LM337T (LM337) Variable Negative Voltage Regulator
LM337T (LM337) Variable Negative Voltage Regulator The LM137 and LM337-N are adjustable 3-terminal negative voltage regulators capable of supplying −1.5 A or more currents over an output voltage range of −1.25 V to −37 V. It requires only two external resistors to set the output voltage and one output capacitor for frequency compensation. The circuit design has been optimized for excellent regulation and low thermal transients. Further, the LM137 and LM337-N feature internal current limiting, thermal shutdown, and safe area compensation, making it virtually blowout-proof against overloads. The LM137 and LM337-N are ideal complements to the LM117 and LM317 adjustable positive regulators. The LM137 has a wider operating temperature range than the LM337-N and is also offered in military and space-qualified versions. The IC commonly used in Adjustable Lab Voltage generators in combination with the LM317 IC. It can also be used as Current Regulators and negative voltage protection circuits, refer to the datasheet linked below for application circuits.
The IC has three pins, in which the input voltage is supplied to the VIN pin then using a pair of resistors (potential divider) we set a voltage at Adjust pin which will decide the output voltage of the IC that is given out at VOUT pin. Now to make it act as a variable voltage regulator we have to set variable voltages which can be done by using a potentiometer in the potential divider (R2 shown below). The below circuit is shown for reference from the LM337 datasheet.
The output voltage thus obtained can be calculated using the below formulae
VOUT = – 1.25 × (1 + (R2/R1))
The actual formulae in the datasheet will also include Iadj (Current through the adjust pin), but for simplification purposes, we have assumed Iadj to be 50uA constant which will slightly differ in practical application. Also note that the output current of the IC will not be 1.5A always, if the difference voltage between the input and output voltage is high the output current will also decrease. Refer to the difference voltage vs Output Current graph from the datasheet for more information.
- Output Voltage Range: −1.25V to −37V
- Output Current: 1.5A
- Line Regulation 0.01%/V (Typical)
- Load Regulation 0.3% (Typical)
- 77-dB Ripple Rejection
- 50 ppm/°C Temperature Coefficient
- Thermal Overload Protection
- Internal Short-Circuit Current Limiting Protections
- Package: To-220
- Length: 15.1mm
- Width: 10.16mm
- Heigh: 4.45mm
- Approx Weight: 4gm
- Used for Positive voltage regulations
- Variable power supply
- Current limiting circuits
- Reverse polarity circuits
- Commonly used in Desktop PC, DVD and other consumer products
- Used in motor control circuits
- Industrial Power Supplies
- Factory Automation Systems
- Building Automation Systems
- PLC Systems
- IGBT Drive Negative Gate Supplies
- Set-Top Boxes
1 X LM337T (LM337) Variable Negative Voltage Regulator
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