LDQ40 - 40V Low Quiescent Current LDO Regulator | STMicroelectronics
MPN: LDQ40 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.85 | $0.85 |
| 10 | $0.76 | $7.60 |
| 100 | $0.68 | $68.00 |
| 500 | $0.61 | $305.00 |
| 1,000 | $0.55 | $550.00 |
Drop-in alternatives for LDQ40 — 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:
LDQ40M
✅ Drop-In📋 Reference alternative (not in catalog)
TLV70033
✅ Drop-In📋 Reference alternative (not in catalog)
MC78LC50
✅ Drop-In📋 Reference alternative (not in catalog)
LDQ40 Maximum Ratings & Electrical Characteristics
| Output Type | Fixed |
| Output Voltage | 5.0 V |
| Maximum Output Current | 250 mA |
| Input Voltage Range | 4 V to 40 V |
| Dropout Voltage | 300 mV at 250 mA |
| Quiescent Current | 40 µA (typical) |
| Output Voltage Accuracy | ±2% |
| Line Regulation | 0.5% (typical) |
| Load Regulation | 1% (typical) |
| Operating Temperature Range | -40°C to +125°C |
| Package | SOT-23-5 |
| Mounting Type | Surface Mount |
| MSL Level | 1 (unlimited) |
| RoHS Status | Compliant |
| Protection Features | Short-circuit, thermal shutdown, reverse polarity |
LDQ40 Pin Configuration
| Pin 1 | IN — Input voltage (4V to 40V) |
| Pin 2 | GND — Ground |
| Pin 3 | EN — Enable (active high) |
| Pin 4 | NC — No connect |
| Pin 5 | OUT — Regulated 5.0V output |
Safe Operating Area (SOA) & Thermal Characteristics
No official SOA curve available for this component. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.
Typical Applications
LDQ40 is suitable for 6 applications: Automotive Body Control Module, Industrial Sensor Node, Infotainment System, Portable Medical Device, Smart Home Hub, Telecom Power Supply.
Automotive Body Control Module
The LDQ40 provides a stable 5.0V rail for microcontrollers and sensors in body control modules. Its wide input voltage range (4V to 40V) allows direct connection to the vehicle battery, while the low quiescent current (40µA) minimizes battery drain when the vehicle is off. The reverse polarity protection ensures robustness against miswiring. In a typical body control module, the LDQ40 is placed after the battery input, with a 1µF ceramic capacitor on the input and output, powering the MCU and CAN transceiver. The thermal shutdown protects the regulator during high ambient temperatures under the hood.
Recommended
Industrial Sensor Node
In industrial sensor nodes, the LDQ40 regulates a 24V industrial bus down to 5V for sensors and microcontrollers. The low quiescent current is critical for battery-powered or energy-harvesting nodes, extending operational life. The wide temperature range (-40°C to +125°C) ensures reliable operation in harsh factory environments. The LDQ40 is placed after a reverse polarity protection diode, with a 10µF electrolytic capacitor on the input and a 1µF ceramic on the output to handle transient loads. The short-circuit protection safeguards the sensor interface.
Recommended
Infotainment System
The LDQ40 powers audio codecs, display controllers, and communication modules in infotainment systems. Its low noise and stable 5V output ensure clean power for sensitive analog circuits. The wide input range accommodates voltage fluctuations during engine start-stop. In an infotainment system, the LDQ40 is used as a post-regulator after a buck converter, providing a clean 5V rail for the audio DAC. A 2.2µF ceramic output capacitor is recommended for optimal transient response. The thermal shutdown prevents overheating in confined dashboard spaces.
Recommended
Portable Medical Device
The LDQ40 is used in portable medical devices such as glucose monitors and pulse oximeters, where low power consumption is essential. The 40µA quiescent current extends battery life, and the small SOT-23-5 package fits compact designs. The device operates from a 9V battery, providing a stable 5V rail for the sensor and MCU. A 1µF ceramic capacitor on the output ensures stability. The wide temperature range allows use in various environmental conditions. The reverse polarity protection prevents damage from incorrect battery insertion.
Recommended
Smart Home Hub
The LDQ40 provides a regulated 5V supply for smart home hubs, powering Wi-Fi modules, sensors, and microcontrollers. Its low quiescent current is ideal for always-on devices, reducing standby power consumption. The wide input range allows operation from various power sources, including USB and battery backup. In a smart home hub, the LDQ40 is placed after a 12V wall adapter, with a 10µF input capacitor and 1µF output capacitor. The thermal shutdown protects the device during prolonged operation. The small package enables compact hub designs.
Recommended
Telecom Power Supply
The LDQ40 is used in telecom equipment to provide a clean 5V rail for line cards and control logic. Its wide input range (4V to 40V) accommodates 24V and 48V telecom buses, and the low quiescent current reduces power loss in always-on equipment. The device is placed after a DC-DC converter, with a 1µF ceramic output capacitor for stability. The short-circuit protection prevents damage to downstream circuitry. The wide temperature range ensures reliable operation in central office environments.
Recommended
Recommended Products Summary
Engineering reference data for LDQ40 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LDQ40M | TLV70033 | MC78LC50 |
|---|---|---|---|---|
| Package | SOT-23-5 | SOT-23-5 - same | SOT-23-5 - same | SOT-23-5 - same |
| Brand | STMicroelectronics | STMicroelectronics | Texas Instruments | NXP Semiconductors |
| Output Voltage | 5.0V | 5.0V | 3.3V | 5.0V |
| Maximum Output Current | 250mA | 250mA | 200mA | 100mA |
| Input Voltage Range | 4V to 40V | 4V to 40V | 2.7V to 5.5V | 2.7V to 12V |
| Dropout Voltage | 300mV at 250mA | 300mV at 250mA | 200mV at 200mA | 350mV at 100mA |
| Quiescent Current | 40µA | 40µA | 30µA | 50µA |
| Operating Temperature Range | -40°C to +125°C | -40°C to +125°C | -40°C to +125°C | -40°C to +85°C |
Key Differentiators
- Wide input voltage range up to 40V (vs TLV70033)
- Higher output current of 250mA (vs MC78LC50)
- Low quiescent current of 40µA (vs MC78LC50)
Design Notes
Place a 1µF ceramic capacitor on the input and output pins as close to the LDQ40 as possible. For high input voltage applications (e.g., 24V), consider a larger input capacitor (10µF) to handle transients. The output capacitor must be at least 1µF for stability, but larger values improve transient response.
At VIN=24V, VOUT=5V, and 250mA load, power dissipation is (24-5)*0.25 = 4.75W. The SOT-23-5 package has a thermal resistance of approximately 250°C/W (theta_JA), resulting in a junction temperature rise of 1187°C, which is far beyond the absolute maximum. Therefore, the LDQ40 is not suitable for such high differentials at full load. For high input voltages, reduce output current or use a pre-regulator. Ensure adequate copper area on the PCB to dissipate heat.
Do not exceed the maximum input voltage of 40V. The EN pin is active high; leave it unconnected or tie to IN for always-on operation. The NC pin must be left floating. Ensure the output capacitor is rated for the output voltage and temperature. Reverse polarity protection is built-in, but an external diode may be needed for higher surge currents.
Compliance Information
RoHS compliant per STMicroelectronics product page. AEC-Q100 qualification not specified for this part; for automotive use, verify with manufacturer.
