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Texas Instruments LM3503SQX-44/NOPB
- Part No.:
- LM3503SQX-44/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQX-44/NOPB.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,421
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Product details
Overview
LM3503SQX-44/NOPB from Texas Instruments is a dual-display constant-current white LED driver IC with analog brightness control, 44 V over-voltage protection, 1 MHz switching frequency, and support for up to 10 LEDs (5 per display). It operates from 2.5 V to 5.5 V input and delivers precise current regulation in portable backlighting systems.
For engineers reviewing the LM3503SQX-44/NOPB datasheet, LM3503SQX-44/NOPB pinout, LM3503SQX-44/NOPB application, or LM3503SQX-44/NOPB equivalent, this page provides verified technical context, package mapping, real-world use cases, and validated alternative options for dual-display LED backlighting designs.
Technical Context
The LM3503SQX-44/NOPB implements an asynchronous current-mode PWM controller with integrated NMOS power switch (N1), PMOS bypass switch (P1), and NMOS bypass switch (N2) to independently regulate MAIN and SUB LED strings. Its feedback loop uses a 0.55 V typical reference voltage at the Fb pin, dynamically adjusted via analog voltage on the Cntrl pin (0.2–3.5 V range).
It features dedicated protection circuitry including under-voltage lockout (2.4 V turn-on), thermal shutdown, cycle-by-cycle current limiting (750 mA typ. for 44 V version), and output over-voltage protection set to 40.5–43.5 V (on-threshold). Soft-start eliminates inrush current during startup.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output OVP Threshold | 40.5–43.5 V (enables safe operation with 44 V-rated external capacitors and diodes) |
| Input Voltage Range | 2.5 V to 5.5 V (supports single-cell Li-ion and multi-cell alkaline battery inputs) |
| Switching Frequency | 0.8–1.2 MHz (allows compact 2.2 µH inductor and low-profile ceramic output capacitor) |
| LED Current Control | Analog voltage (0.2–3.5 V) on Cntrl pin sets feedback reference; enables smooth dimming without PWM filtering |
| Peak Efficiency | >80% (achieved at 15 mA per string with VIN = 3.6 V and 4 LEDs total) |
| Current Limit (ICL) | 450–1050 mA (typ. 750 mA at TJ = 25°C; protects internal N1 switch under overload or open-LED fault) |
| Enable Logic | En1 ≥1.4 V enables MAIN display; En2 ≥1.4 V enables SUB display; both ≤0.3 V forces shutdown |
Pinout & Package
LM3503SQX-44/NOPB is packaged in a 10-bump thin DSBGA (0.8 mm × 0.8 mm, 0.4 mm pitch, <1 mm height) with die attach pad (DAP) for thermal dissipation.
| 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 input ripple and EMI |
| Sw | Drain of internal NMOS power switch (N1) | Connects to inductor; high dv/dt node requiring short, wide PCB trace to reduce EMI and conduction loss |
| En1 | PMOS FET (P1) enable control | ≥1.4 V turns OFF P1, enabling MAIN display; ≤0.3 V turns ON P1, disabling MAIN display |
| En2 | NMOS FET (N2) enable control | ≥1.4 V turns OFF N2, enabling SUB display; ≤0.3 V turns ON N2, disabling SUB display |
| Fb | Feedback voltage sensing node | Monitors regulated output voltage; internal error amplifier compares to 0.55 V reference |
| Cntrl | Analog brightness control input | 0.2–3.5 V DC input scales LED current; 0 V does not guarantee zero current-shutdown required for full off |
| AGND | Analog ground reference | Must be connected directly to PGND to avoid noise coupling into feedback path |
| PGND | Power ground return | High-current return path for Sw, VOUT1, VOUT2; solder DAP to solid ground plane for thermal management |
| VOUT1 | OVP sense node & PMOS source | Connects to cathode of Schottky diode and output capacitor; OVP comparator monitors this node |
| VOUT2 | Drain of internal NMOS/PMOS switches (N2/P1) | Used for SUB display string; if unused, connect 100 nF capacitor to ground per datasheet recommendation |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent display control | Separate En1/En2 logic enables MAIN and SUB LED strings independently-no external FETs needed |
| Integrated 44 V OVP | Hardware-level protection prevents damage when LED string opens or disconnects; eliminates need for external OVP circuit |
| 1 MHz fixed-frequency operation | Enables use of small 2.2 µH inductors and 1 µF ceramic output capacitors-reduces board area and BOM count |
| Analog brightness control | DC voltage on Cntrl pin directly modulates LED current without requiring RC-filtered PWM, simplifying system timing |
| Internal soft-start | Gradually ramps current limit at startup to prevent inrush into output capacitor-eliminates need for external soft-start circuit |
| Thermal shutdown & UVP | Protects device during overtemperature (>150°C) or brownout (<2.3 V); ensures robust operation in battery-powered systems |
Applications
| Cellular Phone Dual Display | PDA Main + Subscreen Backlight |
|---|---|
Use Scenario: Simultaneous illumination of main LCD and secondary status OLED in compact handheld devices with space-constrained PCB layout. IC Role / Device Role / Timing Role: Constant-current LED driver providing independent analog dimming for two physically separate LED strings using single inductor and shared feedback architecture. Use Value: Reduces component count by eliminating discrete MOSFETs and external current-sense resistors while maintaining >80% efficiency across 2–5 LED per string. |
Use Scenario: Powering primary TFT display (4–5 white LEDs) and auxiliary monochrome sub-display (2–3 white LEDs) from single Li-ion cell. IC Role / Device Role / Timing Role: Dual-channel boost converter with hardware-enabling logic (En1/En2) to activate either display segment without software intervention. Use Value: Enables instant display switching with no firmware latency; supports always-on sub-display while main screen sleeps. |
| Portable Media Player UI Lighting | Smartwatch Dual-Panel Backlight |
Use Scenario: Illuminating front-panel button backlight and rear LCD simultaneously in battery-operated media players with dynamic brightness requirements. IC Role / Device Role / Timing Role: Analog-controlled current source delivering stable 15 mA per string with <±5% matching between MAIN and SUB outputs. Use Value: Eliminates visible brightness mismatch between panels; maintains consistent color temperature across dimming range (0.2–3.5 V Cntrl). |
Use Scenario: Driving circular main display and linear status bar on ultra-thin wearable devices where height <1 mm is mandatory. IC Role / Device Role / Timing Role: Ultra-low-profile DSBGA-packaged LED driver enabling direct placement under glass cover lens with minimal Z-height impact. Use Value: Achieves 0.8 mm × 0.8 mm footprint and <1 mm profile-critical for wrist-worn form factors with tight mechanical stack-up constraints. |
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; lower ICL (400–800 mA); identical pinout and control interface | Suitable only for ≤25 V LED strings; cannot replace LM3503SQX-44/NOPB in 44 V systems without redesign | Select when output voltage remains below 23 V and higher OVP margin is unnecessary |
| TPS61165DRVR | Single-output, 40 V OVP, 1.2 MHz switching, no dual-string enable logic; WQFN-16 package | Requires external FETs and logic for dual-display control; lacks En1/En2 hardware enable pins | Choose when only one display is needed or when design flexibility justifies added components and layout complexity |
Compared with LM3503SQX-25/NOPB, the LM3503SQX-44/NOPB provides 19 V higher OVP headroom for robust open-circuit protection; compared with TPS61165DRVR, it integrates dual-string control logic and reduces bill-of-materials by eliminating two external MOSFETs and associated gate-drive circuitry.
Availability
LM3503SQX-44/NOPB is available at Aetrix Electronics and suitable for cellular phone backlighting, PDA dual-display systems, and portable media player UI lighting requiring stable component supply and long-term production continuity.
Supply support for LM3503SQX-44/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 and embedded processing technologies with broad portfolio coverage in power management and signal chain solutions.
The LM3503 product line was designed specifically for dual-display white LED backlighting in space-constrained portable electronics, emphasizing integration, efficiency, and hardware-based display control.
FAQ
What is the maximum number of LEDs supported by LM3503SQX-44/NOPB?
The LM3503SQX-44/NOPB supports up to 10 white LEDs total-5 per display string (MAIN and SUB). This assumes typical forward voltage of 3.2 V per LED and 5.5 V input, yielding ~16 V required for MAIN and ~16 V for SUB, well within the 44 V OVP limit. The actual count depends on LED VF distribution and minimum input voltage.
Does LM3503SQX-44/NOPB require external compensation components?
No, LM3503SQX-44/NOPB operates with no external compensation. Its current-mode PWM architecture and internal error amplifier are factory-tuned for stability across all operating conditions. Only external passive components-inductor, Schottky diode, input/output capacitors, and optional RC filter for PWM dimming-are required.
How does the Cntrl pin voltage relate to LED current in LM3503SQX-44/NOPB?
In LM3503SQX-44/NOPB, the Cntrl pin voltage (0.2–3.5 V) linearly scales the internal feedback reference: VFb = 0.156 × VCntrl. LED current is then set by ILED = VFb / RSET, where RSET is the external sense resistor from Fb to ground. At VCntrl = 1.6 V, VFb ≈ 0.25 V yields ~15 mA with 16.7 Ω RSET.
Can LM3503SQX-44/NOPB drive both MAIN and SUB displays simultaneously?
Yes, LM3503SQX-44/NOPB can drive both MAIN and SUB displays concurrently. Apply ≥1.4 V to both En1 and En2 pins to enable P1 and N2 switches, routing current through VOUT1→LEDs→VOUT2→Fb path. The device regulates total current across the combined string while maintaining OVP protection on VOUT1.
What thermal performance can be expected from LM3503SQX-44/NOPB in its DSBGA package?
LM3503SQX-44/NOPB in the 10-bump DSBGA package has a junction-to-ambient thermal resistance (θJA) of 65°C/W. With 150°C max junction temperature and 25°C ambient, maximum continuous power dissipation is ~1.92 W. Proper DAP soldering to a 1-in² ground plane improves thermal performance significantly in real layouts.
LM3503SQX-44/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:
- 44V
- Current - Output / Channel:
- 750mA (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-44/NOPB FAQ
1.How can I place an order for LM3503SQX-44/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQX-44/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-44/NOPB reliable?
The price and inventory of LM3503SQX-44/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-44/NOPB is usually 5 days.
3.What payment methods are accepted for LM3503SQX-44/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQX-44/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQX-44/NOPB?
LM3503SQX-44/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQX-44/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-44/NOPB?
For technical support, including LM3503SQX-44/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQX-44/NOPB requirements.
6.How does Aetrix verify that LM3503SQX-44/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3503SQX-44/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-44/NOPB meets industry standards.
7.What is the process for return or replacement of LM3503SQX-44/NOPB?
All LM3503SQX-44/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQX-44/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-44/NOPB part is unused and in its original packaging.
Return procedure for LM3503SQX-44/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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