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Texas Instruments LM3503SQ-35/NOPB
- Part No.:
- LM3503SQ-35/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQ-35/NOPB.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,550
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Product details
Overview
LM3503SQ-35/NOPB from Texas Instruments is a dual-display constant-current white LED driver IC with analog brightness control, 35V over-voltage protection, 1 MHz switching frequency, and 2.5V–5.5V input range. It drives up to 10 LEDs (5 per display) in portable dual-screen backlighting applications with independent MAIN/SUB segment control via En1/En2 pins.
For engineers reviewing the LM3503SQ-35/NOPB datasheet, LM3503SQ-35/NOPB pinout, LM3503SQ-35/NOPB application, or LM3503SQ-35/NOPB equivalent, key selection criteria include output OVP threshold (35 V), dual-channel enable logic, analog dimming interface (Cntrl pin), and thermal performance in WQFN-16 package for space-constrained handheld designs.
Technical Context
The LM3503SQ-35/NOPB implements an asynchronous current-mode PWM boost controller with integrated NMOS power switch (N1), PMOS bypass switch (P1), and NMOS secondary switch (N2). Its feedback loop regulates LED current via Cntrl pin voltage (0.2–3.5 V), producing a proportional Fb voltage (0.5–0.6 V typical) to set output current.
Protection features include cycle-by-cycle current limiting (750 mA typ. for 35V version), input under-voltage lockout (2.4–2.5 V), thermal shutdown, soft-start, and dedicated 35 V over-voltage protection on VOUT1. The device operates in continuous conduction mode (CCM) or pulse-frequency modulation (PFM) under light loads to maintain regulation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output OVP Threshold | 32.0–35.0 V - sets maximum safe VOUT1 voltage during LED open-circuit or string failure |
| Switching Frequency | 0.8–1.2 MHz - enables compact external inductor (e.g., 2.2 µH) and low-profile ceramic output capacitors |
| Input Voltage Range | 2.5–5.5 V - supports single-cell Li-ion (3.0–4.2 V) and regulated 3.3 V/5 V rails without pre-regulation |
| LED Current Control | Cntrl pin 0.2–3.5 V → Fb 0.5–0.6 V - enables precise analog dimming with <1% current error across temperature |
| Current Limit (35V version) | 450–1050 mA - defines peak inductor current limit; higher limit allows driving more LEDs at lower forward voltage |
| Efficiency | >80% peak - achieved at mid-load (e.g., 15 mA × 4 LEDs @ VIN = 3.6 V), minimizing thermal load in thin devices |
| Enable Logic | En1 ≥1.4 V → MAIN ON; En2 ≥1.4 V → SUB ON; both ≤0.3 V → full shutdown - supports independent display power sequencing |
Pinout & Package
LM3503SQ-35/NOPB uses a 16-pin WQFN package (RGH0016A) with 3.5 mm × 3.5 mm footprint and 0.4 mm pitch. Exposed thermal pad (DAP) must be soldered to PCB ground plane for optimal 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 input ripple and EMI |
| Sw | Drain of internal NMOS power switch (N1) | Connects to inductor; high di/dt node requiring short wide trace to reduce EMI and switching losses |
| En1 | PMOS switch (P1) control for MAIN display | Logic-high (≥1.4 V) disables P1, enabling MAIN LED string between VOUT1 and VOUT2 |
| En2 | NMOS switch (N2) control for SUB display | Logic-high (≥1.4 V) disables N2, enabling SUB LED string between VOUT2 and Fb |
| Fb | Feedback voltage sensing node | Monitors regulated voltage; connects to resistor divider from VOUT2 to set LED current reference |
| Cntrl | Analog brightness control input | 0.2–3.5 V DC input directly scales Fb voltage and thus LED current; RC-filtered PWM also accepted |
| AGND | Analog ground reference | Must be tied directly to PGND to prevent noise coupling into feedback path and current sense circuitry |
| 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 node & PMOS source | Connects to anode of main LED string and Schottky diode cathode; OVP comparator monitors this pin |
| VOUT2 | Drain of P1/N2 switches | Midpoint node between MAIN and SUB strings; 100 nF capacitor recommended if unused to stabilize switching |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent display control | En1/En2 pins enable hardware-selectable MAIN/SUB LED string activation without software intervention |
| 35 V over-voltage protection | Prevents damage during LED open-circuit events in 8–10 LED strings; eliminates need for external OVP clamps |
| Analog + PWM dimming support | Cntrl pin accepts DC voltage or filtered PWM (≥10× RC bandwidth); enables flicker-free brightness control |
| Internal soft-start | Gradually ramps current limit at startup to suppress inrush current into output capacitor and LED string |
| Thermal shutdown protection | Disables switching when junction temperature exceeds +150°C; auto-recovery after cooldown prevents latch-up |
| No external compensation required | Stable operation with standard external components (inductor, diode, caps); reduces BOM count and layout risk |
Applications
| Cellular Phone Dual Display | PDA Main/Sub Backlight |
|---|---|
Use Scenario: Compact smartphone with primary LCD and secondary OLED status display powered from single Li-ion cell. IC Role / Device Role / Timing Role: Constant-current boost driver delivering regulated current to two independent LED strings with hardware-selectable enable. Use Value: Enables simultaneous or selective illumination of main screen and notification bar using only one IC and minimal passives. |
Use Scenario: Handheld PDA with large main display and small sub-display for battery/status icons, operating at ambient temperatures from –40°C to +85°C. IC Role / Device Role / Timing Role: Dual-channel LED driver with robust OVP (35 V) and wide input range (2.5–5.5 V) ensuring reliable backlighting across battery discharge cycle. Use Value: Eliminates need for separate drivers or voltage translators; maintains consistent brightness despite varying input voltage. |
| Portable Media Player UI | Industrial Handheld Terminal |
Use Scenario: Battery-powered media player with high-resolution main screen and touch-sensitive sub-display for playback controls. IC Role / Device Role / Timing Role: Analog-dimming LED driver supporting smooth brightness ramping via DAC-controlled Cntrl pin voltage. Use Value: Delivers flicker-free dimming with <1% current variation over temperature, critical for user interface visual quality. |
Use Scenario: Ruggedized industrial terminal used in warehouses with variable ambient lighting and extended operating life requirements. IC Role / Device Role / Timing Role: High-reliability LED driver with thermal shutdown, UVLO, and cycle-by-cycle current limiting for long-term unattended operation. Use Value: Prevents field failures due to LED string faults or overheating; supports >10-year product lifecycle with no derating needed. |
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-44/NOPB | Higher OVP threshold (44 V vs. 35 V); identical pinout, control logic, and efficiency | Supports longer LED strings (up to 12 LEDs) or higher forward voltage LEDs (e.g., blue/white with Vf > 3.5 V) | Select when output voltage margin must exceed 35 V; otherwise LM3503SQ-35/NOPB offers tighter OVP tolerance and lower cost |
| TPS61165DRVR | Single-output boost LED driver (not dual-channel); 40 V OVP; I²C interface instead of analog Cntrl pin | Lacks independent MAIN/SUB enable; requires microcontroller for brightness control and sequencing | Choose when system already includes I²C bus and only one display needs driving; not suitable for hardware-only dual-display control |
Compared with LM3503SQ-44/NOPB and TPS61165DRVR, the LM3503SQ-35/NOPB uniquely balances 35 V OVP headroom, dual independent enable logic, and analog dimming-making it optimal for cost-sensitive, microcontroller-free dual-display portable devices where LED string count is fixed at ≤10.
Availability
LM3503SQ-35/NOPB is available at Aetrix Electronics and suitable for cellular phone backlighting, PDA dual-display systems, and portable media player UI illumination requiring stable component supply and long-lifecycle support.
Supply support for LM3503SQ-35/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 LED driver innovation.
The LM3503 product line was designed specifically for dual-display portable electronics, integrating dual-channel switching, analog dimming, and robust protection in ultra-thin packages for space-constrained handheld applications.
FAQ
What is the exact over-voltage protection threshold for LM3503SQ-35/NOPB?
The LM3503SQ-35/NOPB has a guaranteed over-voltage protection (OVP) turn-off threshold of 31.0–34.0 V and turn-on threshold of 32.0–35.0 V on the VOUT1 pin. This 35 V rating is factory-trimmed and applies specifically to the -35 variant; other versions (e.g., -16, -25, -44) have different thresholds. The OVP circuit latches off the internal NMOS switch until VIN drops below UVLO or the device is reset via En1/En2.
How does the Cntrl pin control LED current in LM3503SQ-35/NOPB?
The Cntrl pin on LM3503SQ-35/NOPB accepts a DC voltage from 0.2 V to 3.5 V, which linearly scales the internal reference voltage at the Fb pin (0.5–0.6 V typical). This directly sets the regulated LED current via the external sense resistor: ILED = VFb/Rsense. At Cntrl = 0 V, residual current may persist due to internal offsets; true zero current requires full shutdown via En1/En2 ≤0.3 V.
Can LM3503SQ-35/NOPB drive both MAIN and SUB displays simultaneously?
Yes, LM3503SQ-35/NOPB can drive both MAIN and SUB displays simultaneously by setting En1 ≥1.4 V and En2 ≥1.4 V. This configures the internal PMOS (P1) and NMOS (N2) switches to route current through both LED strings: MAIN (VOUT1→VOUT2) and SUB (VOUT2→Fb). The total current is shared across both strings, with combined LED count limited by the 35 V OVP and current limit specifications.
What package type and thermal characteristics does LM3503SQ-35/NOPB use?
LM3503SQ-35/NOPB uses a 16-pin WQFN package (RGH0016A) measuring 3.5 mm × 3.5 mm with 0.4 mm pitch and an exposed thermal pad (DAP). Its junction-to-ambient thermal resistance is 49°C/W when properly soldered to a 1-in² copper pour. Maximum junction temperature is +150°C, with continuous operation rated from –40°C to +125°C junction temperature.
Is LM3503SQ-35/NOPB pin-compatible with other LM3503 variants?
Yes, all LM3503 variants-including LM3503SQ-16/NOPB, LM3503SQ-25/NOPB, LM3503SQ-35/NOPB, and LM3503SQ-44/NOPB-share identical WQFN-16 (RGH0016A) packaging, pinout, and control interface. Only the OVP threshold and corresponding current limit values differ between variants; no PCB layout change is required when upgrading or downgrading within the LM3503 family.
LM3503SQ-35/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:
- 35V
- 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)
LM3503SQ-35/NOPB FAQ
1.How can I place an order for LM3503SQ-35/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQ-35/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-35/NOPB reliable?
The price and inventory of LM3503SQ-35/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-35/NOPB is usually 5 days.
3.What payment methods are accepted for LM3503SQ-35/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQ-35/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQ-35/NOPB?
LM3503SQ-35/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQ-35/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-35/NOPB?
For technical support, including LM3503SQ-35/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQ-35/NOPB requirements.
6.How does Aetrix verify that LM3503SQ-35/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3503SQ-35/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-35/NOPB meets industry standards.
7.What is the process for return or replacement of LM3503SQ-35/NOPB?
All LM3503SQ-35/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQ-35/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-35/NOPB part is unused and in its original packaging.
Return procedure for LM3503SQ-35/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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