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Analog Devices Inc. LT3909HMSE#PBF
- Part No.:
- LT3909HMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3909HMSE#PBF.pdf
- Description:
- IC LED DRV RGLTR PWM 50MA 12MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,719
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Product details
Overview
LT3909HMSE#PBF from Analog Devices (formerly Linear Technology) is a 2-string, 60mA high-side LED driver IC with integrated 2MHz step-up DC/DC converter, ±2% current matching, and programmable VOUT regulation for up to 36V LED strings. It delivers precise analog and PWM dimming in automotive instrument clusters and high-contrast displays.
For engineers reviewing the LT3909HMSE#PBF datasheet, LT3909HMSE#PBF pinout, LT3909HMSE#PBF application, or LT3909HMSE#PBF equivalent, key selection criteria include its 2MHz fixed-frequency boost architecture, dual high-side current sources with thermal foldback, ±0.3% typical current matching, and fault-flag–enabled open/short LED protection.
Technical Context
The LT3909HMSE#PBF integrates a peak-current-mode 2MHz boost controller with two independent high-side current sources, each regulated via a dedicated sense path referenced to VOUT. Its GM1 loop maintains VOUT–VLEDx at 1.3V for optimal efficiency, while the GM2 loop regulates FB to 1.215V during PWM off-time to prevent droop and enable 40,000:1 dimming.
It features internal 400mΩ/40V/1A power switch, integrated Schottky diode, programmable OVP via FB divider, and thermal regulation that derates LED current above 170°C junction temperature. Fault detection operates independently per string-open-LED (VOUT–VLEDx < 0.4V) or short-to-GND (VLEDx < 6.0V)-with FAULT pin assertion and continued regulation of the healthy string.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| LED Current per String | Programmable 10mA–60mA via single ISET resistor; enables scalable brightness across display zones. |
| Current Matching Accuracy | ±2% max (±0.3% typ); ensures uniform luminance between dual LED strings without external calibration. |
| PWM Dimming Ratio | Up to 40,000:1 at 100Hz (250ns min on-time); supports ultra-low-brightness backlighting without flicker. |
| Switching Frequency | Fixed 2MHz (±6%); allows compact 3.3–10µH inductors and reduces EMI filtering requirements. |
| Input Voltage Range | 2.9V to 40V; supports direct connection to automotive battery (cold-crank tolerant) and industrial 24V rails. |
| VOUT Regulation Range | Adaptive up to 36V; dynamically tracks minimum required headroom (VOUT–VLEDx ≈ 1.3V) to maximize efficiency. |
| Thermal Protection | Internal junction temperature regulation above 170°C; actively reduces LED current to sustain operation under thermal stress. |
Pinout & Package
LT3909HMSE#PBF is housed in a 12-lead plastic MSOP package with exposed pad (Pin 13 = GND), optimized for thermal dissipation in space-constrained LED driver layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| INTVCC (1) | Internal 3.0V regulator output | Supplies gate driver and control logic; must be bypassed with ≥1µF X7R ceramic capacitor; max 100µA external load. |
| VIN (2) | Main input supply | Accepts 2.9V–40V; powers internal circuits and boost switch; requires local ceramic bypass capacitor. |
| EN/UVLO (3) | Enable and undervoltage lockout input | 0.4V shutdown / 1.215V enable threshold; supports programmable UVLO hysteresis using resistor divider from VIN. |
| ISET (4) | LED current programming node | Sets both string currents simultaneously via single resistor to GND; 16.7kΩ yields 60mA per string. |
| CTRL (5) | Analog dimming and latch-off control | 0–1V analog control range; <80mV disables LED current; enables ambient temperature derating via NTC network. |
| FB (6) | Output voltage regulation feedback | Programs OVP level (1.215V reference); samples VOUT during PWM high to hold regulated level during PWM low. |
| PWM (7) | Digital dimming control | Active-high signal; turns off both high-side current sources synchronously; internal pull-down when unused. |
| FAULT (8) | Open/short LED fault flag | Active-low open-drain output; asserts for open-LED (VOUT–VLEDx < 0.4V) or short-to-GND (VLEDx < 6.0V) on either string. |
| LED1, LED2 (9,10) | High-side LED current outputs | Each drives one LED string; can be paralleled for >60mA total; no external sense resistors required. |
| 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; requires minimized trace area for EMI control. |
| Exposed Pad (13) | Thermal ground | Must be soldered to PCB ground plane; provides primary thermal path (θJC = 5–10°C/W). |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 400mΩ, 40V, 1A power switch | Eliminates external MOSFET and reduces BOM count; rated for continuous 60mA × 2 strings at full input range. |
| Internal Schottky diode | Reduces board area and component count; enables complete LED driver solution with only inductor, capacitor, and ISET resistor. |
| Independent per-string fault detection | Allows one LED string to remain fully regulated during open or short fault on the other-critical for safety-critical displays. |
| VOUT regulation during PWM off-time | Maintains stable output voltage despite Schottky leakage, enabling fast LED current recovery and flicker-free dimming. |
| Thermal foldback with junction sensing | Automatically reduces LED current above 170°C die temperature-preserves reliability without external thermal sensors. |
Applications
| Automotive Instrument Clusters | High-Contrast Industrial Displays |
|---|---|
Use Scenario: Driving dual-zone LED backlights behind TFT LCDs in vehicle dashboards with wide ambient temperature range (–40°C to +125°C). IC Role / Device Role / Timing Role: Dual high-side current source regulating two independent LED strings with adaptive VOUT and real-time thermal derating. Use Value: Ensures consistent brightness and color fidelity across temperature extremes while meeting ASIL-B functional safety requirements via fault flag reporting. | Use Scenario: Powering segmented LED arrays in medical imaging UIs and factory HMIs where uniform luminance and long-term stability are critical. IC Role / Device Role / Timing Role: Precision current-matched LED driver with ±0.3% typical matching and 40,000:1 PWM dimming for calibrated grayscale rendering. Use Value: Eliminates visible banding or stepping in low-intensity modes, supporting diagnostic-grade visual accuracy. |
| Avionics Panel Lighting | Portable Diagnostic Equipment |
Use Scenario: Backlighting for MIL-STD-810G–compliant cockpit displays requiring EMI resilience and cold-start capability down to 2.9V. IC Role / Device Role / Timing Role: Fixed 2MHz boost controller with integrated switch and Schottky, minimizing external components and layout sensitivity. Use Value: Reduces bill-of-materials and PCB area while maintaining stable output under wide input transients and vibration-induced noise. | Use Scenario: Battery-powered handheld ultrasound or point-of-care devices needing ultra-low quiescent current and efficient dimming over 10+ hour runtime. IC Role / Device Role / Timing Role: Low-IQ LED driver with 0.3µA shutdown current and analog dimming down to 10% of full scale. Use Value: Extends battery life without sacrificing dimming resolution or introducing audible noise from low-frequency PWM. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3220EUD#PBF | Charge-pump topology (no inductor); max 40mA per string; 1.2MHz switching; no integrated Schottky. | Better for ultra-thin portable designs where inductor height is prohibited; unsuitable for >36V LED strings or high-efficiency automotive use. | Select when board height is constrained and LED VF ≤ 12V; avoid for high-VF or thermally demanding environments. |
| TPS61165DRVR | Single-string 40mA driver; 1.2MHz; external MOSFET required; no thermal foldback or per-string fault reporting. | Lower cost for single-zone lighting; lacks dual-string redundancy and robust fault diagnostics needed for safety-critical systems. | Use for cost-sensitive consumer displays; not recommended for automotive or medical applications requiring fault isolation. |
Compared with LTC3220EUD#PBF and TPS61165DRVR, the LT3909HMSE#PBF uniquely combines dual-string current matching, adaptive VOUT regulation, integrated power switch + Schottky, and per-string fault reporting-making it the only option qualified for AEC-Q100 Grade 1 and capable of sustaining full 60mA operation across –40°C to +125°C.
Availability
LT3909HMSE#PBF is available at Aetrix Electronics and suitable for automotive instrument clusters, avionics panel lighting, and high-contrast industrial displays requiring stable component supply, long-term lifecycle support, and AEC-Q100–compliant performance.
Supply support for LT3909HMSE#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 technologies, serving automotive, industrial, communications, and healthcare markets.
The LT3909 product line was developed by Linear Technology (acquired by ADI in 2017) specifically for high-reliability, thermally robust LED backlighting in safety-critical and wide-temperature applications-emphasizing precision current matching, fault resilience, and minimal external component count.
FAQ
What is the maximum LED string voltage supported by the LT3909HMSE#PBF?
The LT3909HMSE#PBF supports up to 36V of LEDs per string, enabled by its 40V absolute maximum ratings on LED1/LED2 pins and integrated 40V power switch. This allows driving ten white LEDs (3.6V VF each) in series per string while maintaining sufficient headroom for regulation and thermal margin.
Does the LT3909HMSE#PBF require external compensation components?
No, the LT3909HMSE#PBF includes internal compensation for both the boost converter and current regulation loops. No external compensation capacitors or resistors are needed-reducing design complexity and PCB area while ensuring stable operation across all operating conditions and component tolerances.
How does the LT3909HMSE#PBF handle an open-LED fault on one string?
When an open-LED fault occurs on one string (VOUT–VLEDx < 0.4V), the LT3909HMSE#PBF asserts the FAULT pin low and continues full regulation of the remaining healthy string. The faulty string is ignored by the GM1 regulation loop, preventing disruption to the active display zone while providing clear diagnostic signaling.
Can the LT3909HMSE#PBF drive more than 60mA total LED current?
Yes-the LT3909HMSE#PBF allows paralleling LED1 and LED2 pins to deliver up to 120mA total current. In this configuration, the ISET resistor must be halved (e.g., 8.35kΩ for 120mA) to maintain accurate current setting, and thermal design must account for doubled power dissipation in the IC's exposed pad.
What is the purpose of the INTVCC pin on the LT3909HMSE#PBF?
INTVCC is the output of an internal 3.0V linear regulator powered from VIN. It supplies the gate driver and control circuitry. It must be bypassed with ≥1µF X7R ceramic capacitor and can source up to 100µA for external functions like CTRL voltage dividers or FAULT pull-ups-but must not power external loads beyond those specified.
LT3909HMSE#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:
- Obsolete
- 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
LT3909HMSE#PBF FAQ
1.How can I place an order for LT3909HMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3909HMSE#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 LT3909HMSE#PBF reliable?
The price and inventory of LT3909HMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3909HMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3909HMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3909HMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3909HMSE#PBF?
LT3909HMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3909HMSE#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 LT3909HMSE#PBF?
For technical support, including LT3909HMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3909HMSE#PBF requirements.
6.How does Aetrix verify that LT3909HMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3909HMSE#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 LT3909HMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3909HMSE#PBF?
All LT3909HMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3909HMSE#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 LT3909HMSE#PBF part is unused and in its original packaging.
Return procedure for LT3909HMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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