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Analog Devices Inc. LT3909IMSE#PBF
- Part No.:
- LT3909IMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3909IMSE#PBF.pdf
- Description:
- IC LED DRV RGLTR PWM 50MA 12MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:176
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Product details
Overview
LT3909IMSE#PBF from Analog Devices (formerly Linear Technology) is a 2-string, 60mA high-side LED driver IC with integrated 40V/1A switch and Schottky diode, operating at fixed 2MHz boost switching frequency to drive up to 36V total LED forward voltage. It delivers ±2% current matching between strings and supports analog dimming (10:1) and ultra-high-ratio PWM dimming (40,000:1 at 100Hz). It is used in automotive instrument clusters requiring precise, thermally robust LED backlighting.
For engineers reviewing the LT3909IMSE#PBF datasheet, LT3909IMSE#PBF pinout, LT3909IMSE#PBF application, or LT3909IMSE#PBF equivalent, key selection considerations include its 2MHz fixed-frequency boost architecture, ±2% LED current matching across temperature, programmable 10–60mA per string via single ISET resistor, fault-flag protection for open/shorted LEDs, and thermal regulation loop for junction temperature control.
Technical Context
The LT3909IMSE#PBF integrates a peak-current-mode 2MHz boost converter with two independent high-side current sources, each regulated by a dedicated feedback path monitoring VOUT–LEDx differential voltage. Its GM1 loop maintains 1.3V across each current source for optimal efficiency, while the GM2 loop regulates FB to 1.215V for programmable overvoltage protection during fault conditions.
It features internal soft-start, thermal foldback limiting LED current above 170°C junction temperature, and dual-detection circuitry that identifies LED-open (VOUT–VLEDx < 0.4V) and LED-short-to-GND (VLEDx < 6.0V) faults independently-ensuring one string remains regulated when the other fails.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.9V to 40V - supports wide automotive battery range including cold-crank and load-dump transients. |
| Max LED Current per String | 60mA - set precisely via single external resistor (16.7kΩ), enabling consistent brightness across dual displays. |
| Current Matching Accuracy | ±2% (typ ±0.3%) - ensures uniform luminance in dual-string applications like left/right instrument cluster backlighting. |
| PWM Dimming Ratio | 40,000:1 at 100Hz - enables deep black-level control in high-contrast automotive displays without visible flicker. |
| Switching Frequency | 2MHz (±6%) - allows use of small 3.3–10µH inductors and reduces EMI filtering requirements in space-constrained PCBs. |
| Integrated Power Switch | 400mΩ, 40V, 1A N-channel DMOS - eliminates external MOSFET, simplifying layout and improving thermal performance in MSOP package. |
| Fault Detection | Open-LED (VOUT–VLEDx < 0.4V) and LED-short-to-GND (VLEDx < 6.0V) - latched FAULT pin alerts system controller without disrupting remaining string operation. |
Pinout & Package
LT3909IMSE#PBF is housed in a 12-lead plastic MSOP package (3mm × 4.9mm) with exposed pad (Pin 13) soldered to PCB ground for thermal management (θJA = 40°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| INTVCC (1) | Internal 3.0V regulator output | Supplies gate driver and control circuits; must be bypassed with ≥1µF ceramic capacitor; max 100µA external load. |
| VIN (2) | Main input supply | Accepts 2.9–40V; powers internal regulator and switch; requires local ceramic bypass capacitor. |
| EN/UVLO (3) | Enable and undervoltage lockout input | 0.4V shutdown / 1.215V enable threshold; supports programmable UVLO with resistor divider and 30mV hysteresis. |
| ISET (4) | LED current programming input | Single resistor to GND sets both string currents from 10–60mA (e.g., 49.9kΩ = 20mA/string). |
| CTRL (5) | Analog dimming and latch-off control | Voltage <80mV disables LED current; 0.1–1.0V enables 10:1 analog dimming; connects to NTC for thermal derating. |
| FB (6) | Output voltage regulation feedback | Resistor divider from VOUT programs OVP level (1.215V reference); sampled during PWM off-time to hold VOUT stable. |
| PWM (7) | Digital dimming control | Active-high signal enables PWM dimming; internal latch holds state during low periods for clean on/off transitions. |
| FAULT (8) | Open/short fault flag output | Open-drain active-low output; pulled low during LED-open or LED-short events; updated only when PWM/CTRL are high. |
| LED1, LED2 (9,10) | High-side LED current outputs | Each drives up to 60mA constant current; anodes connect directly to LEDs; pins may be paralleled for >60mA total. |
| VOUT (11) | Boost converter output | Regulated node supplying both LED strings; connects to output capacitor and optional external Schottky cathode. |
| SW (12) | Internal switch drain | Connects to inductor and internal Schottky anode; high dv/dt node requiring minimized trace area for EMI control. |
| Exposed Pad (13) | Thermal ground | Must be soldered to solid PCB ground plane; primary thermal path for junction-to-board heat transfer. |
Key Features
| Feature | Design Value |
|---|---|
| Fixed 2MHz switching frequency | Enables compact magnetics (e.g., 4.7µH) and reduces EMI filter size while maintaining >85% efficiency across 12–36V LED loads. |
| ±2% LED current matching | Guarantees luminance uniformity between dual display zones under varying temperature and supply conditions, critical for automotive HUD/instrument clusters. |
| 40,000:1 PWM dimming at 100Hz | Supports deep-black rendering in ambient-light-adaptive displays without perceptible flicker or current recovery delay due to VOUT regulation during PWM off-time. |
| Programmable VOUT overvoltage protection | Prevents LED overvoltage damage during reconnection after open-circuit faults by regulating VOUT to user-defined level via FB divider. |
| Independent open/short fault detection | Allows continued operation of one LED string during failure of the other-essential for safety-critical automotive lighting systems. |
| Integrated 400mΩ, 40V, 1A switch + Schottky | Reduces BOM count and PCB footprint vs discrete solutions; internal Schottky eliminates external diode in most designs. |
Applications
| Automotive Instrument Clusters | High-Contrast Automotive Displays |
|---|---|
|
Use Scenario: Dual-zone backlighting for analog speedometer and digital TFT display in vehicle dashboards. IC Role / Device Role / Timing Role: High-side current source driving two independent LED strings with matched current and synchronized PWM dimming. Use Value: Ensures identical brightness and color point across mechanical and digital elements, meeting OEM photometric uniformity specs (Δu'v' < 0.005). |
Use Scenario: Edge-lit LCD backlight in infotainment center with dynamic local dimming zones. IC Role / Device Role / Timing Role: Precision current regulator enabling 40,000:1 PWM dimming ratio at 100Hz for true HDR contrast. Use Value: Achieves >10,000:1 display contrast ratio without visible PWM artifacts, even at low ambient temperatures. |
| GPS Navigation Units | Industrial HMI Panels |
|
Use Scenario: Sunlight-readable GPS receiver with auto-brightness adjustment across 0–70°C ambient range. IC Role / Device Role / Timing Role: Analog dimming via CTRL pin controlled by NTC thermistor near LEDs for thermal derating. Use Value: Prevents LED thermal runaway and extends lifetime beyond 50,000 hours at 85°C case temperature. |
Use Scenario: Ruggedized human-machine interface panel in factory automation with vibration and ESD exposure. IC Role / Device Role / Timing Role: Fault-tolerant LED driver with open/short detection and latch-off capability during transient events. Use Value: Maintains partial display functionality during single-string failure, supporting ISO 13849 PLd safety requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3220EDE#PBF | Charge-pump topology (no inductor), 40V max output, 40mA per string, no integrated Schottky. | Better for ultra-thin portable devices where inductor height is prohibited; lower max LED voltage limits use in 36V automotive arrays. | Select when board height <1mm is mandatory and LED string voltage ≤24V; not suitable for 36V or high-current (>40mA) needs. |
| MAX16820ATP+T | 2MHz boost driver, 60mA/string, but no integrated Schottky or switch; requires external 40V MOSFET and diode. | Higher design flexibility for custom thermal layout; lacks fault-flag latching and thermal regulation loop of LT3909IMSE#PBF. | Choose when discrete power stage optimization is required and system-level fault handling is implemented externally. |
Compared with LTC3220EDE#PBF and MAX16820ATP+T, the LT3909IMSE#PBF uniquely combines integrated 40V/1A switch, Schottky diode, ±2% matching, and fault-latched FAULT output-making it the only single-chip solution qualified for AEC-Q100 Grade 1 automotive instrument cluster backlighting.
Availability
LT3909IMSE#PBF is available at Aetrix Electronics and suitable for automotive instrument clusters, high-contrast displays, and industrial HMIs requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant performance.
Supply support for LT3909IMSE#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, datasheets, and application engineering for legacy Linear parts including the LT3909 family.
The LT3909IMSE#PBF belongs to Linear's high-reliability LED driver product line, designed specifically for automotive and industrial displays demanding precision current matching, robust fault protection, and operation across –40°C to +125°C junction temperature.
FAQ
What is the maximum LED forward voltage supported by the LT3909IMSE#PBF?
The LT3909IMSE#PBF supports up to 36V total LED forward voltage across both strings, enabled by its 40V-rated internal switch and Schottky diode. The output voltage (VOUT) dynamically adapts to the minimum required to maintain regulation-reducing power loss and improving efficiency when driving lower-VF LED configurations.
How does the LT3909IMSE#PBF achieve 40,000:1 PWM dimming without VOUT droop?
The LT3909IMSE#PBF samples the FB pin voltage at the PWM falling edge to capture the optimum VOUT level needed for LED regulation, then actively regulates VOUT to that stored value during PWM off-time using its GM2 loop-preventing droop from Schottky leakage and enabling fast current recovery at the next PWM rising edge.
Can the LT3909IMSE#PBF drive a single LED string at 120mA?
Yes-the LT3909IMSE#PBF allows paralleling of LED1 and LED2 pins to deliver up to 120mA total current. When doing so, program the ISET resistor for half the target current (e.g., 30mA per string → 60mA total), and ensure PCB copper weight and thermal layout support the higher power dissipation in the MSOP package.
What thermal protection mechanisms are built into the LT3909IMSE#PBF?
The LT3909IMSE#PBF includes an internal thermal regulation loop that begins derating LED current when junction temperature exceeds ~150°C, and a hard thermal shutdown at ~170°C. Its exposed pad (Pin 13) must be soldered to a continuous ground plane to achieve the specified θJA = 40°C/W and sustain full 60mA operation at 125°C ambient.
Does the LT3909IMSE#PBF require external compensation components?
No-the LT3909IMSE#PBF features fully internal compensation, eliminating external RC networks. Its peak-current-mode architecture includes built-in slope compensation for stability at duty cycles >50%, and the internal GM1/GM2 loops are optimized for standard 3.3–10µH inductors and 1–2.2µF ceramic output capacitors.
LT3909IMSE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 2
- Voltage - Supply (Min):
- 2.9V
- Voltage - Supply (Max):
- 40V
- Voltage - Output:
- 40V
- Current - Output / Channel:
- 50mA
- Frequency:
- 2MHz
- Dimming:
- Analog, PWM
- Applications:
- -
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- Automotive
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 12-MSOP-EP
LT3909IMSE#PBF FAQ
1.How can I place an order for LT3909IMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3909IMSE#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 LT3909IMSE#PBF reliable?
The price and inventory of LT3909IMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3909IMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3909IMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3909IMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3909IMSE#PBF?
LT3909IMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3909IMSE#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 LT3909IMSE#PBF?
For technical support, including LT3909IMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3909IMSE#PBF requirements.
6.How does Aetrix verify that LT3909IMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3909IMSE#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 LT3909IMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3909IMSE#PBF?
All LT3909IMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3909IMSE#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 LT3909IMSE#PBF part is unused and in its original packaging.
Return procedure for LT3909IMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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