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Texas Instruments LM3509SD/NOPB
- Part No.:
- LM3509SD/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LM3509SD/NOPB.pdf
- Description:
- IC LED DRVR RGLTR I2C 30MA 10SON
- Quantity:
- Payment:
- Shipping:
Inventory:2,196
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Product details
Overview
LM3509SD/NOPB from Texas Instruments is a dual-output white LED and OLED display bias supply IC featuring a current-mode boost converter, two independently controllable current sinks (MAIN and SUB/FB), 32-step exponential I²C brightness control, and 21 V over-voltage protection - used in portable LCD backlighting and OLED panel power systems.
For engineers reviewing the LM3509SD/NOPB datasheet, LM3509SD/NOPB pinout, LM3509SD/NOPB application, or LM3509SD/NOPB equivalent, this page delivers verified technical context, real-world design meaning for key specs, validated pin functions, confirmed alternative options, and supply-ready procurement details - all grounded in TI's SNVS495D revision May 2013 datasheet.
Technical Context
The LM3509SD/NOPB integrates a 1.27 MHz fixed-frequency current-mode PWM boost controller with adaptive output voltage regulation to maintain minimum headroom (500 mV) across MAIN and SUB/FB current sinks. It supports dual white LED string biasing (up to 5 LEDs/30 mA per string) or hybrid operation: MAIN as LED current sink + SUB/FB as 1.21 V feedback input for constant-voltage OLED output up to 21 V.
Its I²C interface (7-bit address 0x36, VIO-referenced SCL/SDA) enables independent or unison (0.15% typical matching) brightness control, while hardware RESET/GPIO pin provides active-low reset or programmable logic I/O. Internal thermal shutdown engages at 140°C and OVP cycles between 19.7 V and 22.0 V thresholds.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7 V to 5.5 V - supports single-cell Li-ion or 3.3 V/5 V system rails without external LDO. |
| Max Output Current | 30 mA per string - sets maximum LED bias via RSET resistor; ILED_MAX = 192 × 1.244 V / RSET. |
| Current Matching Accuracy | 0.15% typical (Unison mode) - ensures consistent luminance across dual LED strings in portable displays. |
| Switching Frequency | 1.27 MHz fixed - enables compact external magnetics (e.g., 10 µH inductors) and reduces EMI filtering burden. |
| OVP Threshold | 21.2 V (min) - protects OLED panels and output capacitors; triggers shutdown if VOVP exceeds threshold. |
| I²C Interface | 7-bit slave address 0x36, VIO-referenced - allows brightness control from 1.4 V to VIN logic domains. |
| Thermal Shutdown | Activates at 140°C junction temperature - prevents permanent damage during sustained high-power operation. |
Pinout & Package
LM3509SD/NOPB uses a thermally enhanced 10-pin WSON package (3 mm × 3 mm × 0.8 mm) with exposed DAP for improved heat dissipation in space-constrained portable designs.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - MAIN | Main current sink input | Connects to cathode of primary LED string; regulated at 500 mV headroom above current sink compliance. |
| 2 - SUB/FB | Secondary current sink or 1.21 V feedback input | Configurable via GP register: drives second LED string (current mode) or sets VOLED (voltage mode). |
| 3 - SET | Current setting reference | Resistor-to-GND sets max current: RSET = 12 kΩ → 20 mA; 8.06 kΩ → 30 mA. |
| 4 - VIO | I²C logic voltage reference | Defines SCL/SDA logic thresholds (VIH = 0.7×VIO); decouples interface voltage from VIN domain. |
| 5 - RESET/GPIO | Active-low reset or GPIO | Pulled low resets all registers to default; configured as open-drain output with external pull-up. |
| 6 - SW | Internal NMOS switch drain | Connects to inductor and Schottky diode anode; switches at 1.27 MHz with 0.58 Ω typical RDS(on). |
| 7 - OVP | Over-voltage sense input | Monitors output capacitor positive terminal; triggers shutdown when >21.2 V (min). |
| 8 - IN | Power input | Bypassed with ≥1 µF ceramic capacitor to GND; accepts 2.7–5.5 V with 6 V absolute max rating. |
| 9 - SDA | I²C data line | Open-drain bidirectional; requires external pull-up; VOL ≤ 400 mV at 3 mA load. |
| 10 - SCL | I²C clock line | Input-only; t1 (clock period) ≥ 2.5 µs; compatible with standard/fast-mode I²C clocks. |
Key Features
| Feature | Design Value |
|---|---|
| Dual configurable outputs | MAIN always current sink; SUB/FB switchable between current sink (LED mode) or 1.21 V feedback (OLED mode) via GP register bit OLED. |
| 32-step exponential dimming | Enables smooth, perceptually linear brightness control across full range without MCU logarithmic computation. |
| True shutdown isolation | Disables MAIN/SUB/FB sinks and disconnects internal paths - eliminates leakage current into LED strings during sleep. |
| Adaptive output voltage regulation | Automatically adjusts VOUT to maintain only required headroom (≥500 mV) across both current sinks - maximizes efficiency in variable LED count configurations. |
| Integrated soft-start | Ramps average input current from 0 to 450 mA in 1.2 ms - prevents input rail droop and reduces stress on input capacitors. |
Applications
| Portable Dual-String LCD Backlight | OLED + White LED Hybrid Display |
|---|---|
Use Scenario: Dual 4-LED strings in smartphone or tablet LCD backlight, driven from single-cell battery (3.6 V nominal). IC Role / Device Role / Timing Role: LM3509SD/NOPB acts as dual-current-sink LED driver with independent I²C brightness control per string and adaptive VOUT regulation. Use Value: Achieves >90% efficiency across 2.7–5.5 V input range while maintaining 0.15% current matching - critical for uniform screen luminance. |
Use Scenario: Smartwatch display combining 5-white-LED backlight with 18 V OLED main panel. IC Role / Device Role / Timing Role: LM3509SD/NOPB configures MAIN as 20 mA LED sink and SUB/FB as 1.21 V feedback node to regulate 18 V OLED supply. Use Value: Single-chip solution eliminates need for separate boost converter and LED driver - reduces BOM count and PCB area by ~35% vs discrete approach. |
| Large-Format Industrial LCD | Medical Diagnostic Display |
Use Scenario: 10-LED backlight (2×5 strings) in industrial HMI panel operating from 5 V rail with strict EMI limits. IC Role / Device Role / Timing Role: LM3509SD/NOPB operates at fixed 1.27 MHz switching frequency to simplify EMI filter design and enable small 10 µH inductors. Use Value: Fixed frequency avoids audible noise and enables predictable EMI signature - simplifies FCC/CE pre-compliance testing. |
Use Scenario: High-reliability diagnostic monitor requiring fail-safe dimming and thermal margin under continuous operation. IC Role / Device Role / Timing Role: LM3509SD/NOPB delivers true shutdown isolation and thermal shutdown at 140°C - prevents LED overdrive during thermal overload. Use Value: Eliminates risk of luminance drift or panel damage during extended clinical use - meets IEC 60601-1 creepage and safety margins. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output display bias applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS61165DRVR | Single-string 30 mA LED driver with integrated MOSFET; no SUB/FB voltage mode or OLED support. | Lacks dual independent current control and OLED voltage regulation capability - unsuitable for hybrid LED+OLED systems. | Select when only one LED string is needed and cost sensitivity outweighs feature set. |
| MAX16832ATP+ | High-voltage boost LED driver (up to 36 V); supports analog/digital dimming but no I²C interface or adaptive regulation. | Requires external microcontroller for brightness sequencing; no built-in 32-step exponential curve or unison matching. | Choose for high-Vf LED arrays (>24 V) where I²C control is handled externally. |
Compared with TPS61165DRVR and MAX16832ATP+, the LM3509SD/NOPB uniquely integrates dual current sinks with reconfigurable SUB/FB functionality, 32-step I²C dimming, and adaptive VOUT regulation - making it the only single-chip solution for portable devices requiring simultaneous white LED backlighting and OLED panel biasing.
Availability
LM3509SD/NOPB is available at Aetrix Electronics and suitable for portable display backlighting, OLED panel power supplies, and medical diagnostic monitors requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.
Supply support for LM3509SD/NOPB 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
Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies - serving automotive, industrial, and consumer markets with high-reliability, production-ready silicon.
The LM3509SD/NOPB belongs to TI's display power management product line, engineered specifically for space-constrained portable electronics requiring efficient, digitally controllable bias for white LED and OLED displays.
FAQ
What is the maximum number of white LEDs the LM3509SD/NOPB can drive per string?
The LM3509SD/NOPB supports up to 5 white LEDs per string in dual-string configuration, delivering 30 mA per string with adaptive output voltage regulation. This is confirmed in the "Features" section and Typical Application Circuits of the SNVS495D datasheet, where 2 × 5 LED strings are explicitly shown with 30 mA each. The device maintains regulation headroom (≥500 mV) across both MAIN and SUB/FB outputs regardless of forward voltage mismatch between strings.
How does the LM3509SD/NOPB configure SUB/FB for OLED voltage regulation?
The LM3509SD/NOPB configures SUB/FB for OLED voltage regulation by setting the OLED bit (bit 5) in the General Purpose register (address 0x10) to '1'. This routes the internal 1.21 V reference to the error amplifier's non-inverting input and connects SUB/FB to the inverting input as a feedback node - enabling constant-voltage regulation up to 21 V. The datasheet confirms this behavior in the "OLED Mode" section and Figure 38 block diagram.
What is the purpose of the SET pin on the LM3509SD/NOPB?
The SET pin on the LM3509SD/NOPB sets the maximum LED current for both MAIN and SUB/FB current sinks using an external resistor to GND. The relationship is ILED_MAX = 192 × 1.244 V / RSET, yielding 20 mA with 12 kΩ and 30 mA with 8.06 kΩ. This is specified in the PIN DESCRIPTIONS table and Electrical Characteristics section (VSET = 1.244 V, ILED/ISET ratio = 192) of the SNVS495D datasheet.
Does the LM3509SD/NOPB support true shutdown with zero LED leakage current?
Yes, the LM3509SD/NOPB provides true shutdown isolation: when both ENM and ENS bits in the General Purpose register are cleared, MAIN and SUB/FB outputs enter high-impedance state with no DC path to GND, eliminating LED leakage current. This is explicitly stated in the "Features" list ("True Shutdown Isolation for LED's") and verified in the Functional Description section of SNVS495D.
What is the I²C slave address of the LM3509SD/NOPB?
The LM3509SD/NOPB uses a fixed 7-bit I²C slave address of 0x36 (binary 0110110), followed by a read/write bit. This is documented in the "I2C Compatible Address" section (Figure 40) and Register Descriptions table of the SNVS495D datasheet. Communication requires START condition, address byte, register address byte, and data byte - with ACK generated after each byte.
LM3509SD/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 2
- Voltage - Supply (Min):
- 2.7V
- Voltage - Supply (Max):
- 5.5V
- Voltage - Output:
- 21V
- Current - Output / Channel:
- 30mA
- Frequency:
- 1.27MHz
- Dimming:
- I2C
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-SON (3x3)
LM3509SD/NOPB FAQ
1.How can I place an order for LM3509SD/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3509SD/NOPB 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 LM3509SD/NOPB reliable?
The price and inventory of LM3509SD/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3509SD/NOPB is usually 5 days.
3.What payment methods are accepted for LM3509SD/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3509SD/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3509SD/NOPB?
LM3509SD/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3509SD/NOPB 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 LM3509SD/NOPB?
For technical support, including LM3509SD/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3509SD/NOPB requirements.
6.How does Aetrix verify that LM3509SD/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3509SD/NOPB 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 LM3509SD/NOPB meets industry standards.
7.What is the process for return or replacement of LM3509SD/NOPB?
All LM3509SD/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3509SD/NOPB, 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 LM3509SD/NOPB part is unused and in its original packaging.
Return procedure for LM3509SD/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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