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Texas Instruments LM3423MHX/NOPB
- Part No.:
- LM3423MHX/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 20-PowerTSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LM3423MHX/NOPB.pdf
- Description:
- IC LED DRIVER CTRLR PWM 20HTSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,500
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Product details
Overview
LM3423MHX/NOPB from Texas Instruments is a high-voltage N-channel MOSFET controller for constant-current LED drivers, supporting buck, boost, buck-boost, and SEPIC topologies. It operates from 4.5 V to 75 V input, features predictive off-time (PRO) control, 2-Ω/1-A peak gate drive, and integrated LED output/fault status flags. Used in outdoor area lighting and automotive LED systems requiring precise current regulation up to 5 A.
For engineers reviewing the LM3423MHX/NOPB datasheet, LM3423MHX/NOPB pinout, LM3423MHX/NOPB application, or LM3423MHX/NOPB equivalent, this page delivers verified technical context, HTSSOP-20 package mapping, real-world dimming interface behavior, thermal shutdown thresholds, and validated alternative controllers for LED driver design.
Technical Context
The LM3423MHX/NOPB implements Predictive Off-Time (PRO) control - a hybrid of peak current-mode regulation and input-voltage-proportional off-timer - enabling stable loop compensation without external slope compensation and inherent input feed-forward. It uses a high-side differential current sense amplifier (HSP/HSN) with 1.24 V reference and 20 mA/V transconductance to regulate LED current via external RSNS, RCSH, and RHSP resistors.
It integrates dual gate drivers: GATE (6 Ω source / 4.5 Ω sink) for main switching FETs and DDRV (30 Ω source / 10 Ω sink) for dimming FETs, plus dedicated pins for PWM dimming (nDIM), overvoltage protection (OVP), fault latching (FLT), and LED ready signaling (LRDY). Thermal shutdown activates at 165°C with 25°C hysteresis.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4.5 V to 75 V - supports wide-input industrial and automotive LED systems without pre-regulation. |
| Switching Frequency | Up to 2 MHz - enables compact magnetics and high-density PCB layouts using RCT-programmed PRO control. |
| GATE Drive Strength | 2 Ω sourcing / 4.5 Ω sinking - drives N-channel MOSFETs up to 1 A peak, minimizing switching losses in high-current LED strings. |
| Current Sense Reference | 1.24 V on CSH pin - sets precise LED current via external resistor network; enables analog dimming by modulating CSH voltage. |
| Thermal Shutdown | 165°C activation with 25°C hysteresis - protects against sustained overload or poor heatsinking in enclosed luminaires. |
| OVP Threshold | 1.24 V on OVP pin - triggers shutdown when output exceeds programmed level; hysteresis provided by 23 µA internal current source. |
| Fault Flag Logic | Open-drain FLT pin - pulls low after timer-latched fault (e.g., overcurrent, overtemperature); requires external pull-up to VIN. |
Pinout & Package
LM3423MHX/NOPB is housed in a thermally enhanced 20-pin HTSSOP (PWP) package (6.50 mm × 4.40 mm) with exposed thermal pad (DAP) connected to AGND/PGND star ground.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VIN | Main input supply | Bypassed with 100 nF ceramic capacitor to AGND; powers internal start-up regulator and high-voltage circuitry. |
| 2 EN | Enable control | Pulled low to disable IC with zero-current shutdown; threshold 2.4 V rising, 0.8 V falling; internal 0.245–2.85 MΩ pulldown. |
| 3 COMP | Error amplifier output | Connects to RC compensation network to AGND; regulates CSH to 1.24 V for stable current loop response. |
| 4 CSH | Current sense amplifier output | Sinks 100 µA nominal signal current; voltage regulated to 1.24 V; used for analog dimming and loop feedback. |
| 5 RCT | PRO timing input | RC network sets predictive off-time and switching frequency; internal 565 mV reference (VIN/25) enables voltage scaling. |
| 6 AGND | Analog ground reference | Star-ground node for CSH, COMP, RCT, TIMR; connected to PGND via DAP copper pad. |
| 7 OVP | Overvoltage protection input | Resistor divider from VO sets 1.24 V trip point; 23 µA hysteresis current ensures clean latch-off recovery. |
| 8 nDIM | PWM dimming & UVLO input | Accepts 0–5 V PWM signal; also programs VIN UVLO with resistor divider (1.24 V threshold). |
| 9 VCC | Internal LDO output | 7.35 V regulated output; bypassed with 2.2–3.3 µF ceramic cap to PGND; powers gate drivers and logic. |
| 10 TIMR | Fault timer timing | Capacitor to AGND sets delay before fault latching; not present on LM3421. |
| 11 LRDY | LED ready flag | Open-drain output pulls low when LED current is out of regulation; requires external pull-up. |
| 12 RPD | Resistor pulldown node | Common return for all external resistor dividers (nDIM, OVP); enables zero-current shutdown when pulled low. |
| 13 IS | Main switch current sense | Connects to MOSFET drain (RDS-ON sensing) or source-sense resistor for cycle-by-cycle current limiting. |
| 14 PGND | Power ground return | Return path for GATE and DDRV drivers; connected to AGND via DAP copper pad. |
| 15 HSP | High-side sense positive | Connects to LED string anode side; forms differential pair with HSN for accurate high-side current measurement. |
| 16 HSN | High-side sense negative | Connects to LED string cathode side; matched bias current cancels offset error when RHSN = RHSP. |
| 17 DDRV | Dimming gate driver | Drives series N- or P-channel dimming FET; 30 Ω source / 10 Ω sink; logic-level compatible. |
| 18 FLT | Fault status flag | Open-drain output latched after TIMR timeout; indicates overcurrent, overtemperature, or OVP fault. |
| 19 GATE | Main gate driver output | Drives high-side or low-side N-channel MOSFET; 6 Ω source / 4.5 Ω sink; rated for 1 A peak. |
| 20 Thermal PAD (DAP) | Thermal and electrical ground | Exposed pad soldered to PCB copper; must be star-connected to AGND and PGND for thermal performance and noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| Predictive Off-Time (PRO) Control | Eliminates sub-harmonic oscillation at >50% duty cycles; enables stable operation in boost/buck-boost without slope compensation. |
| High-Side Differential Current Sense | HSP/HSN inputs support floating LED strings; 1.24 V reference and 20 mA/V transconductance enable ±1% current accuracy with proper resistor matching. |
| Dual Independent Gate Drivers | GATE (main switch) and DDRV (dimming FET) each have separate sourcing/sinking capability and thermal derating curves. |
| Integrated Fault Management | Programmable TIMR-based fault latching, open-drain FLT/LRDY flags, and thermal shutdown with hysteresis simplify system-level safety compliance. |
| Flexible Dimming Interface | nDIM accepts PWM signals up to 20 kHz; CSH supports analog dimming down to 0 V; DPOL pin configures dimming FET polarity. |
Applications
| Automotive Headlamp Driver | Outdoor Area Lighting |
|---|---|
|
Use Scenario: High-brightness LED headlamps in 12 V/24 V vehicle systems requiring EMI-compliant, thermally robust constant-current regulation. IC Role / Device Role / Timing Role: N-channel controller managing buck-boost topology to maintain 1.5 A LED current across 9–16 V input range while rejecting battery ripple. Use Value: PRO control ensures stable regulation during cold-crank (6.5 V) and load-dump (36 V) events; thermal shutdown prevents lens damage under sealed housing conditions. |
Use Scenario: Streetlight LED drivers operating from 120–347 VAC via PFC front-end, delivering 350 mA to 100 W LED arrays. IC Role / Device Role / Timing Role: Boost controller regulating LED current in high-line applications where output voltage exceeds input; RCT sets 500 kHz switching for low EMI. Use Value: 75 V VIN rating eliminates need for intermediate DC-DC stage; high-side sensing avoids ground-loop interference in metal pole-mounted fixtures. |
| Industrial Machine Vision Lighting | Architectural Accent Lighting |
|
Use Scenario: Stroboscopic LED arrays in factory automation cameras requiring microsecond-precision PWM dimming and fast transient response. IC Role / Device Role / Timing Role: Buck-boost controller with DDRV-driven dimming FET; nDIM accepts TTL-level PWM signals synchronized to camera shutter. Use Value: 20 ns leading-edge blanking and 75 ns current-limit delay ensure clean turn-on without false triggering; LRDY flag confirms current regulation before image capture. |
Use Scenario: Low-voltage (12–48 VDC) RGBW LED strips in commercial buildings requiring smooth 0–100% analog dimming and color consistency. IC Role / Device Role / Timing Role: Constant-current buck controller per channel; CSH pin modulated by DAC for linear analog dimming without PWM flicker. Use Value: 1.24 V CSH reference and 100 µA signal current minimize resistor tolerance impact on dimming linearity; AGND/PGND separation reduces crosstalk between channels. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM3421MHX/NOPB | 16-pin HTSSOP; lacks FLT, TIMR, LRDY, DPOL, and DDRV pins; no LED output/fault status flags. | Suitable for cost-sensitive, non-fault-monitored LED drivers where only basic current regulation is required. | Select LM3421MHX/NOPB when system-level fault reporting is handled externally and board space is constrained. |
| LM3409HVMM/NOPB | Fixed-frequency current-mode controller; 6–42 V input; integrated 1.5-A gate driver; no PRO control or high-side sense. | Optimized for buck-only LED drivers with simpler compensation; lacks programmable frequency and high-side sensing flexibility. | Choose LM3409HVMM/NOPB for fixed-input, single-topology designs where PRO complexity is unnecessary and layout simplicity is prioritized. |
Compared with LM3421MHX/NOPB, LM3423MHX/NOPB adds critical fault visibility and dimming control; versus LM3409HVMM/NOPB, it trades fixed-frequency simplicity for topology flexibility and higher input voltage support - making it optimal for multi-voltage, safety-aware LED systems.
Availability
LM3423MHX/NOPB is available at Aetrix Electronics and suitable for outdoor area lighting, automotive LED headlamps, and industrial machine vision systems requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.
Supply support for LM3423MHX/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 LED driver innovation.
The LM342x family was designed specifically for high-reliability, wide-input constant-current LED drivers in automotive, industrial, and architectural lighting - emphasizing topology flexibility, fault resilience, and thermal robustness.
FAQ
What topologies does the LM3423MHX/NOPB support?
The LM3423MHX/NOPB supports buck, boost, buck-boost, and SEPIC LED driver topologies. Its high-side current sense architecture and predictive off-time control allow seamless configuration across these configurations without external compensation redesign. The device's 4.5 V to 75 V input range and ability to drive both high-side and low-side N-channel MOSFETs make it especially suited for boost and buck-boost implementations in high-output-voltage lighting systems. LM3423MHX/NOPB achieves this through dedicated HSP/HSN pins and flexible gate drive outputs (GATE and DDRV).
How does the LM3423MHX/NOPB implement analog dimming?
The LM3423MHX/NOPB implements analog dimming by regulating the CSH pin voltage - normally held at 1.24 V - to a lower value using an external DAC or current source. Since LED current ILED is directly proportional to CSH voltage divided by the sense resistor RSNS, reducing CSH linearly reduces output current. This method avoids PWM flicker and preserves color consistency in sensitive applications like architectural lighting. LM3423MHX/NOPB maintains regulation accuracy down to ~10% of full scale when using matched resistors and proper PCB layout. The CSH pin must remain above 0 V and within its absolute maximum rating of 6 V.
What is the function of the RPD pin on the LM3423MHX/NOPB?
The RPD (Resistor Pulldown) pin on the LM3423MHX/NOPB serves as the common return node for all external resistor dividers - including those connected to nDIM (UVLO) and OVP (OVLO) - enabling zero-current shutdown when pulled low. Internally, RPD connects to a 300 Ω (typical) pulldown transistor. When RPD is grounded, the EN pin is disabled, all gate drivers halt, and quiescent current drops to 1 µA. This feature simplifies system-level power sequencing and fail-safe shutdown in safety-critical lighting applications. LM3423MHX/NOPB requires RPD to be tied to AGND or actively driven low to achieve true zero-power state.
Does the LM3423MHX/NOPB support synchronization to an external clock?
No, the LM3423MHX/NOPB does not support external clock synchronization. Its Predictive Off-Time (PRO) control architecture relies on an internally generated off-time determined by the RCT network and input voltage scaling (VIN/25), which inherently results in variable frequency operation - especially in buck topology - to maintain stability and avoid sub-harmonic oscillation. While this eliminates need for slope compensation and simplifies loop design, it precludes precise frequency locking. For synchronized operation, designers must select fixed-frequency alternatives such as the LM3409HVMM/NOPB or TPS92692. LM3423MHX/NOPB prioritizes robustness over synchronizability.
What thermal management considerations apply to the LM3423MHX/NOPB?
The LM3423MHX/NOPB requires careful thermal management due to its 36.7°C/W junction-to-ambient thermal resistance (HTSSOP-20 package). The exposed thermal pad (DAP) must be soldered to a minimum 200 mm² copper pour connected to both AGND and PGND via multiple vias. Thermal shutdown activates at 165°C with 25°C hysteresis, but continuous operation above 125°C junction temperature degrades reliability. Layout best practices include separating AGND and PGND traces until star connection at DAP, minimizing trace inductance on GATE/DDRIVE paths, and avoiding thermal islands under the IC. LM3423MHX/NOPB datasheet specifies RθJC(bot) = 1.9°C/W - confirming DAP is the primary heat conduction path.
LM3423MHX/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 20-PowerTSSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- DC DC Controller
- Topology:
- SEPIC, Step-Down (Buck), Step-Up (Boost)
- Internal Switch(s):
- No
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 4.5V
- Voltage - Supply (Max):
- 75V
- Voltage - Output:
- -
- Current - Output / Channel:
- -
- Frequency:
- 2MHz
- Dimming:
- Analog, PWM
- Applications:
- -
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-HTSSOP
LM3423MHX/NOPB FAQ
1.How can I place an order for LM3423MHX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3423MHX/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 LM3423MHX/NOPB reliable?
The price and inventory of LM3423MHX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3423MHX/NOPB is usually 5 days.
3.What payment methods are accepted for LM3423MHX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3423MHX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
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LM3423MHX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3423MHX/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 LM3423MHX/NOPB?
For technical support, including LM3423MHX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3423MHX/NOPB requirements.
6.How does Aetrix verify that LM3423MHX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3423MHX/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 LM3423MHX/NOPB meets industry standards.
7.What is the process for return or replacement of LM3423MHX/NOPB?
All LM3423MHX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3423MHX/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 LM3423MHX/NOPB part is unused and in its original packaging.
Return procedure for LM3423MHX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM3423MHX/NOPB Tags
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BCR430UXTSA2
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CL2N8-G
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