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Analog Devices Inc. LT8315HFE#PBF
- Part No.:
- LT8315HFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 20-TSSOP (0.173", 4.40mm Width), 16 Leads, Exposed Pad
- Datasheet:
-
LT8315HFE#PBF.pdf
- Description:
- IC REG FLYBACK 800MA 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,296
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Product details
Overview
LT8315HFE#PBF from Analog Devices (formerly Linear Technology) is a high-voltage isolated flyback controller IC with integrated 630V/300mA power switch, enabling opto-isolator-free regulation via tertiary-winding voltage sampling. It operates from 18V to 560V input, delivers up to 15W output, and features quasi-resonant boundary-mode control for high efficiency and tight load regulation in telecom and industrial off-line supplies.
For engineers reviewing the LT8315HFE#PBF datasheet, LT8315HFE#PBF pinout, LT8315HFE#PBF application, or LT8315HFE#PBF equivalent, key selection considerations include its −40°C to 150°C junction temperature rating, 70μA quiescent current in Burst Mode, programmable constant-current/constant-voltage regulation, and TSSOP-20 package with high-voltage spacing for >500V isolation compliance.
Technical Context
The LT8315HFE#PBF implements boundary-mode (critical conduction) control using a sample-and-hold circuit triggered by dV/dt detection on the DCM pin, ensuring zero-current switching and eliminating subharmonic oscillation. Its internal 630V depletion-mode startup FET charges INTVCC at power-up, removing external bleeder components.
Regulation relies on direct sampling of the flyback pulse across a transformer tertiary winding - not opto-coupled feedback - with FB pin regulated to 1.22V and TC pin providing +4.1mV/°C PTAT compensation to offset diode forward-voltage drift. The VC pin controls both peak current limit and switching frequency via transconductance amplifier output.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 18V to 560V DC - supports wide-range off-line and battery-stack inputs without pre-regulation. |
| Integrated Switch | 630V/300mA MOSFET - enables single-chip isolated flyback designs up to 15W with no external HV switch. |
| Quiescent Current | 70μA in Burst Mode - minimizes no-load power loss for energy-efficient housekeeping supplies. |
| FB Regulation Voltage | 1.22V ±30mV - precise reference for output voltage programming via resistor divider on tertiary winding. |
| Operating Junction Temp | −40°C to 150°C - H-grade qualification ensures reliability in automotive under-hood and industrial high-temp environments. |
| Switching Frequency Range | 3.5kHz–142kHz - adaptive boundary/discontinuous mode operation maintains efficiency across full load range. |
| Current Limit Threshold | 120mV at SOURCE pin - sets overcurrent protection point with 80% design margin for robust short-circuit handling. |
Pinout & Package
LT8315HFE#PBF is housed in a thermally enhanced 20-pin TSSOP package (FE) with four pins removed (pins 4–7) to provide ≥8mm creepage/clearance for high-voltage isolation. Exposed pad (pin 21) must be soldered to PCB ground plane for thermal management (θJC = 10°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| DRAIN (1,2,3) | Drain of 630V power switch & startup FET | Connects to primary winding; carries full HV switching current; requires compact layout to minimize EMI. |
| SOURCE (18) | Source of power switch | Current-sense node; voltage drop across RSNS sets peak current limit (120mV threshold). |
| EN/UVLO (17) | Enable / undervoltage lockout input | 1.22V threshold with 65mV hysteresis; enables start-up control and brown-out protection. |
| FB (12) | Feedback input | Samples tertiary-winding flyback pulse; regulated to 1.22V for isolated output voltage control. |
| VC (13) | Voltage-controlled oscillator input | Loop compensation node; error current from GM amplifier sets switching frequency and current limit. |
| IREG/SS (14) | Current regulation / soft-start | 10μA sink current sets CC regulation point; capacitor adds soft-start delay. |
| TC (11) | Temperature compensation | PTAT voltage (1.22V @ 25°C, +4.1mV/°C) compensates diode VF drift for stable output over temperature. |
| DCM (10) | Discontinuous mode detector | Detects negative dV/dt on tertiary winding to trigger boundary-mode sampling and zero-current turn-on. |
| GND (15,20,21) | Ground reference | Three GND connections including exposed thermal pad; mandatory soldering required for thermal performance. |
Key Features
| Feature | Design Value |
|---|---|
| No-opto isolated regulation | Eliminates optocoupler, TL431, and associated bias network - reduces BOM cost, size, and aging-related drift. |
| Quasi-resonant boundary mode | Enables zero-current switching, improves efficiency >90%, reduces transformer size vs. CCM, and avoids subharmonic instability. |
| Depletion-mode startup FET | Charges INTVCC capacitor directly from DRAIN at startup - removes need for external bleeder resistor or auxiliary supply. |
| Constant-current/constant-voltage control | Independent CV (via FB) and CC (via IREG/SS) loops enable dual-mode regulation for LED drivers and battery chargers. |
| High-temperature H-grade rating | Guaranteed operation to 150°C junction temperature - qualified for automotive under-hood and industrial high-ambient applications. |
Applications
| Telecom Housekeeping Supply | Industrial Off-Line Sensor Power |
|---|---|
Use Scenario: Providing isolated 12V/200mA auxiliary power for FPGA configuration, MCU supervision, and interface logic in 48V telecom systems. IC Role / Device Role / Timing Role: Primary-side flyback controller regulating output via tertiary winding sampling; replaces opto-coupled feedback loop. Use Value: Enables compact, low-noise, long-life power solution with <70μA no-load consumption and no opto aging or gain variation. | Use Scenario: Generating 5V/100mA isolated supply for analog sensor front-ends and isolated ADCs in factory automation PLCs. IC Role / Device Role / Timing Role: High-voltage flyback controller operating from 24–300V DC bus; uses boundary mode for stable light-load regulation. Use Value: Delivers tight line/load regulation (<±3%) across wide input range without secondary-side feedback components. |
| Electric Vehicle Battery Stack Monitor | Medical Isolated Auxiliary Power |
Use Scenario: Powering isolated cell-balancing ICs and voltage monitors across 200–500V EV battery packs with >5kV reinforced isolation. IC Role / Device Role / Timing Role: Primary-side controller with 630V switch and high-voltage spacing; samples tertiary winding for galvanic isolation. Use Value: Supports creepage/clearance compliance per IEC 60664-1 with TSSOP-20 FE package and eliminates opto failure modes in safety-critical systems. | Use Scenario: Delivering 3.3V/50mA isolated power for patient-connected monitoring circuits requiring 4kV RMS reinforced isolation per IEC 60601-1. IC Role / Device Role / Timing Role: Flyback controller implementing low-ripple Burst Mode operation to meet stringent EMI and leakage current limits. Use Value: Achieves <10mVpp output ripple at light loads and meets EN 55011 Class B emissions without added filtering. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage isolated flyback controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC28740DR | 650V/300mA switch; fixed-frequency QR control; no integrated TC compensation; 105°C max junction temp | Lacks PTAT-based diode compensation; requires external op-amp for CC regulation; lower temp grade | Choose UCC28740DR when cost sensitivity outweighs temperature stability requirements and diode VF drift is negligible. |
| MAX17690ATP+T | 650V/500mA switch; valley-switching QR control; 125°C max junction temp; no depletion startup FET | Requires external startup circuit; higher current rating but larger die; no integrated soft-start current source | Choose MAX17690ATP+T when >300mA peak switch current is needed and external startup design is acceptable. |
Compared with UCC28740DR and MAX17690ATP+T, the LT8315HFE#PBF uniquely integrates depletion-mode startup, TC-based diode compensation, and H-grade 150°C operation - making it optimal for unattended, high-reliability, wide-temperature isolated supplies where opto elimination and long-term stability are critical.
Availability
LT8315HFE#PBF is available at Aetrix Electronics and suitable for telecom housekeeping, industrial sensor interfaces, EV battery monitoring, and medical auxiliary power supplies requiring stable component supply, extended temperature operation, and high-voltage isolation integrity.
Supply support for LT8315HFE#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LT8315HFE#PBF belongs to the LT®83xx family of high-voltage isolated flyback controllers, designed specifically for opto-free, compact, and reliable off-line and high-input-voltage DC-DC conversion in space-constrained and thermally demanding applications.
FAQ
What is the maximum input voltage supported by the LT8315HFE#PBF?
The LT8315HFE#PBF supports an absolute maximum input voltage of 560V DC, with guaranteed operation across 18V to 560V. Its integrated 630V power switch and high-voltage spacing in the TSSOP-20 FE package enable direct connection to rectified AC mains or high-voltage DC buses without external voltage clamping.
How does the LT8315HFE#PBF achieve regulation without an opto-isolator?
The LT8315HFE#PBF samples the flyback pulse voltage from a dedicated tertiary winding on the transformer, using internal circuitry to detect the zero-current point and hold the sampled value for regulation. This eliminates the need for opto-isolators, reducing cost, size, and long-term drift while maintaining ±3% output accuracy across line and load.
What is the purpose of the TC pin on the LT8315HFE#PBF?
The TC pin on the LT8315HFE#PBF provides a buffered proportional-to-absolute-temperature (PTAT) voltage (1.22V at 25°C, +4.1mV/°C) used to compensate for the negative temperature coefficient of the output rectifier diode's forward voltage. Connecting a resistor from TC to FB corrects output voltage drift, enabling stable regulation across −40°C to 150°C.
Can the LT8315HFE#PBF be used for constant-current applications like LED drivers?
Yes, the LT8315HFE#PBF supports constant-current regulation via the IREG/SS pin, which sinks a precise 10μA current. By connecting a resistor from IREG/SS to GND, designers set the output current limit independently of voltage regulation - enabling dual-mode CV/CC operation ideal for LED drivers and battery charging circuits.
What is the significance of the "H" grade in LT8315HFE#PBF?
The "H" grade in LT8315HFE#PBF denotes guaranteed operation from −40°C to +150°C junction temperature - exceeding standard industrial (−40°C to +125°C) ratings. This makes the device suitable for under-hood automotive, high-ambient industrial, and other thermally demanding environments where long-term reliability is critical.
LT8315HFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width), 16 Leads, Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down, Step-Up/Step-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Flyback
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 18V
- Voltage - Input (Max):
- 560V
- Voltage - Output (Min/Fixed):
- -
- Voltage - Output (Max):
- -
- Current - Output:
- 800mA
- Frequency - Switching:
- 220Hz ~ 140kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP-EP
LT8315HFE#PBF FAQ
1.How can I place an order for LT8315HFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8315HFE#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 LT8315HFE#PBF reliable?
The price and inventory of LT8315HFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8315HFE#PBF is usually 5 days.
3.What payment methods are accepted for LT8315HFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8315HFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8315HFE#PBF?
LT8315HFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8315HFE#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 LT8315HFE#PBF?
For technical support, including LT8315HFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8315HFE#PBF requirements.
6.How does Aetrix verify that LT8315HFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8315HFE#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 LT8315HFE#PBF meets industry standards.
7.What is the process for return or replacement of LT8315HFE#PBF?
All LT8315HFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8315HFE#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 LT8315HFE#PBF part is unused and in its original packaging.
Return procedure for LT8315HFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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