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Texas Instruments LM3503SQX-35/NOPB
- Part No.:
- LM3503SQX-35/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQX-35/NOPB.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,567
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Product details
Overview
LM3503SQX-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-designed for independent MAIN/SUB backlight control in portable dual-screen devices.
For engineers reviewing the LM3503SQX-35/NOPB datasheet, LM3503SQX-35/NOPB pinout, LM3503SQX-35/NOPB application, or LM3503SQX-35/NOPB equivalent, this page delivers verified technical context, package-specific pin functions, real-world application cards, and two validated alternative parts for dual-display LED backlighting designs requiring OVP = 35V.
Technical Context
The LM3503SQX-35/NOPB implements an asynchronous current-mode PWM boost controller with integrated dual FET switches (PMOS at VOUT1, NMOS at VOUT2) to drive two independent white LED strings-MAIN (VOUT1–VOUT2) and SUB (VOUT2–Fb). It uses cycle-by-cycle current limiting, internal soft-start, and dedicated UVP/OVP comparators (OVP threshold = 32.0–35.0 V).
Control logic relies on En1/En2 pins to enable/disable MAIN/SUB segments independently: En1 ≥1.4 V enables MAIN; En2 ≥1.4 V enables SUB; both ≤0.3 V forces shutdown. Analog brightness is set via Cntrl pin (0.2–3.5 V), which linearly scales feedback voltage (VFb = 0.156 × VCntrl) and thus LED current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Protection | 35 V OVP threshold (32.0–35.0 V turn-off range) - enables safe operation with 9–10 white LEDs per string at typical forward voltage. |
| Switching Frequency | 1 MHz ±20% - allows compact external components (e.g., 22 µH inductor, 1 µF output cap) and reduces EMI filtering burden. |
| Input Voltage Range | 2.5 V to 5.5 V - supports single-cell Li-ion (3.0–4.2 V), Li-polymer, or dual-cell alkaline/nickel-based supplies without pre-regulation. |
| LED Current Control | Analog Cntrl pin (0.2–3.5 V) sets VFb from 0.031–0.546 V - provides smooth, flicker-free dimming without external PWM filtering. |
| Peak Efficiency | >80% at 15 mA per string (VIN = 3.6 V, 4 LEDs/string) - minimizes thermal load in space-constrained handheld enclosures. |
| Thermal Resistance | 65 °C/W (DSBGA package) - requires minimal PCB copper area for thermal relief in thin-profile portable designs. |
| Enable Logic Thresholds | En1/En2 high-threshold = ≥1.4 V; low-threshold = ≤0.3 V - compatible with standard GPIOs and avoids false triggering in noisy environments. |
Pinout & Package
LM3503SQX-35/NOPB is packaged in a 10-bump, 1.5 mm × 1.5 mm, 0.5 mm pitch, <0.65 mm height DSBGA (Thin DSBGA, YPA0010) with die attach pad (DAP) for thermal grounding.
| 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 input ripple and EMI. |
| Sw | Drain of internal NMOS power switch (N1) | Connects to boost inductor; trace must be short/wide to reduce switching losses and radiated noise. |
| En1 | PMOS FET (P1) enable for MAIN display | ≥1.4 V enables MAIN segment; ≤0.3 V disables MAIN; internal pull-down ensures default OFF state. |
| En2 | NMOS FET (N2) enable for SUB display | ≥1.4 V enables SUB segment; ≤0.3 V disables SUB; floating or grounded if VOUT2 unused. |
| Fb | Feedback voltage sensing node | Monitors regulated output; connects to resistor divider from VOUT2; sets LED current via error amplifier. |
| Cntrl | Analog brightness control input | DC voltage (0.2–3.5 V) directly scales VFb; no external RC filter needed for analog dimming. |
| AGND | Analog ground reference | Must be tied directly to PGND to prevent noise coupling into feedback path and current regulation. |
| PGND | Power ground return | High-current return path for Sw, VOUT1, VOUT2; connect DAP and PGND to same solid ground plane. |
| VOUT1 | OVP sense node & PMOS source (P1) | Connects to anode of MAIN LED string and Schottky diode cathode; OVP comparator monitors this pin. |
| VOUT2 | Drain of P1/N2 FETs & SUB LED string node | Shared node between MAIN and SUB strings; 100 nF capacitor required if unused to stabilize OVP detection. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent LED string control | Separate En1/En2 logic enables MAIN and SUB displays independently-supports asymmetric backlighting (e.g., 4 LEDs MAIN + 2 LEDs SUB) without external multiplexing. |
| 35 V over-voltage protection | Hardware OVP circuit clamps output at 35 V nominal, protecting LEDs and external diode/capacitor during open-circuit or LED failure conditions. |
| 1 MHz fixed-frequency PWM | Eliminates audible noise and simplifies EMI filtering; enables use of small 22 µH inductors and 1 µF ceramic output capacitors. |
| Analog brightness interface | Cntrl pin accepts DC voltage (not PWM) - removes need for external RC filters, reduces BOM count, and avoids phase-shift-induced dimming nonlinearity. |
| Internal soft-start | Gradually ramps current limit at startup - prevents inrush current spikes that could brown-out battery or trigger upstream LDO shutdown. |
| Thermal shutdown & UVP | Shuts down NMOS switch if junction exceeds 150 °C or VIN drops below 2.2–2.3 V - protects IC and system during fault or low-battery conditions. |
Applications
| Smartphone Dual Display | Tablet Secondary Screen |
|---|---|
Use Scenario: Main LCD and secondary status OLED panel powered from shared battery in ultra-thin smartphone chassis. IC Role / Device Role / Timing Role: LM3503SQX-35/NOPB drives MAIN (LCD backlight) and SUB (OLED status indicator) strings independently using En1/En2 logic. Use Value: Enables simultaneous or selective illumination with zero cross-talk; 35 V OVP supports up to 10 white LEDs in series per string at 3.2 V VF. |
Use Scenario: Detachable keyboard with integrated status LEDs and tablet display sharing one Li-ion cell. IC Role / Device Role / Timing Role: LM3503SQX-35/NOPB powers tablet main backlight (VOUT1–VOUT2) and keyboard LED indicators (VOUT2–Fb) as separate current-regulated loads. Use Value: Eliminates need for two discrete LED drivers; 1 MHz switching allows compact layout in tight keyboard hinge region. |
| Portable Medical Monitor | Industrial Handheld Terminal |
Use Scenario: Battery-powered vital signs monitor with primary diagnostic screen and secondary alert LED bar. IC Role / Device Role / Timing Role: LM3503SQX-35/NOPB regulates MAIN display brightness via Cntrl pin and activates SUB alert LEDs only during critical alarms using En2. Use Value: Analog dimming ensures flicker-free viewing during clinical observation; 80%+ efficiency extends runtime between charges. |
Use Scenario: Ruggedized field terminal with sunlight-readable main display and low-power status backlight for night operation. IC Role / Device Role / Timing Role: LM3503SQX-35/NOPB drives MAIN (high-brightness mode) and SUB (low-power night mode) strings with independent enable control. Use Value: Dual-string architecture reduces standby current by disabling SUB when not needed-extending battery life in intermittent-use applications. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-display constant-current LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM3503SQX-25/NOPB | 25 V OVP threshold (vs. 35 V); identical pinout, control logic, and efficiency. | Suitable for ≤7 white LEDs per string (2.8 V avg VF); lower OVP margin limits max string voltage. | Select when total LED string Vf < 23 V and cost optimization is prioritized over headroom. |
| LM3503SQX-44/NOPB | 44 V OVP threshold (vs. 35 V); same DSBGA package, timing, and feature set. | Supports up to 13 white LEDs per string; higher OVP increases component stress margin but adds no functional benefit below 35 V requirement. | Choose only if future-proofing for higher-VF LEDs or extended string count is confirmed in design roadmap. |
Compared with LM3503SQX-25/NOPB, LM3503SQX-35/NOPB provides 10 V higher OVP headroom-critical for reliability with aging LEDs or elevated temperature VF drift-while maintaining identical board layout and firmware control. Versus LM3503SQX-44/NOPB, it avoids unnecessary voltage derating and associated cost premium without sacrificing safety margin for typical 9–10 LED strings.
Availability
LM3503SQX-35/NOPB is available at Aetrix Electronics and suitable for smartphone dual-display backlighting, portable medical monitor interfaces, industrial handheld terminals, and tablet secondary screen applications requiring stable component supply and long-term production continuity.
Supply support for LM3503SQX-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 delivering analog, embedded processing, and connectivity solutions with focus on power efficiency, reliability, and system integration.
The LM3503 product line targets portable dual-display backlighting systems, integrating dual FET switches, analog dimming, and programmable OVP to simplify LED power management in space- and battery-constrained devices.
FAQ
What is the over-voltage protection threshold for LM3503SQX-35/NOPB?
The LM3503SQX-35/NOPB features a nominal 35 V over-voltage protection threshold, with guaranteed turn-off between 31.0 V and 34.0 V and turn-on between 32.0 V and 35.0 V. This OVP level is factory-trimmed and applies specifically to the VOUT1 pin, protecting the internal PMOS switch and external components during LED open-circuit or string failure events.
Can LM3503SQX-35/NOPB drive both MAIN and SUB LED strings simultaneously?
Yes, LM3503SQX-35/NOPB can drive both MAIN and SUB strings simultaneously by setting En1 ≥1.4 V and En2 ≥1.4 V. In this configuration, the MAIN string (VOUT1–VOUT2) and SUB string (VOUT2–Fb) operate concurrently with independent current regulation determined by the Cntrl pin voltage and respective LED counts.
What package type does LM3503SQX-35/NOPB use, and what are its thermal characteristics?
LM3503SQX-35/NOPB uses a 10-bump Thin DSBGA (YPA0010) package measuring 1.5 mm × 1.5 mm with 0.5 mm pitch and <0.65 mm height. Its junction-to-ambient thermal resistance is 65 °C/W, requiring direct soldering of the die attach pad (DAP) to a PCB ground plane for effective heat dissipation in continuous operation.
How is LED brightness controlled on LM3503SQX-35/NOPB?
LED brightness on LM3503SQX-35/NOPB is controlled via the Cntrl pin using a DC voltage from 0.2 V to 3.5 V. This voltage linearly scales the internal feedback reference (VFb = 0.156 × VCntrl), directly adjusting regulated LED current without requiring external PWM filtering or microcontroller-based digital dimming routines.
Is LM3503SQX-35/NOPB pin-compatible with other LM3503 variants?
Yes, LM3503SQX-35/NOPB shares identical pinout, package dimensions, and control interface with LM3503SQX-16/NOPB, LM3503SQX-25/NOPB, and LM3503SQX-44/NOPB-all in the same 10-bump DSBGA (YPA0010) package. Only the OVP threshold differs; no PCB layout change is required when substituting within this family.
LM3503SQX-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)
LM3503SQX-35/NOPB FAQ
1.How can I place an order for LM3503SQX-35/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQX-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 LM3503SQX-35/NOPB reliable?
The price and inventory of LM3503SQX-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 LM3503SQX-35/NOPB is usually 5 days.
3.What payment methods are accepted for LM3503SQX-35/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQX-35/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQX-35/NOPB?
LM3503SQX-35/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQX-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 LM3503SQX-35/NOPB?
For technical support, including LM3503SQX-35/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQX-35/NOPB requirements.
6.How does Aetrix verify that LM3503SQX-35/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3503SQX-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 LM3503SQX-35/NOPB meets industry standards.
7.What is the process for return or replacement of LM3503SQX-35/NOPB?
All LM3503SQX-35/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQX-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 LM3503SQX-35/NOPB part is unused and in its original packaging.
Return procedure for LM3503SQX-35/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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