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Lm317mdt-Tr
The LM317MDT-TR is a three-terminal positive adjustable linear regulator manufactured by STMicroelectronics, packaged in a TO-252 (DPAK) surface-mount housing. It provides an output voltage adjustable from 1.2V to 37V using two external resistors, with a minimum guaranteed output current of 500mA at low input-to-output differential. The device integrates short-circuit current limiting, thermal overload shutdown, and output transistor safe-operating-area compensation. Supplied in tape-and-reel format, it suits automated SMT assembly in industrial control, instrumentation, and power supply designs.
The LM317MDT-TR maintains a 1.25V reference voltage between its output and adjustment terminals. By connecting a resistive divider (R1 from output to adjust, R2 from adjust to ground), designers set the output voltage according to the formula V_O = 1.25V × (1 + R2/R1). This eliminates the need to stock multiple fixed-voltage regulators and supports programmable output designs.
Per STMicroelectronics datasheet DS0522 Rev 12, the LM317MDT-TR achieves a typical line regulation of 0.01%/V at T_J = 25°C with V_I-V_O ranging from 3V to 40V. Load regulation is typically 0.1% for output voltages of 5V and above (I_O = 10mA to 500mA), and typically 5mV for output voltages below 5V. These specifications apply under the stated test conditions and should be verified against the official datasheet for design-critical applications.
The regulator integrates three protection mechanisms: short-circuit current limiting, thermal overload shutdown, and safe-operating-area (SOA) compensation for the output transistor. Notably, the protection circuitry remains active even when the adjustment pin is disconnected, preventing device damage under fault conditions. The thermal shutdown feature resets automatically when the junction temperature returns within the operating range.
The DPAK package includes an exposed thermal pad that connects to the PCB copper area for heat dissipation. Thermal resistance is 8°C/W junction-to-case and 100°C/W junction-to-ambient for the DPAK package. Designers should allocate sufficient copper area around the tab to maintain junction temperature within the 0°C to 125°C operating range. The device is supplied in tape-and-reel packaging compatible with standard pick-and-place equipment.
Model | LM317MDT-TR |
|---|---|
Manufacturer | STMicroelectronics |
Device Type | Positive Adjustable Linear Regulator |
Package | TO-252 (DPAK) SMD |
Output Voltage Range | 1.2 V - 37 V |
Max Input Voltage | 40 V |
Continuous Output Current | 500 mA |
Typical Line Regulation | 0.01 %/V |
Typical Load Regulation | 0.1 % |
Protection Function | Short-circuit limit, thermal shutdown, SOA protection |
Operating Junction Temp | 0 ℃ - +125 ℃ |
Packaging | Tape and Reel |
Compliance | RoHS Lead-free |
Additional verified parameters from STMicroelectronics datasheet DS0522 Rev 12:
Parameter | Specification | Test Condition |
|---|---|---|
Reference Voltage | 1.25V typical (1.2V min, 1.3V max) | V_I-V_O = 3V to 40V, I_O = 10mA to 500mA |
Minimum Load Current | 3.5mA typical, 5mA maximum | V_I-V_O = 40V |
Maximum Output Current | 500mA minimum, 1000mA typical | V_I-V_O ≤ 15V |
Maximum Output Current at High Differential | 200mA | V_I-V_O = 40V, P_d < P_DMAX, T_J = 25°C |
Input-to-Output Differential | 40V maximum | Absolute maximum rating |
Ripple Rejection | Approximately 80dB at 120Hz | With 10µF adjustment capacitor, 10V output |
Thermal Resistance (Junction-to-Case) | 8°C/W | DPAK package |
Thermal Resistance (Junction-to-Ambient) | 100°C/W | DPAK package |
Storage Temperature | -55°C to +150°C | - |
Product Status | Active | - |
Note: The 40V rating refers to the maximum input-to-output differential voltage (V_I-V_O), not the absolute input voltage. As a floating regulator, the LM317MDT-TR can be used in high-voltage applications provided the differential voltage does not exceed 40V.
The LM317MDT-TR generates custom low-voltage and medium-voltage rails on industrial control PCBs. Its built-in protection functions suit factory environments where input transients and load faults may occur. System integrators use the device for auxiliary power rails in PLC modules, sensor interface boards, and motor control peripherals.
The regulator provides low-noise power for industrial sensors, testing instruments, and measurement circuits. The specified load regulation helps maintain stable supply voltage under varying sensor load conditions, contributing to consistent measurement accuracy in data acquisition systems.
By connecting a fixed resistor between the output and adjustment pins, the LM317MDT-TR can be configured as a precision constant current source. The output current is calculated as I_O = 1.25V / R1. This configuration is used for LED driving, battery charging circuits, and sensor excitation in industrial and commercial equipment.
The LM317MDT-TR supplies regulated power for audio amplifier stages, household control boards, and commercial electronic terminals. Adding a 10µF capacitor on the adjustment pin improves ripple rejection to approximately 80dB at 120Hz, reducing power-supply noise in audio and signal-processing circuits.
At higher output currents and larger input-to-output differentials, power dissipation (P_d = (V_I - V_O) × I_O) must be managed through PCB copper area attached to the DPAK tab. Designers should calculate junction temperature using T_J = T_A + P_d × R_thJA and ensure it stays within 0°C to 125°C.
A 0.1µF ceramic or 1µF tantalum input bypass capacitor is recommended when the regulator is located far from the power supply filter. A 1µF solid tantalum or 25µF aluminum electrolytic output capacitor ensures stability. For output voltages above 25V or high capacitance values, protection diodes should be added per the datasheet application circuit.
The LM317MDT-TR is supplied in tape-and-reel packaging for automated SMT assembly. Commercial buyers should verify reel quantities and lead times with the supplier before placing production orders. The device is classified as Active in the STMicroelectronics product portfolio, indicating ongoing production and long-term availability.
The output voltage can be continuously adjusted from 1.2V to 37V using two external resistors configured as a voltage divider between the output and adjustment pins.
The LM317MDT-TR guarantees a minimum output current of 500mA when the input-to-output differential is 15V or less. The typical output current under this condition is 1000mA. When the differential reaches 40V, the maximum output current is limited to approximately 200mA due to power dissipation constraints.
No. The 40V rating is the maximum input-to-output differential voltage (V_I - V_O). The LM317MDT-TR is a floating regulator, meaning it can operate at higher absolute input voltages as long as the difference between input and output does not exceed 40V.
Yes. By connecting a fixed resistor (R1) between the output and adjustment pins and leaving the adjustment pin as the current output terminal, the device regulates current according to I_O = 1.25V / R1. This configuration is used for LED driving and battery charging applications.
The DPAK package has a junction-to-ambient thermal resistance of 100°C/W. Designers should provide adequate PCB copper area connected to the exposed tab to dissipate heat. The junction temperature must remain within 0°C to 125°C for normal operation.
The regulator is internally stable without an output capacitor, but adding a 1µF solid tantalum or 25µF aluminum electrolytic output capacitor is recommended to ensure stability under all load conditions. A 0.1µF input bypass capacitor is recommended when the device is far from the source filter capacitor.
Yes, the LM317MDT-TR is RoHS lead-free compliant. It is supplied in tape-and-reel packaging suitable for automated surface-mount assembly lines.
