operating temperature range for the LTC3857IUH#TRPBF?
The LTC3857IUH#TRPBF is specified for –40°C to 125°C junction temperature and is qualified for automotive and industrial applications. Its electrical characteristics - including 0.800V feedback reference, 50μA sleep IQ, and 22/43/64 mV current sense thresholds - are guaranteed across this full range, with thermal resistance θJA = 34°C/W when the exposed pad (Pin 33) is properly soldered to PCB ground.
How does the LTC3857IUH#TRPBF achieve ultra-low quiescent current?
The LTC3857IUH#TRPBF achieves 50μA quiescent current with one channel active through dedicated sleep-mode circuitry: when ITH drops below 0.425V, internal logic disables most bias currents and parks ITH at 0.450V while maintaining PGOOD monitoring and RUN pin responsiveness. This architecture preserves fast wake-up (<10μs) without sacrificing standby efficiency - a key differentiator versus standard controllers.
Can the LTC3857IUH#TRPBF synchronize to an external clock source?
Yes, the LTC3857IUH#TRPBF supports external synchronization via the PLLIN/MODE pin (Pin 5). When an external clock is applied, its phase-locked loop forces TG1's rising edge to align with the external clock's rising edge. The device accepts 75kHz–850kHz input clocks and maintains lock even under frequency modulation - enabling EMI reduction and deterministic timing in multi-controller systems.
What are the key differences between the LTC3857IUH#TRPBF and LTC3857-1?
The LTC3857IUH#TRPBF supports dual PGOOD outputs, phase modulation (PHASMD pin), CLKOUT daisy-chaining, and full 75kHz–850kHz PLL sync range. In contrast, the LTC3857-1 uses a 28-lead SSOP package, offers only one PGOOD, lacks PHASMD/CLKOUT, and omits phase modulation - making it a simplified variant for cost-sensitive, single-PGOOD applications without advanced synchronization needs.
How does the EXTVCC pin improve system efficiency in the LTC3857IUH#TRPBF?
The EXTVCC pin (Pin 20) allows the LTC3857IUH#TRPBF to derive INTVCC power from an efficient external source - such as its own 8.5V output rail - instead of the less-efficient VIN-based LDO. When EXTVCC exceeds 4.7V, the internal VIN LDO shuts off and the EXTVCC LDO activates, reducing total power loss and heat generation. This feature is especially valuable in multi-rail systems where one output can self-bias the controller.
LTC3857IUH#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 32-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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:
- Current Limit, Enable, Frequency Control, Phase Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-QFN (5x5)
LTC3857IUH#TRPBF FAQ
1.How can I place an order for LTC3857IUH#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3857IUH#TRPBF 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 LTC3857IUH#TRPBF reliable?
The price and inventory of LTC3857IUH#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3857IUH#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3857IUH#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3857IUH#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3857IUH#TRPBF?
LTC3857IUH#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3857IUH#TRPBF 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 LTC3857IUH#TRPBF?
For technical support, including LTC3857IUH#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3857IUH#TRPBF requirements.
6.How does Aetrix verify that LTC3857IUH#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3857IUH#TRPBF 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 LTC3857IUH#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3857IUH#TRPBF?
All LTC3857IUH#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3857IUH#TRPBF, 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 LTC3857IUH#TRPBF part is unused and in its original packaging.
Return procedure for LTC3857IUH#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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