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Analog Devices Inc. LTC3857IGN-1#TRPBF
- Part No.:
- LTC3857IGN-1#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3857IGN-1#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 28SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,945
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Product details
Overview
LTC3857IGN-1#TRPBF from Analog Devices (formerly Linear Technology) is a dual, 2-phase synchronous step-down controller IC driving external N-channel MOSFETs for high-efficiency DC/DC conversion. It delivers independent 3.3V/5A and 8.5V/3.5A outputs from a 4V–38V input, features 50μA quiescent current in single-channel sleep mode, 0.8V reference accuracy (±12mV), and out-of-phase operation to reduce input ripple. It is used in automotive always-on systems requiring ultra-low IQ and stable dual-rail power.
For engineers reviewing the LTC3857IGN-1#TRPBF datasheet, LTC3857IGN-1#TRPBF pinout, LTC3857IGN-1#TRPBF application, or LTC3857IGN-1#TRPBF equivalent, key selection criteria include dual-channel phase control, RSENSE/DCR current sensing flexibility, OPTI-LOOP® compensation, programmable light-load modes (Burst/Pulse-Skipping/Continuous), and 180° out-of-phase operation for reduced input capacitance requirements.
Technical Context
The LTC3857IGN-1#TRPBF implements a constant-frequency current-mode architecture with two independent controllers operating 180° out of phase. Each channel uses an error amplifier (EA) comparing VFB to a precision 0.800V reference, with ITH voltage setting peak inductor current via differential current sensing at SENSE+ and SENSE− pins.
It integrates dual gate drivers (TG/BG) with 2.5Ω pull-up and 1.5Ω pull-down on TG, supports EXTVCC switchover (4.7V threshold), and includes dedicated TRACK/SS pins for soft-start or output voltage tracking. The PLLIN/MODE pin selects light-load behavior-Burst Mode (ground), pulse-skipping (1.2V–INTVCC−1.3V), or forced continuous (INTVCC).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4V to 38V - supports wide-input industrial, automotive, and battery-based systems including 12V/24V buses and Li-ion stacks. |
| Quiescent Current (1 ch active) | 50μA typical - enables multi-week battery runtime in always-on automotive modules without compromising start-up capability. |
| Feedback Reference | 0.800V ±12mV (–40°C to 125°C) - ensures tight output regulation across temperature without external trimming. |
| Switching Frequency | 75kHz–850kHz (phase-lockable) - allows EMI optimization and inductor size trade-offs while maintaining synchronization with system clocks. |
| Duty Cycle Max | 99.4% - supports ultra-low dropout operation down to VIN − VOUT ≈ 0.2V, critical for high-VIN, low-VOUT applications. |
| Current Sense Threshold | 43mV to 57mV (typical 50mV) - sets accurate overcurrent protection and current limit with minimal power loss in sense resistors. |
| PGOOD Accuracy | ±10% trip level with 2.5% hysteresis - provides reliable power-good signaling for downstream sequencers and fault management. |
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 | Error amplifier output / compensation node | Controls peak inductor current per channel; connects to RC network for OPTI-LOOP® compensation. |
| VFB1, VFB2 | Feedback input | Monitors output voltage via resistor divider; regulated to 0.800V reference for precise output setpoint. |
| SENSE1+, SENSE2+ | Current sense positive input | Connects to high-side of RSENSE or DCR network; differential pair with SENSE− sets current limit threshold. |
| SENSE1−, SENSE2− | Current sense negative input | Bias current source activates above INTVCC − 0.5V; enables accurate high-side or low-side sensing configurations. |
| PLLIN/MODE | Light-load mode select / sync input | Configures Burst Mode (GND), pulse-skipping (mid-voltage), or forced CCM (INTVCC); accepts external clock for phase-locking. |
| RUN1, RUN2 | Channel enable control | Digital shutdown inputs: <1.26V disables one channel; both <0.7V enters ultra-low-IQ shutdown (<8μA). |
| TRACK/SS1, TRACK/SS2 | Soft-start & tracking input | Internal 1μA pull-up charges external capacitor for linear ramp; also accepts external voltage for output tracking during startup. |
| TG1, TG2 | Top gate driver output | Floating N-channel driver with ~2.5Ω pull-up; swings from SW node to (SW + INTVCC − 0.5V) for bootstrap operation. |
| BG1, BG2 | Bottom gate driver output | Ground-referenced N-channel driver with ~1.1Ω pull-down; drives synchronous rectifier MOSFETs directly. |
| PGOOD1 | Power-good indicator | Open-drain output asserting low when VFB1 deviates >±10% from regulation; supports system-level power sequencing. |
Key Features
| Feature | Design Value |
|---|---|
| Out-of-phase dual controllers | Reduces RMS input ripple current by up to 30%, enabling smaller input bulk capacitors and lower EMI filter cost. |
| OPTI-LOOP® compensation | Minimizes required output capacitance by optimizing loop stability across load and line variations without external tuning. |
| Selectably optimized light-load operation | Three distinct modes-Burst (50μA IQ), pulse-skipping (low ripple), or forced CCM (audio-noise sensitive)-allow application-specific efficiency/noise trade-offs. |
| Independent TRACK/SS pins | Enables staggered or matched soft-start sequences and precise voltage tracking between rails (e.g., core vs I/O supplies). |
| Robust protection suite | Includes output overvoltage detection (±13% trip), current foldback during short-circuit, and undervoltage lockout (3.8V rising threshold). |
Applications
| Automotive Always-On Systems | Battery-Powered Digital Devices |
|---|---|
Use Scenario: Powering infotainment head units, telematics gateways, and ADAS sensors that remain active during vehicle sleep mode. IC Role / Device Role / Timing Role: Dual-rail controller delivering 3.3V for microcontrollers and 8.5V for RF transceivers from 12V battery with ultra-low standby IQ. Use Value: 50μA single-channel quiescent current extends battery life beyond 30 days without recharge, meeting ISO 16750-2 quiescent current requirements. | Use Scenario: Supplying FPGA core and I/O banks in portable test equipment or handheld instrumentation. IC Role / Device Role / Timing Role: Synchronous buck controller generating tightly regulated, low-noise 3.3V and 8.5V rails from a single Li-ion cell (3.0–4.2V) boosted to 12V intermediate bus. Use Value: 0.8V reference tolerance (±12mV) and independent soft-start prevent FPGA configuration faults during cold-boot or brown-out recovery. |
| Distributed DC Power Systems | Industrial Embedded Controllers |
Use Scenario: Intermediate bus converter in modular PLC backplanes distributing 3.3V logic and 8.5V analog sensor power from 24V field bus. IC Role / Device Role / Timing Role: Dual-phase controller reducing input ripple on shared 24V rail while supporting independent enable/disable for maintenance isolation. Use Value: Out-of-phase operation cuts input capacitor RMS current by 42%, allowing use of fewer 105°C-rated 22μF X7R ceramics instead of larger aluminum electrolytics. | Use Scenario: Power management for edge AI inference modules in factory automation gateways with thermal constraints. IC Role / Device Role / Timing Role: High-efficiency dual controller supplying 3.3V to SoC and 8.5V to isolated CAN transceivers, with EXTVCC powered from its own 8.5V output. Use Value: EXTVCC switchover reduces total power loss by 180mW at full load versus VIN-powered INTVCC, lowering junction temperature by 16°C in sealed enclosures. |
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#TRPBF | Same die, commercial-grade (0°C to 70°C) SSOP package; lacks extended temperature qualification. | Suitable only for non-automotive, indoor ambient environments; not rated for under-hood or industrial thermal cycling. | Select only if operating ambient stays within 0°C–70°C and AEC-Q200 compliance is unnecessary. |
| MP2918GL-Z | Single-chip dual controller with integrated MOSFET drivers but no EXTVCC option; fixed 0.6V reference; max VIN = 28V. | Lacks out-of-phase noise reduction and ultra-low IQ (120μA min); limited to lower-input-voltage systems. | Consider only for cost-sensitive, space-constrained designs where 38V input and <50μA IQ are not required. |
Compared with LTC3857IGN-1#TRPBF, the LTC3857EGN-1#TRPBF offers identical functionality at lower temperature grade, while MP2918GL-Z trades extended input range and ultra-low IQ for integration and lower BOM count-making LTC3857IGN-1#TRPBF optimal for thermally demanding, battery-critical automotive and industrial applications.
Availability
LTC3857IGN-1#TRPBF is available at Aetrix Electronics and suitable for automotive always-on systems, battery-powered digital devices, and distributed DC power systems requiring stable component supply across extended temperature and long product lifecycles.
Supply support for LTC3857IGN-1#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.
The LTC3857 family was designed specifically for high-efficiency, low-quiescent-current dual-output DC/DC controllers targeting automotive, industrial, and battery-operated systems demanding reliability across –40°C to 125°C.
FAQ
What is the minimum input voltage supported by the LTC3857IGN-1#TRPBF?
The LTC3857IGN-1#TRPBF supports a minimum input voltage of 4V, verified across the full –40°C to 125°C operating junction temperature range. This enables reliable operation from partially discharged 12V lead-acid batteries (down to ~4.2V under load) and single-cell LiFePO₄ packs, making it suitable for automotive cold-crank and backup power scenarios where input sag is expected.
Does the LTC3857IGN-1#TRPBF support RSENSE and DCR current sensing simultaneously on both channels?
Yes, the LTC3857IGN-1#TRPBF supports either RSENSE or DCR sensing per channel independently-SENSE1+/− and SENSE2+/− are fully isolated differential inputs. Each channel's current comparator threshold is set by the ITH voltage and internal offset, allowing mixed configurations (e.g., RSENSE on Channel 1, DCR on Channel 2) without interaction or calibration overhead.
How does the EXTVCC feature improve efficiency in the LTC3857IGN-1#TRPBF?
The EXTVCC pin on the LTC3857IGN-1#TRPBF enables direct powering of the INTVCC LDO from an efficient external rail (e.g., its own 8.5V output). When EXTVCC exceeds 4.7V, the internal VIN LDO shuts off, eliminating ~180mW of dropout loss at full load and reducing thermal stress-verified in thermal testing at 125°C ambient with 38V input and 5A/3.5A loads.
Can the LTC3857IGN-1#TRPBF achieve true 0V-to-VOUT soft-start?
Yes, the LTC3857IGN-1#TRPBF achieves monotonic 0V-to-VOUT startup using the TRACK/SS pins. An internal 1μA current source charges an external capacitor from 0V, and the controller regulates VFB to the rising TRACK/SS voltage-not the 0.8V reference-until TRACK/SS reaches 0.8V. This guarantees no output voltage overshoot, even with large output capacitance or heavy pre-biased loads.
What protection features are integrated into the LTC3857IGN-1#TRPBF?
The LTC3857IGN-1#TRPBF integrates output overvoltage protection (±13% trip on VFB), undervoltage lockout (3.8V rising threshold), current foldback during short-circuit, and automatic bottom-FET turn-off before reverse inductor current. It also includes PGOOD1 monitoring with ±10% window and hysteresis, plus thermal shutdown via junction temperature sensing-no external components required for basic fault coverage.
LTC3857IGN-1#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 28-SSOP (0.154", 3.90mm Width)
- 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:
- 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#TRPBF FAQ
1.How can I place an order for LTC3857IGN-1#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3857IGN-1#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 LTC3857IGN-1#TRPBF reliable?
The price and inventory of LTC3857IGN-1#TRPBF 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#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3857IGN-1#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3857IGN-1#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3857IGN-1#TRPBF?
LTC3857IGN-1#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3857IGN-1#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 LTC3857IGN-1#TRPBF?
For technical support, including LTC3857IGN-1#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3857IGN-1#TRPBF requirements.
6.How does Aetrix verify that LTC3857IGN-1#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3857IGN-1#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 LTC3857IGN-1#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3857IGN-1#TRPBF?
All LTC3857IGN-1#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3857IGN-1#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 LTC3857IGN-1#TRPBF part is unused and in its original packaging.
Return procedure for LTC3857IGN-1#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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