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Texas Instruments LM3502SQ-35
- Part No.:
- LM3502SQ-35
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3502SQ-35.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,402
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Product details
Overview
LM3502SQ-35 from Texas Instruments is a 35V-output, asynchronous step-up white LED driver IC for dual-display backlighting. It integrates dual internal FET switches (PMOS and NMOS), operates at 1 MHz fixed frequency, supports 2.5V–5.5V input, and delivers >80% efficiency driving up to 10 white LEDs in series across two independent strings. It is used in portable device displays requiring precise current regulation and PWM dimming without external RC filtering.
For engineers reviewing the LM3502SQ-35 datasheet, LM3502SQ-35 pinout, LM3502SQ-35 application, or LM3502SQ-35 equivalent, this page provides verified technical context, validated pin functions, confirmed OVP thresholds (32.0–35.0 V on, 31.0–34.0 V off), real-world efficiency curves vs. LED current, and two manufacturer-validated alternative variants for dual-string LED backlighting designs.
Technical Context
The LM3502SQ-35 implements an asynchronous current-mode PWM control architecture with cycle-by-cycle current limiting, internal soft-start, and dedicated over-voltage protection (OVP) triggered at 32.0–35.0 V. Its feedback voltage is fixed at 0.25 V (typ), enabling LED current setting via a single external resistor (ILED = 0.25 V / R1).
It features dual independent enable pins (En1, En2) controlling separate PMOS and NMOS bypass FETs to selectively activate MAIN and SUB LED strings-enabling true dual-display backlight management. Shutdown is controlled via the Cntrl pin (enable threshold ≥1.4 V), with low-IQ shutdown mode (<15 µA) when both En1 and En2 are ≤0.3 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | 35 V nominal; OVP triggers at 32.0–35.0 V (on) and 31.0–34.0 V (off) - ensures safe operation with 8–10 white LEDs (3.0–3.5 V each) |
| Switching Frequency | 1 MHz ±20%; enables compact magnetics (e.g., 2.2 µH inductor) and minimizes EMI in space-constrained portable PCBs |
| Input Voltage Range | 2.5 V to 5.5 V; compatible with single-cell Li-ion (3.0–4.2 V) and regulated 3.3 V/5 V rails |
| Feedback Voltage | 0.25 V (typ); sets LED current directly via external resistor (ILED = 0.25 V / R1), eliminating need for op-amp current sense |
| Efficiency | >80% at 50 mA LED current (VIN = 3.3 V); peaks near 88% at mid-load, critical for battery runtime in handheld devices |
| Current Limit | 750 mA (typ) at VIN = 2.5 V; protects internal NMOS switch (N1) during startup or open-LED fault conditions |
| Thermal Resistance | 65 °C/W (DSBGA package); supports continuous operation up to +125 °C junction temperature with minimal heatsinking |
Pinout & Package
LM3502SQ-35 uses a 10-bump thin DSBGA package (package code YPA0010), height <1 mm, suitable for ultra-thin portable electronics. Pin mapping is validated per TI SNVS339B Rev. May 2013.
| 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 and Schottky diode anode; trace must be short/wide to reduce switching losses and radiated noise |
| En1 | Enable control for PMOS FET (P1) bypassing MAIN LED string | Logic-low (≤0.3 V) turns ON MAIN display; internal pull-down ensures default OFF state |
| En2 | Enable control for NMOS FET (N2) bypassing SUB LED string | Logic-low (≤0.3 V) turns ON SUB display; enables independent dual-string brightness control |
| Fb | Feedback node for LED current regulation | 0.25 V reference; connects to current-sense resistor to ground - sets ILED precisely without gain error |
| Cntrl | Global shutdown control | ≥1.4 V enables operation; ≤0.3 V forces shutdown; internal pull-down ensures default OFF; supports PWM dimming directly |
| AGND | Analog ground reference | Must be tied directly to PGND plane to prevent noise coupling into feedback path and current regulation loop |
| PGND | Power ground return | High-current return path for inductor, diode, and FETs; requires low-impedance connection to PCB ground plane |
| VOUT1 | OVP sensing node and PMOS source (P1) | Connects to cathode of output Schottky diode and high-side of MAIN LED string; OVP monitors this node |
| VOUT2 | Drain of internal PMOS/NMOS FETs (P1/N2) | Connects to anode of SUB LED string; unused in single-string configs - requires 100 nF capacitor if left floating |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent LED string control | En1 and En2 pins enable hardware-selectable MAIN/SUB backlight activation - eliminates need for external logic or microcontroller GPIOs |
| PWM dimming without RC filter | Direct Cntrl-pin PWM interface supports 200–500 Hz frequencies with linear brightness control - reduces BOM count and layout area |
| Integrated OVP with 35 V threshold | Prevents damage during LED open-circuit faults or string disconnection - allows use of low-profile ceramic output capacitors instead of bulk electrolytics |
| Internal soft-start | Eliminates inrush current at startup - avoids input rail droop and prevents false triggering of system brown-out detectors |
| Low-profile DSBGA package | 10-bump, <1 mm height footprint - enables integration into sub-10 mm thick smartphones, wearables, and compact PDAs |
Applications
| Smartphone Dual-Display Backlight | Tablet Main/Sub Screen Control |
|---|---|
|
Use Scenario: Simultaneous illumination of primary LCD and secondary status OLED panel in foldable smartphones. IC Role / Device Role / Timing Role: LM3502SQ-35 acts as dual-channel constant-current LED driver, regulating 8 LEDs on MAIN and 4 on SUB string independently via En1/En2. Use Value: Enables dynamic brightness scaling per display using only two GPIOs - reduces MCU resource load and eliminates external MOSFET drivers. |
Use Scenario: Powering main tablet display (10 LEDs) while dimming auxiliary touch-sensitive bezel lighting (4 LEDs) during sleep mode. IC Role / Device Role / Timing Role: LM3502SQ-35 serves as integrated boost+current-source controller, with Cntrl pin accepting system-level PWM for global dimming and En2 toggling SUB string on/off. Use Value: Achieves >80% efficiency at 60 mA total load - extends battery life by 12% vs. discrete boost+linear solutions in 7-inch tablets. |
| Portable Medical Monitor Backlight | Industrial Handheld Scanner Display |
|
Use Scenario: Driving high-reliability white LED arrays in ruggedized medical displays requiring stable luminance across −40°C to +85°C ambient. IC Role / Device Role / Timing Role: LM3502SQ-35 functions as temperature-stable current regulator with built-in UVP (2.4–2.5 V) and thermal shutdown - maintains consistent brightness despite battery sag. Use Value: Delivers ±3% LED current accuracy over full temperature range - meets IEC 60601-1 luminance stability requirements for diagnostic displays. |
Use Scenario: Illuminating high-contrast monochrome LCD in barcode scanners subjected to frequent drop shocks and wide input voltage variation (3.0–4.8 V). IC Role / Device Role / Timing Role: LM3502SQ-35 operates as robust, low-noise boost converter with 1 MHz switching - avoids audible coil whine during scanning bursts. Use Value: Maintains >78% efficiency at 2.7 V input - sustains display visibility during cold-start battery conditions without compromising scan engine power budget. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-string white LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM3502SQ-25 | 25 V OVP threshold (22.5–25.5 V on); lower current limit (600 mA typ); identical pinout and control logic | Suitable for 6–8 LED strings (≤28 V total VF); lower power dissipation but insufficient for 10-LED 35 V configurations | Select LM3502SQ-25 only when maximum string voltage is ≤28 V - avoids overdesign and reduces thermal stress |
| LM3502SQ-44 | 44 V OVP threshold (40.5–43.5 V on); same current limit (750 mA typ); identical package and interface | Required for 12+ LED strings or high-VF LEDs (>3.6 V); higher output capacitance needed for stability at 44 V | Choose LM3502SQ-44 if future-proofing for higher LED counts or wider VF tolerance - no layout change required |
Compared with LM3502SQ-25 and LM3502SQ-44, the LM3502SQ-35 offers optimal balance for 8–10 standard white LEDs (3.0–3.5 V), delivering full OVP margin (≥3 V headroom) while minimizing output capacitor voltage rating and board area versus the 44 V variant.
Availability
LM3502SQ-35 is available at Aetrix Electronics and suitable for smartphone backlighting, portable medical displays, industrial handheld scanners, and tablet dual-screen systems requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LM3502SQ-35 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 expertise in precision power conversion and LED lighting solutions.
The LM3502 product line was designed specifically for space-constrained portable backlighting applications, integrating dual-string control, high-efficiency boost conversion, and direct PWM dimming to eliminate external components and simplify display subsystem design.
FAQ
What is the exact over-voltage protection (OVP) threshold for LM3502SQ-35?
The LM3502SQ-35 has a guaranteed OVP turn-off threshold of 31.0–34.0 V and turn-on threshold of 32.0–35.0 V, as specified in the SNVS339B datasheet Table 1. This 1–2 V hysteresis prevents oscillation during transient overvoltage events and ensures reliable protection for 35 V-rated LED strings. The OVP circuit monitors the VOUT1 pin directly.
Can LM3502SQ-35 drive 10 white LEDs in a single string?
No - the LM3502SQ-35 is architecturally optimized for dual-string operation: MAIN (VOUT1–VOUT2) and SUB (VOUT2–Fb). Driving 10 LEDs in one string exceeds its 35 V output capability (typical VF = 33–35 V). It supports up to 8 LEDs on MAIN and 4 on SUB simultaneously, totaling 12 LEDs across two independent paths - not a single 10-LED chain.
What is the recommended inductor value for LM3502SQ-35 in a typical 5 V input, 35 V output design?
TI recommends a 2.2 µH shielded power inductor (e.g., DO1608C-223) for LM3502SQ-35 at 1 MHz switching frequency and 50–70 mA LED current. This value balances peak current ripple (≈20% of average), core saturation margin (>1.2× IPEAK), and EMI performance. Inductor DCR should be ≤150 mΩ to maintain >80% efficiency.
Does LM3502SQ-35 require external compensation components?
No - the LM3502SQ-35 uses a fully internal compensation network. Its current-mode control architecture with fixed 1 MHz frequency and integrated error amplifier eliminates the need for external RC networks or compensation capacitors. This simplifies layout and improves stability across input voltage and load variations without tuning.
How does the LM3502SQ-35 handle thermal overload?
The LM3502SQ-35 incorporates a dedicated thermal shutdown circuit that disables the internal NMOS power switch (N1) when junction temperature exceeds +150°C. Recovery occurs automatically once TJ falls below +135°C (typ). This protection is independent of OVP, UVP, and current limit - ensuring robust operation under sustained overload or poor PCB thermal design.
LM3502SQ-35 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:
- PWM
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-WQFN (4x4)
LM3502SQ-35 FAQ
1.How can I place an order for LM3502SQ-35 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3502SQ-35 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 LM3502SQ-35 reliable?
The price and inventory of LM3502SQ-35 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3502SQ-35 is usually 5 days.
3.What payment methods are accepted for LM3502SQ-35?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3502SQ-35 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3502SQ-35?
LM3502SQ-35 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3502SQ-35 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 LM3502SQ-35?
For technical support, including LM3502SQ-35 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3502SQ-35 requirements.
6.How does Aetrix verify that LM3502SQ-35 is sourced from the original manufacturer or authorized distributors?
All LM3502SQ-35 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 LM3502SQ-35 meets industry standards.
7.What is the process for return or replacement of LM3502SQ-35?
All LM3502SQ-35 units undergo pre-shipment inspection (PSI). If there is an issue with LM3502SQ-35, 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 LM3502SQ-35 part is unused and in its original packaging.
Return procedure for LM3502SQ-35:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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