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Analog Devices Inc. LTC3835IUFD#PBF
- Part No.:
- LTC3835IUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 20-WFQFN Exposed Pad
- Datasheet:
-
LTC3835IUFD#PBF.pdf
- Description:
- IC REG CTRLR BUCK 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:274
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Product details
Overview
LTC3835IUFD#PBF from Analog Devices (formerly Linear Technology) is a high-performance, low-quiescent-current synchronous step-down switching regulator controller driving dual N-channel MOSFETs. It delivers 0.8V to 10V output voltage from a 4V–36V input, operates up to 650kHz with phase-lock capability, and features OPTI-LOOP® compensation, 0.8V ±1% reference, and power-good monitoring - ideal for battery-powered telecom and automotive DC/DC systems.
For engineers reviewing the LTC3835IUFD#PBF datasheet, LTC3835IUFD#PBF pinout, LTC3835IUFD#PBF application, or LTC3835IUFD#PBF equivalent, key selection criteria include its 80µA no-load IQ, 99.4% max duty cycle for ultra-low dropout, selectable light-load modes (Burst Mode®, pulse-skipping, continuous), EXTVCC-supported gate drive efficiency, and 20-pin 4mm × 5mm QFN package with exposed thermal pad.
Technical Context
The LTC3835IUFD#PBF implements a constant-frequency current-mode control architecture with an error amplifier (EA) outputting to the ITH pin to set peak inductor current. Its phase-locked loop (PLL) accepts external clock inputs from 140kHz to 650kHz via PLLIN/MODE and uses PLLLPF as a loop filter node for synchronization.
It integrates dual gate drivers (TG and BG) with 50ns/40ns rise/fall times, internal LDOs supporting both VIN- and EXTVCC-derived INTVCC (5.25V or 7.5V), and precision current sensing with foldback limiting. The TRACK/SS pin enables soft-start or supply tracking by regulating VFB to the smaller of 0.8V or the applied TRACK/SS voltage.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 36V - supports 12V/24V automotive, telecom, and wide-range battery systems without pre-regulation. |
| Output Voltage Range | 0.8V to 10V - programmable via external resistor divider; 0.8V ±1% reference ensures tight regulation across load/temperature. |
| No-Load Quiescent Current | 80µA - extends runtime in always-on battery systems such as IoT sensors and portable medical devices. |
| Switching Frequency | 140kHz to 650kHz (phase-lockable) - balances efficiency vs. size; higher frequencies allow smaller magnetics and capacitors. |
| Max Duty Cycle | 99.4% - enables operation with minimal VIN–VOUT differential (e.g., 5V→4.95V), critical for high-efficiency low-dropout conversion. |
| Light-Load Modes | Burst Mode®, pulse-skipping, or forced continuous - selectable via PLLIN/MODE pin to optimize efficiency, ripple, or EMI per application need. |
| Package | 20-pin 4mm × 5mm QFN (UFD) with exposed thermal pad - provides low θJA = 37°C/W and compact footprint for space-constrained PCBs. |
Pinout & Package
Package: 20-pin plastic QFN (4mm × 5mm), exposed thermal pad (Pin 21) connected to SGND. Requires soldering of exposed pad for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ITH (Pin 1) | Error amplifier output / compensation node | Sets peak inductor current; connects to RC network for OPTI-LOOP® compensation across wide COUT/ESR ranges. |
| TRACK/SS (Pin 2) | Soft-start and tracking input | Internal 1µA pull-up charges external capacitor for linear VOUT ramp; also accepts resistor divider for supply tracking during startup. |
| VFB (Pin 3) | Feedback input | Compares divided output voltage to 0.8V reference; accuracy ±1% ensures stable regulation under load transients. |
| SGND (Pin 4, Pin 21) | Small-signal ground | Must be routed separately from PGND to avoid noise coupling into feedback and control loops. |
| PGND (Pin 5) | Power ground | Return path for bottom MOSFET source, Schottky anode, and input capacitor - critical for current-sense accuracy and EMI control. |
| BG (Pin 6) | Bottom gate driver output | Drives synchronous N-MOSFET source-to-ground; swing = 0V to INTVCC (5.25V or 7.5V). |
| INTVCC (Pin 7) | Internal LDO output | Powers control circuitry and gate drivers; bypassed with ≥4.7µF low-ESR capacitor to PGND. |
| EXTVCC (Pin 8) | External VCC input | Enables higher-efficiency INTVCC sourcing from secondary rail (e.g., converter output); switchover at 4.7V with 0.2V hysteresis. |
| VIN (Pin 9) | Main input supply | Connects to bulk input capacitor; absolute max 36V; powers internal LDO when EXTVCC is inactive. |
| SW (Pin 10) | Switch node | Connects to inductor and top MOSFET drain; voltage swings from ~–0.3V (Schottky drop) to VIN. |
| TG (Pin 11) | Top gate driver output | Floating driver output referenced to SW; swing = SW to (SW + INTVCC – 0.5V); requires bootstrap capacitor (BOOST–SW). |
| BOOST (Pin 12) | Bootstrap supply | Charged via external Schottky diode from INTVCC; supplies floating bias for TG driver during high-side conduction. |
| RUN (Pin 13) | Enable/shutdown control | Logic-level input; <0.7V disables controller, reducing IQ to 10µA; internal 0.5µA pull-up enables auto-start. |
| SENSE– (Pin 14) | Current sense negative input | Connects to low-side of RSENSE; used with SENSE+ for differential current sensing and foldback limiting. |
| SENSE+ (Pin 15) | Current sense positive input | Connects to high-side of RSENSE; combined with SENSE– and ITH voltage to set current trip threshold (80–115mV range). |
| PGOOD (Pin 16) | Power-good indicator | Open-drain output pulled low if VFB deviates >±10% from 0.8V; used for system sequencing and fault reporting. |
| PLLIN/MODE (Pin 17) | PLL sync input / light-load mode select | Accepts external clock (140–650kHz) for PolyPhase® sync; also selects Burst Mode® (GND), continuous (INTVCC), or pulse-skipping (mid-voltage). |
| PHASMD (Pin 18) | Phase selector | Configures CLKOUT phase relationship relative to TG for multi-phase interleaving (e.g., 0° or 180° offset). |
| CLKOUT (Pin 19) | Output clock signal | Open-drain clock output for daisy-chaining additional controllers; frequency matches internal oscillator or synced PLL. |
| PLLLPF (Pin 20) | PLL low-pass filter | Connects to RC network for PLL loop filtering when synchronizing to external clock; sets lock range and stability. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance and allows stable operation with wide-ranging ESR values - reduces BOM cost and layout sensitivity. |
| 80µA No-Load Quiescent Current | Extends battery life in standby or intermittent-use applications without sacrificing transient response or regulation accuracy. |
| Dual N-Channel MOSFET Drive | Enables high-efficiency synchronous rectification with external discrete FETs - avoids Schottky losses and improves thermal performance. |
| Adjustable Soft-Start / Tracking | Prevents inrush current and enables controlled power-up sequencing with other rails - essential for FPGA, ASIC, and multi-rail SoC systems. |
| Output Overvoltage Protection | PGOOD asserts low if VFB exceeds ±10% of 0.8V - provides fail-safe monitoring for downstream load protection. |
| EXTVCC-Powered INTVCC | Reduces power loss by sourcing gate drive from efficient secondary rail instead of main input - improves overall system efficiency by up to 1–2%. |
Applications
| Automotive Infotainment Power | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering 3.3V/5V logic rails in head-unit MCU, display interface, and audio codecs from 12V battery with cold-crank tolerance. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing high-current, low-noise DC/DC conversion with precise soft-start and PGOOD sequencing. Use Value: 4V–36V input range handles automotive transients; 80µA IQ preserves battery during sleep; PGOOD enables safe boot order with MCU and peripherals. | Use Scenario: Generating isolated 5V and 3.3V supplies for analog sensor front-ends and digital communication interfaces in DIN-rail mounted controllers. IC Role / Device Role / Timing Role: High-reliability step-down controller delivering stable output under variable industrial loads and temperature extremes (–40°C to 85°C). Use Value: ±1% VOUT accuracy ensures ADC reference stability; EXTVCC support enables efficient cascaded regulation; 99.4% duty cycle maintains regulation during brownouts. |
| Telecom Base Station Bias Supply | Portable Medical Diagnostic Device |
Use Scenario: Providing tightly regulated 5V/1.2V rails for RF amplifiers and FPGA configuration in remote radio units powered from 48V PoE or battery backup. IC Role / Device Role / Timing Role: Phase-lockable controller enabling synchronized PolyPhase® operation across multiple converters to reduce input/output ripple and EMI. Use Value: CLKOUT and PHASMD pins allow precise interleaving; 650kHz max frequency enables compact magnetics; PGOOD supports hot-swap and redundancy management. | Use Scenario: Powering low-power microcontroller, OLED display, and analog front-end in handheld ultrasound or glucose monitor operating from single-cell Li-ion. IC Role / Device Role / Timing Role: Ultra-low-IQ buck controller delivering long standby time while maintaining fast wake-up response and accurate voltage regulation. Use Value: 80µA no-load IQ extends battery life >3× vs standard controllers; TRACK/SS enables smooth ramp-up to avoid sensor initialization errors; 0.8V reference simplifies feedback design. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous step-down controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3833EUFD#PBF | Single-output, no PGOOD, no TRACK/SS, lower max frequency (400kHz), no PLL sync, 16-pin QFN | Lacks sequencing, tracking, and PolyPhase® capability - suitable only for basic fixed-VOUT applications | Select only if PGOOD, soft-start, and synchronization are unnecessary and board space permits larger inductors due to lower fSW. |
| MP2918GL-Z | Monolithic 30V synchronous buck (integrated FETs), 100µA IQ, no EXTVCC, no PLL, 16-pin QFN | Integrated solution eliminates external MOSFETs but limits max current and thermal flexibility; no EXTVCC reduces efficiency in multi-rail systems | Choose when board area is critical and output current ≤12A; avoid when gate drive optimization, EXTVCC efficiency, or PolyPhase® sync is required. |
Compared with LTC3833EUFD#PBF and MP2918GL-Z, the LTC3835IUFD#PBF uniquely combines ultra-low IQ, full-feature sequencing (TRACK/SS, PGOOD), phase-lockable PolyPhase® capability, and EXTVCC-enabled gate drive efficiency - making it optimal for high-reliability, multi-rail, and battery-sensitive designs where control flexibility and system-level integration matter.
Availability
LTC3835IUFD#PBF is available at Aetrix Electronics and suitable for automotive infotainment, industrial PLC I/O modules, and portable medical diagnostic devices requiring stable component supply, extended temperature operation (–40°C to 85°C), and long-term lifecycle assurance.
Supply support for LTC3835IUFD#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 its high-performance analog and power management portfolio with rigorous qualification and long-term support.
The LTC3835IUFD#PBF belongs to Linear's high-efficiency synchronous controller product line, designed specifically for demanding DC/DC conversion in automotive, telecom, and battery-powered systems where low IQ, precision regulation, and flexible light-load operation are critical.
FAQ
What is the maximum guaranteed phase-lockable frequency range for the LTC3835IUFD#PBF?
The LTC3835IUFD#PBF guarantees phase-lock capability from 140kHz to 650kHz when an external clock is applied to the PLLIN/MODE pin. This range is validated across temperature and process corners, and requires an external RC filter on the PLLLPF pin for stable lock. Operation outside this band may not achieve reliable synchronization.
How does the EXTVCC pin improve efficiency in the LTC3835IUFD#PBF?
The EXTVCC pin allows the LTC3835IUFD#PBF to derive INTVCC from an external rail (e.g., a secondary converter output) instead of VIN. When EXTVCC > 4.7V, the internal LDO switches from 5.25V (VIN-sourced) to 7.5V (EXTVCC-sourced), reducing gate drive losses and improving overall system efficiency - especially beneficial in cascaded or multi-output power architectures.
Can the LTC3835IUFD#PBF operate in dropout, and what is its minimum on-time?
Yes, the LTC3835IUFD#PBF supports ultra-low dropout operation with up to 99.4% duty cycle. Its minimum on-time is 180ns (typical), enabling stable regulation even when VIN approaches VOUT - critical for high-efficiency point-of-load conversion in battery-fed systems where input voltage sags under load.
What are the key differences between Burst Mode®, pulse-skipping, and forced continuous operation in the LTC3835IUFD#PBF?
The LTC3835IUFD#PBF selects light-load behavior via the PLLIN/MODE pin: Burst Mode® (GND) maximizes efficiency (<100µA IQ) but increases ripple; pulse-skipping (mid-voltage) maintains constant frequency down to ~1% load with low ripple and moderate efficiency; forced continuous (INTVCC) eliminates ripple discontinuity but sacrifices light-load efficiency. All three are supported without external components.
Is the LTC3835IUFD#PBF pin-compatible with the LTC3835-1 variant?
No, the LTC3835IUFD#PBF is not pin-compatible with the LTC3835-1. The LTC3835-1 uses a 16-pin 3mm × 5mm DFN (GN16) package and omits CLKOUT, EXTVCC, and PGOOD functions. The LTC3835IUFD#PBF uses a 20-pin 4mm × 5mm QFN (UFD) package and includes all three features - requiring distinct PCB layout and schematic implementation.
LTC3835IUFD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 4V ~ 36V
- Frequency - Switching:
- 250kHz ~ 530kHz
- Duty Cycle (Max):
- 99.4%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Enable, Phase Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-QFN (4x5)
LTC3835IUFD#PBF FAQ
1.How can I place an order for LTC3835IUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3835IUFD#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 LTC3835IUFD#PBF reliable?
The price and inventory of LTC3835IUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3835IUFD#PBF is usually 5 days.
3.What payment methods are accepted for LTC3835IUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3835IUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3835IUFD#PBF?
LTC3835IUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3835IUFD#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 LTC3835IUFD#PBF?
For technical support, including LTC3835IUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3835IUFD#PBF requirements.
6.How does Aetrix verify that LTC3835IUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3835IUFD#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 LTC3835IUFD#PBF meets industry standards.
7.What is the process for return or replacement of LTC3835IUFD#PBF?
All LTC3835IUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3835IUFD#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 LTC3835IUFD#PBF part is unused and in its original packaging.
Return procedure for LTC3835IUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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