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Texas Instruments LM3421Q1MHX/NOPB
- Part No.:
- LM3421Q1MHX/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-PowerTSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LM3421Q1MHX/NOPB.pdf
- Description:
- IC LED DRIVER CTRLR PWM 16HTSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,778
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Product details
Overview
LM3421Q1MHX/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, adjustable high-side current sense (1.24 V threshold), and integrated UVLO/OVLO protection. Used in automotive LED lighting systems requiring robust thermal shutdown (165°C) and PWM/analog dimming.
For engineers reviewing the LM3421Q1MHX/NOPB datasheet, LM3421Q1MHX/NOPB pinout, LM3421Q1MHX/NOPB application, or LM3421Q1MHX/NOPB equivalent, key selection considerations include its AEC-Q100 Grade 1 qualification (–40°C to +125°C), HTSSOP-16 package with exposed thermal pad, 16-pin predictive off-time architecture, and compatibility with external N-channel main/dimming FETs in high-side current-sense configurations.
Technical Context
The LM3421Q1MHX/NOPB implements Predictive Off-Time (PRO) control - a hybrid of peak current-mode regulation and input-voltage-proportional off-timer - enabling stable loop compensation and inherent input feed-forward without sub-harmonic oscillation up to 100% duty cycle. Its high-side differential current sense amplifier (gM = 20 mA/V, bandwidth = 250–500 kHz) interfaces directly with HSP/HSN pins and regulates CSH to 1.24 V for precise LED current control.
It integrates a 6.3–7.35 V internal start-up regulator (20 mA current limit), programmable switching frequency up to 2 MHz via RCT pin, cycle-by-cycle current limiting on IS pin (215–275 mV threshold), and dual dimming support: PWM via nDIM (1.24 V threshold, 23 µA hysteresis) and analog via CSH voltage injection. 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 battery rails without external pre-regulation. |
| Switching Frequency | Up to 2 MHz - set by external RCT network; enables compact magnetics and low-output-ripple designs. |
| Current Sense Threshold | 1.24 V (±5%) at CSH - sets LED current accuracy; used with external RHSP/RCSH/RSNS for ±1% typical ILED regulation. |
| GATE Driver Strength | 2 Ω sourcing / 4.5 Ω sinking - drives N-channel MOSFET gates with <35 ns turn-on/off delay, supporting >5 A LED loads. |
| Thermal Shutdown | 165°C activation with 25°C hysteresis - protects against sustained overloads; junction temperature monitored internally. |
| UVLO & OVLO | nDIM pin: 1.24 V turn-on with 23 µA hysteresis; OVP pin: 1.24 V trip with 23 µA hysteresis - ensures safe startup and overvoltage fault response. |
| Quiescent Current | 3 mA (typical) at VEN = 3 V - enables low-power standby operation; drops to 1 µA in shutdown mode. |
Pinout & Package
LM3421Q1MHX/NOPB uses a 16-pin HTSSOP (PWP) package with 5.00 mm × 4.40 mm body size and exposed thermal pad (DAP) for enhanced thermal dissipation. The DAP must be star-grounded to both AGND and PGND per TI layout guidelines.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VIN | Main input supply | Bypassed with 100 nF ceramic capacitor to AGND; powers internal regulator and high-voltage logic. |
| 2 EN | Enable input | Active-high enable; 2.4 V threshold with 0.245–2.85 MΩ internal pulldown; connects to AGND for zero-current shutdown. |
| 3 COMP | Error amplifier output | Connects to AGND via RC network for loop compensation; regulates CSH to 1.24 V for current control. |
| 4 CSH | Current sense reference | Sense amplifier output node regulated to 1.24 V; used for analog dimming and feedback loop stability. |
| 5 RCT | Off-time timing input | External RC network sets predictive off-time and thus switching frequency; VIN/25 reference (565 mV typ) applied internally. |
| 6 AGND | Analog ground | Reference for CSH, COMP, RCT, nDIM; connected to PGND via DAP copper pad for low-noise sensing. |
| 7 OVP | Overvoltage protection input | Resistor divider from VO sets 1.24 V OVLO threshold; 23 µA hysteresis current source enables clean latch-off. |
| 8 nDIM | PWM dimming & UVLO input | Accepts PWM signal or resistor divider from VIN; 1.24 V threshold with 23 µA hysteresis enables input undervoltage lockout. |
| 9 VCC | Internal LDO output | 6.3–7.35 V regulated supply; bypassed with 2.2–3.3 µF ceramic cap to PGND; powers gate driver and logic. |
| 10 GATE | Main MOSFET gate driver | 2 Ω sourcing / 4.5 Ω sinking output; drives N-channel switch gate; requires external bootstrap or isolated gate drive for high-side FETs. |
| 11 PGND | Power ground | Return path for GATE and DDRV; star-connected to AGND via DAP to minimize noise coupling into analog circuits. |
| 12 DDRV | Dimming MOSFET gate driver | 30 Ω sourcing / 10 Ω sinking output; drives series N-channel dimming FET; polarity controlled by DPOL (not present on LM3421). |
| 13 IS | Main switch current sense | Connects to MOSFET drain (RDS(on) sensing) or source resistor; 215–275 mV cycle-by-cycle current limit threshold. |
| 14 HSN | High-side sense negative | Low-side terminal of LED current sense resistor; forms differential pair with HSP for accurate high-side current measurement. |
| 15 HSP | High-side sense positive | High-side terminal of LED current sense resistor; forces VHSP = VHSN via feedback to maintain VSNS across RSNS. |
| 16 RPD | Resistor pulldown | Common return for all external resistor dividers (nDIM, OVP); enables zero-current shutdown when pulled to AGND. |
Key Features
| Feature | Design Value |
|---|---|
| Predictive Off-Time (PRO) Control | Eliminates sub-harmonic oscillation at any duty cycle; simplifies compensation with inherent input voltage feed-forward and stable CCM operation. |
| Adjustable High-Side Current Sense | 1.24 V reference at CSH enables precise LED current regulation using external RSNS/RHSP/RCSH; supports >5 A output with low power loss. |
| Integrated Protection Suite | Input UVLO (via nDIM), output OVLO (via OVP), thermal shutdown (165°C), and cycle-by-cycle current limiting (IS pin) ensure robust system-level safety. |
| Dual Dimming Interface | PWM dimming via nDIM pin (1.24 V threshold) and analog dimming via CSH voltage injection - supports flicker-free brightness control down to 0.1%. |
| AEC-Q100 Qualified | Grade 1 qualification (–40°C to +125°C) with production-tested reliability - validated for automotive headlamp, tail lamp, and interior lighting applications. |
Applications
| Automotive Headlamp Drivers | Industrial Area Lighting |
|---|---|
|
Use Scenario: Constant-current LED driver for adaptive front-lighting systems (AFS) in 12 V/24 V vehicle platforms with wide input transients. IC Role / Device Role / Timing Role: N-channel controller managing boost topology with high-side current sense to regulate 1–3 A LED strings independent of battery voltage fluctuations. Use Value: PRO control maintains stable regulation during cold-crank (4.5 V) and load-dump (75 V) events; thermal shutdown prevents LED degradation under sealed-housing conditions. |
Use Scenario: Outdoor parking lot luminaires powered from 24–48 V DC microgrids with ambient temperatures from –40°C to +85°C. IC Role / Device Role / Timing Role: Buck-boost controller driving 4–12 V LED arrays with analog dimming for daylight harvesting and occupancy-based intensity control. Use Value: 75 V max VIN and AEC-Q100 Grade 1 rating ensure long-term reliability in unregulated outdoor power environments; RCT-programmable frequency avoids EMI-sensitive bands. |
| Commercial Signage Backlighting | Architectural Accent Lighting |
|
Use Scenario: RGBW LED modules in digital signage requiring synchronized PWM dimming across multiple channels with minimal color shift. IC Role / Device Role / Timing Role: Controller implementing SEPIC topology to maintain constant current despite varying forward voltage across mixed-color LED strings. Use Value: Dual dimming (PWM + analog) enables fine-grained intensity control; high-side sensing eliminates ground-referencing constraints in floating-string configurations. |
Use Scenario: Linear LED strips embedded in aluminum extrusions for façade lighting, requiring thermal-aware current regulation and surge immunity. IC Role / Device Role / Timing Role: Boost controller with external N-channel FET and high-side current sense, operating in continuous conduction mode for low ripple and acoustic noise. Use Value: 165°C thermal shutdown and 2.85 MΩ EN pulldown resistance prevent thermal runaway in confined heatsink assemblies; PGND/AGND star grounding minimizes EMI in sensitive RF environments. |
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 |
|---|---|---|---|
| LM3423Q1MHX/NOPB | 20-pin HTSSOP; adds FLT flag, TIMR timer, LRDY status, and DPOL polarity control - no pin compatibility with LM3421Q1MHX/NOPB. | Required for designs needing fault latching, LED-ready indication, or P-channel dimming FET support. | Select LM3423Q1MHX/NOPB only if fault diagnostics or flexible dimming polarity are mandatory; PCB redesign required. |
| LM3409Q1MHX/NOPB | HTSSOP-16; supports only buck topology; lacks high-side sense (uses low-side CS); no RCT-programmable frequency (fixed 500 kHz). | Suitable for cost-sensitive, lower-voltage (<40 V) automotive interior lighting where topology flexibility is not needed. | Choose LM3409Q1MHX/NOPB for simplified buck-only designs with tighter BOM cost targets; not interchangeable for boost/buck-boost use cases. |
Compared with LM3423Q1MHX/NOPB, LM3421Q1MHX/NOPB offers identical topology support and protection but omits diagnostic flags - reducing component count and layout complexity. Versus LM3409Q1MHX/NOPB, it delivers broader VIN range, topology flexibility, and programmable frequency at higher design effort.
Availability
LM3421Q1MHX/NOPB is available at Aetrix Electronics and suitable for automotive lighting, industrial area illumination, and architectural accent lighting requiring stable component supply across extended temperature ranges and high-reliability certifications.
Supply support for LM3421Q1MHX/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 high-reliability power management solutions, with decades of automotive-grade product development and manufacturing excellence.
The LM342x family was designed specifically for high-efficiency, high-voltage constant-current LED driver applications - targeting automotive, industrial, and commercial solid-state lighting systems requiring AEC-Q100 compliance and flexible topology support.
FAQ
What topology configurations does the LM3421Q1MHX/NOPB support?
The LM3421Q1MHX/NOPB supports buck, boost, buck-boost, and SEPIC topologies through external component configuration. Its high-side current sense architecture and predictive off-time control enable stable operation across all four, unlike fixed-topology controllers. Designers select topology based on input/output voltage relationship and efficiency targets - for example, boost for 12 V input → 36 V LED string, or buck-boost for wide-input automotive applications. LM3421Q1MHX/NOPB does not require topology-specific IC variants.
How is LED current regulated using the high-side sense feature of LM3421Q1MHX/NOPB?
LM3421Q1MHX/NOPB regulates LED current via its high-side differential amplifier connected to HSP and HSN pins. The device forces VHSP = VHSN, causing the LED current ILED to generate a sense voltage VSNS across external resistor RSNS. This voltage appears across RHSP, producing signal current ICSH = VSNS / RHSP, which flows out of the CSH pin. The error amplifier holds CSH at 1.24 V, so ILED = 1.24 V / RSNS. LM3421Q1MHX/NOPB achieves ±1% typical regulation using this method.
Does LM3421Q1MHX/NOPB support both PWM and analog dimming simultaneously?
LM3421Q1MHX/NOPB supports PWM dimming via the nDIM pin and analog dimming via voltage injection at the CSH pin, but not simultaneously in a single channel without external circuitry. PWM dimming modulates the EN pin or uses external FET gating; analog dimming adjusts the CSH reference to scale the 1.24 V setpoint. Using both concurrently would require careful sequencing to avoid control loop instability. LM3421Q1MHX/NOPB is typically configured for one method per design - PWM for high-frequency flicker-free control, analog for smooth low-end dimming.
What is the purpose of the RPD pin on LM3421Q1MHX/NOPB?
The RPD (Resistor Pulldown) pin on LM3421Q1MHX/NOPB serves as the common low-side connection point for all external resistor dividers - including those for nDIM (UVLO) and OVP (OVLO). Internally, it connects to a 300 Ω pulldown (145 Ω typ), allowing zero-current shutdown when pulled to AGND. This eliminates the need for separate pull-down resistors on each divider, reduces component count, and ensures coordinated disable behavior across protection functions. LM3421Q1MHX/NOPB relies on RPD for deterministic shutdown sequencing.
Is LM3421Q1MHX/NOPB pin-compatible with standard LM3421 variants?
Yes, LM3421Q1MHX/NOPB is pin-compatible with the commercial-grade LM3421MHX/NOPB and shares identical HTSSOP-16 pinout, electrical specifications, and functional behavior. The "Q1" suffix denotes AEC-Q100 Grade 1 qualification (–40°C to +125°C) and enhanced process controls - no changes to pin assignment, timing, or interface logic. LM3421Q1MHX/NOPB can replace LM3421MHX/NOPB in automotive designs without layout modification, provided thermal and lifetime validation align with Grade 1 requirements.
LM3421Q1MHX/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:
- Automotive
- Qualification:
- AEC-Q100
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-HTSSOP
LM3421Q1MHX/NOPB FAQ
1.How can I place an order for LM3421Q1MHX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3421Q1MHX/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 LM3421Q1MHX/NOPB reliable?
The price and inventory of LM3421Q1MHX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3421Q1MHX/NOPB is usually 5 days.
3.What payment methods are accepted for LM3421Q1MHX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3421Q1MHX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3421Q1MHX/NOPB?
LM3421Q1MHX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3421Q1MHX/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 LM3421Q1MHX/NOPB?
For technical support, including LM3421Q1MHX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3421Q1MHX/NOPB requirements.
6.How does Aetrix verify that LM3421Q1MHX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3421Q1MHX/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 LM3421Q1MHX/NOPB meets industry standards.
7.What is the process for return or replacement of LM3421Q1MHX/NOPB?
All LM3421Q1MHX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3421Q1MHX/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 LM3421Q1MHX/NOPB part is unused and in its original packaging.
Return procedure for LM3421Q1MHX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM3421Q1MHX/NOPB Tags
-
BCR402RE6327HTSA1
Infineon Technologies
-
BCR430UXTSA2
Infineon Technologies
-
BCR420UE6433HTMA1
Infineon Technologies
-
BCR420UE6327HTSA1
Infineon Technologies
-
BCR421UE6327HTSA1
Infineon Technologies
-
LYT1604D-TL
Power Integrations
-
HV9910CLG-G
Microchip Technology
-
CL2N8-G
Microchip Technology
-
BCR420UW6-7
Diodes Incorporated
-
BCR421UW6-7
Diodes Incorporated
-
BCR420UFD-7
Diodes Incorporated
-
BCR421UFD-7
Diodes Incorporated
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