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Analog Devices Inc. LTC3873ITS8-5#TRMPBF
- Part No.:
- LTC3873ITS8-5#TRMPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- SOT-23-8 Thin, TSOT-23-8
- Datasheet:
-
LTC3873ITS8-5#TRMPBF.pdf
- Description:
- IC REG CTRLR MULT TOP TSOT23-8
- Quantity:
- Payment:
- Shipping:
Inventory:2,756
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Product details
Overview
LTC3873ITS8-5#TRMPBF from Analog Devices (formerly Linear Technology) is a constant-frequency current-mode DC/DC controller for boost, flyback, and SEPIC topologies, driving external N-channel MOSFETs in high-input-voltage telecom and automotive power supplies. It delivers ±1.5% output voltage accuracy, 200kHz fixed switching frequency, 4.1V VCC undervoltage lockout threshold, and operates across –40°C to +125°C with 300μA quiescent current.
For engineers reviewing the LTC3873ITS8-5#TRMPBF datasheet, LTC3873ITS8-5#TRMPBF pinout, LTC3873ITS8-5#TRMPBF application, or LTC3873ITS8-5#TRMPBF equivalent, key selection criteria include its No RSENSE current sensing capability, internal 9.3V shunt regulator for high-VIN biasing, programmable soft-start via RUN/SS pin, and compatibility with wide input/output voltage ranges defined by external components-not IC limits.
Technical Context
The LTC3873ITS8-5#TRMPBF implements peak current-mode control with built-in slope compensation to prevent subharmonic oscillation at duty cycles >50%. Its error amplifier outputs a control voltage at the ITH pin (0.7V–1.9V range), which sets the current comparator threshold dynamically during load transients.
It supports three current limit configurations via the IPRG pin (tied to GND, VIN, or floating), yielding peak sense thresholds of 95mV, 265mV, or 165mV respectively at low duty cycle. The 80% maximum duty cycle clamp prevents transformer saturation in flyback designs and constrains boost conversion ratio per VOUT(MAX) = VIN(MIN) / (1 − 0.8).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 200 kHz fixed - enables predictable EMI filtering and consistent loop compensation design. |
| Output Voltage Accuracy | ±1.5% - ensures stable regulation under line/load/temperature variation without trimming. |
| VCC UVLO Threshold | Rising: 4.1 V - guarantees sufficient gate drive voltage for logic-level N-MOSFETs before enabling operation. |
| Quiescent Current | 300 μA normal / 50 μA shutdown - minimizes standby power loss in battery-backed or always-on systems. |
| Max Duty Cycle | 80% typical - limits transformer core reset time in flyback and defines max boost ratio (e.g., 5× step-up at VIN = 12V → VOUT ≤ 60V). |
| Current Sense Options | No RSENSE (MOSFET RDS(ON)) or external resistor - eliminates sense resistor losses and improves efficiency in high-current designs. |
| Package | 8-lead TSOT-23 (ThinSOT) - 3mm × 1.75mm footprint with 0.65mm pitch, optimized for compact high-density PCB layouts. |
Pinout & Package
Package: 8-lead TSOT-23 (ThinSOT), 3.0mm × 1.75mm × 1.0mm height, lead-free, RoHS-compliant, rated for –40°C to +125°C operating temperature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| IPRG (Pin 1) | Current limit select input | Configures peak current threshold: GND = 95 mV, float = 165 mV, VIN = 265 mV - enables optimization for MOSFET RDS(ON) or precision resistor sensing. |
| ITH (Pin 2) | Error amplifier output / compensation node | 0.7–1.9 V range controls PWM duty cycle; external RC network here sets loop bandwidth and phase margin. |
| VFB (Pin 3) | Feedback input | Compares divided output voltage to 1.2 V internal reference; 25 nA input bias allows high-value resistive dividers to minimize loading. |
| GND (Pin 4) | Analog and power ground reference | Common return for feedback, error amp, and internal regulators - must be low-impedance connection to minimize noise coupling. |
| NGATE (Pin 5) | N-channel MOSFET gate driver output | Drives external high-side switch with rail-to-rail swing (0 V to VIN); 40 ns rise/fall times support fast switching with minimal dead-time loss. |
| VCC (Pin 6) | Supply input with internal 9.3 V shunt regulator | Accepts up to 9 V directly or higher VIN via series resistor; 25 mA max sink capacity defines minimum bias resistor value. |
| RUN/SS (Pin 7) | Shutdown enable / soft-start timing | Pulled below 0.7 V disables controller; open-circuit enables 3.3 ms internal soft-start; external capacitor extends ramp time linearly (3 μA charge current). |
| SW (Pin 8) | Switch node / current sense input | Connects to MOSFET drain and inductor; senses voltage drop across RDS(ON) or external resistor; rated to 60 V absolute max. |
Key Features
| Feature | Design Value |
|---|---|
| No RSENSE current sensing | Eliminates power loss and board space for external sense resistor; leverages MOSFET RDS(ON) for current limiting in high-efficiency boost/flyback converters. |
| Internal 9.3 V shunt regulator | Enables direct high-VIN biasing (e.g., 36–75 V telecom rails) using only a single series resistor - simplifies auxiliary supply design. |
| Programmable soft-start | Prevents inrush current and output overshoot via RUN/SS pin capacitor; 3.3 ms default or user-extended ramp avoids stress on input capacitors and MOSFETs. |
| 200 kHz fixed-frequency operation | Ensures consistent EMI signature and simplifies filter design; avoids variable-frequency jitter while maintaining light-load efficiency via cycle skipping. |
| –40°C to +125°C operation | Qualified for automotive under-hood and industrial environments where thermal derating and long-term reliability are critical. |
Applications
| Telecom Housekeeping Supply | Automotive 12V Boost Converter |
|---|---|
Use Scenario: Generating isolated 10V/100mA bias for control circuitry in 36–75V telecom rectifier modules. IC Role / Device Role / Timing Role: Primary-side flyback controller regulating output via optocoupler feedback; 200kHz switching synchronizes with system clock domains. Use Value: No RSENSE sensing reduces component count and improves efficiency over discrete current-sense solutions at 1W output. | Use Scenario: Stepping up 9–15V vehicle battery to stable 12V for infotainment head units during cold-crank conditions. IC Role / Device Role / Timing Role: Constant-frequency boost controller with 4.1V UVLO ensuring operation only when battery exceeds MOSFET gate threshold. Use Value: 300μA quiescent current prevents excessive battery drain during vehicle sleep mode. |
| Industrial PoE Midspan Power | Isolated Negative Buck Converter |
Use Scenario: Providing 48V-to-56V boost for IEEE 802.3at PoE midspan injectors delivering up to 30W per port. IC Role / Device Role / Timing Role: High-efficiency boost controller driving low-RDS(ON) MOSFET; IPRG pin configured for precise current limit during short-circuit events. Use Value: Adjustable current limit (95–265mV) enables accurate Class 4 PoE current limiting without calibration. | Use Scenario: Generating –5V from –10V to –15V input in legacy industrial instrumentation requiring negative rail sequencing. IC Role / Device Role / Timing Role: Negative-to-negative buck (inverting) controller using flyback topology with polarity-reversed transformer winding. Use Value: Internal 1.2V reference and ±1.5% accuracy maintain tight regulation despite wide input variation and temperature drift. |
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 | 200kHz fixed frequency, same TSOT-23 package, but no internal shunt regulator - requires external bias supply. | Limited to lower-input-voltage applications (<9V) unless externally powered; lacks No RSENSE capability. | Select when VIN < 9V and cost-sensitive designs omit shunt regulator complexity. |
| LTC3872EDDB-5#TRPBF | Same No RSENSE architecture and 200kHz frequency, but in 3mm × 2mm DFN package with exposed thermal pad. | Better thermal performance for >2A output currents; pinout differs - not pin-compatible with LTC3873ITS8-5#TRMPBF. | Choose for higher-power density or improved thermal management where PCB layout allows DFN rework. |
Compared with LTC3873ITS8-5#TRMPBF, LTC3803ETS8-5#TRPBF lacks high-VIN biasing and current-sense flexibility, while LTC3872EDDB-5#TRPBF offers superior thermal handling but requires layout revision due to different pinout and package footprint.
Availability
LTC3873ITS8-5#TRMPBF is available at Aetrix Electronics and suitable for telecom power supplies, automotive body electronics, and PoE midspan injectors requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC3873ITS8-5#TRMPBF 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-branded power management ICs.
The LTC3873 family was designed specifically for high-efficiency, high-voltage DC/DC conversion in space-constrained telecom and industrial systems - emphasizing No RSENSE sensing, wide input range, and robust thermal performance.
FAQ
What is the maximum input voltage that can safely power the LTC3873ITS8-5#TRMPBF?
The LTC3873ITS8-5#TRMPBF does not have a fixed maximum input voltage rating because it is powered via its VCC pin, which features an internal 9.3V shunt regulator. When biased through a resistor from a high-voltage source (e.g., 75V telecom rail), the shunt regulator clamps VCC to ~9.3V as long as current into VCC remains ≤25mA. Therefore, the practical upper limit depends on resistor selection and power dissipation - not the IC itself. The SW pin is rated to 60V, defining the maximum voltage seen at the switch node.
Does the LTC3873ITS8-5#TRMPBF support synchronous rectification?
No, the LTC3873ITS8-5#TRMPBF does not support synchronous rectification. It drives only a single external N-channel MOSFET via the NGATE pin and relies on an external diode (e.g., Schottky) for rectification in boost and flyback topologies. For synchronous designs, consider the LTC3703 or LTC3872 families, which provide complementary gate drive outputs.
How is the output voltage set on the LTC3873ITS8-5#TRMPBF?
The output voltage of the LTC3873ITS8-5#TRMPBF is set using a resistive divider from VOUT to GND, connected to the VFB pin. The internal reference is 1.2V, so VOUT = 1.2V × (1 + R1/R2), where R1 connects between VOUT and VFB, and R2 connects between VFB and GND. The VFB pin draws only 25nA, allowing high-resistance dividers (e.g., R1 = 24kΩ, R2 = 24kΩ for 2.4V output) to minimize static power loss.
Can the LTC3873ITS8-5#TRMPBF be used in SEPIC converter designs?
Yes, the LTC3873ITS8-5#TRMPBF is explicitly qualified for SEPIC (Single-Ended Primary Inductance Converter) topologies, as confirmed in its datasheet title, feature list, and typical application circuits. Its current-mode architecture, 200kHz fixed frequency, and ability to regulate with either MOSFET RDS(ON) or external sense resistor make it well-suited for non-inverting buck-boost applications requiring continuous input-output voltage overlap.
What is the purpose of the IPRG pin on the LTC3873ITS8-5#TRMPBF?
The IPRG pin on the LTC3873ITS8-5#TRMPBF selects the peak current limit threshold for the internal current comparator: tying IPRG to GND sets 95mV, leaving it floating sets 165mV, and connecting it to VIN sets 265mV (at low duty cycle). This allows designers to match the current limit to their chosen MOSFET's RDS(ON) or external sense resistor value - enabling precise overcurrent protection without recalculating sense networks across variants.
LTC3873ITS8-5#TRMPBF 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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TSOT-23-8
LTC3873ITS8-5#TRMPBF FAQ
1.How can I place an order for LTC3873ITS8-5#TRMPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3873ITS8-5#TRMPBF 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 LTC3873ITS8-5#TRMPBF reliable?
The price and inventory of LTC3873ITS8-5#TRMPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3873ITS8-5#TRMPBF is usually 5 days.
3.What payment methods are accepted for LTC3873ITS8-5#TRMPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3873ITS8-5#TRMPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3873ITS8-5#TRMPBF?
LTC3873ITS8-5#TRMPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3873ITS8-5#TRMPBF 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 LTC3873ITS8-5#TRMPBF?
For technical support, including LTC3873ITS8-5#TRMPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3873ITS8-5#TRMPBF requirements.
6.How does Aetrix verify that LTC3873ITS8-5#TRMPBF is sourced from the original manufacturer or authorized distributors?
All LTC3873ITS8-5#TRMPBF 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 LTC3873ITS8-5#TRMPBF meets industry standards.
7.What is the process for return or replacement of LTC3873ITS8-5#TRMPBF?
All LTC3873ITS8-5#TRMPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3873ITS8-5#TRMPBF, 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 LTC3873ITS8-5#TRMPBF part is unused and in its original packaging.
Return procedure for LTC3873ITS8-5#TRMPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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