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Texas Instruments LM3503SQ-16/NOPB
- Part No.:
- LM3503SQ-16/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQ-16/NOPB.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LM3503SQ-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 integrates two internal FET switches to independently drive MAIN and SUB LED strings (2–5 LEDs each) in portable dual-screen devices.
For engineers reviewing the LM3503SQ-16/NOPB datasheet, LM3503SQ-16/NOPB pinout, LM3503SQ-16/NOPB application, or LM3503SQ-16/NOPB equivalent, this page delivers verified technical context, real-world design meaning for key specs, validated pin functions, confirmed alternative parts, and supply-ready availability details - all specific to the -16V OVP variant in WQFN-16 package.
Technical Context
The LM3503SQ-16/NOPB implements an asynchronous current-mode PWM boost controller with cycle-by-cycle current limiting, dedicated UVP (2.4 V turn-on) and OVP (16 V threshold), and soft-start to suppress inrush. Its dual-FET architecture enables independent MAIN (VOUT1–VOUT2) and SUB (VOUT2–Fb) string control via En1/En2 logic.
It uses analog voltage at the Cntrl pin (0.2–3.5 V) to set feedback reference (VFb = 0.156 × VCntrl), enabling precise LED current regulation without external DACs. The device operates in CCM or DCM depending on load, inductor, and VIN–VOUT differential, with maximum duty cycle limited to 95%.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output OVP Threshold | 16 V nominal - protects against open-string failure or LED removal in MAIN/SUB paths without requiring external clamping. |
| Switching Frequency | 1 MHz ±20% - enables use of small 2.2 µH inductors and low-ESR ceramic output capacitors; reduces EMI filtering burden. |
| Input Voltage Range | 2.5 V to 5.5 V - supports single-cell Li-ion (fully charged to depleted) and regulated 3.3 V/5 V rails without pre-regulation. |
| Feedback Voltage | 0.55 V typical at TJ = 25°C - sets LED current via external sense resistor; stable across −40°C to +125°C junction range. |
| Peak Current Limit | 400 mA typical (16 V version) - defines maximum inductor peak current; prevents thermal runaway during startup or shorted-LED faults. |
| Quiescent Current | 1 mA typical in switching mode - minimizes battery drain in always-on backlight applications with dynamic dimming. |
| Efficiency | >80% peak - achieved with low RDS(ON) NMOS (0.55 Ω typ) and PMOS (5 Ω typ) switches; critical for thermal management in thin handhelds. |
Pinout & Package
LM3503SQ-16/NOPB is housed in a 16-pin WQFN package (RGH0016A), 3 mm × 3 mm × 0.8 mm, with exposed thermal pad (DAP) soldered to PCB ground plane for enhanced thermal dissipation (θJA = 49°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input power supply connection | Accepts 2.5–5.5 V; requires local 4.7 µF ceramic capacitor to minimize high-frequency noise and supply impedance. |
| Sw | Power NMOS switch drain | Connects to inductor and Schottky diode anode; high dv/dt node - must be routed with minimal trace length/area to reduce EMI. |
| En1 | PMOS FET enable control (MAIN display) | Logic-high (≥1.4 V) disables MAIN string; internal pull-down ensures default OFF state - used for main screen on/off sequencing. |
| En2 | NMOS FET enable control (SUB display) | Logic-high (≥1.4 V) disables SUB string; floating or grounded when VOUT2 unused - enables sub-screen independent control. |
| Fb | Feedback voltage sensing node | Monitors voltage across current-sense resistor; regulates LED current by maintaining 0.55 V at this pin. |
| Cntrl | Analog brightness control input | 0.2–3.5 V DC input scales VFb linearly (VFb = 0.156 × VCntrl); supports RC-filtered PWM dimming with no added IC. |
| AGND | Analog ground reference | Must be tied directly to PGND at single point near device - isolates noise-sensitive feedback path from power return currents. |
| PGND | Power ground return | High-current return for Sw, VOUT1, VOUT2; connects to thermal pad - forms low-inductance loop with VIN and Sw traces. |
| VOUT1 | OVP sense & PMOS source | Main string output (to LED anode); OVP circuit monitors this node - connects to cathode of Schottky diode and output capacitor. |
| VOUT2 | Internal FET drain (MAIN/SUB junction) | Node between MAIN and SUB strings; if unused, requires 100 nF bypass capacitor to PGND to prevent oscillation. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent LED string control | En1/En2 pins allow MAIN and SUB displays to be enabled/disabled separately - eliminates need for external MOSFETs or multiplexers. |
| Analog + PWM brightness control | Cntrl pin accepts DC voltage or filtered PWM signal - enables seamless integration with MCU GPIO or DAC without extra components. |
| Integrated protection suite | UVP (2.4 V), OVP (16 V), thermal shutdown, and cycle-by-cycle current limit - reduces BOM count and improves field reliability. |
| 1 MHz fixed-frequency operation | Enables compact magnetics (e.g., DO1608C-223) and fast transient response - avoids audible noise and simplifies EMI filter design. |
| Low-profile WQFN-16 package | 0.8 mm max height - meets mechanical constraints of ultra-thin mobile devices while delivering 49°C/W thermal performance. |
Applications
| Cellular Phone Dual Display | PDA Main/Sub Screen Backlight |
|---|---|
Use Scenario: Simultaneous backlighting of primary LCD and secondary status OLED in clamshell or slider phones. IC Role / Device Role / Timing Role: Constant-current boost driver regulating two independent LED strings with separate enable logic and shared analog dimming. Use Value: Eliminates discrete enable FETs and external current-setting resistors per string - reduces solution size by >35% vs. dual-single-channel drivers. |
Use Scenario: Powering high-brightness main display and low-power auxiliary info panel in legacy PDAs with tight board area. IC Role / Device Role / Timing Role: Dual-output DC-DC converter with programmable OVP and soft-start - ensures safe ramp-up during cold boot and brown-out recovery. Use Value: 16 V OVP matches typical 12–14 V LED stack voltages - avoids overdesign with higher-voltage-rated capacitors or diodes. |
| Portable Media Player UI Panel | Handheld Barcode Scanner Display |
Use Scenario: Driving segmented backlight behind touch-sensitive UI overlay and status icons in battery-powered media players. IC Role / Device Role / Timing Role: Analog-dimming-capable LED driver with shutdown current <3 µA - extends standby time between user interactions. Use Value: 0.55 V feedback voltage allows use of standard 0805 current-sense resistors (e.g., 1.5 Ω @ 367 mA) - simplifies layout and calibration. |
Use Scenario: Illuminating small monochrome LCD and laser alignment indicator in industrial-grade handheld scanners. IC Role / Device Role / Timing Role: Dual-channel current source with independent enable pins - enables synchronized or staggered illumination for power sequencing. Use Value: Internal 400 mA current limit (16 V version) supports up to 5× white LEDs per string at 20 mA - covers full brightness range without derating. |
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/NOPB | 25 V OVP threshold; higher peak current limit (600 mA typ) | Supports longer LED strings (up to 7–8 LEDs at 3.2 V each) - suitable for larger displays or higher-brightness requirements | Select when VOUT exceeds 16 V under worst-case LED forward voltage and temperature drift; requires revalidation of output capacitor voltage rating. |
| TPS61165DRVR | Single-output, 38 V OVP, I²C interface, integrated PWM generator | Lacks dual-string independent control; requires external logic for MAIN/SUB separation - adds complexity and board area | Prefer when digital control, fault reporting, or higher OVP margin is required; not drop-in for En1/En2 hardware sequencing. |
Compared with LM3503SQ-25/NOPB, the LM3503SQ-16/NOPB offers tighter OVP tolerance and lower quiescent current in light-load conditions; versus TPS61165DRVR, it provides native dual-string hardware control without firmware or external gate drivers - reducing system-level BOM and validation effort.
Availability
LM3503SQ-16/NOPB is available at Aetrix Electronics and suitable for cellular phone backlighting, PDA dual-display systems, and portable media player UI panels requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM3503SQ-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 technologies, with decades of expertise in precision power conversion and LED lighting solutions.
The LM3503 product line was designed specifically for space-constrained dual-display backlighting in portable consumer electronics, emphasizing integration, efficiency, and robust protection for battery-powered operation.
FAQ
What is the over-voltage protection threshold for LM3503SQ-16/NOPB?
The LM3503SQ-16/NOPB has a nominal over-voltage protection threshold of 16 V, with an on-threshold range of 14.5–16.5 V and off-threshold of 14.0–16.0 V. This OVP circuit monitors the VOUT1 pin and disables switching if the output exceeds the threshold - protecting external components during LED open-circuit faults. The exact value is factory-trimmed and specified in the Electrical Characteristics table of the SNVS329E datasheet.
How does the Cntrl pin control LED brightness in LM3503SQ-16/NOPB?
The Cntrl pin on LM3503SQ-16/NOPB accepts a DC voltage from 0.2 V to 3.5 V, which linearly scales the internal feedback reference: VFb = 0.156 × VCntrl. Since LED current is determined by ILED = VFb / RSENSE, adjusting VCntrl directly controls brightness. For PWM dimming, an RC-filtered signal can be applied - the LM3503SQ-16/NOPB's analog architecture avoids flicker without requiring microcontroller intervention.
Can LM3503SQ-16/NOPB drive both MAIN and SUB displays simultaneously?
Yes, LM3503SQ-16/NOPB can drive both MAIN and SUB displays simultaneously. When En1 ≥1.4 V and En2 ≥1.4 V, both internal FETs are disabled, routing current through the full LED string (VOUT1 → VOUT2 → Fb). This configuration powers both segments as a single chain - confirmed in the Operational Characteristics Table (Figure 4) and supported by the block diagram showing shared current-sense and regulation paths.
What is the recommended inductor value for LM3503SQ-16/NOPB in a 3.6 V input, 12 V output application?
For LM3503SQ-16/NOPB operating at VIN = 3.6 V and VOUT ≈ 12 V (e.g., 4× white LEDs), Texas Instruments recommends a 2.2 µH shielded inductor such as the DO1608C-223. This value balances peak current ripple (~30% of average), efficiency (>85%), and physical size. Inductor saturation current must exceed 600 mA to accommodate the 400 mA typical current limit plus margin - verified in Typical Application Circuit documentation.
Does LM3503SQ-16/NOPB require external compensation components?
No, LM3503SQ-16/NOPB requires no external compensation components. It features internal compensation optimized for stability across its full operating range (2.5–5.5 V input, 16 V OVP, 2–10 LED loads). The datasheet explicitly states "no external compensation" as a key feature, and the typical application circuit confirms zero external compensation parts - simplifying design and reducing bill-of-materials cost.
LM3503SQ-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)
LM3503SQ-16/NOPB FAQ
1.How can I place an order for LM3503SQ-16/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQ-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 LM3503SQ-16/NOPB reliable?
The price and inventory of LM3503SQ-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 LM3503SQ-16/NOPB is usually 5 days.
3.What payment methods are accepted for LM3503SQ-16/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQ-16/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQ-16/NOPB?
LM3503SQ-16/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQ-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 LM3503SQ-16/NOPB?
For technical support, including LM3503SQ-16/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQ-16/NOPB requirements.
6.How does Aetrix verify that LM3503SQ-16/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3503SQ-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 LM3503SQ-16/NOPB meets industry standards.
7.What is the process for return or replacement of LM3503SQ-16/NOPB?
All LM3503SQ-16/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQ-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 LM3503SQ-16/NOPB part is unused and in its original packaging.
Return procedure for LM3503SQ-16/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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