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Analog Devices Inc. LT3959EFE#PBF
- Part No.:
- LT3959EFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 38-TFSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3959EFE#PBF.pdf
- Description:
- IC REG BOOST CUK ADJ 6A 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:119
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Product details
Overview
LT3959EFE#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, features PGOOD status reporting, programmable 100kHz–1MHz switching frequency, and is optimized for automotive post-regulation (e.g., 12V-to-12V SEPIC).
For engineers reviewing the LT3959EFE#PBF datasheet, LT3959EFE#PBF pinout, LT3959EFE#PBF application, or LT3959EFE#PBF equivalent, key selection criteria include its dual-polarity feedback architecture, internal 6A switch rating, thermal-enhanced TSSOP-38 package, soft-start programmability, and INTVCC dual-LDO supply flexibility (VIN- or DRIVE-powered).
Technical Context
The LT3959EFE#PBF implements fixed-frequency current-mode control with dual error amplifiers-one for +1.6V regulation (positive outputs) and one for –0.8V regulation (negative outputs)-enabling topology-agnostic voltage programming via FBX. Its oscillator supports resistor-programmed frequency (100kHz–1MHz) or external synchronization (SYNC pin), with automatic frequency foldback during low-FBX conditions to maintain current limit integrity.
It integrates two independent LDOs: a DRIVE-powered 4.75V regulator and a VIN-powered 3.75V regulator, both feeding INTVCC; automatic LDO selection ensures optimal dropout performance. The EN/UVLO pin provides accurate 1.22V falling threshold with externally programmable hysteresis, while PGOOD asserts only when INTVCC > 2.7V and FBX is within ±5% of its regulation target.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 1.6V to 40V - supports cold-crank automotive (down to 1.6V) and industrial 24V/36V rails without external pre-regulation. |
| Internal Switch | 6A/40V N-MOSFET - eliminates need for external high-current switch in medium-power SEPIC/boost designs up to ~30W. |
| FBX Regulation | +1.6V or –0.8V - enables single-pin configuration of positive or negative regulated outputs without topology-specific IC variants. |
| Switching Frequency | 100kHz to 1MHz (RT-programmable) - balances efficiency (lower fSW) vs. size (higher fSW); supports sync to external clock with 20% slower RT setting. |
| PGOOD Threshold | ±5% window around FBX regulation voltage - provides reliable power-good signaling for downstream sequencing or fault detection. |
| Shutdown IQ | <1µA - enables ultra-low quiescent operation in battery-backed or always-on automotive modules. |
| Operating Temp | –40°C to +125°C junction - qualified for under-hood automotive and industrial environments per E-grade specification. |
Pinout & Package
LT3959EFE#PBF is housed in a thermally enhanced 38-lead plastic TSSOP package (FE package), featuring exposed pads at pins 39 (SGND) and 40 (SW) that must be soldered to respective PCB planes for thermal and electrical integrity. Pin count and layout match the LT3959IUHE#PBF QFN variant but differ in mechanical form factor and thermal path.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Primary input supply and VIN-LDO input | Bypass with ≥1µF ceramic near pin; powers internal bias and VIN-LDO (3.75V INTVCC) when DRIVE is inactive. |
| DRIVE | Alternate LDO input and gate driver supply | Can be tied to VIN or driven by quasi-regulated rail; enables 4.75V INTVCC via DRIVE-LDO for lower dropout operation. |
| SW | Drain of internal 6A/40V N-MOSFET | Exposed pad (Pin 40) must be soldered to SW plane; carries full switch current and requires low-inductance routing. |
| FBX | Dual-polarity feedback input | Sets output voltage: VOUT = 1.6V×(1+R2/R1) for positive, or –0.8V×(1+R2/R1) for negative configurations. |
| PGOOD | Open-collector status output | Asserts low when INTVCC > 2.7V and FBX is within ±5% of regulation target-used for system power sequencing. |
| EN/UVLO | Enable and undervoltage lockout input | 1.22V falling threshold with programmable hysteresis; resets soft-start on undervoltage event. |
| RT | Frequency programming node | Resistor to SGND sets switching frequency (100kHz–1MHz); open-circuit disables operation. |
| SS | Soft-start timing capacitor node | 10µA pull-up charges external capacitor; discharge resets start-up current limiting during faults. |
| INTVCC | Regulated internal supply (3.75V or 4.75V) | Must be bypassed with ≥4.7µF ceramic to SGND; powers gate driver and internal circuitry. |
| GNDK | Kelvin sense return for GND | Connect directly to SGND plane near IC to minimize sensing error in current-loop regulation. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-polarity feedback architecture | Single FBX pin supports both +1.6V and –0.8V regulation references-eliminates need for separate ICs or external polarity-reversal circuitry. |
| Programmable frequency foldback | Automatically reduces switching frequency when FBX voltage drops near 0V (e.g., during start-up or short-circuit), preventing inductor current runaway due to minimum on-time limitation. |
| Thermally optimized TSSOP-38 | Exposes SW (Pin 40) and SGND (Pin 39) on dedicated thermal pads-enables >1.5W dissipation in standard 2-layer PCB layouts without heatsinks. |
| Independent dual-LDO INTVCC supply | Chooses between VIN-LDO (3.75V) and DRIVE-LDO (4.75V) based on input conditions-ensures stable gate drive across wide VIN range and varying load states. |
| Accurate EN/UVLO with hysteresis | 1.22V nominal falling threshold with user-defined rising hysteresis via external resistor divider-supports robust brown-in/brown-out behavior in automotive battery systems. |
Applications
| Automotive Post-Regulation | Industrial 24V-to-12V Conversion |
|---|---|
Use Scenario: Regulating 12V output from a noisy, wide-range automotive battery (5V–16V) while maintaining tight tolerance during cold-crank (down to 1.6V). IC Role / Device Role / Timing Role: SEPIC controller with integrated 6A switch, using FBX to set +12V output and PGOOD to enable downstream ECUs only after stable regulation. Use Value: Eliminates external high-current switch and discrete UVLO circuitry; maintains regulation through 1.6V cold-crank events without output collapse. | Use Scenario: Generating isolated 12V rail from unregulated 24V industrial bus with high ripple and transient content. IC Role / Device Role / Timing Role: Boost controller operating at 300kHz (RT = 27.4kΩ), leveraging DRIVE pin to power INTVCC from local 5V rail for improved efficiency and reduced VIN loading. Use Value: Reduces total BOM count by integrating switch and dual-LDO supply; achieves >90% efficiency at 1.5A load with minimal external components. |
| Negative Bias Supply for Op-Amps | LED Driver with Programmable Polarity |
Use Scenario: Providing –5V bias for precision instrumentation op-amps in mixed-signal data acquisition systems. IC Role / Device Role / Timing Role: Inverting converter configured via FBX to regulate –0.8V reference, scaling output to –5V using R1/R2 divider; PGOOD confirms stable negative rail before ADC initialization. Use Value: Delivers clean, regulated negative voltage without transformer or charge-pump limitations-supports low-noise analog front-ends with <10mV ripple. | Use Scenario: Driving high-brightness LEDs requiring either constant-current boost (anode-positive) or buck-boost (cathode-negative) configurations. IC Role / Device Role / Timing Role: Configurable topology controller: boost mode for +VLED, inverting mode for –VLED; soft-start (SS pin) prevents LED surge current during turn-on. Use Value: Single IC supports both LED polarity requirements-reduces inventory and simplifies design reuse across lighting product families. |
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. | Targets higher-efficiency, higher-power (>50W) applications where synchronous rectification and wider VIN range are critical. | Select LTC3789EFE#PBF when efficiency >94% and output power >35W are required; avoid if BOM cost sensitivity or integration level favors monolithic solution. |
| LT8330EDD#PBF | Monolithic 5A boost/SEPIC/inverting converter; 3V–40V input; fixed 2MHz switching; no SYNC or frequency foldback. | Optimized for compact, high-frequency designs where small magnetics outweigh need for programmable frequency or fault recovery features. | Select LT8330EDD#PBF for space-constrained applications needing 2MHz operation and simpler layout; avoid when cold-crank (1.6V) support or PGOOD sequencing is mandatory. |
Compared with LTC3789EFE#PBF and LT8330EDD#PBF, the LT3959EFE#PBF uniquely combines integrated 6A switching, 1.6V cold-crank capability, dual-polarity FBX regulation, and frequency foldback-making it the only option among the three qualified for automotive-grade 12V post-regulation with guaranteed –40°C to +125°C operation and monolithic simplicity.
Availability
LT3959EFE#PBF is available at Aetrix Electronics and suitable for automotive post-regulation, industrial 24V-to-12V conversion, and negative bias supply applications requiring stable component supply, long-term lifecycle support, and AEC-Q200-aligned reliability.
Supply support for LT3959EFE#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3959 belongs to ADI's Power by Linear™ portfolio of high-reliability DC/DC controllers and regulators, designed specifically for demanding automotive, industrial, and telecom power systems requiring wide input range, integrated switching, and robust fault protection.
FAQ
What is the minimum input voltage required for LT3959EFE#PBF to start switching?
The LT3959EFE#PBF has a guaranteed start-up voltage of 2.5V (typical 2.65V) when RT = 27.4kΩ and FBX = 0V. Below this, the device remains in undervoltage lockout. However, once started, it continues switching down to 1.6V input-critical for automotive cold-crank operation. This behavior is confirmed in the Absolute Maximum Ratings and Electrical Characteristics tables of the official LT3959 datasheet, where VIN Operating Voltage is specified from 1.6V to 40V.
Can LT3959EFE#PBF generate both positive and negative output voltages using the same pin configuration?
Yes, the LT3959EFE#PBF uses a single FBX pin to regulate either positive or negative outputs: connect a resistor divider from VOUT to SGND to pull FBX to +1.6V for positive regulation (e.g., boost/SEPIC), or to –0.8V for negative regulation (e.g., inverting topology). The internal dual-error-amplifier architecture automatically selects the active path. This capability is explicitly documented in the "Description" and "Pin Functions" sections of the LT3959 datasheet and verified in typical application circuits (TA01a and TA01b).
What is the purpose of the GNDK pin on LT3959EFE#PBF, and how should it be connected?
The GNDK (Kelvin ground) pin on LT3959EFE#PBF provides a dedicated Kelvin connection between the internal switch source and the signal ground plane, minimizing voltage drop errors in the current-sense path. It must be connected directly to the SGND plane near the IC-separate from high-current GND returns-to ensure accurate peak-current-mode regulation. This requirement is specified in the "Pin Functions" section and reinforced in the "Board Layout" guidance of the LT3959 datasheet.
Does LT3959EFE#PBF support external clock synchronization, and what are the constraints?
Yes, LT3959EFE#PBF supports external synchronization via the SYNC pin, which accepts a digital clock signal whose positive edge aligns the internal oscillator. To ensure reliable locking, the RT resistor must be selected to program a free-running frequency at least 20% slower than the SYNC frequency. The SYNC pin is ignored during frequency foldback or when INTVCC falls below 2.7V. These conditions and timing requirements are detailed in the "Operating Frequency and Synchronization" section of the LT3959 datasheet.
How does the soft-start function work on LT3959EFE#PBF, and can it be triggered by faults?
The LT3959EFE#PBF implements soft-start via the SS pin, which controls VC clamp voltage to limit peak inductor current during startup. A 10µA internal current source charges an external capacitor to set the ramp time. Crucially, soft-start is also re-triggered by INTVCC undervoltage lockout or thermal shutdown-Q3 discharges the SS capacitor, and restart begins only after SS falls below 0.2V. This multi-fault recovery behavior is described in the "Soft-Start" subsection of the Applications Information section in the LT3959 datasheet.
LT3959EFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 38-TFSOP (0.173", 4.40mm Width) 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:
- 38-TSSOP-EP
LT3959EFE#PBF FAQ
1.How can I place an order for LT3959EFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3959EFE#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 LT3959EFE#PBF reliable?
The price and inventory of LT3959EFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3959EFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3959EFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3959EFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3959EFE#PBF?
LT3959EFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3959EFE#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 LT3959EFE#PBF?
For technical support, including LT3959EFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3959EFE#PBF requirements.
6.How does Aetrix verify that LT3959EFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3959EFE#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 LT3959EFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3959EFE#PBF?
All LT3959EFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3959EFE#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 LT3959EFE#PBF part is unused and in its original packaging.
Return procedure for LT3959EFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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