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Analog Devices Inc. LT3959EUHE#PBF
- Part No.:
- LT3959EUHE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3959EUHE#PBF.pdf
- Description:
- IC REG BOOST CUK ADJ 6A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,990
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Product details
Overview
LT3959EUHE#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 LT3959EUHE#PBF datasheet, LT3959EUHE#PBF pinout, LT3959EUHE#PBF application, or LT3959EUHE#PBF equivalent, key selection criteria include its programmable 100kHz–1MHz switching frequency, PGOOD output voltage status reporting, internal soft-start, input UVLO with hysteresis, and thermal-enhanced 36-lead QFN (5mm × 6mm) package.
Technical Context
The LT3959EUHE#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 minimum on/off times of 150ns each.
It integrates two independent LDOs (DRIVE LDO: 4.75V, VIN LDO: 3.75V) to supply INTVCC, supports external synchronization via SYNC pin with 20% slower RT-programmed frequency, and includes frequency foldback during low-FBX conditions to prevent inductor current runaway during start-up or short-circuit faults.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 1.6V to 40V - supports direct connection to automotive battery rails including cold-crank (≈4.5V) and load-dump (up to 40V) transients. |
| Switch Rating | 6A continuous, 40V drain-source - enables high-current SEPIC/boost designs without external FETs. |
| Feedback Regulation | +1.6V or –0.8V reference - allows single-pin programming of either polarity output voltage via resistor divider. |
| Switching Frequency | 100kHz to 1MHz (RT-programmable) - balances efficiency (lower fSW) vs. size (higher fSW) with external resistor tuning. |
| PGOOD Threshold Accuracy | ±5% window around VFBX(REG) - provides reliable output voltage status indication for system sequencing and fault detection. |
| Shutdown Current | <1µA - ensures ultra-low quiescent draw in battery-backed or always-on automotive modules. |
| Operating Temperature | –40°C to +125°C junction - qualified for under-hood automotive and industrial environments. |
Pinout & Package
LT3959EUHE#PBF is housed in a thermally enhanced 36-lead plastic QFN package (5mm × 6mm), with exposed pads for SGND (Pin 37) and SW (Pin 38) requiring solder connection to respective PCB planes per layout guidelines.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main power input | Bypassed locally to GND; powers VIN LDO and internal bias circuits; withstands 40V absolute max. |
| SW | Drain of internal N-MOSFET | High-current switching node; connects directly to inductor/diode; exposed pad (Pin 38) must be soldered to SW plane. |
| FBX | Feedback input | Dual-function pin: sets +1.6V or –0.8V regulation point; also drives PGOOD window comparators and frequency foldback. |
| PGOOD | Open-collector status output | Asserts low when INTVCC > 2.7V and FBX within ±5% of regulation voltage-used for power-good signaling and sequencing. |
| RT | Frequency programming | Resistor-to-SGND sets oscillator frequency from 100kHz to 1MHz; open-circuit prohibited. |
| SS | Soft-start control | Capacitor-to-SGND sets ramp time; internal 10µA current source charges SS to limit inrush current during startup and fault recovery. |
| EN/UVLO | Enable & undervoltage lockout | 1.22V falling threshold with user-programmable hysteresis; resets soft-start on undervoltage event. |
| INTVCC | Internal regulated supply | 4.75V (from DRIVE) or 3.75V (from VIN); requires ≥4.7µF ceramic bypass to SGND adjacent to pin. |
| SGND | Signal ground reference | Must be connected directly to signal ground plane; reference for FBX, EN/UVLO dividers, RT, SS, VC, and INTVCC capacitor. |
| GNDK | Kelvin sense for GND | Provides accurate current sensing by separating power GND return path from signal GND reference. |
Key Features
| Feature | Design Value |
|---|---|
| Topology Flexibility | Single IC supports boost, SEPIC, and inverting configurations-reduces BOM count and simplifies design reuse across multiple output polarity requirements. |
| Integrated Power Switch | 6A/40V N-channel MOSFET eliminates need for external high-side driver and discrete FET-reducing layout complexity and component count. |
| Programmable UVLO Hysteresis | External resistor divider sets precise turn-on/turn-off thresholds (e.g., 8V ON / 6.5V OFF)-prevents oscillation during brown-out conditions. |
| Frequency Synchronization | SYNC pin accepts external clock up to 1MHz; RT must be set 20% below sync frequency-enables EMI reduction via spread-spectrum or system-level clock alignment. |
| Output Polarity Agnostic Control | Single FBX pin automatically selects between +1.6V or –0.8V regulation based on topology-eliminates need for separate positive/negative controllers. |
Applications
| Automotive Post-Regulator | Industrial Dual-Polarity Supply |
|---|---|
|
Use Scenario: Regulating 12V battery rail to stable 12V output after alternator transients and cold-crank dips. IC Role / Device Role / Timing Role: SEPIC controller maintaining regulated output despite input dropping to 2.5V or surging to 40V. Use Value: Delivers 1.5A at VIN > 8V with <1µA shutdown current-meets automotive ISO 16750-2 load-dump and cold-crank compliance. |
Use Scenario: Generating ±12V rails from a single 24V industrial bus for op-amp or ADC front-ends. IC Role / Device Role / Timing Role: Inverting converter producing negative output while sharing same feedback network as positive variant. Use Value: Eliminates need for dual-controller solutions; leverages identical FBX pin behavior for both polarities-reducing design validation effort. |
| Telecom Intermediate Bus Converter | LED Driver Bias Supply |
|
Use Scenario: Stepping 48V telecom backplane down to 12V intermediate bus with tight transient response. IC Role / Device Role / Timing Role: Boost controller operating at 300kHz with synchronized switching to minimize conducted EMI. Use Value: RT-programmable frequency and SYNC capability enable deterministic noise placement-critical for sensitive RF subsystems. |
Use Scenario: Providing isolated bias voltage for LED string drivers in architectural lighting systems. IC Role / Device Role / Timing Role: SEPIC regulator delivering constant 12V output despite wide input variation (e.g., 5–24V battery range). Use Value: Internal 6A switch handles peak currents during dimming transitions; PGOOD confirms stable bias before enabling LED PWM stage. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3789EUF#PBF | 4-switch synchronous buck-boost controller; no integrated FET; supports 4V–36V input; requires external MOSFETs. | Higher efficiency at high current (>3A); wider input range but lacks integrated switch and negative-output capability. | Select when higher efficiency and bidirectional power flow are required; not drop-in due to external FET requirement and different topology. |
| LM5122MMX/NOPB | Current-mode boost/buck-boost controller; 3V–65V input; no integrated switch; supports PFM/PWM; no negative output mode. | Broader input range and lower IQ (2.5µA), but lacks FBX-based polarity selection and PGOOD reporting. | Choose for high-voltage boost applications where negative output is unnecessary and external FETs are acceptable. |
Compared with LTC3789EUF#PBF and LM5122MMX/NOPB, LT3959EUHE#PBF uniquely integrates a 6A/40V switch and supports ±output regulation from one pin-making it optimal for space-constrained, moderate-current SEPIC/inverting designs where BOM reduction and polarity flexibility are critical.
Availability
LT3959EUHE#PBF is available at Aetrix Electronics and suitable for automotive post-regulation, industrial dual-polarity supplies, telecom intermediate bus conversion, and LED bias generation requiring stable component supply across extended temperature and high-reliability environments.
Supply support for LT3959EUHE#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 LT3959EUHE#PBF belongs to Linear's high-voltage DC/DC controller family designed specifically for ruggedized power conversion in automotive, industrial, and telecom infrastructure-emphasizing wide VIN, integrated switching, and topology versatility.
FAQ
What is the maximum output current achievable with the LT3959EUHE#PBF in SEPIC configuration?
The LT3959EUHE#PBF delivers up to 1.5A output current when VIN exceeds 8V in a properly designed SEPIC configuration, as confirmed in the Typical Application circuit (TA01a). At lower inputs (e.g., VIN = 2.5V), output current is limited to 500mA due to duty-cycle and thermal constraints. The internal 6A switch supports peak currents well above this, but sustained output depends on layout, inductor saturation rating, and thermal management.
Does the LT3959EUHE#PBF support negative output voltage generation?
Yes, the LT3959EUHE#PBF natively supports negative output voltage generation in inverting converter configuration. It uses the same FBX pin to regulate –0.8V reference, enabling straightforward design of negative rails without additional components or controller variants. This is explicitly documented in the Block Diagram and Applications Information sections of the datasheet.
What is the purpose of the GNDK pin on the LT3959EUHE#PBF?
The GNDK (Kelvin ground) pin on the LT3959EUHE#PBF provides a dedicated Kelvin connection between the power GND and SGND planes, improving accuracy of the internal current-sense amplifier by eliminating IR drop errors in the ground return path. It must be routed separately to the SGND plane near the IC, as specified in the Pin Functions section and Layout Guidelines.
Can the LT3959EUHE#PBF be synchronized to an external clock, and what are the requirements?
Yes, the LT3959EUHE#PBF supports external synchronization via the SYNC pin. To ensure reliable locking, the RT resistor must be selected to program an internal frequency 20% slower than the external clock frequency, and the SYNC pulse must have a minimum width of 200ns. Synchronization is disabled during frequency foldback or when INTVCC falls below 2.7V.
How does the LT3959EUHE#PBF handle overvoltage protection during start-up?
The LT3959EUHE#PBF incorporates dual overvoltage comparators (A11 and A12) that monitor FBX voltage. If FBX exceeds +1.6V by 7.5% (or –0.8V by 7.5%), the internal MOSFET is immediately turned off and held off until the condition clears. This prevents output overshoot during start-up or short-circuit recovery-protecting downstream loads without requiring external circuitry.
LT3959EUHE#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)
LT3959EUHE#PBF FAQ
1.How can I place an order for LT3959EUHE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3959EUHE#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 LT3959EUHE#PBF reliable?
The price and inventory of LT3959EUHE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3959EUHE#PBF is usually 5 days.
3.What payment methods are accepted for LT3959EUHE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3959EUHE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3959EUHE#PBF?
LT3959EUHE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3959EUHE#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 LT3959EUHE#PBF?
For technical support, including LT3959EUHE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3959EUHE#PBF requirements.
6.How does Aetrix verify that LT3959EUHE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3959EUHE#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 LT3959EUHE#PBF meets industry standards.
7.What is the process for return or replacement of LT3959EUHE#PBF?
All LT3959EUHE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3959EUHE#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 LT3959EUHE#PBF part is unused and in its original packaging.
Return procedure for LT3959EUHE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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