LM61440 - 4A 36V Low EMI Sync Buck Converter | TI
MPN: LM61440 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.65 | $3.65 |
| 10 | $3.28 | $32.80 |
| 100 | $2.75 | $275.00 |
| 500 | $2.4 | $1,200.00 |
| 1,000 | $2.1 | $2,100.00 |
LM61440 Overview
A synchronous buck converter is a DC-DC step-down regulator that uses both high-side and low-side switches to efficiently convert a higher input voltage to a lower output voltage. Unlike asynchronous converters that use a diode for the low-side path, synchronous converters replace the diode with a low-resistance MOSFET, reducing conduction losses and improving efficiency at high output currents. Synchronous buck converters are a cornerstone of power management ICs, enabling compact, high-efficiency point-of-load power supplies across automotive, industrial, and networking systems.
Key features of the LM61440 include soft recovery from dropout, which eliminates output overshoot when the input voltage dips close to the regulated output, ensuring stable behavior during cold-crank and sag conditions. The device incorporates pseudo-random spread spectrum to reduce peak EMI, adjustable SW node rise time to optimize the efficiency-versus-EMI trade-off, and a low-EMI VQFN-HR package with minimized switch node ringing.
Technically, the LM61440 uses current-mode control with integrated compensation, providing fast transient response and stability across a wide range of output capacitors. The adjustable output goes down to 1 V, suiting modern low-voltage digital cores. The integrated MOSFETs eliminate external FETs, reducing board space and BOM complexity, while the PowerVFQFN exposed pad enables high power density designs.
Typical applications include automotive power supplies, industrial control, telecom and networking equipment, and general-purpose point-of-load conversion from 12 V or 24 V rails. The wide input range and 42 V tolerance make it ideal where input spikes are common, and the low EMI features benefit automotive and communications designs with strict CISPR-class requirements.
When designing with the LM61440, select input and output capacitors per the TI datasheet recommendations to maintain stability and low ripple; the adjustable SW slew rate lets you trade efficiency for EMI margin.
Drop-in alternatives for LM61440 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with LM61440 (same form factor and footprint) — differing in Package, Input Voltage Range, Topology, Dropout Behavior, Output Voltage.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LM61440Q-Q1
✅ Drop-In✓ In Stock
$2.78 / Unit
View Datasheet →LM61440AANRJRR
✅ Drop-In✓ In Stock
$2.9706 / Unit
View Datasheet →LM61460AASRJRRQ1
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
LM61460
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
LM61440 Maximum Ratings & Electrical Characteristics
| Topology | Synchronous Step-Down (Buck) |
| Input Voltage Range | 3.0 V to 36 V |
| Input Transient Tolerance | 42 V |
| Maximum Output Current | 4 A |
| Output Voltage | Adjustable, down to 1 V |
| Number of Outputs | 1 |
| Control Topology | Current-mode control with integrated compensation |
| Integrated MOSFETs | Yes (high-side and low-side) |
| EMI Features | Pseudo-random spread spectrum, adjustable SW node rise time |
| Dropout Behavior | Soft recovery from dropout, no output overshoot |
| Package | 14-PowerVFQFN (RJR), VQFN-HR low-EMI |
| Mounting Type | Surface Mount |
| Switching Regulator Type | Buck switching regulator IC, positive adjustable output |
| Automotive Grade Variant | LM61440-Q1 (AEC-Q100 qualified) |
LM61440 Pin Configuration
| Pin 1 | PVIN — Power input voltage to integrated MOSFETs |
| Pin 2 | VIN — Input supply for control circuitry |
| Pin 3 | EN — Enable input, adjust undervoltage lockout threshold |
| Pin 4 | RT/SYNC — Switching frequency set resistor or external synchronization |
| Pin 5 | AGND — Analog ground for control circuitry |
| Pin 6 | FB — Feedback input for output voltage regulation |
| Pin 7 | SS/TRK — Soft-start and output voltage tracking |
| Pin 8 | BOOT — Bootstrap capacitor for high-side gate driver |
| Pin 9 | SW — Switch node, connection point for output inductor |
| Pin 10 | PGND — Power ground for MOSFET current return |
| Pin 11 | PWRGD — Power good open-drain output flag |
| Pin 12 | AVIN — Analog input supply |
| Pin 13 | VREG5 — Internal 5 V LDO output, bypass capacitor |
| Pin 14 | PGND — Power ground |
| Pin 15 | PAD — Exposed thermal pad, connect to PGND plane |
Typical Applications
LM61440 is suitable for 6 applications: Automotive Power Supplies, Industrial Control and Automation, Telecom and Networking Equipment, Point-of-Load Conversion from 12V Rails, Battery-Powered Test and Measurement Instruments, Motor Drive and Actuator Logic Supplies.
Automotive Power Supplies
The LM61440-Q1 variant, AEC-Q100 qualified, is purpose-built for automotive 12 V battery systems. Its 42 V transient tolerance absorbs load-dump and surge events that would destroy lower-rated converters, while soft recovery from dropout maintains a monotonic output during cold-crank sags where battery voltage dips near the regulated output. The pseudo-random spread spectrum and low-ringing VQFN-HR package help designs meet automotive EMC requirements without heavy filtering, reducing BOM cost and board space in body, infotainment, and ADAS power trees.
Recommended
Industrial Control and Automation
In factory automation and PLC I/O modules, the LM61440 converts 24 V industrial buses to point-of-load rails with 4 A capacity. The 36 V continuous input rating plus 42 V tolerance provides natural headroom against industrial surge conditions, and current-mode control with integrated compensation keeps the design stable across varied output capacitor choices. Adjustable SW rise time lets engineers trade a little efficiency for additional EMI margin near sensitive analog front ends and encoders, simplifying EMC compliance of the whole control cabinet.
Recommended
Telecom and Networking Equipment
Networking switches, routers, and optical modules powered from 12 V or intermediate buses benefit from the LM61440's combination of 4 A output and low EMI. The pseudo-random spread spectrum reduces peak radiated emissions, which is valuable in dense racks where multiple converters operate close together. Its adjustable 1 V minimum output supports modern low-voltage DSP, PHY, and FPGA core rails, while the 14-pin VQFN-HR exposed-pad package achieves high power density for compact line-card and SFP-based designs.
Recommended
Point-of-Load Conversion from 12V Rails
For general 12 V to low-voltage point-of-load conversion, the LM61440's integrated MOSFETs eliminate external FET selection, driver design, and loop compensation, shrinking the power stage to one small IC plus a few passives. The 4 A rating covers FPGA I/O banks, microcontroller clusters, and memory rails, and the soft recovery behavior prevents output overshoot during input brown-out events. The exposed-pad VQFN-HR layout with minimized switch-node ringing also reduces the near-field noise coupling into adjacent high-speed signal lines.
Recommended
Battery-Powered Test and Measurement Instruments
Portable and bench instruments require wide-input converters tolerant of adaptor surges and battery sag. The LM61440's 3 V to 36 V input, 42 V transient tolerance, and soft dropout recovery keep output rails clean across the full battery discharge curve. The spread-spectrum EMI feature prevents switching harmonics from corrupting precision ADC front ends - pairing it with TI's ADS or OPA precision families yields low-noise signal chains. Its 4 A output easily powers displays, processors, and interface circuitry simultaneously.
Recommended
Motor Drive and Actuator Logic Supplies
In brushed and BLDC motor-drive boards, gate-driver and controller rails must stay stable while the shared supply bus carries switching noise. The LM61440 converts the noisy 12 V or 24 V bus into a clean 1 V to 5 V logic rail with fast current-mode transient response, riding through bus dips with no overshoot thanks to soft dropout recovery. Adjustable SW slew-rate control reduces high-frequency emissions that otherwise couple into motor phase-current sensing paths, supporting clean operation of TI DRV-series gate drivers.
Recommended
Recommended Products Summary
Engineering reference data for LM61440 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LM61440Q-Q1 | LM61440AANRJRR | LM61460AASRJRRQ1 |
|---|---|---|---|---|
| Package | 14-PowerVFQFN (RJR) | 14-PowerVFQFN (RJR) - same | 14-PowerVFQFN (RJR) - same | 14-PowerVFQFN (RJR) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Input Voltage Range | 3.0 V to 36 V (42 V tolerant) | 3.0 V to 36 V (42 V tolerant) | 3.0 V to 36 V (42 V tolerant) | 3.0 V to 36 V (42 V tolerant) |
| Output Current | 4 A | 4 A | 4 A | 6 A |
| Minimum Output Voltage | 1 V | 1 V | 1 V | 1 V |
| Automotive Grade | No (use Q1 variant) | Yes (AEC-Q100) | No | Yes (AEC-Q100) |
| EMI Features | Spread spectrum, adjustable SW rise time, VQFN-HR | Same feature set | Same feature set | Same feature set |
| Dropout Recovery | Soft recovery, no overshoot | Soft recovery | Soft recovery | Soft recovery |
Key Differentiators
- 42 V input transient tolerance on a 36 V rated converter (vs LM61440AANRJRR (same die))
- Soft recovery from dropout eliminates output overshoot (vs Conventional 36 V bucks)
- Pin-compatible 6 A upgrade path (vs LM61460AASRJRRQ1)
Design Notes
Connect the exposed pad of the 14-pin VQFN-HR (RJR) package to a solid PGND plane with an array of thermal vias; the pad is the primary thermal path for the integrated MOSFETs. Keep the input capacitor loop (PVIN/PGND) as short as possible, and minimize SW-node copper area to cut radiated EMI. Place the FB divider away from the SW node to prevent noise coupling into regulation. Follow the TI datasheet layout example for the reference design.
The LM61440 offers two EMI tuning levers: pseudo-random spread spectrum and adjustable SW node rise time. Increasing rise time lowers high-frequency emissions at the cost of switching efficiency - use it when radiated emissions testing nears CISPR-class limits. Enable spread spectrum for conducted emissions around the fundamental switching frequency. The VQFN-HR package already suppresses switch node ringing, so external RC snubbers are usually unnecessary.
Do not exceed the 36 V continuous input rating even though the device tolerates 42 V transients - 42 V is surge tolerance, not continuous operation. Size the inductor for peak current above the 4 A rating plus ripple. For automotive designs, use the LM61440-Q1 variant and add input TVS protection for load dump. Verify bootstrap capacitor value and VREG5 bypassing per datasheet, since these affect gate-drive integrity.
At high step-down ratios (e.g., 24 V to 1 V) the LM61440 runs at low duty cycle, concentrating losses in the high-side switch and dead-time conduction; check junction temperature with the datasheet thermal model and copper-pour thetaJA. If the thermal budget is exceeded at 4 A, consider the pin-compatible LM61460 at reduced load or improve airflow and copper area.
Compliance Information
Standard LM61440 is not automotive qualified; the LM61440-Q1 variant is AEC-Q100 qualified per TI. RoHS/REACH status not present in provided web data - verify on ti.com product page.
