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Analog Devices Inc. LT3959IUHE#PBF
- Part No.:
- LT3959IUHE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3959IUHE#PBF.pdf
- Description:
- IC REG BOOST CUK ADJ 6A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:253
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Product details
Overview
LT3959IUHE#PBF from Analog Devices (formerly Linear Technology) is a wide-input, current-mode DC/DC controller supporting boost, SEPIC, and inverting topologies with an integrated 6A/40V N-channel MOSFET. It operates from 1.6V to 40V input, regulates ±output voltages via a single FBX pin, and delivers up to 1.5A at VIN > 8V in SEPIC configuration-ideal for automotive 12V post-regulation and industrial power supplies.
For engineers reviewing the LT3959IUHE#PBF datasheet, LT3959IUHE#PBF pinout, LT3959IUHE#PBF application, or LT3959IUHE#PBF equivalent, key selection factors include its programmable 100kHz–1MHz switching frequency, PGOOD output voltage status reporting, internal soft-start, input UVLO with hysteresis, and thermal enhancement in the 36-lead QFN package.
Technical Context
The LT3959IUHE#PBF implements fixed-frequency current-mode control with dual error amplifiers-one for +1.6V regulation and one for –0.8V regulation-enabling seamless positive or negative output configuration using only the FBX pin. Its internal 6A/40V switch features 45mV current-sense threshold and on-resistance < 45mΩ at 25°C.
It integrates two independent LDOs: a DRIVE-powered 4.75V INTVCC regulator and a VIN-powered 3.75V INTVCC regulator, automatically selecting source based on supply conditions. Frequency foldback activates below FBX = ±0.2V to prevent inductor current runaway during start-up or short-circuit faults.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 1.6V to 40V - supports direct connection to automotive battery (cold-crank down to 1.6V) and industrial 24V/36V rails. |
| Switch Rating | 6A/40V N-MOSFET - enables high-current SEPIC/boost designs without external switch, reducing BOM count and layout complexity. |
| FBX Regulation | +1.6V or –0.8V - single feedback pin supports both polarities; precision reference ensures ±1.2% output accuracy over temperature. |
| Switching Frequency | 100kHz to 1MHz (resistor-programmable) - allows optimization of efficiency vs. size: 300kHz typical for automotive EMI compliance. |
| PGOOD Threshold | ±5% window around FBX reference - provides reliable output voltage status for system sequencing and fault detection. |
| Shutdown IQ | <1µA - enables always-on monitoring in battery-backed systems without significant drain. |
| Package | 36-lead 5mm × 6mm QFN with exposed SW and SGND pads - thermally enhanced for 6A continuous operation at TJ ≤ 125°C. |
Pinout & Package
LT3959IUHE#PBF is housed in a thermally enhanced 36-lead plastic QFN (UHE package), 5mm × 6mm, with exposed pads for SW (Pin 38) and SGND (Pin 37) requiring solder connection to respective PCB copper planes.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Primary input supply and VIN-LDO input | Bypass with ≥1µF ceramic near pin; powers internal bias and gate driver when DRIVE is unused. |
| SW | Drain of internal 6A/40V N-MOSFET | Exposed pad (Pin 38) must be soldered to high-current SW plane; connects to inductor/diode node in all topologies. |
| FBX | Feedback input for ±voltage regulation | Single pin accepts resistor divider from VOUT to SGND; selects +1.6V or –0.8V reference automatically per topology. |
| PGOOD | Open-collector output status indicator | Asserts low when INTVCC > 2.7V and FBX within ±5% of regulation voltage-used for power-good sequencing. |
| RT | Frequency programming input | Resistor to SGND sets switching frequency (e.g., 27.4kΩ = 300kHz); open circuit disables operation. |
| SS | Soft-start timing control | Capacitor to SGND sets ramp time (TSS = CSS × 125ms/µF); resets on UVLO or thermal fault. |
| EN/UVLO | Enable and input undervoltage lockout | 1.22V falling threshold with user-programmable hysteresis; pulls shutdown IQ to <1µA when ≤0.4V. |
| INTVCC | Regulated internal supply (3.75V or 4.75V) | Bypass with ≥4.7µF ceramic to SGND; powers gate driver and analog circuitry-critical for stability. |
Key Features
| Feature | Design Value |
|---|---|
| Topology Flexibility | Single IC supports boost, SEPIC, and inverting configurations-eliminates need for separate controllers per polarity or topology. |
| Integrated Power Switch | 6A/40V N-MOSFET with 45mV current-sense threshold-reduces external component count and improves reliability vs. discrete FET solutions. |
| Dual LDO Architecture | Auto-selects between DRIVE- or VIN-powered INTVCC regulation-enables efficient gate drive under varying input conditions. |
| Frequency Foldback | Reduces switching frequency when FBX < ±0.2V-prevents inductor saturation and switch overcurrent during start-up or short-circuit recovery. |
| Programmable UVLO Hysteresis | External resistor divider sets precise turn-on/turn-off thresholds-ensures clean power sequencing in automotive and industrial environments. |
Applications
| Automotive Post-Regulator | Industrial 24V-to-±12V Supply |
|---|---|
|
Use Scenario: Regulating 12V battery rail to stable 12V output after engine cranking (VIN dips to 1.6V). IC Role / Device Role / Timing Role: SEPIC controller maintaining regulated output despite wide VIN transients and load steps. Use Value: Delivers 1.5A at VIN > 8V with <1µA shutdown current-meets automotive quiescent requirements while surviving cold-crank. |
Use Scenario: Generating ±12V rails from a 24V industrial bus for op-amp and sensor signal conditioning. IC Role / Device Role / Timing Role: Inverting converter topology using single FBX pin to regulate –12V output. Use Value: Eliminates need for dual controllers or isolated transformers-reduces board area and BOM cost by 30% vs. discrete solutions. |
| LED Driver for High-Voltage Strings | Telecom DC-DC Bias Supply |
|
Use Scenario: Driving 36V LED strings from 12V input in signage or backlighting applications. IC Role / Device Role / Timing Role: Boost controller with PGOOD monitoring for LED current regulation loop enable. Use Value: Internal 6A switch supports up to 3A LED current with external sense resistor-no external FET required for mid-power strings. |
Use Scenario: Providing isolated bias voltage for telecom line interface circuits operating from –48V or +24V inputs. IC Role / Device Role / Timing Role: SEPIC controller generating +5V or –5V from negative input rails without transformer. Use Value: Wide 1.6V–40V input range accommodates legacy –48V telecom systems with wide input tolerance-no pre-regulator needed. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3757AIMSE#PBF | Wider VIN (2.8V–100V), no integrated switch, requires external MOSFET; supports flyback/SEPIC/boost. | Better suited for >40V inputs (e.g., telecom –48V or industrial 48V) but adds FET, driver, and layout complexity. | Select when input exceeds 40V or higher voltage isolation is required; not drop-in due to external switch requirement. |
| TPS40210DGQ | Fixed 1.25V FB reference, no negative output support, 4.5V–52V input, external switch only. | Limited to positive-output topologies; lacks PGOOD, soft-start programmability, and dual-LDO flexibility. | Choose for cost-sensitive positive-only boost/SEPIC where ±output and advanced protection are unnecessary. |
Compared with LT3959IUHE#PBF, LT3757AIMSE#PBF extends input range but increases design effort with external FET drive, while TPS40210DGQ reduces feature set and topology flexibility-making LT3959IUHE#PBF optimal for compact, dual-polarity, automotive-grade SEPIC/boost designs.
Availability
LT3959IUHE#PBF is available at Aetrix Electronics and suitable for automotive post-regulation, industrial 24V-to-±12V conversion, and telecom bias supply applications requiring stable component supply across extended temperature ranges.
Supply support for LT3959IUHE#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 full product support, documentation, and manufacturing continuity for the LT® series.
The LT3959 belongs to Linear's high-voltage DC/DC controller family, designed specifically for robust, wide-input power conversion in automotive, industrial, and telecom environments where reliability under voltage transients is critical.
FAQ
What is the maximum output current achievable with LT3959IUHE#PBF in SEPIC configuration?
The LT3959IUHE#PBF supports up to 1.5A output current when VIN > 8V in SEPIC configuration, as confirmed in the Typical Application schematic (TA01a). This assumes proper thermal management using the exposed SW and SGND pads, 300kHz switching, and appropriate external components including 47µF/16V output capacitance and 22µF/50V input capacitance.
Does LT3959IUHE#PBF support negative output voltage generation?
Yes, LT3959IUHE#PBF natively supports negative output voltage generation in inverting converter topology. The FBX pin regulates to –0.8V when configured for negative output, enabling precise –12V or –5V rails from a single feedback network-no additional ICs or polarity-reversal circuitry required.
What is the purpose of the DRIVE pin on LT3959IUHE#PBF?
The DRIVE pin on LT3959IUHE#PBF supplies the DRIVE-LDO that regulates INTVCC to 4.75V. When connected to a quasi-regulated rail (e.g., DC/DC output), it improves efficiency and reduces noise coupling into INTVCC. If unused, DRIVE must be tied to VIN per datasheet guidance to ensure proper operation.
How does the PGOOD function work on LT3959IUHE#PBF?
The PGOOD pin on LT3959IUHE#PBF is an open-collector output that asserts low when INTVCC exceeds 2.7V and FBX voltage is within ±5% of its regulation point (+1.6V or –0.8V). It provides system-level power-good signaling for microcontroller reset sequencing or downstream enable logic-verified across –40°C to 125°C.
Can LT3959IUHE#PBF be synchronized to an external clock?
Yes, LT3959IUHE#PBF supports external clock synchronization via the SYNC pin. An external digital clock applied to SYNC overrides the RT-programmed frequency, provided the RT resistor is selected for a frequency 20% slower than the SYNC signal. SYNC is ignored during frequency foldback or if INTVCC < 2.7V.
LT3959IUHE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-WFQFN, 28 Leads, Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up, Step-Up/Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Boost, Cuk, SEPIC
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 1.6V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 40V (Switch)
- Current - Output:
- 6A (Switch)
- Frequency - Switching:
- 100kHz ~ 1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-QFN (5x6)
LT3959IUHE#PBF FAQ
1.How can I place an order for LT3959IUHE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3959IUHE#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 LT3959IUHE#PBF reliable?
The price and inventory of LT3959IUHE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3959IUHE#PBF is usually 5 days.
3.What payment methods are accepted for LT3959IUHE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3959IUHE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3959IUHE#PBF?
LT3959IUHE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3959IUHE#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 LT3959IUHE#PBF?
For technical support, including LT3959IUHE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3959IUHE#PBF requirements.
6.How does Aetrix verify that LT3959IUHE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3959IUHE#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 LT3959IUHE#PBF meets industry standards.
7.What is the process for return or replacement of LT3959IUHE#PBF?
All LT3959IUHE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3959IUHE#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 LT3959IUHE#PBF part is unused and in its original packaging.
Return procedure for LT3959IUHE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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