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Texas Instruments LM3503SQ-25/NOPB
- Part No.:
- LM3503SQ-25/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQ-25/NOPB.pdf
- Description:
- IC LED DRIVER RGLTR DIM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,399
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Product details
Overview
LM3503SQ-25/NOPB from Texas Instruments is a dual-display constant-current white LED driver IC with analog brightness control, 25V 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 NMOS/PMOS FET switches and feedback-controlled current regulation.
For engineers reviewing the LM3503SQ-25/NOPB datasheet, LM3503SQ-25/NOPB pinout, LM3503SQ-25/NOPB application, or LM3503SQ-25/NOPB equivalent, key selection criteria include OVP threshold (25 V), dual-enable logic for MAIN/SUB display segmentation, analog dimming via Cntrl pin (0.2–3.5 V), and thermal shutdown with 125°C max junction temperature.
Technical Context
The LM3503SQ-25/NOPB implements an asynchronous current-mode PWM controller with cycle-by-cycle current limiting, soft-start, and dedicated UVP (2.5 V on-threshold) and OVP (24 V nominal on-threshold) comparators. Its dual-FET architecture enables independent MAIN (VOUT1–VOUT2) and SUB (VOUT2–Fb) string control via En1/En2 logic pins.
It operates in continuous conduction mode (CCM) or discontinuous conduction mode (DCM) depending on load, inductor value, and input/output voltage differential. Feedback voltage is regulated to 0.55 V typical at the Fb pin, with current set by VCntrl via VFb = 0.156 × VCntrl - enabling precise analog dimming without external DACs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| OVP Threshold | 25 V nominal on-threshold; disables switching when VOUT1 exceeds 24–25.5 V to protect LEDs and output capacitor. |
| Input Voltage Range | 2.5 V to 5.5 V; supports single-cell Li-ion (3.0–4.2 V) and dual-cell alkaline (3.0–3.6 V) battery inputs directly. |
| Switching Frequency | 1 MHz ±20%; enables compact magnetics (e.g., 2.2 µH inductors) and reduces EMI filtering requirements. |
| Feedback Voltage | 0.55 V typical; sets LED current via external resistor network (ILED = VFb/RSET). |
| Current Limit (NMOS) | 600 mA typical at 25 V OVP version; defines maximum peak inductor current to prevent FET overstress. |
| Quiescent Current | 1 mA typical in switching mode; ensures low standby power in always-on backlight applications. |
| Junction Temp Range | −40°C to +125°C; validated for industrial and extended-temperature portable device operation. |
Pinout & Package
LM3503SQ-25/NOPB uses a 16-pin WQFN package (RGH0016A) with 3.0 mm × 3.0 mm footprint and 0.5 mm pitch. The exposed DAP (Die Attach Pad) must be soldered to PCB ground for thermal dissipation (θJA = 49°C/W).
| 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 noise and inrush. |
| Sw | Power NMOS drain | Connects to inductor and Schottky diode anode; high dv/dt node requiring short, wide traces to reduce EMI. |
| En1 / En2 | MAIN/SUB display enable controls | Logic-level inputs (0.3 V/1.4 V thresholds); En1 enables MAIN segment (VOUT1–VOUT2), En2 enables SUB segment (VOUT2–Fb). |
| Fb | Feedback voltage sensing | Monitors output current via resistor divider; regulates to 0.55 V to maintain constant LED current. |
| Cntrl | Analog brightness control | 0.2–3.5 V input scales Fb reference linearly (VFb = 0.156 × VCntrl); enables smooth analog dimming without PWM filtering. |
| VOUT1 | OVP sense & PMOS source | Primary output node; connects to LED anodes and OVP circuitry; requires local 1 µF ceramic capacitor. |
| VOUT2 | NMOS/PMOS drain junction | Interconnect node between MAIN and SUB strings; unused in single-string configs - must be grounded or bypassed with 100 nF. |
| AGND / PGND | Analog & power ground returns | Separate ground pins; AGND must tie directly to PGND near device to avoid noise coupling into feedback path. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent display control | En1/En2 logic enables MAIN-only, SUB-only, both, or shutdown - eliminating need for external multiplexers in dual-screen devices. |
| Integrated OVP options | 25 V OVP threshold eliminates need for external overvoltage clamping components in mid-range LED string designs. |
| 1 MHz fixed-frequency PWM | Enables use of small, low-ESR ceramic capacitors and miniature inductors (e.g., DO1608C-223), reducing board area by >30% vs. 500 kHz alternatives. |
| Analog brightness control | Cntrl pin accepts DC voltage (not PWM) - avoids flicker and EMI from RC-filtered PWM, simplifying system timing design. |
| Internal soft-start | Gradually ramps current limit during startup, preventing inrush into large output capacitance and avoiding display flash artifacts. |
Applications
| Cellular Phone Dual Display | PDA Main/Sub Screen Backlight |
|---|---|
Use Scenario: Simultaneous illumination of main LCD and secondary status OLED in clamshell or slider phones with shared LED driver resources. IC Role / Device Role / Timing Role: Constant-current source regulating two independent LED strings (5 LEDs each) with dynamic brightness scaling via analog Cntrl voltage. Use Value: Reduces BOM count by replacing two discrete drivers with one IC; En1/En2 sequencing enables zero-flicker transition between displays. | Use Scenario: Powering primary TFT display and auxiliary monochrome sub-display in handheld PDAs with battery life constraints. IC Role / Device Role / Timing Role: Dual-output step-up converter delivering stable 20 mA per string across 2.7–4.2 V battery range using internal FETs and 1 MHz switching. Use Value: 80%+ peak efficiency minimizes heat generation in thermally constrained plastic enclosures; 125°C junction rating ensures reliability under sustained use. |
| Portable Media Player UI Lighting | Smartwatch Dual-Panel Backlight |
Use Scenario: Driving front-panel icons and rear touch-sensitive keys with separate brightness control in compact media players. IC Role / Device Role / Timing Role: Analog-dimming-capable LED driver supporting independent MAIN (UI) and SUB (keypad) current control via Cntrl and En2 pins. Use Value: Eliminates need for external DAC or PWM generator; Cntrl pin's 0.2–3.5 V range maps directly to 0–100% brightness with <1% linearity error. | Use Scenario: Illuminating circular main display and rectangular notification bar in ultra-thin smartwatches with strict height limits (<1 mm). IC Role / Device Role / Timing Role: Low-profile WQFN-packaged driver delivering 15 mA per string while maintaining <1 mm Z-height with integrated FETs and no external MOSFETs. Use Value: Enables mechanical stack-up compliance in wearables; thermal resistance of 49°C/W allows full brightness operation 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-16/NOPB | 16 V OVP threshold; lower current limit (400 mA typ); identical pinout and control interface. | Suitable for shorter LED strings (≤4 LEDs per string) with lower output voltage requirements. | Select when total Vf of MAIN+SUB strings remains below 14 V - reduces risk of false OVP triggering. |
| LM3503SQ-44/NOPB | 44 V OVP threshold; same 600 mA current limit; identical functional block diagram and timing behavior. | Required for long LED strings (≥8 LEDs per string) or high-Vf LEDs (e.g., blue/white with 3.6 V drop). | Choose for future-proofing or multi-platform designs where string count may vary; no layout change needed. |
Compared with LM3503SQ-16/NOPB and LM3503SQ-44/NOPB, the LM3503SQ-25/NOPB provides optimal headroom for 5-LED white LED strings (typical Vf ≈ 17–20 V), balancing OVP margin against unnecessary voltage overhead that increases switching losses.
Availability
LM3503SQ-25/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, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM3503SQ-25/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 over 50 years of innovation in power conversion and signal conditioning ICs.
The LM3503 product line was designed specifically for space-constrained portable electronics requiring dual independent LED backlight control with analog dimming, high efficiency, and robust protection - targeting smartphones, PDAs, and wearable displays.
FAQ
What is the exact over-voltage protection threshold for LM3503SQ-25/NOPB?
The LM3503SQ-25/NOPB has a nominal over-voltage protection (OVP) on-threshold of 24 V, with guaranteed range of 22.5 V to 25.5 V across temperature and process variation. This threshold applies to the VOUT1 pin and disables switching when exceeded, protecting the output capacitor and LED strings. The off-threshold is 21.5–24.5 V, providing hysteresis to prevent oscillation near trip point. This OVP setting is factory-trimmed and fixed for the -25 variant - not user-adjustable.
How does the Cntrl pin on LM3503SQ-25/NOPB set LED current?
The Cntrl pin on LM3503SQ-25/NOPB sets LED current by scaling the internal feedback reference: VFb = 0.156 × VCntrl. With VFb regulated to 0.55 V typical, the LED current is 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, yielding 15.6 mA through a 20 Ω resistor. The Cntrl voltage range is 0.2–3.5 V, enabling full 0–100% brightness control without external DACs or PWM filters.
Can LM3503SQ-25/NOPB drive both MAIN and SUB displays simultaneously?
Yes, LM3503SQ-25/NOPB can drive both MAIN and SUB displays simultaneously by setting En1 ≥1.4 V and En2 ≥1.4 V. In this state, the internal PMOS (P1) and NMOS (N2) FETs are both off, allowing current to flow through the full LED string from VOUT1 → VOUT2 → Fb. The device regulates total current across both segments as a single string. This configuration is used when uniform brightness is required across both displays - unlike independent control where only one segment is active at a time.
What is the recommended inductor value for LM3503SQ-25/NOPB in a 5-LED per string design?
For a 5-LED per string design with VIN = 3.6 V and Vf = 3.4 V per LED (total VOUT ≈ 34 V), TI recommends a 2.2 µH shielded inductor such as the DO1608C-223. This value balances peak current ripple (target <30% of average LED current), efficiency (>80% at 15 mA), and physical size. Inductor saturation current must exceed 600 mA to accommodate the LM3503SQ-25/NOPB's current limit, and DCR should be ≤150 mΩ to minimize conduction loss. Placement must minimize loop area with Sw, VOUT1, and PGND.
Does LM3503SQ-25/NOPB require external compensation components?
No, LM3503SQ-25/NOPB requires no external compensation components. It uses an internally compensated current-mode PWM architecture with built-in error amplifier, oscillator, and duty-limit comparator. The control loop is stable with the standard application circuit: 4.7 µF input capacitor, 1 µF output capacitor, 2.2 µH inductor, and Schottky diode. Adding external compensation would destabilize the regulator. Layout best practices - including tight AGND/PGND tie, short Sw trace, and local decoupling - are sufficient for robust operation across temperature and load.
LM3503SQ-25/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:
- 25V
- Current - Output / Channel:
- 600mA (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-25/NOPB FAQ
1.How can I place an order for LM3503SQ-25/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQ-25/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-25/NOPB reliable?
The price and inventory of LM3503SQ-25/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-25/NOPB is usually 5 days.
3.What payment methods are accepted for LM3503SQ-25/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQ-25/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQ-25/NOPB?
LM3503SQ-25/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQ-25/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-25/NOPB?
For technical support, including LM3503SQ-25/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQ-25/NOPB requirements.
6.How does Aetrix verify that LM3503SQ-25/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3503SQ-25/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-25/NOPB meets industry standards.
7.What is the process for return or replacement of LM3503SQ-25/NOPB?
All LM3503SQ-25/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQ-25/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-25/NOPB part is unused and in its original packaging.
Return procedure for LM3503SQ-25/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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