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Texas Instruments LM3421MHX/NOPB
- Part No.:
- LM3421MHX/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-PowerTSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LM3421MHX/NOPB.pdf
- Description:
- IC LED DRIVER CTRLR PWM 16HTSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,052
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Product details
Overview
LM3421MHX/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 high-side adjustable current sensing with 1.24 V reference. It enables precise LED current regulation in automotive headlamps and outdoor area lighting.
For engineers reviewing the LM3421MHX/NOPB datasheet, LM3421MHX/NOPB pinout, LM3421MHX/NOPB application, or LM3421MHX/NOPB equivalent, key selection considerations include VIN range (4.5–75 V), PRO control architecture, high-side current sense interface (HSP/HSN), programmable switching frequency up to 2 MHz, and integrated UVLO/OVLO protection.
Technical Context
The LM3421MHX/NOPB implements Predictive Off-Time (PRO) control-a hybrid of peak current-mode control and input-voltage-proportional off-timer-enabling stable loop compensation and inherent input voltage feed-forward without external compensation networks. It uses a high-side transconductance amplifier (gM = 20 mA/V) with HSP/HSN differential inputs to sense LED current via external RSNS, regulating CSH to 1.24 V.
Its gate driver delivers 1-A peak sourcing/sinking capability with RDS(ON) of 2 Ω (source) and 1.3 Ω (sink) at 25°C, optimized for fast turn-on/turn-off of N-channel power MOSFETs. The device integrates a 7-V internal LDO (VCCREG), thermal shutdown at 165°C, and cycle-by-cycle current limiting triggered by IS pin voltage exceeding 245 mV (typ).
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 low-output-ripple designs using small inductors/capacitors. |
| Current Sense Reference | 1.24 V on CSH - sets LED current accuracy and enables analog dimming via CSH voltage modulation. |
| GATE Driver Strength | 1-A peak, 2-Ω source / 1.3-Ω sink - ensures fast MOSFET switching with <35 ns current-limit delay and 210 ns LEB. |
| Thermal Shutdown | 165°C with 25°C hysteresis - protects against sustained overloads while allowing brief transient operation. |
| UVLO Threshold | nDIM pin: 1.24 V turn-on with 23 µA hysteresis current - provides clean enable/disable with resistor-divider programming. |
| OVP Threshold | OVP pin: 1.24 V trip with 23 µA hysteresis current - allows precise output overvoltage lockout via external divider. |
Pinout & Package
LM3421MHX/NOPB is housed in a 16-pin HTSSOP (PWP) package measuring 5.00 mm × 4.40 mm with exposed thermal pad (DAP) for enhanced thermal performance.
| 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 circuits. |
| 2 EN | Enable input | Logic-level enable with 2.4 V threshold; internal 0.245–2.85 MΩ pulldown enables zero-current shutdown when grounded. |
| 3 COMP | Error amplifier output | Connects to RC network for loop compensation; regulates CSH to 1.24 V to maintain LED current setpoint. |
| 4 CSH | Current sense high reference | Serves as regulated 1.24 V node for high-side current sense amplifier; also used for analog dimming control. |
| 5 RCT | Predictive off-time timing | RC network sets switching frequency; VRCT = VIN/25 (565 mV typ at VIN = 14 V) defines off-time base. |
| 6 AGND | Analog ground reference | Star-ground connection point for CSH, COMP, RCT, nDIM; tied to PGND via DAP copper pad. |
| 7 OVP | Output overvoltage sense | Resistor divider from VO sets 1.24 V OVLO trip; 23 µA hysteresis current enables programmable hysteresis. |
| 8 nDIM | PWM dimming & UVLO input | Accepts PWM signal for digital dimming; also programs VIN UVLO threshold via resistor divider to AGND. |
| 9 VCC | Internal LDO output | 7.35 V regulated supply (6.3–7.35 V); bypassed with 2.2–3.3 µF ceramic cap to PGND for gate driver stability. |
| 10 GATE | Main MOSFET gate driver | 1-A peak push-pull output; drives N-channel switch with 2 Ω source / 1.3 Ω sink resistance at 25°C. |
| 11 PGND | Power ground return | Low-impedance return path for GATE and DDRV; connected to AGND via DAP for thermal and noise control. |
| 12 DDRV | Dimming MOSFET driver | Open-drain output for series dimming FET; 30 Ω source / 10 Ω sink resistance enables fast PWM dimming. |
| 13 IS | Main switch current sense | Monitors MOSFET RDS(ON) or external sense resistor; triggers cycle-by-cycle limit at 245 mV (typ). |
| 14 HSN | High-side sense negative | Differential input to high-side transconductance amplifier; paired with HSP to measure RSNS voltage drop. |
| 15 HSP | High-side sense positive | Differential input referenced to HSN; forces VHSP = VHSN via feedback to enable accurate VSNS measurement. |
| 16 RPD | Resistor pulldown | Common return for all external resistor dividers (nDIM, OVP); enables zero-current shutdown when pulled low. |
Key Features
| Feature | Design Value |
|---|---|
| Predictive Off-Time (PRO) Control | Eliminates sub-harmonic oscillation at >50% duty cycles; enables stable operation across full VIN/VO range without slope compensation. |
| High-Side Adjustable Current Sense | 1.24 V CSH reference with 20 mA/V transconductance amplifier allows ±1.5 µA input offset and 50 mV minimum VSNS for <1% error. |
| Integrated Protection Suite | Input UVLO (programmable via nDIM), output OVLO (via OVP), thermal shutdown (165°C), and cycle-by-cycle current limiting (245 mV). |
| 2-MHz Capable Gate Driver | 1-A peak drive with 2 Ω source / 1.3 Ω sink ensures <50 ns MOSFET transition times; supports high-frequency, low-size designs. |
| Flexible Dimming Interface | Hardware PWM dimming via nDIM pin + analog dimming via CSH voltage modulation - enables dual-dimming schemes in single design. |
Applications
| Automotive Headlamp Drivers | Outdoor Area Lighting |
|---|---|
|
Use Scenario: High-brightness LED arrays in vehicle forward lighting requiring robust EMI control, thermal resilience, and wide input range (9–16 V nominal, up to 75 V load dump). IC Role / Device Role / Timing Role: N-channel controller implementing boost topology to regulate 1–5 A LED current; PRO control maintains stability during battery transients. Use Value: Enables single-chip solution for AEC-Q100-compliant designs (via LM3421-Q1 variant); 75 V rating withstands ISO 7637-2 pulse 5a. |
Use Scenario: Streetlight and parking lot luminaires operating from 120/277 VAC rectified supplies, requiring high efficiency (>92%) and long lifetime. IC Role / Device Role / Timing Role: Buck-boost controller driving 36–72 V LED strings; high-side sensing isolates current regulation from ground noise. Use Value: 2 MHz switching reduces inductor size by >40% vs. 500 kHz alternatives; thermal pad ensures <39°C/W junction-to-ambient rise at 2 A. |
| Industrial Machine Vision Lighting | Architectural Accent Lighting |
|
Use Scenario: High-CRI, strobed LED arrays in automated inspection systems demanding precise current repeatability (<±1.5%) and microsecond dimming response. IC Role / Device Role / Timing Role: Constant-current regulator with analog dimming (CSH) and hardware PWM (nDIM); cycle-by-cycle limiting prevents LED damage during flash bursts. Use Value: 1.24 V CSH reference and 100 µA signal current yield <0.5% LED current drift over –40°C to +125°C junction temperature. |
Use Scenario: Low-profile linear LED modules in façade and interior cove lighting, where PCB space is constrained and thermal management is passive. IC Role / Device Role / Timing Role: SEPIC controller enabling buck-boost operation from 12–48 V DC input; RCT-programmed frequency avoids audible noise bands. Use Value: HTSSOP package with thermal pad achieves 38.9°C/W θJA, enabling 2.5 W dissipation at <60°C ambient without heatsink. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar N-channel LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM3423MHX/NOPB | 20-pin HTSSOP; adds FLT fault flag, TIMR timer, LRDY LED-ready flag, and DPOL dim polarity control. | Required for systems needing fault latching, status reporting, or P-channel dimming FET support. | Select LM3423MHX/NOPB only if fault diagnostics or dual-dimming-FET control are mandatory; otherwise LM3421MHX/NOPB offers lower cost and footprint. |
| LT3761EFE#PBF | 40 V max VIN; includes integrated 5 V bias supply and spread-spectrum frequency modulation. | Better suited for lower-voltage commercial lighting; lacks 75 V rating and high-side sensing flexibility. | Choose LT3761EFE#PBF for cost-sensitive 12–36 V applications where integrated bias simplifies BOM; avoid for automotive/load-dump environments. |
Compared with LM3423MHX/NOPB, LM3421MHX/NOPB saves board space and cost by omitting diagnostic pins, while retaining identical core control, protection, and dimming functionality. Against LT3761EFE#PBF, it trades integrated bias for higher voltage resilience and flexible high-side sensing-critical for ruggedized LED systems.
Availability
LM3421MHX/NOPB is available at Aetrix Electronics and suitable for automotive lighting, outdoor area illumination, and industrial machine vision systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM3421MHX/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 for industrial, automotive, and consumer markets.
The LM3421MHX/NOPB belongs to TI's LED controller product line, designed specifically for high-efficiency, high-reliability constant-current LED drivers in demanding environments including automotive front lighting and outdoor infrastructure.
FAQ
What is the maximum input voltage supported by the LM3421MHX/NOPB?
The LM3421MHX/NOPB supports an absolute maximum input voltage of 76 V and a recommended operating range of 4.5 V to 75 V. This wide VIN range enables direct operation from 12 V, 24 V, and 48 V industrial or automotive supplies-including handling of ISO 7637-2 load-dump transients up to 75 V without external clamping. The internal start-up regulator functions reliably across this full span.
How does the LM3421MHX/NOPB implement high-side current sensing?
The LM3421MHX/NOPB uses dedicated HSP and HSN pins to interface with an external high-side current sense resistor (RSNS). Its internal transconductance amplifier forces VHSP = VHSN, causing the sensed voltage (VSNS) to develop across RHSP and generate a proportional signal current (ICSH) flowing out of the CSH pin. The error amplifier regulates CSH to 1.24 V, enabling precise LED current calculation independent of ground path noise.
Can the LM3421MHX/NOPB be used for both PWM and analog dimming simultaneously?
Yes - the LM3421MHX/NOPB supports concurrent PWM and analog dimming. PWM dimming is applied directly to the nDIM pin, while analog dimming is achieved by modulating the voltage on the CSH pin (which is normally regulated to 1.24 V). This dual-dimming capability allows fine-grained brightness control across multiple decades, useful in applications like architectural lighting where smooth transitions and deep dimming are required.
What is the purpose of the RPD pin on the LM3421MHX/NOPB?
The RPD (Resistor Pulldown) pin on the LM3421MHX/NOPB serves as the common low-side connection for all external resistor dividers - including those used for nDIM-based UVLO and OVP-based OVLO. When RPD is pulled low, it disables all such divider networks, placing the device into zero-current shutdown mode. This simplifies system-level power sequencing and enables coordinated shutdown across multiple protection functions.
Does the LM3421MHX/NOPB require external compensation components?
Yes - the LM3421MHX/NOPB requires an external RC network connected to the COMP pin for loop compensation. Because it uses Predictive Off-Time (PRO) control, the compensation is significantly simplified compared to traditional current-mode controllers: typically only a single series RC (e.g., 10 kΩ + 1 nF) is needed to stabilize the error amplifier. No slope compensation is required, reducing component count and design iteration time.
LM3421MHX/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 16-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:
- 3V ~ 72V
- 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:
- 16-HTSSOP
LM3421MHX/NOPB FAQ
1.How can I place an order for LM3421MHX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3421MHX/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 LM3421MHX/NOPB reliable?
The price and inventory of LM3421MHX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3421MHX/NOPB is usually 5 days.
3.What payment methods are accepted for LM3421MHX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3421MHX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3421MHX/NOPB?
LM3421MHX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3421MHX/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 LM3421MHX/NOPB?
For technical support, including LM3421MHX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3421MHX/NOPB requirements.
6.How does Aetrix verify that LM3421MHX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3421MHX/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 LM3421MHX/NOPB meets industry standards.
7.What is the process for return or replacement of LM3421MHX/NOPB?
All LM3421MHX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3421MHX/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 LM3421MHX/NOPB part is unused and in its original packaging.
Return procedure for LM3421MHX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM3421MHX/NOPB Tags
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BCR402RE6327HTSA1
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BCR430UXTSA2
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BCR420UE6433HTMA1
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BCR420UE6327HTSA1
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BCR421UE6327HTSA1
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LYT1604D-TL
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HV9910CLG-G
Microchip Technology
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CL2N8-G
Microchip Technology
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BCR420UW6-7
Diodes Incorporated
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BCR421UW6-7
Diodes Incorporated
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BCR420UFD-7
Diodes Incorporated
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BCR421UFD-7
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