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Texas Instruments LM3503SQ-16
- Part No.:
- LM3503SQ-16
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQ-16.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,696
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Product details
Overview
LM3503SQ-16 from Texas Instruments is a dual-display constant-current white LED driver IC with analog brightness control, designed for portable device backlighting. It delivers up to 10 white LEDs (5 per display), supports 2.5V–5.5V input, provides 16V over-voltage protection on VOUT1, and operates at 1 MHz switching frequency for compact filter design in cellular phones and PDAs.
For engineers reviewing the LM3503SQ-16 datasheet, LM3503SQ-16 pinout, LM3503SQ-16 application, or LM3503SQ-16 equivalent, key selection considerations include its dual independent enable logic (En1/En2), internal NMOS/PMOS FET switch architecture, analog-controlled current regulation via Cntrl pin voltage (0.2–3.5 V), and thermal shutdown with cycle-by-cycle current limiting.
Technical Context
The LM3503SQ-16 implements an asynchronous current-mode PWM controller with dedicated feedback (Fb) and control (Cntrl) paths. Its dual-FET topology separates MAIN (VOUT1–VOUT2) and SUB (VOUT2–Fb) LED string segments, enabling independent display activation via En1 and En2 logic thresholds (≤0.3 V / ≥1.4 V).
Protection features include input under-voltage lockout (2.4 V turn-on), output over-voltage protection (14.5–16.5 V threshold), soft-start, and thermal shutdown. The device uses no external compensation and integrates cycle-by-cycle current limiting with NMOS power switch current limit of 250–650 mA depending on OVP version.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| OVP Rating | 16 V - Sets maximum regulated output voltage on VOUT1 to protect LEDs and external diode/capacitor during open-circuit or LED failure. |
| Input Voltage Range | 2.5 V to 5.5 V - Matches single-cell Li-ion and Li-poly battery systems without requiring pre-regulation. |
| Switching Frequency | 1 MHz (±20%) - Enables use of small 2.2 µH inductors and low-ESR ceramic capacitors for space-constrained PCB layouts. |
| LED Current Control | Analog voltage (0.2–3.5 V) on Cntrl pin - Directly scales feedback reference to set LED current without external DAC or PWM filtering. |
| Enable Logic | En1/En2 with 0.3 V low / 1.4 V high thresholds - Supports independent MAIN/SUB display activation or full shutdown when both ≤0.3 V. |
| Peak Efficiency | >80% - Achieved across 4–10 LED loads at typical VIN = 3.6 V, minimizing thermal load in handheld devices. |
| Junction Temp Range | −40°C to +125°C - Qualified for operation in extended ambient environments including automotive infotainment displays. |
Pinout & Package
LM3503SQ-16 is housed in a 16-pin WQFN package (RGH0016A) with 3.5 mm × 3.5 mm footprint and <1 mm height, featuring an exposed die attach pad (DAP) soldered to PCB ground 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 between VIN and PGND to suppress high-frequency ripple. |
| Sw | Power NMOS drain | Connects to inductor; must use wide, short trace to minimize EMI and conduction loss (RDS(ON) = 0.55–1.1 Ω). |
| En1 | MAIN display PMOS enable | Drives MAIN segment (VOUT1–VOUT2); ≤0.3 V turns ON PMOS (MAIN off), ≥1.4 V turns OFF PMOS (MAIN on). |
| En2 | SUB display NMOS enable | Drives SUB segment (VOUT2–Fb); ≤0.3 V turns ON NMOS (SUB off), ≥1.4 V turns OFF NMOS (SUB on). |
| Fb | Feedback voltage node | Senses regulated current via external resistor; internal reference is 0.5–0.6 V, scaled by Cntrl pin voltage. |
| Cntrl | Analog brightness control | 0.2–3.5 V input adjusts LED current linearly; bias current ≤14 µA enables direct MCU GPIO or RC-filtered PWM drive. |
| AGND | Analog ground reference | Must be tied directly to PGND to avoid noise coupling into feedback path and ensure stable regulation. |
| PGND | Power ground return | High-current return path for Sw, VOUT1, VOUT2; requires low-impedance connection to DAP and system ground plane. |
| VOUT1 | OVP sense & PMOS source | Output node for MAIN display; connects to Schottky diode anode and output capacitor; OVP threshold fixed at 16 V. |
| VOUT2 | NMOS/PMOS drain junction | Midpoint between MAIN and SUB strings; unused versions require 100 nF capacitor to PGND to prevent oscillation. |
| L | Inductor connection point | Not a pin - label on schematic indicating external 2.2 µH inductor between Sw and VOUT1. |
| DAP | Thermal pad | Exposed copper pad under package; must be soldered to solid ground plane for θJA = 49°C/W thermal performance. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent display control | En1 and En2 pins allow MAIN and SUB backlight segments to be activated/deactivated separately without external logic or sequencing. |
| Analog brightness interface | Cntrl pin accepts DC voltage (not PWM) to directly scale LED current-eliminates need for RC filters or DACs in simple dimming designs. |
| Integrated protection suite | Includes UVP (2.4 V), OVP (16 V), thermal shutdown, soft-start, and cycle-by-cycle current limiting-reduces BOM count and layout complexity. |
| No external compensation required | Stable operation across all load conditions without loop compensation components-simplifies design validation and reduces board area. |
| Low-profile WQFN package | 3.5 mm × 3.5 mm × 0.8 mm footprint with thermal DAP enables thin portable form factors while maintaining 49°C/W thermal resistance. |
Applications
| Cellular Phone Main/Sub Display | PDA Dual-Screen Backlighting |
|---|---|
Use Scenario: Simultaneous or selective illumination of primary and secondary LCD panels in clamshell or slider phones with shared LED string architecture. IC Role / Device Role / Timing Role: Constant-current step-up driver regulating two independent LED current paths using internal PMOS/NMOS switches controlled by En1/En2. Use Value: Eliminates need for two separate boost drivers or discrete MOSFETs-reducing component count, PCB area, and power loss by >30% versus dual-IC solutions. | Use Scenario: Powering front and rear displays in handheld PDAs where battery life and thermal envelope are critical constraints. IC Role / Device Role / Timing Role: Analog-dimmed LED driver with 1 MHz switching frequency enabling compact 2.2 µH inductors and low-ESR ceramic output caps. Use Value: Achieves >80% efficiency at 15 mA per string, extending runtime by ~12% compared to lower-efficiency alternatives at same brightness. |
| Portable Media Player UI Lighting | Smartwatch Dual-Panel Interface |
Use Scenario: Dynamic backlight control for menu navigation and status indicators on media players with segmented OLED/LCD hybrid displays. IC Role / Device Role / Timing Role: Dual-channel current source supporting variable LED counts (2–5 per channel) and analog dimming via MCU GPIO or DAC output. Use Value: Enables smooth brightness transitions without flicker-Cntrl pin response time <10 µs ensures sub-millisecond dimming updates. | Use Scenario: Ultra-thin wearable device requiring minimal profile (<1 mm) and robust operation across −40°C to +85°C ambient range. IC Role / Device Role / Timing Role: Compact WQFN-packaged LED driver with integrated thermal shutdown and 125°C max junction temperature rating. Use Value: Maintains stable LED current regulation despite skin-contact thermal cycling-no derating needed up to 85°C ambient. |
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 |
|---|---|---|---|
| LM3503SQ-25 | 25 V OVP threshold instead of 16 V; identical pinout, package, and control logic. | Supports longer LED strings (up to 8 LEDs per channel at 3.2 V VF) but requires higher-voltage Schottky diode and output capacitor. | Select LM3503SQ-25 only if main display uses ≥7 white LEDs or system requires headroom above 16 V OVP trip point. |
| TPS61165DRVR | Single-output, 40 V OVP, I²C programmable current, 2.7–5.5 V input, 20-pin WQFN. | Requires external I²C host and firmware support; lacks dual-enable logic for independent MAIN/SUB control. | Choose TPS61165DRVR only when digital dimming granularity, fault reporting, or multi-device synchronization is required. |
Compared with LM3503SQ-25 and TPS61165DRVR, the LM3503SQ-16 offers optimal balance of analog simplicity, dual-display independence, and 16 V OVP headroom for standard 4–5 LED strings-making it the preferred choice for cost-sensitive, space-constrained portable designs without digital control requirements.
Availability
LM3503SQ-16 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, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for LM3503SQ-16 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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and personal electronics markets.
The LM3503 product line was developed specifically for dual-display backlighting in battery-powered portable devices, emphasizing analog dimming simplicity, high efficiency at low input voltages, and integrated protection to reduce system-level design risk.
FAQ
What is the maximum number of white LEDs the LM3503SQ-16 can drive per display channel?
The LM3503SQ-16 supports up to 5 white LEDs per channel (MAIN or SUB), totaling 10 LEDs. This assumes typical forward voltage of 3.2 V per LED and 16 V OVP rating-leaving ~0.5 V margin for diode drop and trace losses. Driving more than 5 LEDs risks exceeding the 16 V OVP threshold and triggering shutdown.
How does the Cntrl pin voltage relate to LED current in the LM3503SQ-16?
The LM3503SQ-16 uses the Cntrl pin voltage (0.2–3.5 V) to scale the internal feedback reference. At Cntrl = 0 V, LED current is near zero; at Cntrl = 3.5 V, full-scale current is achieved. The relationship is linear: ILED = RSET × (0.156 × VCntrl) / 0.55 V, where RSET is the external sense resistor connected to the Fb pin.
Can the LM3503SQ-16 operate with only the MAIN display active while disabling the SUB display?
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) on VOUT1 while turning ON the NMOS switch (N2) on VOUT2, routing all current through the MAIN string (VOUT1→VOUT2). The SUB string (VOUT2→Fb) remains inactive.
What is the purpose of the VOUT2 pin in the LM3503SQ-16, and is it required for single-display operation?
VOUT2 serves as the common node between MAIN and SUB LED strings. In single-display operation, VOUT2 is not used as an output but must be grounded or decoupled with a 100 nF capacitor to PGND to prevent instability. Leaving VOUT2 floating may cause erratic regulation or oscillation due to parasitic capacitance.
Does the LM3503SQ-16 require external compensation components for stable operation?
No. The LM3503SQ-16 uses an internally compensated current-mode PWM architecture that ensures stability across all valid input voltages (2.5–5.5 V), LED loads (2–5 per channel), and output capacitors. No external compensation network is needed-simplifying layout and eliminating tuning effort during design validation.
LM3503SQ-16 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)
LM3503SQ-16 FAQ
1.How can I place an order for LM3503SQ-16 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQ-16 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 LM3503SQ-16 reliable?
The price and inventory of LM3503SQ-16 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3503SQ-16 is usually 5 days.
3.What payment methods are accepted for LM3503SQ-16?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQ-16 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQ-16?
LM3503SQ-16 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQ-16 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 LM3503SQ-16?
For technical support, including LM3503SQ-16 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQ-16 requirements.
6.How does Aetrix verify that LM3503SQ-16 is sourced from the original manufacturer or authorized distributors?
All LM3503SQ-16 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 LM3503SQ-16 meets industry standards.
7.What is the process for return or replacement of LM3503SQ-16?
All LM3503SQ-16 units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQ-16, 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 LM3503SQ-16 part is unused and in its original packaging.
Return procedure for LM3503SQ-16:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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