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Analog Devices Inc. LT3956IUHE#PBF
- Part No.:
- LT3956IUHE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3956IUHE#PBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 3.3A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,006
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Product details
Overview
LT3956IUHE#PBF from Analog Devices (formerly Linear Technology) is a high-voltage constant-current/constant-voltage DC/DC controller IC designed for driving high-power LED strings in automotive headlamps, industrial lighting, and battery-powered LED systems. It integrates an 84V/3.3A internal N-channel MOSFET, supports 4.5V–80V input, delivers up to 80V output, and enables true-color PWM dimming up to 3000:1.
For engineers reviewing the LT3956IUHE#PBF datasheet, LT3956IUHE#PBF pinout, LT3956IUHE#PBF application, or LT3956IUHE#PBF equivalent, this page provides verified technical context on high-side current sensing, buck/boost/buck-boost topology support, programmable switching frequency (100kHz–1MHz), open-LED protection, and thermal-safe analog dimming via CTRL pin voltage scaling.
Technical Context
The LT3956IUHE#PBF employs a fixed-frequency current-mode architecture with internal slope compensation, enabling stable regulation across wide VIN (4.5V–80V) and VOUT (up to 80V) ranges. Its high-side current sense amplifier (250mV full-scale threshold, adjustable via CTRL pin) interfaces directly with ISP/ISN pins and operates over 2.9V–80V common-mode range - critical for boost and SEPIC topologies where ISN floats above ground.
It features dual-loop control: the VC error amplifier regulates either LED current (via ISP–ISN differential) or output voltage (via FB pin at 1.232V nominal), with automatic loop dominance management. The VMODE pin signals FB loop activation (e.g., open-LED fault), while PWMOUT drives external disconnect FETs for overvoltage protection when FB exceeds VFB + 60mV.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 80V - supports 12V/24V/48V battery systems and transient-tolerant automotive supply rails. |
| Output Voltage Capability | Up to 80V - enables direct drive of long LED strings (e.g., 20× white LEDs @ 3.2V each) without external boost stages. |
| Integrated Switch Rating | 84V VDS, 3.3A continuous - eliminates need for external high-voltage switch in most ≤25W LED driver designs. |
| Current Sense Threshold | 250mV (full-scale, CTRL ≥ 1.2V); adjustable down to 0mV - enables precise LED current programming and zero-current shutdown. |
| Switching Frequency Range | 100kHz to 1MHz (RT-programmable) - allows optimization of inductor size, efficiency, and EMI performance. |
| Dimming Ratio | 3000:1 true-color PWM - preserves LED chromaticity across full brightness range without color shift. |
| Operating Temperature | –40°C to +125°C junction - qualified for under-hood automotive and industrial ambient environments. |
Pinout & Package
LT3956IUHE#PBF is housed in a thermally enhanced 36-lead (5mm × 6mm) plastic QFN package with two exposed pads: Pin 37 (GND) and Pin 38 (SW). The package requires soldering both exposed pads to PCB copper for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input power supply connection | Accepts 4.5V–80V; must be bypassed with ≥0.22µF ceramic capacitor to PGND near pin. |
| SW | Drain of internal N-MOSFET | Exposed pad (Pin 38); connects directly to external inductor; carries high di/dt switching current. |
| ISP / ISN | High-side LED current sense inputs | Differential pair referenced to floating ISN node; supports 2.9V–80V common-mode range for boost/SEPIC. |
| FB | Voltage feedback input | Regulates output to 1.232V nominal; enables CV mode and open-LED detection; triggers VMODE/PWMOUT faults. |
| CTRL | Current threshold adjustment | Scales ISP–ISN threshold linearly (0–1V) or fixes at 250mV (>1.2V); used for analog dimming or thermal foldback. |
| PWM | Digital dimming control | Active-low input; enables 3000:1 PWM dimming; places IC in low-IQ idle state when low. |
| VMODE | Open-LED status indicator | Open-drain output pulled low when FB drops below VFB – 50mV - signals CV loop takeover or open-circuit condition. |
| PWMOUT | LED disconnect driver | Buffered PWM signal referenced to INTVCC; driven low during FB overvoltage (VFB + 60mV) to isolate LED load. |
| EN/UVLO | Enable and input undervoltage lockout | 1.22V falling threshold with user-programmable hysteresis; shuts down IC below VIN threshold to prevent brownout operation. |
| INTVCC | Internal LDO output | 7.15V regulated supply for gate driver and logic; requires 4.7µF local ceramic bypass; can be tied to VIN if VIN ≤ 7V. |
Key Features
| Feature | Design Value |
|---|---|
| High-side current sensing | Enables flexible topology selection (boost, buck, buck-boost, SEPIC, flyback) without ground-referenced current path constraints. |
| Programmable current threshold | CTRL pin adjusts ISP–ISN threshold from 0mV to 250mV - supports analog dimming, thermal derating, and zero-current shutdown. |
| Open-LED and overvoltage protection | VMODE asserts on FB drop (open LED); PWMOUT forces low on FB rise (overvoltage) - isolates LEDs without external circuitry. |
| Low shutdown current | <1µA quiescent current when EN/UVLO = 0V - meets automotive "always-on" battery drain requirements. |
| Adjustable soft-start | SS pin controls startup ramp time via external capacitor - prevents inrush current and output overshoot during power-up. |
Applications
| Automotive Headlamp Driver | Battery-Powered LED Lighting |
|---|---|
Use Scenario: 25W white LED headlamp in 12V/24V vehicle electrical system with 80V load dump tolerance. IC Role / Device Role / Timing Role: Constant-current controller regulating 700mA LED string; manages boost conversion from 6V–16V input to 36V output. Use Value: 94% peak efficiency at 24VIN enables passive thermal design; 3000:1 PWM dimming meets adaptive driving beam (ADB) requirements. |
Use Scenario: Portable high-lumen LED work light powered by 3S Li-ion battery (9V–12.6V). IC Role / Device Role / Timing Role: Buck-mode LED driver delivering 1.2A at 12V output; uses high-side sensing to maintain regulation as battery discharges. Use Value: Wide 4.5V–80V input range accommodates full battery discharge curve; CTRL-based analog dimming extends runtime at low brightness. |
| Industrial High-Voltage LED Array | Constant-Current Battery Charger |
Use Scenario: 48V industrial lighting system driving 15-series white LED string (48V forward voltage). IC Role / Device Role / Timing Role: Constant-voltage regulator operating in buck-boost mode; maintains 48V output while accepting 36V–72V input. Use Value: Dual-loop control ensures stable output despite input ripple; ISP/ISN short-circuit protection safeguards during cold-start or fault conditions. |
Use Scenario: Precision 2A/28V lithium-iron-phosphate (LiFePO₄) battery charger with CC/CV profile. IC Role / Device Role / Timing Role: Accurate current-limited voltage regulator; uses FB pin for CV termination and ISP/ISN for CC phase. Use Value: 250mV current sense threshold enables ±1% LED current accuracy - directly transferable to ±0.5% charge current accuracy with matched Rsense. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar constant-current/constant-voltage LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3783EFE#PBF | Requires external MOSFETs; no integrated switch; supports higher output currents (>5A) but needs more board area and layout complexity. | Better suited for >50W LED drivers or multi-string configurations where discrete FETs offer thermal flexibility. | Select LTC3783EFE#PBF when output power exceeds 30W or when custom FET selection (e.g., SiC) is required for efficiency at high frequency. |
| LM3410XSDX/NOPB | Lower voltage rating (42V max VIN, 40V max VOUT); 1.25A switch; fixed 1.6MHz frequency; no CTRL-based analog dimming. | Targeted at compact, low-power (<10W) portable LED applications with simpler BOM and smaller inductors. | Choose LM3410XSDX/NOPB for space-constrained, cost-sensitive designs below 10W where 80V capability and analog dimming are unnecessary. |
Compared with LTC3783EFE#PBF and LM3410XSDX/NOPB, the LT3956IUHE#PBF uniquely combines integrated 84V/3.3A switching, programmable 100kHz–1MHz frequency, and dual-loop CV/CC control in a single 5mm × 6mm QFN - making it optimal for 10W–25W automotive and industrial LED drivers requiring minimal external components and robust fault protection.
Availability
LT3956IUHE#PBF is available at Aetrix Electronics and suitable for automotive lighting, industrial LED arrays, and battery-charged LED systems requiring stable component supply, extended temperature operation, and high-voltage transient resilience.
Supply support for LT3956IUHE#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving automotive, industrial, communications, and healthcare markets.
The LT3956IUHE#PBF belongs to Linear's high-voltage LED driver product line, engineered specifically for demanding constant-current applications in automotive headlamps, emergency lighting, and industrial signage where reliability, efficiency, and fault resilience are critical.
FAQ
What is the maximum LED string voltage supported by the LT3956IUHE#PBF?
The LT3956IUHE#PBF supports output voltages up to 80V, enabling direct drive of LED strings with combined forward voltage up to 80V - for example, 24 white LEDs at 3.2V each (76.8V total). This rating is validated across the full –40°C to +125°C operating junction temperature range and accounts for worst-case tolerances in internal reference and sense amplifier.
Does the LT3956IUHE#PBF require an external MOSFET for operation?
No, the LT3956IUHE#PBF integrates a fully rated 84V/3.3A N-channel MOSFET switch, eliminating the need for an external high-voltage transistor in most ≤25W LED driver designs. The SW pin (exposed pad Pin 38) connects directly to the inductor, and the internal gate driver is powered by the 7.15V INTVCC regulator.
How does the CTRL pin function in the LT3956IUHE#PBF?
The CTRL pin on the LT3956IUHE#PBF scales the ISP–ISN current sense threshold linearly from 0mV to 250mV as voltage increases from 0V to 1V, enabling precise analog dimming or thermal foldback. At CTRL ≥ 1.2V, the threshold locks at 250mV for full-scale current regulation. Leaving CTRL unconnected is not allowed; tie to VREF (2V) for default 250mV operation.
Can the LT3956IUHE#PBF operate in buck mode with high-side current sensing?
Yes - the LT3956IUHE#PBF supports buck-mode operation using high-side current sensing by connecting the ISP–ISN sense resistor between the LED anode and VIN rail. This configuration maintains accurate current regulation even as input voltage varies, and is explicitly validated in the datasheet's Figure 3 application circuit for buck/buck-boost topologies.
What protection features are built into the LT3956IUHE#PBF?
The LT3956IUHE#PBF includes open-LED detection (via FB pin monitoring and VMODE assertion), output overvoltage protection (PWMOUT forced low when FB > VFB + 60mV), ISP/ISN short-circuit detection (335mV threshold when ISN < 3V), thermal shutdown (165°C), and programmable undervoltage lockout on EN/UVLO. All protections are hardware-based and require no external components.
LT3956IUHE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-WFQFN, 28 Leads, Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Flyback, SEPIC, Step-Down (Buck), Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 4.5V
- Voltage - Supply (Max):
- 80V
- Voltage - Output:
- 80V
- Current - Output / Channel:
- 3.3A (Switch)
- Frequency:
- 100kHz ~ 1MHz
- Dimming:
- Analog, PWM
- Applications:
- -
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-QFN (5x6)
LT3956IUHE#PBF FAQ
1.How can I place an order for LT3956IUHE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3956IUHE#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 LT3956IUHE#PBF reliable?
The price and inventory of LT3956IUHE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3956IUHE#PBF is usually 5 days.
3.What payment methods are accepted for LT3956IUHE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3956IUHE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3956IUHE#PBF?
LT3956IUHE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3956IUHE#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 LT3956IUHE#PBF?
For technical support, including LT3956IUHE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3956IUHE#PBF requirements.
6.How does Aetrix verify that LT3956IUHE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3956IUHE#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 LT3956IUHE#PBF meets industry standards.
7.What is the process for return or replacement of LT3956IUHE#PBF?
All LT3956IUHE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3956IUHE#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 LT3956IUHE#PBF part is unused and in its original packaging.
Return procedure for LT3956IUHE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3956IUHE#PBF Tags
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