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Analog Devices Inc. LTC3857IGN-1#PBF
- Part No.:
- LTC3857IGN-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3857IGN-1#PBF.pdf
- Description:
- IC REG CTRLR BUCK 28SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,858
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Product details
Overview
LTC3857IGN-1#PBF from Analog Devices (formerly Linear Technology) is a dual, 2-phase synchronous step-down controller driving two independent N-channel MOSFET stages for high-efficiency DC/DC 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 range - ideal for automotive always-on systems and battery-powered digital devices.
For engineers reviewing the LTC3857IGN-1#PBF datasheet, LTC3857IGN-1#PBF pinout, LTC3857IGN-1#PBF application, or LTC3857IGN-1#PBF equivalent, key selection criteria include out-of-phase dual-channel operation to reduce input capacitance, OPTI-LOOP® compensation minimizing output capacitance, selectable light-load modes (Burst Mode®, pulse-skipping, or forced continuous), and phase-lockable frequency from 75kHz to 850kHz.
Technical Context
The LTC3857IGN-1#PBF implements a constant-frequency current-mode architecture with two 180° out-of-phase controllers, each featuring independent error amplifiers (ITH1/ITH2), differential current sensing (SENSE1±/SENSE2±), and precision 0.800V feedback reference (VFB1/VFB2). Its dual-loop design enables coordinated soft-start via TRACK/SS1/SS2 pins and independent RUN1/RUN2 shutdown control.
It integrates dual gate drivers (TG1/BG1 and TG2/BG2) with 2.5Ω pull-up and 1.5Ω pull-down on top-side drivers, supports RSENSE or DCR current sensing, and includes internal LDOs for INTVCC generation from VIN or EXTVCC (switchover at 4.7V). Output overvoltage protection triggers at ±10% of regulated VFB, and PGOOD1 monitors only Channel 1.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports wide intermediate bus voltages and battery chemistries including 12V automotive and 24V industrial rails. |
| Quiescent Current (One Channel Active) | 50μA - extends battery life in always-on systems without compromising startup responsiveness. |
| Feedback Reference Voltage | 0.800V ±12mV (–40°C to 125°C) - enables precise output regulation across temperature with minimal external resistor tolerance impact. |
| Switching Frequency Range | 75kHz–850kHz (phase-lockable) or 50kHz–900kHz (programmable) - balances efficiency vs. size: lower frequencies reduce MOSFET switching loss; higher frequencies shrink magnetics. |
| Duty Cycle Max | 99.4% - ensures stable regulation even during deep dropout (e.g., VIN = 3.6V → VOUT = 3.3V). |
| Current Sense Threshold | 43mV to 57mV (typ. 50mV) - sets accurate current limit with low-loss RSENSE or DCR networks, minimizing power dissipation in sense elements. |
| PGOOD Output | Open-drain PGOOD1 only for Channel 1 - provides reliable power-good signaling for system sequencing; no PGOOD for Channel 2. |
Pinout & Package
Package: 28-Lead Plastic SSOP (GN), –40°C to 125°C operating junction temperature, θJA = 90°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ITH1, ITH2 (1, 13) | Error amplifier outputs & compensation nodes | Set peak inductor current trip point per channel; connect RC network for OPTI-LOOP® compensation. |
| VFB1, VFB2 (2, 12) | Feedback inputs | Monitor output voltage via resistive divider; regulate to 0.800V reference with ±12mV accuracy over full temp range. |
| SENSE1+, SENSE2+ (3, 11) | Current sense positive inputs | Connect to high-side of RSENSE or DCR network; differential with SENSE– sets current limit threshold. |
| SENSE1–, SENSE2– (4, 10) | Current sense negative inputs | Reference point for current comparator; supplies bias current when > INTVCC – 0.5V. |
| FREQ (5) | Frequency programming input | Resistor-to-GND sets frequency 50–900kHz; tied to GND = 350kHz, to INTVCC = 535kHz. |
| PLLIN/MODE (6) | Sync input & light-load mode select | Ground = Burst Mode®; INTVCC = forced continuous; 1.2V–(INTVCC–1.3V) = pulse-skipping. |
| RUN1, RUN2 (8, 9) | Independent enable inputs | <1.26V disables respective channel; both <0.7V shuts down entire IC with 8μA IQ. |
| TRACK/SS1, TRACK/SS2 (14, 28) | Soft-start & tracking inputs | Internal 1μA current source ramps capacitor for controlled startup; also accepts external voltage for supply tracking. |
| PGOOD1 (27) | Power-good indicator | Open-drain output pulled low if VFB1 deviates >±10% from setpoint - used for system power sequencing. |
| TG1, TG2 (15, 26) | Top N-MOSFET gate drivers | Floating drivers with swing = INTVCC – 0.5V superimposed on SW node; 2.5Ω pull-up, 1.5Ω pull-down. |
| BG1, BG2 (18, 23) | Bottom N-MOSFET gate drivers | Ground-referenced drivers swinging 0V to INTVCC; 2.4Ω pull-up, 1.1Ω pull-down. |
| BOOST1, BOOST2 (17, 24) | Bootstrap supplies | Charge pump supplies for top drivers; connect Schottky diode + capacitor between BOOST and SW pins. |
| SW1, SW2 (16, 25) | Switch node connections | Connect to inductor high-side terminals; carry high di/dt switching currents - require tight layout. |
| VIN (22) | Main input supply | Primary power source for internal LDO; bypassed to SGND with ≥4.7μF ceramic capacitor. |
| EXTVCC (20) | External auxiliary supply | Enables more efficient INTVCC generation when >4.7V; bypassed to PGND with ≥4.7μF ceramic capacitor. |
| INTVCC (19) | Internal LDO output | 5.1V ±3%, powers all drivers and logic; must be decoupled locally - not for external loads. |
| SGND (7) | Small-signal ground | Reference for analog circuitry (error amps, comparators); must be routed separately from PGND. |
| PGND (21) | Power ground | Return path for high-current bottom FETs and input capacitors - connect to CIN(–) and MOSFET sources. |
Key Features
| Feature | Design Value |
|---|---|
| Out-of-phase dual-channel operation | Reduces RMS input ripple current by ~30%, allowing smaller input bulk capacitance and lower EMI. |
| OPTI-LOOP® compensation | Minimizes required output capacitance while maintaining stability across load and line variations. |
| Selectably optimized light-load efficiency | Burst Mode® (50μA IQ), pulse-skipping (low ripple), or forced continuous (lowest noise) - configurable per system need. |
| Independent soft-start and tracking | Separate TRACK/SS1 and TRACK/SS2 pins enable staggered or synchronized startup with other rails. |
| Robust fault protection | Output overvoltage protection (±10%), no current foldback at startup, and dropout detection with forced refresh for bootstrap caps. |
Applications
| Automotive Always-On Systems | Battery-Powered Digital Devices |
|---|---|
Use Scenario: Powering infotainment, telematics, and ADAS modules that remain active during vehicle sleep mode. IC Role / Device Role / Timing Role: Dual-output controller generating 3.3V for microcontrollers and 8.5V for RF transceivers from 9–16V battery rail. Use Value: 50μA quiescent current prevents excessive battery drain over weeks of parking; 99.4% duty cycle maintains regulation during cold-crank (VIN dip to 3.6V). | Use Scenario: Supplying FPGA core (3.3V/5A) and I/O banks (8.5V/3.5A) in portable test equipment with Li-ion battery input. IC Role / Device Role / Timing Role: Primary DC/DC controller managing two independent power domains with coordinated soft-start and independent enable control. Use Value: Independent RUN1/RUN2 pins allow dynamic power gating of subsystems; Burst Mode® extends runtime by >3× versus forced continuous at light loads. |
| Distributed DC Power Systems | Industrial Embedded Controllers |
Use Scenario: Generating local 3.3V and 8.5V rails from a 24V intermediate bus in modular PLC backplanes. IC Role / Device Role / Timing Role: High-efficiency dual buck controller reducing heat generation and enabling compact board layout with shared input cap. Use Value: Out-of-phase operation cuts input capacitor RMS current, permitting smaller 1206-size ceramics instead of larger tantalums - saving board space and cost. | Use Scenario: Powering ARM-based HMI controllers requiring tightly regulated 3.3V and auxiliary 8.5V for display backlight drivers. IC Role / Device Role / Timing Role: Precision voltage controller with 0.800V ±12mV reference and PGOOD1 for safe boot sequencing. Use Value: ±10% PGOOD1 threshold ensures reliable system reset assertion before firmware execution begins - preventing brown-out lockup. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual synchronous step-down controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3857EGN-1#PBF | Same die, commercial-grade (0°C to 70°C) temperature range; identical pinout and electrical specs. | Suitable for non-automotive, non-industrial environments where extended temperature is not required. | Select when ambient operating temperature stays within 0°C–70°C and cost sensitivity outweighs extended temp qualification. |
| LTC3857IGN-1#TRPBF | Identical specifications and package; supplied in tape-and-reel (2,500 pcs) instead of tube (75 pcs). | Optimized for automated SMT assembly lines requiring reel-fed placement. | Choose for high-volume production with pick-and-place machines; same performance and reliability as tube-packaged LTC3857IGN-1#PBF. |
Compared with LTC3857EGN-1#PBF, the LTC3857IGN-1#PBF offers guaranteed operation to 125°C junction temperature - critical for under-hood automotive use. Versus LTC3857IGN-1#TRPBF, the tube version supports low-volume prototyping and manual rework without reel-handling infrastructure.
Availability
LTC3857IGN-1#PBF is available at Aetrix Electronics and suitable for automotive always-on systems, battery-operated digital devices, and distributed DC power systems requiring stable component supply across extended temperature ranges and long product lifecycles.
Supply support for LTC3857IGN-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 technical and manufacturing continuity for its high-performance power management portfolio.
The LTC3857IGN-1#PBF belongs to Linear's high-efficiency dual-phase synchronous controller family, designed specifically for demanding automotive, industrial, and portable applications requiring ultra-low quiescent current and robust multi-rail power sequencing.
FAQ
What is the maximum input voltage rating for the LTC3857IGN-1#PBF?
The LTC3857IGN-1#PBF has an absolute maximum input supply voltage (VIN) rating of 40V. Its operational input range is specified from 4V to 38V, making it suitable for 24V industrial buses and 12V automotive systems including cold-crank conditions. Exceeding 40V risks permanent damage per Absolute Maximum Ratings.
Does the LTC3857IGN-1#PBF support phase synchronization with an external clock?
Yes, the LTC3857IGN-1#PBF supports external synchronization via the PLLIN/MODE pin. When an external clock signal is applied, its phase-locked loop forces the rising edge of TG1 to align 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 LTC3857IGN-1#PBF achieve ultra-low quiescent current in sleep mode?
The LTC3857IGN-1#PBF achieves 50μA quiescent current (one channel active) by disconnecting the error amplifier output from the ITH pin and parking ITH at 0.450V when the ITH voltage drops below 0.425V. This disables gate drive and most internal circuitry while retaining fast wake-up capability - critical for battery longevity in always-on automotive modules.
Can the LTC3857IGN-1#PBF monitor both output channels for power-good status?
No, the LTC3857IGN-1#PBF provides only one open-drain PGOOD1 output, which monitors Channel 1 (VFB1) only. It asserts low when VFB1 deviates more than ±10% from its regulated setpoint. Channel 2 has no dedicated PGOOD output; system designers must implement external monitoring if dual-rail sequencing is required.
What is the purpose of the EXTVCC pin on the LTC3857IGN-1#PBF?
The EXTVCC pin on the LTC3857IGN-1#PBF allows powering the internal INTVCC LDO from an external regulated supply (e.g., one of the LTC3857IGN-1#PBF's own output rails) when voltage exceeds 4.7V. This bypasses the less-efficient VIN-based LDO, reducing overall power loss and thermal stress - especially beneficial in multi-stage converter designs.
LTC3857IGN-1#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 28-SSOP (0.154", 3.90mm Width)
- 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, Tracking
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SSOP
LTC3857IGN-1#PBF FAQ
1.How can I place an order for LTC3857IGN-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3857IGN-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 LTC3857IGN-1#PBF reliable?
The price and inventory of LTC3857IGN-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 LTC3857IGN-1#PBF is usually 5 days.
3.What payment methods are accepted for LTC3857IGN-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3857IGN-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3857IGN-1#PBF?
LTC3857IGN-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3857IGN-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 LTC3857IGN-1#PBF?
For technical support, including LTC3857IGN-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3857IGN-1#PBF requirements.
6.How does Aetrix verify that LTC3857IGN-1#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3857IGN-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 LTC3857IGN-1#PBF meets industry standards.
7.What is the process for return or replacement of LTC3857IGN-1#PBF?
All LTC3857IGN-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3857IGN-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 LTC3857IGN-1#PBF part is unused and in its original packaging.
Return procedure for LTC3857IGN-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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