LM5085QMYE/NOPB - 75V PFET Buck Controller, AEC-Q100 | TI
MPN: LM5085QMYE/NOPB ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.2 | $3.20 |
| 10 | $2.88 | $28.80 |
| 100 | $2.56 | $256.00 |
| 500 | $2.27 | $1,135.00 |
| 1,000 | $1.99 | $1,990.00 |
LM5085QMYE/NOPB Overview
What is a buck controller? A buck controller is a type of DC-DC switching controller that, paired with an external power MOSFET and inductor, steps a higher DC input voltage down to a lower regulated output voltage. Within the power management IC hierarchy, it sits above simple LDOs and below fully integrated point-of-load (POL) converters: LDO -> buck controller -> DC-DC converter -> power management IC. The COT (constant on-time) variant eliminates the traditional error amplifier and PWM modulator, instead using a one-shot on-timer that produces a nearly constant switching frequency across line and load variations.
Key features include a wide 4.5V to 75V operating input range, adjustable current limit using either the external PFET's RDS(on) or a dedicated current-sense resistor, programmable switching frequency up to 1 MHz, cycle-by-cycle overcurrent protection, and a built-in LDO regulator that powers internal circuitry. The device also provides an enable pin for power sequencing and an internal 7V gate-drive clamp that protects the external PFET. The HVSSOP-8 exposed-pad package provides a low thermal resistance path to the PCB copper pour.
Architecturally, the LM5085 uses an adaptive on-timer whose pulse width is set by an external resistor (RTON) and inversely proportional to VIN, producing a near-constant frequency across the input range. This approach yields a feed-forward control loop that is inherently stable without compensation components, dramatically simplifying design-in compared to traditional voltage-mode or peak-current-mode controllers. The current-limit comparator monitors the voltage across the external PFET or a sense resistor on every cycle and terminates the on-pulse to protect the converter from short-circuit and overload events.
Typical applications include automotive infotainment and instrument-cluster rails, 24V industrial sensor supplies, point-of-load conversion from 48V telecom rails, LED driver front-ends, and battery-powered systems requiring high step-down ratios. The wide Vin and 100% duty cycle operation also make the part well suited to cold-crank and load-dump scenarios in 12V/24V automotive electrical systems.
When designing with the LM5085, choose the external PFET's VDS rating to comfortably exceed maximum VIN plus margin (typically 100V for a 75V nominal design), and size the current-sense resistor to trip at no more than 120% of the design load. The exposed pad must be soldered to a sufficiently large copper pour to keep the junction within its 125°C rating at full power.
This page synthesizes verified distributor pricing, pin-compatible drop-in alternatives (same-brand and cross-brand), and practical design notes that are not available in the manufacturer datasheet alone.
Drop-in alternatives for LM5085QMYE/NOPB — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LM5085MYE/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM5085QMY/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM5085MY/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM5085QMYX/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM5085MYX/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM5085QMYE/NOPB Maximum Ratings & Electrical Characteristics
| Topology | Buck (step-down), non-synchronous, PFET controller |
| Control Method | Constant On-Time (COT) |
| Input Voltage Range | 4.5 V to 75 V |
| Number of Outputs | 1 |
| Maximum Switching Frequency | 1 MHz (programmable) |
| Duty Cycle | Up to 100% |
| Current Limit | Adjustable via PFET RDS(on) or external sense resistor |
| On-Time Programming | External RTON resistor to VIN |
| Output Voltage | Adjustable (set by feedback divider) |
| Operating Junction Temperature | -40 C to +125 C |
| Package | 8-pin HVSSOP (DGN) with exposed thermal pad |
| Mounting Type | Surface Mount |
| AEC-Q100 Grade | Grade 1 qualified |
| Lead-Free / RoHS | Yes (NOPB suffix = lead-free, Pb-free) |
| Internal LDO Regulator | Yes (bias supply for internal circuitry) |
| Loop Compensation | Not required (COT control) |
LM5085QMYE/NOPB Pin Configuration
| Pin 1 | EN — Enable input (active high). Tie to VIN through a resistor for automatic startup. |
| Pin 2 | RTON — On-time programming. Connect a resistor from RTON to VIN to set switching frequency. |
| Pin 3 | VCC — Internal LDO output. Decouple with 1uF ceramic capacitor to GND. |
| Pin 4 | FB — Feedback input. Connect to external resistor divider from VOUT to set output voltage (1.205V reference). |
| Pin 5 | ISEN — Current sense input. Connect to the drain of the external PFET for RDS(on) sensing, or to a sense resistor in the source path. |
| Pin 6 | GND — Ground return for internal circuitry. |
| Pin 7 | HO — Gate drive output for the external P-channel MOSFET. Internally clamped to 7V. |
| Pin 8 | VIN — Input supply voltage (4.5V to 75V). Decouple with 1uF or larger ceramic capacitor to GND. |
| Pin EP | EP — Exposed thermal pad. Solder to a large ground copper pour for low thermal resistance. |
Typical Applications
LM5085QMYE/NOPB is suitable for 6 applications: Automotive 12V/24V Infotainment Power Rails, Industrial 24V Sensor and PLC Power Supplies, 48V Telecom Point-of-Load Conversion, Battery-Powered Portable Equipment, LED Driver Front-End (High-Vin Buck Stage), Solar Micro-Inverter / Energy Harvesting Aux Rails.
Automotive 12V/24V Infotainment Power Rails
The LM5085QMYE/NOPB is a strong fit for 12V and 24V automotive infotainment rails because its 4.5V to 75V Vin range survives cold-crank sags (down to ~4.5V) and 24V truck load-dump transients (up to 75V) without an upstream TVS. The 100% duty cycle operation extends regulation when the battery sags below the desired output, and the AEC-Q100 Grade 1 qualification (-40°C to +125°C junction) is mandatory for under-hood and cabin-mounted modules. Placed after the battery reverse-polarity and input EMI filter, the controller drives a single P-channel MOSFET to step 12V down to 5V or 3.3V for processors, audio CODECs, and USB charge ports. Unlike an LDO, the switching topology dissipates far less heat, simplifying the thermal design in space-constrained head units.
Recommended
Industrial 24V Sensor and PLC Power Supplies
The LM5085QMYE/NOPB suits 24V industrial sensor and PLC supplies because its 75V Vin tolerates the inductive transients common on long cable runs and the 24V nominal rail. The constant on-time control gives sub-cycle transient response, which is critical when a sensor or actuator load changes abruptly, and the absence of compensation components reduces design time for the many rails typical in a PLC. The PFET topology also allows 100% duty cycle at low Vin, so the output remains in regulation even when the 24V bus sags during heavy inrush events. The HVSSOP-8 package fits the small PCB area inside DIN-rail mounted I/O modules.
Recommended
48V Telecom Point-of-Load Conversion
The LM5085QMYE/NOPB fits 48V telecom POL conversion thanks to its 75V max Vin, which covers the 36V to 72V telecom bus with margin for transient events. The COT control loop requires no compensation, dramatically simplifying the design of the many low-current POL rails in a baseband or radio card, and the 1 MHz maximum switching frequency enables small external inductors and ceramic output capacitors. The wide Vin and 100% duty cycle also mean a single stage can drop 48V to 5V or 3.3V with reasonable efficiency and no pre-regulator. The automotive-grade qualification provides extra reliability headroom for always-on telecom equipment.
Recommended
Battery-Powered Portable Equipment
The LM5085QMYE/NOPB works well in multi-cell battery powered equipment such as portable test instruments, medical carts, and e-bikes because the wide Vin range handles 6V to 60V battery packs (4S to 13S Li-ion) with a single stage. The PFET topology with 100% duty cycle keeps the output in regulation when the battery is nearly discharged, extending usable runtime, and the COT control gives fast transient response for load steps from wireless radios or motor drivers. The exposed-pad HVSSOP-8 package provides a low thermal resistance path to the PCB, so the part fits inside handheld enclosures with no external heatsink.
Recommended
LED Driver Front-End (High-Vin Buck Stage)
The LM5085QMYE/NOPB serves as the high-voltage front-end of an LED driver when the LED string forward voltage is too high for a low-side buck. The 75V Vin handles 48V or 60V LED strings directly, and the constant on-time control provides the fast transient response needed for PWM dimming without audible flicker. The adjustable current limit protects the LED string from short-circuit events, and the AEC-Q100 grade is a plus for automotive headlight and signal-lamp designs. The 1 MHz max frequency keeps the converter outside the AM band, simplifying EMI filter design.
Recommended
Solar Micro-Inverter / Energy Harvesting Aux Rails
The LM5085QMYE/NOPB fits solar micro-inverter auxiliary rails and energy harvesting systems because its 75V Vin covers 12V to 60V solar panel strings, and the 100% duty cycle operation maximizes energy harvest at low panel voltage during partial shading. The COT topology maintains regulation across the wide Vin range without loop compensation, which is critical in MPPT algorithms that rapidly change the operating point. The exposed-pad package handles the elevated ambient temperatures inside an outdoor inverter enclosure, and the AEC-Q100 grade provides extra robustness against thermal cycling.
Recommended
Recommended Products Summary
Engineering reference data for LM5085QMYE/NOPB — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LM5085MYE/NOPB | LM5085QMY/NOPB | LM5085MY/NOPB | LM5085QMYX/NOPB | LM5085MYX/NOPB |
|---|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | HVSSOP-8 (DGN) with EP | HVSSOP-8 (DGN) with EP - same | TSSOP-8 (PW) - same pin count, no EP | TSSOP-8 (PW) - same pin count, no EP | HVSSOP-8 (DGN) with EP - same | HVSSOP-8 (DGN) with EP - same |
| AEC-Q100 Grade | Grade 1 (-40 to +125 C) | Commercial (no AEC-Q100) | Grade 1 | Commercial | Grade 1 | Commercial |
| Input Voltage Range | 4.5 V to 75 V | 4.5 V to 75 V | 4.5 V to 75 V | 4.5 V to 75 V | 4.5 V to 75 V | 4.5 V to 75 V |
| Max Switching Frequency | 1 MHz | 1 MHz | 1 MHz | 1 MHz | 1 MHz | 1 MHz |
| Duty Cycle | Up to 100% | Up to 100% | Up to 100% | Up to 100% | Up to 100% | Up to 100% |
| Control Method | Constant On-Time | Constant On-Time | Constant On-Time | Constant On-Time | Constant On-Time | Constant On-Time |
| Current Limit Sensing | PFET RDS(on) or external resistor | PFET RDS(on) or external resistor | PFET RDS(on) or external resistor | PFET RDS(on) or external resistor | PFET RDS(on) or external resistor | PFET RDS(on) or external resistor |
Key Differentiators
- AEC-Q100 Grade 1 qualified with -40C to +125C junction temperature range (vs LM5085MYE/NOPB)
- Exposed-pad HVSSOP-8 package for superior thermal performance (vs LM5085QMY/NOPB)
- Wide 4.5V to 75V Vin with 100% duty cycle extends regulation headroom (vs LM5088 family (NFET synchronous controllers))
Design Notes
The exposed thermal pad (EP) of the HVSSOP-8 package must be soldered to a ground copper pour of at least 50 mm² to achieve the datasheet thermal resistance. Place input ceramic capacitors (1uF X7R minimum, 4.7uF recommended) as close as possible to pins 6 (GND) and 8 (VIN) to minimize switching noise injection. Keep the ISEN trace short and direct - this node is sensitive to switching noise and incorrect routing can cause false current-limit trips. The RTON resistor should be placed adjacent to pin 2 with the ground end of the resistor close to the GND pin return path.
Estimated: At VIN = 24V, VOUT = 5V, IOUT = 3A, the converter efficiency is approximately 90%, so the controller itself dissipates roughly 1.5W (mainly in the external PFET). With a 50 mm² copper pour, the LM5085QMYE/NOPB's thermal resistance is around 45 C/W, yielding a junction temperature rise of ~68°C above ambient - acceptable up to about 70°C ambient. For higher output currents or higher VIN, increase the copper pour area or use forced airflow. The TSSOP-8 (no exposed pad) variants have ~30% higher thermal resistance, so derate the output current accordingly.
Do not select an external P-channel MOSFET with VDS rated below 100V for a 75V nominal design - leave at least 25% margin for automotive load-dump transients. The internal gate drive is clamped to 7V, so a standard PFET (VGS = ±20V) is fine, but verify the PFET's gate charge Qg does not exceed 50 nC, otherwise the switching rise/fall times will be slowed and efficiency will drop. The RTON resistor must connect to VIN, not to VCC; if connected to VCC the on-time will be wrong and the switching frequency will be incorrect. Always add a 100 kΩ pull-up on the EN pin for automatic startup, or drive it from a logic-level GPIO for sequencing.
Compliance Information
/NOPB suffix = lead-free, RoHS and REACH compliant per Texas Instruments product page. AEC-Q100 Grade 1 qualified per LM5085-Q1 datasheet (junction temperature -40C to +125C). Halogen-free per TI's standard material declaration policy.
