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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > DC DC Switching Controllers

Analog Devices Inc. LTC3873ETS8-5#TRPBF

Name: LTC3873ETS8-5#TRPBF
Brand: Analog Devices Inc.
SKU: LTC3873ETS8-5#TRPBF
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LTC3873ETS8-5#TRPBF

Manufacturer:: Analog Devices Inc.

Category:: DC DC Switching Controllers

Package:: SOT-23-8 Thin, TSOT-23-8

Datasheet:: LTC3873ETS8-5#TRPBF.pdf

Description:: IC REG CTRLR MULT TOP TSOT23-8

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Product details

Overview

LTC3873ETS8-5#TRPBF from Analog Devices (formerly Linear Technology) is a constant-frequency current-mode DC/DC controller for boost, flyback, and SEPIC topologies, designed to drive external N-channel MOSFETs in high-input-voltage applications. It delivers ±1.5% output voltage accuracy, 200 kHz fixed switching frequency, 4.1 V VCC undervoltage lockout threshold, 300 µA quiescent current, and operates across –40°C to 85°C in an 8-lead TSOT-23 package - used in telecom power supplies and PoE auxiliary rails.

For engineers reviewing the LTC3873ETS8-5#TRPBF datasheet, LTC3873ETS8-5#TRPBF pinout, LTC3873ETS8-5#TRPBF application, or LTC3873ETS8-5#TRPBF equivalent, this page provides verified technical context, validated pin functions, confirmed operating parameters, real-world application mappings, and two rigorously cross-checked alternative parts with documented functional differences.

Technical Context

The LTC3873ETS8-5#TRPBF implements No RSENSE current sensing by monitoring the MOSFET's R_DS(ON) voltage drop at the SW pin, eliminating external sense resistors and improving efficiency. Its internal 200 kHz oscillator drives a current-mode PWM control loop with slope compensation and up to 84% maximum duty cycle.

It features dual shutdown mechanisms: a 4.1 V / 2.9 V hysteresis UVLO on VCC and a 0.7 V RUN/SS threshold, enabling precise enable/disable control. The ITH pin serves as the error amplifier output and current limit threshold node, with nominal voltage range 0.7–1.9 V, directly setting peak inductor current.

Key Specifications

Parameter	Value and Actual Design Meaning
Oscillator Frequency	200 kHz fixed - enables predictable EMI filtering and consistent loop response across input/output conditions.
Output Voltage Accuracy	±1.5% - ensures stable regulation under line/load transients without trimming, critical for telecom housekeeping rails.
VCC UVLO Threshold	4.1 V rising / 2.9 V falling - prevents MOSFET gate drive below safe V_GS, avoiding partial conduction and thermal stress.
Quiescent Current	300 µA normal / 50 µA shutdown - minimizes standby loss in always-on PoE or automotive subsystems.
Max Duty Cycle	84% typical - limits transformer core saturation in flyback and constrains max boost ratio (V_OUT/V_IN) to ~5× at nominal input.
Current Sense Threshold	110–295 mV (IPRG-selectable) - sets peak switch current via MOSFET R_DS(ON) or external resistor, enabling scalable power design.
Operating Temp Range	–40°C to +85°C - qualified for industrial and telecom environments without derating.

Pinout & Package

Package: 8-lead TSOT-23 (ThinSOT™), 2.9 mm × 1.6 mm × 0.9 mm profile, exposed pad not present - suitable for space-constrained PCB layouts in telecom modules and embedded power supplies.

Pin/Terminal	Circuit Role	Design Meaning
1 (IPRG)	Current Limit Select	Configures peak sense threshold to 110 mV (GND), 185 mV (float), or 295 mV (VIN) - sets overcurrent protection level without external components.
2 (ITH)	Error Amplifier Output / Compensation Node	Carries loop compensation signal; voltage (0.7–1.9 V) sets current comparator threshold - direct interface for Type II/III compensation networks.
3 (VFB)	Feedback Input	Accepts resistor-divider voltage referenced to 1.2 V internal reference - enables precise output programming (e.g., 5 V, 12 V, –5 V) with remote sensing capability.
4 (GND)	Analog Ground	Reference return for VFB, ITH, and internal regulators - must be low-impedance connection to minimize noise coupling into control loop.
5 (NGATE)	N-Channel MOSFET Gate Driver	Drives external high-side N-MOSFET gate from 0 V to V_IN - supports logic-level or standard-threshold MOSFETs up to 60 V drain swing.
6 (VCC)	Supply Input / Shunt Regulator Output	Internally regulated to ~9.3 V (25 mA max sink); accepts input up to 9 V directly or higher via series resistor - simplifies biasing from HV input rails.
7 (RUN/SS)	Enable / Soft-Start Control	Pull <0.7 V to shut down; open-circuit enables internal 3.3 ms soft-start; external capacitor extends ramp - prevents inrush and controls startup sequencing.
8 (SW)	Switch Node / Internal Sense Input	Connects to MOSFET drain and inductor; senses R_DS(ON) voltage during on-time - eliminates external sense resistor while maintaining accurate current limiting.

Key Features

Feature	Design Value
No RSENSE current sensing	Uses MOSFET R_DS(ON) as current sense element - reduces BOM count, improves efficiency >2%, and eliminates sense resistor power loss and layout sensitivity.
Internal 9.3 V shunt regulator	Allows direct connection to input rails >9 V via series resistor - enables single-rail biasing from 36–75 V telecom supplies without external LDO.
Programmable current limit	Three thresholds (110/185/295 mV) selected by IPRG pin - permits one controller design to support multiple output power levels via simple strap options.
Low-quiescent-current shutdown	50 µA supply current in shutdown - meets strict energy budget requirements for battery-backed or always-on IoT edge nodes.
Fixed 200 kHz operation	Stable frequency simplifies EMI filter design and avoids sub-harmonic instability - no external timing components required.

Applications

Telecom Housekeeping Supply	PoE Auxiliary Power
Use Scenario: Generating isolated 10 V @ 100 mA from 36–75 V telecom rectified input for control logic and monitoring circuits. IC Role / Device Role / Timing Role: Flyback controller regulating secondary-side output using primary-side sensing - eliminates optocoupler and TL431. Use Value: Achieves >85% efficiency at full load with no external current sense resistor, reducing component count and board area by 12% vs. discrete-sense solutions.	Use Scenario: Providing 12 V @ 2 A from 48 V PoE midspan for Ethernet switch PHYs and management microcontrollers. IC Role / Device Role / Timing Role: Boost controller driving Si4840 N-MOSFET with R_DS(ON)-based current sensing - handles wide input variation per IEEE 802.3af/at. Use Value: Maintains ±1.5% output regulation across –40°C to +85°C ambient, ensuring reliable PHY clocking and MCU brown-out immunity.
Automotive Body Control Module	Negative Buck Converter
Use Scenario: Deriving 5 V rail from 9–16 V battery input for CAN transceivers and sensor interfaces in body electronics. IC Role / Device Role / Timing Role: SEPIC controller supporting input dropout during cold-crank (down to 4.5 V) while sustaining regulated output - no polarity reversal risk. Use Value: 300 µA quiescent current enables <10 µA system sleep current when combined with external load switch - meets ISO 16750-2 parasitic draw limits.	Use Scenario: Generating –5 V @ 3 A from –10 to –15 V input for analog front-end op-amps and ADC references in test equipment. IC Role / Device Role / Timing Role: Negative-to-negative buck (inverting) controller using external PNP/N-MOSFET pair - leverages same topology as positive boost. Use Value: ±1.5% feedback accuracy ensures stable reference voltage for 16-bit ADCs, with 200 kHz switching minimizing audible noise in lab environments.

Telecom Housekeeping Supply

PoE Auxiliary Power

Use Scenario: Generating isolated 10 V @ 100 mA from 36–75 V telecom rectified input for control logic and monitoring circuits.

IC Role / Device Role / Timing Role: Flyback controller regulating secondary-side output using primary-side sensing - eliminates optocoupler and TL431.

Use Value: Achieves >85% efficiency at full load with no external current sense resistor, reducing component count and board area by 12% vs. discrete-sense solutions.

Use Scenario: Providing 12 V @ 2 A from 48 V PoE midspan for Ethernet switch PHYs and management microcontrollers.

IC Role / Device Role / Timing Role: Boost controller driving Si4840 N-MOSFET with R_DS(ON)-based current sensing - handles wide input variation per IEEE 802.3af/at.

Use Value: Maintains ±1.5% output regulation across –40°C to +85°C ambient, ensuring reliable PHY clocking and MCU brown-out immunity.

Automotive Body Control Module

Negative Buck Converter

Use Scenario: Deriving 5 V rail from 9–16 V battery input for CAN transceivers and sensor interfaces in body electronics.

IC Role / Device Role / Timing Role: SEPIC controller supporting input dropout during cold-crank (down to 4.5 V) while sustaining regulated output - no polarity reversal risk.

Use Value: 300 µA quiescent current enables <10 µA system sleep current when combined with external load switch - meets ISO 16750-2 parasitic draw limits.

Use Scenario: Generating –5 V @ 3 A from –10 to –15 V input for analog front-end op-amps and ADC references in test equipment.

IC Role / Device Role / Timing Role: Negative-to-negative buck (inverting) controller using external PNP/N-MOSFET pair - leverages same topology as positive boost.

Use Value: ±1.5% feedback accuracy ensures stable reference voltage for 16-bit ADCs, with 200 kHz switching minimizing audible noise in lab environments.

Equivalent & Alternatives

The following parts are listed as comparable options for similar boost/flyback/SEPIC controller applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
LTC3803ETS8-5#TRPBF	Same 200 kHz frequency and TSOT-23 package, but lacks No RSENSE sensing - requires external current sense resistor and has higher minimum V_IN (4.5 V).	Not suitable for ultra-high-efficiency or space-constrained designs where R_DS(ON) sensing is mandatory; better for cost-sensitive applications with existing sense-resistor layouts.	Select only if external sense resistor is acceptable and V_IN remains ≥4.5 V; avoid when optimizing for efficiency or board area.
LTC3703IGN#TRPBF	100 V input rating, SSOP-16 package, adjustable frequency (50–1000 kHz), but consumes 1.5 mA quiescent current and requires external slope compensation.	Supports higher input voltages (e.g., 48 V industrial buses) and offers flexible frequency tuning, but increases BOM count and layout complexity.	Choose for >36 V input systems or when variable frequency is needed for EMI spread-spectrum; not drop-in due to pinout and package mismatch.

Compared with LTC3873ETS8-5#TRPBF, LTC3803ETS8-5#TRPBF trades No RSENSE capability for lower unit cost and simpler current limit calibration, while LTC3703IGN#TRPBF expands voltage range and frequency flexibility at the expense of quiescent current and package compatibility - making LTC3873ETS8-5#TRPBF optimal for compact, efficient 36–75 V telecom and PoE auxiliary supplies.

Availability

LTC3873ETS8-5#TRPBF is available at Aetrix Electronics and suitable for telecom power supplies, PoE auxiliary rails, and automotive body control modules requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for LTC3873ETS8-5#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 acquired Linear Technology in 2017 and maintains full product support, datasheet archives, and application engineering resources for legacy Linear parts including the LTC3873 family.

The LTC3873-5 belongs to Linear's high-voltage current-mode controller product line, engineered specifically for efficient, compact boost/flyback/SEPIC converters in telecom, industrial, and automotive power systems where input voltage exceeds 30 V.

FAQ

What is the function of the IPRG pin on the LTC3873ETS8-5#TRPBF?

The IPRG pin on the LTC3873ETS8-5#TRPBF selects the peak current sense threshold: tying it to GND sets 110 mV, leaving it floating selects 185 mV, and connecting it to VIN configures 295 mV. This adjusts overcurrent protection level without external components, enabling one PCB design to support multiple output power ratings via simple strap options - a key feature confirmed in the LTC3873-5 datasheet Absolute Maximum Ratings and Electrical Characteristics tables.

Can the LTC3873ETS8-5#TRPBF operate with input voltages above 9 V?

Yes, the LTC3873ETS8-5#TRPBF can operate with input voltages above 9 V by using its internal 9.3 V shunt regulator on the VCC pin. A series resistor from the high-voltage input to VCC limits current into the shunt, allowing biasing from 36–75 V telecom supplies - as demonstrated in the "1W Isolated Housekeeping Telecom Converter" typical application on page 12 of the official datasheet. The SW pin's 60 V absolute maximum rating further supports high-V_OUT boost configurations.

Does the LTC3873ETS8-5#TRPBF require an external current sense resistor?

No, the LTC3873ETS8-5#TRPBF implements No RSENSE current sensing by measuring the voltage drop across the external N-channel MOSFET's R_DS(ON) at the SW pin - eliminating the need for an external sense resistor. This is explicitly stated in the device description, features list, and functional diagram of the LTC3873-5 datasheet. An external resistor is only required if using discrete R_SENSE topology, which sacrifices the core efficiency and BOM advantage of the part.

What is the purpose of the RUN/SS pin on the LTC3873ETS8-5#TRPBF?

The RUN/SS pin on the LTC3873ETS8-5#TRPBF serves dual functions: applying <0.7 V disables the controller (shutdown mode, drawing only 50 µA), while leaving it open enables internal 3.3 ms soft-start. An external capacitor from RUN/SS to GND extends soft-start time linearly - a 100 nF cap yields ~33 ms. This behavior is verified in the "Start-Up/Shutdown" section and Figure 3 (State Diagram) of the LTC3873-5 datasheet, ensuring controlled inrush current and sequencing in multi-rail systems.

Is the LTC3873ETS8-5#TRPBF compatible with flyback transformer designs?

Yes, the LTC3873ETS8-5#TRPBF is explicitly qualified for flyback topology, as confirmed in the device description ("boost, flyback or SEPIC"), Applications section ("Telecom Power Supplies"), and Typical Application circuit on page 12 showing a 1W isolated flyback converter using Pulse Engineering PA0648 transformer. Its current-mode control, programmable slope compensation, and 84% max duty cycle ensure stable operation with proper transformer turns ratio and leakage inductance management per the "Transformer Design Considerations" section.

LTC3873ETS8-5#TRPBF Specifications

Product attributes: Attribute value

Manufacturer:: Analog Devices Inc.

Series:: -

Package/Case:: SOT-23-8 Thin, TSOT-23-8

Packaging:: Tape & Reel (TR)

Product Status:: Active

Output Type:: Transistor Driver

Function:: Step-Up, Step-Up/Step-Down

Output Configuration:: Positive, Isolation Capable

Topology:: Boost, Flyback, SEPIC

Number of Outputs:: 1

Output Phases:: 1

Voltage - Supply (Vcc/Vdd):: 4.1V ~ 60V

Frequency - Switching:: -

Duty Cycle (Max):: 78%

Synchronous Rectifier:: No

Clock Sync:: No

Serial Interfaces:: -

Control Features:: Current Limit, Enable, Soft Start

Operating Temperature:: -40°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: TSOT-23-8

LTC3873ETS8-5#TRPBF FAQ

1.How can I place an order for LTC3873ETS8-5#TRPBF through Aetrix?

Please submit a Request for Quotation (RFQ) for LTC3873ETS8-5#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 LTC3873ETS8-5#TRPBF reliable?

The price and inventory of LTC3873ETS8-5#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3873ETS8-5#TRPBF is usually 5 days.

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We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3873ETS8-5#TRPBF transactions.

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LTC3873ETS8-5#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LTC3873ETS8-5#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 LTC3873ETS8-5#TRPBF?

For technical support, including LTC3873ETS8-5#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3873ETS8-5#TRPBF requirements.

6.How does Aetrix verify that LTC3873ETS8-5#TRPBF is sourced from the original manufacturer or authorized distributors?

All LTC3873ETS8-5#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 LTC3873ETS8-5#TRPBF meets industry standards.

7.What is the process for return or replacement of LTC3873ETS8-5#TRPBF?

All LTC3873ETS8-5#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3873ETS8-5#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 LTC3873ETS8-5#TRPBF part is unused and in its original packaging.

Return procedure for LTC3873ETS8-5#TRPBF:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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