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Analog Devices Inc. LTC3868IGN-1
- Part No.:
- LTC3868IGN-1
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3868IGN-1.pdf
- Description:
- IC POWER MANAGEMENT
- Quantity:
- Payment:
- Shipping:
Inventory:1,051
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Product details
Overview
LTC3868IGN-1 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 features 170μA no-load quiescent current, 0.8V reference accuracy (±1.5%), 4V–24V input range, and supports out-of-phase operation to reduce input ripple. Used in battery-powered portable instruments requiring dual regulated outputs (e.g., 3.3V/5A and 8.5V/3.5A).
For engineers reviewing the LTC3868IGN-1 datasheet, LTC3868IGN-1 pinout, LTC3868IGN-1 application, or LTC3868IGN-1 equivalent, key selection criteria include phase-lockable frequency (75–850kHz), RSENSE/DCR current sensing, OPTI-LOOP® compensation, soft-start control per channel, and output overvoltage/short-circuit latchoff protection.
Technical Context
The LTC3868IGN-1 implements a constant-frequency current-mode architecture with two independent 180° out-of-phase controllers, each featuring a transconductance error amplifier (gm = 2 mmho), programmable current limit via ITH voltage, and precision 0.8V feedback reference (±1.5% over temperature). Its dual-channel design enables interleaved operation to halve input capacitor RMS current and suppress EMI.
It integrates internal LDOs powering gate drivers from VIN or EXTVCC (switchover at 4.7V), supports three light-load modes (Burst Mode®, pulse-skipping, forced continuous), and includes dedicated short-circuit latchoff with arming/latch thresholds (2.0V/1.5V on SS pins) and foldback current limiting activated below 70% VOUT.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 24V - supports wide intermediate bus and multi-cell Li-ion battery inputs. |
| Quiescent Current (One Channel On) | 170μA - extends runtime in always-on portable systems without compromising regulation. |
| Feedback Reference Voltage | 0.8V ±1.5% - enables accurate output regulation down to sub-1V with external resistor dividers. |
| Switching Frequency Range | 75kHz to 850kHz - allows optimization of size (high f) vs. efficiency (low f) and EMI compliance. |
| Output Short-Circuit Protection | Latchoff with SS-pin timeout - disables output after ~12ms fault (with 0.1μF SS cap) to prevent thermal runaway. |
| Gate Driver Strength | TG/BG pull-up: 2.5Ω/2.4Ω - ensures fast MOSFET turn-on with <30ns transition times into 3300pF load. |
| Current Sensing Options | RSENSE or DCR - eliminates need for dedicated sense resistors in high-current inductor designs. |
Pinout & Package
Package: 28-Lead Plastic SSOP (0.150" width), RoHS-compliant, operating temperature range –40°C to +85°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SENSE1+, SENSE2+ | Differential current sense (+) inputs | Connect to DCR network or sense resistor high side; sets peak current trip point with ITH voltage. |
| SENSE1–, SENSE2– | Differential current sense (–) inputs | Connect to MOSFET source or DCR low side; supplies bias current above INTVCC – 0.5V. |
| VFB1, VFB2 | Feedback inputs | Monitor output voltage via resistor divider; regulate to 0.8V reference with ±1.5% accuracy. |
| ITH1, ITH2 | Error amplifier outputs | Set current limit threshold; voltage directly controls peak inductor current per channel. |
| SS1, SS2 | Soft-start / latchoff timer inputs | Internal 1μA pull-up ramps voltage for controlled startup; discharges during short-circuit to trigger latchoff. |
| RUN1, RUN2 | Independent enable inputs | Logic-level shutdown: <1.26V disables one channel; both <0.7V reduces IQ to 8μA globally. |
| PGOOD1 | Power-good open-drain output | Asserts low when VFB1 deviates >±10% from setpoint - used for system sequencing and fault reporting. |
| TG1, TG2 / BG1, BG2 | Top/bottom gate drivers | Drive N-MOSFET gates with 2.5Ω/2.4Ω pull-up and 1.5Ω/1.1Ω pull-down for <30ns transitions. |
| BOOST1, BOOST2 | Floating bootstrap supplies | Charge pump supplies for top MOSFET drivers; swing from INTVCC to (VIN + INTVCC). |
| SW1, SW2 | Switch node connections | Connect to inductor high side and MOSFET drains; handle full switching dv/dt and peak currents. |
| INTVCC, EXTVCC | Internal LDO outputs/inputs | INTVCC = 5.1V ±1.1%; EXTVCC switchover at 4.7V enables efficient self-biasing from output rails. |
| PLLIN/MODE | Sync input / light-load mode select | Pull to GND → Burst Mode®; to INTVCC → forced continuous; to 1.2–3.8V → pulse-skipping. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Enables stable loop response across wide COUT/ESR variations without redesigning compensation network. |
| Out-of-Phase Dual Control | Reduces input capacitor RMS current by ~70% and lowers conducted EMI compared to in-phase operation. |
| Programmable Light-Load Mode | Selects Burst Mode® (highest efficiency), pulse-skipping (low noise), or forced continuous (lowest output ripple). |
| Independent Soft-Start & Latchoff | Each channel has dedicated SS pin enabling staggered startup and autonomous short-circuit shutdown. |
| 99% Duty Cycle Dropout Operation | Maintains regulation even when VIN approaches VOUT, critical for Li-ion battery end-of-discharge support. |
Applications
| Portable Instrument Power | Notebook System Rail Generation |
|---|---|
Use Scenario: Dual-rail power supply for handheld oscilloscopes with isolated analog front-end (8.5V) and digital logic core (3.3V). IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing independent output voltages, sequencing, and fault isolation. Use Value: 170μA quiescent current extends battery life; out-of-phase operation minimizes input capacitance and EMI in compact enclosures. | Use Scenario: Mainboard VRM generating CPU core (3.3V/5A) and peripheral I/O (8.5V/3.5A) rails from 12V intermediate bus. IC Role / Device Role / Timing Role: High-efficiency dual controller with phase modulation and PLL synchronization to system clock. Use Value: Phase interleaving cuts input ripple by half; OPTI-LOOP® ensures stability across varying motherboard capacitance loads. |
| Battery-Powered Digital Device | Distributed DC Power System |
Use Scenario: Power management for ruggedized field data logger using single-cell Li-ion (3.0–4.2V) boosted to 5V and 8.5V outputs. IC Role / Device Role / Timing Role: Dual-output buck controller with ultra-low IQ sleep mode and dropout support down to 99% duty cycle. Use Value: 8μA shutdown current preserves battery during idle; adjustable current limit protects against sensor short circuits. | Use Scenario: Intermediate bus converter in telecom shelf supplying 3.3V and 8.5V to distributed line cards from 24V backplane. IC Role / Device Role / Timing Role: Robust dual-phase controller with EXTVCC self-biasing, PGOOD monitoring, and latchoff protection per rail. Use Value: EXTVCC input allows efficient biasing from local 5V rail; independent RUN pins enable hot-swap sequencing and redundancy control. |
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 |
|---|---|---|---|
| LTC3868EUFD-1#TRPBF | Same die, 28-lead 4mm × 5mm QFN package; θJA = 43°C/W vs. 90°C/W for SSOP. | Better thermal performance in space-constrained PCB layouts; requires different land pattern and reflow profile. | Choose for higher power density or improved thermal margin; verify layout compatibility. |
| MP8765GL-Z | Monolithic dual buck (integrated MOSFETs); fixed 500kHz fSW; no PLL sync or DCR sensing. | Simpler BOM but limited to ≤3A/channel; lacks independent soft-start, latchoff, and wide fSW range. | Choose for cost-sensitive, lower-current designs where integration outweighs configurability. |
Compared with LTC3868EUFD-1#TRPBF, the LTC3868IGN-1 offers identical functionality in a thermally less efficient but legacy-compatible SSOP package; versus MP8765GL-Z, it provides higher current capability, greater flexibility in frequency and sensing, and robust fault protection - essential for industrial and portable instrumentation.
Availability
LTC3868IGN-1 is available at Aetrix Electronics and suitable for portable instruments, notebook computing, battery-operated digital devices, and distributed DC power systems requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant sourcing.
Supply support for LTC3868IGN-1 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 LTC3868IGN-1 belongs to Linear's high-performance synchronous controller family designed for demanding dual-output DC/DC conversion in portable, industrial, and telecom applications where efficiency, low IQ, and robust protection are critical.
FAQ
What is the maximum input voltage rating for the LTC3868IGN-1?
The LTC3868IGN-1 has an absolute maximum input supply voltage (VIN) of 28V. Its operational input range is specified from 4V to 24V, making it suitable for 12V and 24V intermediate bus systems and multi-cell Li-ion battery inputs. Exceeding 28V may cause permanent damage per Absolute Maximum Ratings.
Does the LTC3868IGN-1 support phase synchronization with an external clock?
Yes, the LTC3868IGN-1 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. The supported sync frequency range is 75kHz to 850kHz, enabling EMI reduction and system-level timing coordination.
How does the short-circuit latchoff function work on the LTC3868IGN-1?
The LTC3868IGN-1 uses the SS1 and SS2 pins for independent short-circuit latchoff. Once the SS pin voltage exceeds 2.0V (arming threshold), a 9μA discharge current pulls it down if VFB drops below 70% of regulation. If SS falls below 1.5V, the channel latches off. The timeout is programmable via CSS: tLATCH ≈ CSS × (VSS − 1.5V) / 9μA.
Can the LTC3868IGN-1 operate with only one output enabled?
Yes, the LTC3868IGN-1 supports independent channel control. Pulling RUN1 low disables Channel 1 while Channel 2 remains active, and vice versa. With one channel active and the other shut down, quiescent current drops to 170μA. Both RUN pins must be pulled below 0.7V to enter global 8μA shutdown mode.
What is the purpose of the EXTVCC pin on the LTC3868IGN-1?
The EXTVCC pin on the LTC3868IGN-1 provides an alternative input to the internal LDO that powers INTVCC. When EXTVCC exceeds 4.7V, the device switches from VIN-based to EXTVCC-based regulation, delivering 5.1V to INTVCC. This enables efficient self-biasing from a clean, regulated output rail (e.g., 5V from Channel 1), reducing power loss and heat generation.
LTC3868IGN-1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 2
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 4V ~ 24V
- 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 ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SSOP
LTC3868IGN-1 FAQ
1.How can I place an order for LTC3868IGN-1 through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3868IGN-1 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 LTC3868IGN-1 reliable?
The price and inventory of LTC3868IGN-1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3868IGN-1 is usually 5 days.
3.What payment methods are accepted for LTC3868IGN-1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3868IGN-1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3868IGN-1?
LTC3868IGN-1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3868IGN-1 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 LTC3868IGN-1?
For technical support, including LTC3868IGN-1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3868IGN-1 requirements.
6.How does Aetrix verify that LTC3868IGN-1 is sourced from the original manufacturer or authorized distributors?
All LTC3868IGN-1 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 LTC3868IGN-1 meets industry standards.
7.What is the process for return or replacement of LTC3868IGN-1?
All LTC3868IGN-1 units undergo pre-shipment inspection (PSI). If there is an issue with LTC3868IGN-1, 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 LTC3868IGN-1 part is unused and in its original packaging.
Return procedure for LTC3868IGN-1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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