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Analog Devices Inc. LT3959IUHE#TRPBF
- Part No.:
- LT3959IUHE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3959IUHE#TRPBF.pdf
- Description:
- IC REG BOOST CUK ADJ 6A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,007
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Product details
Overview
LT3959IUHE#TRPBF 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 regulates positive or negative outputs from a single FBX pin, operates from 1.6V to 40V input, delivers up to 1.5A at VIN > 8V in SEPIC configuration, and targets automotive post-regulation where input transients exceed 24V.
For engineers reviewing the LT3959IUHE#TRPBF datasheet, LT3959IUHE#TRPBF pinout, LT3959IUHE#TRPBF application, or LT3959IUHE#TRPBF equivalent, key selection criteria include its dual-polarity feedback architecture, programmable 100kHz–1MHz switching frequency, PGOOD status reporting, internal 6A switch, and thermally enhanced 36-lead QFN package rated for –40°C to 125°C junction temperature.
Technical Context
The LT3959IUHE#TRPBF implements fixed-frequency current-mode control with dual error amplifiers-one for +1.6V regulation (positive output), one for –0.8V regulation (negative output)-selected automatically based on FBX voltage polarity. Its oscillator supports resistor-programmed frequency (100kHz–1MHz) or external synchronization via SYNC pin, with built-in frequency foldback during low-FBX conditions to maintain current limit integrity.
It integrates two independent LDOs: a DRIVE-powered 4.75V INTVCC regulator and a VIN-powered 3.75V INTVCC regulator, both with dropout < 400mV and load regulation < ±1%. The EN/UVLO pin provides accurate 1.22V falling threshold with externally programmable hysteresis, while the PGOOD pin asserts only when INTVCC > 2.7V and FBX is within ±5% of its regulation voltage (±80mV for +1.6V, ±40mV for –0.8V).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 1.6V to 40V - supports cold-crank automotive (≥1.6V) and load-dump transient immunity (≤40V) |
| Internal Switch Rating | 6A/40V N-channel MOSFET - enables high-current SEPIC/boost without external switch |
| Feedback Regulation Voltages | +1.6V and –0.8V - single FBX pin supports both positive and negative output programming |
| Switching Frequency Range | 100kHz to 1MHz - adjustable via RT resistor; allows optimization of efficiency vs. size trade-off |
| PGOOD Threshold Accuracy | ±5% window around FBX reference - provides reliable output voltage status for system sequencing |
| Operating Temperature Range | –40°C to 125°C - qualified for under-hood automotive and industrial environments |
| Shutdown Quiescent Current | <1µA - enables ultra-low-power disable mode for battery-backed systems |
Pinout & Package
LT3959IUHE#TRPBF is housed in a 36-lead (5mm × 6mm) plastic QFN package with exposed thermal pads: Pin 37 is SGND (soldered to signal ground plane), Pin 38 is SW (soldered to switch node copper). The package features thermally enhanced construction (θJC = 3°C/W) and is RoHS-compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Primary power input and VIN LDO supply | Bypass with ≥1µF ceramic capacitor; powers internal bias and INTVCC when DRIVE is inactive |
| SW | Drain of internal 6A/40V N-MOSFET | Connects directly to inductor/diode node; requires low-inductance layout due to high di/dt |
| FBX | Dual-polarity feedback input | Regulates +1.6V (positive output) or –0.8V (negative output); also enables PGOOD and frequency foldback |
| PGOOD | Open-collector status output | Asserts low when INTVCC > 2.7V and FBX is within ±5% of regulation voltage |
| RT | Frequency programming input | Resistor to SGND sets switching frequency (100kHz–1MHz); must not be left floating |
| SS | Soft-start timing control | External capacitor sets soft-start duration; resets on UVLO or thermal fault |
| EN/UVLO | Enable and undervoltage lockout input | 1.22V falling threshold with programmable hysteresis; disables IC and reduces IQ to <1µA |
| INTVCC | Regulated internal supply (4.75V or 3.75V) | Bypass with ≥4.7µF ceramic capacitor adjacent to pin; powers gate driver and analog circuitry |
| SGND | Signal ground reference | Mandatory connection point for FBX/EN/UVLO dividers, RT, SS, VC, and INTVCC capacitors |
| GNDK | Kelvin sense for GND | Must be connected to SGND plane near IC to minimize sensing error in current path |
Key Features
| Feature | Design Value |
|---|---|
| Dual-polarity feedback architecture | Single FBX pin supports +1.6V or –0.8V regulation-eliminates need for separate positive/negative controllers in dual-rail systems |
| Programmable frequency with sync capability | 100kHz–1MHz range set by RT resistor; SYNC pin accepts external clock for EMI reduction or multi-phase coordination |
| Integrated dual-LDO INTVCC supply | DRIVE-powered 4.75V or VIN-powered 3.75V regulation-enables flexible power sourcing and eliminates external bias rail |
| Automatic frequency foldback | Reduces switching frequency when FBX approaches SGND-prevents inductor current runaway during start-up or short-circuit |
| Accurate EN/UVLO with hysteresis | 1.22V nominal falling threshold with user-defined rising hysteresis-ensures clean enable/disable behavior across input transients |
| Thermally optimized QFN package | 36-lead 5mm × 6mm QFN with dual exposed pads (SGND and SW)-delivers θJC = 3°C/W for high-power density designs |
Applications
| Automotive Post-Regulator | Industrial Dual-Rail Supply |
|---|---|
Use Scenario: Regulating 12V battery-derived input to stable 12V output despite cold-crank (down to 1.6V) and load-dump (up to 40V) transients. IC Role / Device Role / Timing Role: SEPIC controller with integrated 6A switch, managing energy transfer through coupled inductors to maintain regulated output during wide VIN excursions. Use Value: Eliminates need for external high-voltage switch and discrete UVLO circuitry while sustaining 1.5A output above 8V input. |
Use Scenario: Generating isolated ±12V rails from a single 24V industrial bus for op-amp biasing or sensor excitation. IC Role / Device Role / Timing Role: Inverting converter controller using FBX to regulate –12V output, with same IC reused in boost mode for +12V rail in companion design. Use Value: Reduces BOM count by enabling dual-polarity output generation from identical controller hardware and layout. |
| Telecom DC-DC Module | LED Driver Power Stage |
Use Scenario: Providing 48V intermediate bus regulation in telecom shelf systems where input varies from 36V–72V. IC Role / Device Role / Timing Role: Boost controller operating at 300kHz with SYNC locked to system clock, minimizing conducted EMI in dense backplane environments. Use Value: Achieves >90% efficiency at 1A load while meeting CISPR-22 Class B emissions with minimal filtering. |
Use Scenario: Driving high-brightness LED strings requiring constant current with dimming interface compatibility. IC Role / Device Role / Timing Role: Boost controller with PGOOD used for LED fault detection and SS pin synchronized to PWM dimming signal for smooth brightness ramp. Use Value: Enables precise current regulation and fast fault response without adding secondary monitoring circuitry. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3789EFE#PBF | 4-switch synchronous buck-boost controller; no integrated switch; supports 4V–36V input; requires external MOSFETs | Used in higher-efficiency, higher-current (>3A) buck-boost applications where layout space permits discrete FETs | Select when >95% efficiency at 3A+ is required and board area allows external power stage |
| LM5122MMX/NOPB | Current-mode boost/SEPIC controller; 3V–65V input; no integrated switch; 100kHz–1MHz programmable frequency; PGOOD included | Targets wider input range (e.g., 48V telecom) but lacks dual-polarity feedback and integrated 6A switch | Select when input exceeds 40V or when external 100V+ FETs are preferred for reliability margin |
Compared with LTC3789EFE#PBF and LM5122MMX/NOPB, LT3959IUHE#TRPBF uniquely integrates a 6A/40V switch and dual-polarity feedback in a single QFN package-reducing component count and PCB area for mid-power SEPIC/inverting designs operating within 1.6V–40V input, while maintaining automotive-grade temperature rating and robust fault protection.
Availability
LT3959IUHE#TRPBF is available at Aetrix Electronics and suitable for automotive post-regulation, industrial dual-rail supplies, telecom DC-DC modules, and LED driver power stages requiring stable component supply across extended temperature and high-reliability environments.
Supply support for LT3959IUHE#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 its legacy of high-performance analog and power management ICs with rigorous automotive and industrial qualification standards.
The LT3959 product line delivers wide-input, multi-topology DC/DC controllers targeting harsh-environment applications including automotive under-hood systems, industrial automation, and telecom infrastructure where input transients, thermal stress, and reliability are critical.
FAQ
What topology configurations does the LT3959IUHE#TRPBF support?
The LT3959IUHE#TRPBF supports boost, SEPIC, and inverting converter topologies. Its dual-error-amplifier architecture automatically selects between +1.6V and –0.8V regulation based on FBX pin voltage polarity, enabling positive or negative output generation from a single feedback network. This eliminates the need for separate controllers in dual-rail designs and simplifies layout for automotive post-regulators using SEPIC to handle wide input transients.
How is the switching frequency programmed on the LT3959IUHE#TRPBF?
The LT3959IUHE#TRPBF switching frequency is set using an external resistor from the RT pin to SGND, covering 100kHz to 1MHz. For example, a 27.4kΩ resistor yields ~300kHz operation. The RT pin must never be left floating. When synchronization is required, the SYNC pin accepts an external clock, and the RT resistor should be selected to program a frequency ~20% slower than the SYNC signal to ensure reliable locking.
What is the role of the PGOOD pin on the LT3959IUHE#TRPBF?
The PGOOD pin on the LT3959IUHE#TRPBF is an open-collector output that asserts low when two conditions are met: INTVCC exceeds 2.7V and the FBX voltage is within ±5% of its regulation voltage (+1.6V or –0.8V). This provides unambiguous system-level confirmation that both internal bias and output regulation are stable-critical for power sequencing in automotive and industrial systems where downstream logic must not activate until rail integrity is verified.
Can the LT3959IUHE#TRPBF operate with input voltages below 2.5V?
Yes-the LT3959IUHE#TRPBF has a minimum operating input voltage of 1.6V and a start-up threshold of 2.5V (typical) when RT = 27.4kΩ. Below 2.5V, the device remains in shutdown until VIN rises sufficiently to initiate start-up. This 1.6V–40V range makes it suitable for automotive cold-crank scenarios where battery voltage dips below 6V, provided the EN/UVLO pin is configured to avoid premature disable during transient sags.
What thermal management considerations apply to the LT3959IUHE#TRPBF QFN package?
The LT3959IUHE#TRPBF uses a 36-lead QFN with two exposed thermal pads: Pin 37 (SGND) must be soldered to the signal ground plane, and Pin 38 (SW) to the switch-node copper pour. This dual-pad structure achieves θJC = 3°C/W, enabling efficient heat extraction from both the power switch and ground path. Layout must minimize thermal resistance between these pads and their respective planes-especially for SW-to sustain 6A continuous conduction without exceeding 125°C junction temperature.
LT3959IUHE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-WFQFN, 28 Leads, Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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#TRPBF FAQ
1.How can I place an order for LT3959IUHE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3959IUHE#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 LT3959IUHE#TRPBF reliable?
The price and inventory of LT3959IUHE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3959IUHE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3959IUHE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3959IUHE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3959IUHE#TRPBF?
LT3959IUHE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3959IUHE#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 LT3959IUHE#TRPBF?
For technical support, including LT3959IUHE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3959IUHE#TRPBF requirements.
6.How does Aetrix verify that LT3959IUHE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3959IUHE#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 LT3959IUHE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3959IUHE#TRPBF?
All LT3959IUHE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3959IUHE#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 LT3959IUHE#TRPBF part is unused and in its original packaging.
Return procedure for LT3959IUHE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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