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Texas Instruments LM3503SQX-16/NOPB
- Part No.:
- LM3503SQX-16/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQX-16/NOPB.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,265
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Product details
Overview
LM3503SQX-16/NOPB from Texas Instruments is a dual-display constant-current white LED driver IC with analog brightness control, 16 V over-voltage protection, 1 MHz switching frequency, and 2.5–5.5 V input range. It drives up to 10 LEDs (5 per display) in portable dual-backlight systems using internal PMOS/NMOS FET switches and feedback-controlled current regulation.
For engineers reviewing the LM3503SQX-16/NOPB datasheet, LM3503SQX-16/NOPB pinout, LM3503SQX-16/NOPB application, or LM3503SQX-16/NOPB equivalent, this page delivers verified technical context, package-specific pin functions, real-world dual-display use cases, and validated alternative options for backlight power management design.
Technical Context
The LM3503SQX-16/NOPB implements an asynchronous current-mode PWM controller with cycle-by-cycle current limiting, dedicated OVP (16 V threshold), UVP (2.5 V turn-on), soft-start, and thermal shutdown. Its dual-FET architecture enables independent MAIN/SUB display control via En1 and En2 pins, supporting dynamic segment enable/disable without external MOSFETs.
It uses analog voltage at the Cntrl pin (0.2–3.5 V) to set feedback reference (VFb = 0.156 × VCntrl), directly scaling LED current from near-zero to full output. The device operates in CCM/DCM modes depending on load and inductance, with maximum duty cycle limited to 95% to prevent inductor saturation and ensure stability without external compensation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output OVP Threshold | 16 V nominal - sets hard limit for VOUT1 to protect LEDs and output capacitor during open-circuit or LED failure |
| Switching Frequency | 1 MHz ±20% - enables compact external components (22 µH inductor, 1 µF ceramic output cap) and reduces EMI filtering burden |
| Input Voltage Range | 2.5 V to 5.5 V - supports single-cell Li-ion (3.0–4.2 V) and dual-cell alkaline/NiMH (2.4–3.6 V) battery inputs without LDO pre-regulation |
| LED Current Control | Analog Cntrl pin (0.2–3.5 V) → VFb = 0.156 × VCntrl - provides linear, noise-immune dimming without PWM filtering complexity |
| Peak Efficiency | >80% at 15 mA per string - achieved via low RDS(ON) NMOS (0.55 Ω typ) and optimized gate drive, minimizing conduction loss in boost path |
| Thermal Resistance θJA | 49 °C/W (WQFN-16) - enables 350 mW max dissipation at TA = 85 °C, sufficient for dual 5-LED strings at 20 mA each |
Pinout & Package
LM3503SQX-16/NOPB is packaged in a 16-pin WQFN (RGH0016A) with 3.5 mm × 3.5 mm footprint and 0.5 mm pitch. Exposed DAP must be soldered to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input supply connection | Accepts 2.5–5.5 V; requires local 4.7 µF ceramic capacitor to minimize high-frequency ripple and EMI |
| Sw | Power NMOS drain node | Connects to boost inductor; high dv/dt node requiring short, wide trace to reduce EMI and switching losses |
| En1 | PMOS switch enable (MAIN display) | Logic-high (≥1.4 V) disables MAIN segment; internal pull-down ensures default OFF state when floating |
| En2 | NMOS switch enable (SUB display) | Logic-high (≥1.4 V) disables SUB segment; must be grounded if VOUT2 unused to prevent undefined operation |
| Fb | Feedback voltage sensing | Monitors regulated output current via resistor divider; 0.55 V typical reference sets LED current ILED = VFb / RSET |
| Cntrl | Analog brightness control input | 0.2–3.5 V DC input scales VFb linearly; no external RC filter needed for smooth analog dimming |
| AGND | Analog ground reference | Must be tied directly to PGND at single point to avoid noise coupling into feedback loop |
| PGND | Power ground return | High-current return path for Sw, VOUT1, VOUT2; requires low-impedance connection to DAP and PCB ground plane |
| VOUT1 | OVP sense & PMOS source | Primary output node; connects to anode of MAIN LED string and cathode of Schottky flyback diode |
| VOUT2 | NMOS/PMOS drain junction | Intermediate node between MAIN and SUB strings; connect 100 nF capacitor if unused to suppress ringing |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent display control | En1/En2 pins enable hardware-selectable MAIN/SUB LED string activation-no firmware or external logic required |
| Integrated OVP with 16 V threshold | Prevents overvoltage damage during LED open-circuit faults; eliminates need for external Zener clamp or supervisor IC |
| No external compensation required | Stable operation across all loads and input voltages without loop compensation components-reduces BOM count and layout area |
| Internal soft-start | Gradually ramps current limit at startup to limit inrush into output capacitor-prevents input voltage droop and system reset |
| 16-pin WQFN package | 3.5 mm × 3.5 mm, 0.5 mm pitch with exposed DAP-supports high-density portable designs while enabling efficient thermal transfer |
Applications
| Smartphone Dual-Display Backlight | PDA Main/Sub Screen Lighting |
|---|---|
Use Scenario: Simultaneous illumination of main LCD and secondary status OLED in compact handheld devices with shared battery rail. IC Role / Device Role / Timing Role: Constant-current boost driver regulating two independent LED strings with hardware-enabling via En1/En2 pins. Use Value: Eliminates need for two separate drivers or discrete FETs-reducing component count by ≥40% and PCB area by 25 mm². |
Use Scenario: Powering primary touchscreen and auxiliary keypad backlight from single Li-ion cell in legacy PDA platforms. IC Role / Device Role / Timing Role: Dual-channel analog-dimming LED driver with 1 MHz fixed-frequency operation to minimize audible noise and EMI. Use Value: Enables flicker-free dimming down to 1% brightness using only DC voltage on Cntrl pin-no PWM generator or filtering required. |
| Portable Medical Display Module | Industrial Handheld Terminal |
Use Scenario: Reliable backlighting for critical diagnostic screen and secondary alert indicator under variable temperature and battery conditions. IC Role / Device Role / Timing Role: Over-voltage protected (16 V), -40°C to +85°C rated LED driver with UVP and thermal shutdown. Use Value: Ensures fail-safe operation during LED string disconnection or cold-start battery sag-meets IEC 60601-1 safety margins. |
Use Scenario: Ruggedized field terminal with main display and status LED bar operating from 2xAA or rechargeable pack. IC Role / Device Role / Timing Role: High-efficiency (≥80%) boost driver supporting 2–5 LEDs per channel with minimal external components. Use Value: Extends battery life by 18% vs. linear drivers; WQFN package withstands vibration and thermal cycling in industrial enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-display LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM3503SQX-25/NOPB | 25 V OVP threshold; higher current limit (400–600 mA) and RDS(ON) (5 Ω PMOS, 2.5 Ω NMOS) | Suitable for longer LED strings (up to 8 LEDs per channel) or higher-current displays (≥25 mA) | Select when driving >5 LEDs per string or requiring higher fault margin beyond 16 V |
| TPS61165DRVR | Single-output, 38-V OVP, I²C programmable, 1.2-MHz switching, integrated Schottky | Lacks dual-string hardware control; requires MCU interface for multi-display sequencing | Choose for systems needing digital brightness control or where space allows separate drivers per display |
Compared with LM3503SQX-25/NOPB and TPS61165DRVR, the LM3503SQX-16/NOPB offers optimal balance of hardware simplicity, 16-V fault protection, and analog dimming for cost-sensitive dual-display portable designs-without MCU dependency or over-engineered voltage headroom.
Availability
LM3503SQX-16/NOPB is available at Aetrix Electronics and suitable for smartphone backlighting, PDA display modules, and portable medical equipment requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM3503SQX-16/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 ICs, with decades of expertise in LED lighting and portable power solutions.
The LM3503 product line was designed specifically for dual-display backlighting in space-constrained portable electronics, integrating dual-channel control, analog dimming, and robust protection in a single WQFN package.
FAQ
What is the maximum number of LEDs the LM3503SQX-16/NOPB can drive per channel?
The LM3503SQX-16/NOPB supports up to 5 white LEDs per channel (MAIN or SUB), based on its 16 V over-voltage protection threshold and typical forward voltage of 3.2 V per LED at 20 mA. Driving more than 5 LEDs risks exceeding the 16 V OVP limit under worst-case Vf and temperature conditions, triggering shutdown. Always verify total string Vf against the 14.5–16.5 V OVP window in your specific application.
How does the Cntrl pin voltage translate to actual LED current in the LM3503SQX-16/NOPB?
In the LM3503SQX-16/NOPB, the Cntrl pin voltage (VCntrl) linearly scales the internal feedback reference: VFb = 0.156 × VCntrl. LED current is then calculated as ILED = VFb / RSET, where RSET is the external sense resistor from Fb to ground. For example, at VCntrl = 2.0 V, VFb = 0.312 V; with RSET = 10 Ω, ILED = 31.2 mA. This direct analog mapping avoids PWM filtering and ensures smooth, low-noise dimming.
Can the LM3503SQX-16/NOPB operate with only the MAIN display active?
Yes. To activate only the MAIN display, apply ≥1.4 V to En1 and ≤0.3 V to En2. This turns off the PMOS switch (P1) controlling MAIN while turning on the NMOS switch (N2) controlling SUB-effectively disabling SUB. If VOUT2 is unused, En2 must be grounded (not floating) per TI's design guidance to prevent undefined behavior. The LM3503SQX-16/NOPB will regulate current only through the MAIN string connected to VOUT1 and Fb.
What is the purpose of the 100 nF capacitor recommended at VOUT2 for the LM3503SQX-16/NOPB?
The 100 nF capacitor at VOUT2 in the LM3503SQX-16/NOPB suppresses high-frequency ringing and voltage overshoot when the SUB display is inactive or VOUT2 is left unconnected. Without it, parasitic inductance and capacitance at the VOUT2 node can cause oscillation during switching transitions, potentially violating the 16 V OVP threshold or injecting noise into the Fb loop. TI specifies this capacitor for LM3503-35V and LM3503-44V versions, but recommends it for all variants when VOUT2 is unused-including the LM3503SQX-16/NOPB.
Does the LM3503SQX-16/NOPB require external compensation components?
No. The LM3503SQX-16/NOPB is internally compensated and operates stably across its full input voltage (2.5–5.5 V), load (2–5 LEDs per string), and temperature (−40°C to +85°C) ranges without any external compensation components. This is confirmed in the datasheet's "No External Compensation Required" feature and validated by TI's typical application circuit, which includes only input/output capacitors, inductor, Schottky diode, and current-sense resistor-no op-amps, resistors, or capacitors in the feedback path.
LM3503SQX-16/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- DC DC Regulator
- Topology:
- Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 2
- Voltage - Supply (Min):
- 2.5V
- Voltage - Supply (Max):
- 5.5V
- Voltage - Output:
- 16V
- Current - Output / Channel:
- 400mA (Switch)
- Frequency:
- 1MHz
- Dimming:
- Analog, PWM
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-WQFN (4x4)
LM3503SQX-16/NOPB FAQ
1.How can I place an order for LM3503SQX-16/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQX-16/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 LM3503SQX-16/NOPB reliable?
The price and inventory of LM3503SQX-16/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3503SQX-16/NOPB is usually 5 days.
3.What payment methods are accepted for LM3503SQX-16/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQX-16/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQX-16/NOPB?
LM3503SQX-16/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQX-16/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 LM3503SQX-16/NOPB?
For technical support, including LM3503SQX-16/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQX-16/NOPB requirements.
6.How does Aetrix verify that LM3503SQX-16/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3503SQX-16/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 LM3503SQX-16/NOPB meets industry standards.
7.What is the process for return or replacement of LM3503SQX-16/NOPB?
All LM3503SQX-16/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQX-16/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 LM3503SQX-16/NOPB part is unused and in its original packaging.
Return procedure for LM3503SQX-16/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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