The LM337L is an adjustable 3-pin negative voltage regulator capable of supplying 100 mA
over a –1.2-V to –37-V output range. The LM337L is easy to use and requires only two external
resistors to set the output voltage. Both line and load regulation are better than standard fixed
regulators. The LM337L is packaged in a standard, easy-to-use TO-92 transistor package.
In addition to higher performance than fixed regulators, the LM337L offers full overload
protection. Included on the chip are current limit, thermal overload protection, and safe area
protection. All overload protection circuitry remains fully functional even if the adjustment pin
Normally, only a single 1-µF solid tantalum output capacitor is required unless the
device is situated more than 6 inches from the input filter capacitors, in which case an input
bypass is required. A larger output capacitor can be added to improve transient response. The
adjustment pin can be bypassed to achieve very high ripple rejection ratios, which are difficult to
achieve with standard 3-pin regulators.
Besides replacing fixed regulators, the LM337L is useful in a wide variety of other
applications. Because the regulator is floating and monitors
only the input-to-output differential voltage, supplies of several hundred volts can be regulated
as long as the maximum input-to-output differential is not exceeded.
The LM337L makes a simple adjustable switching regulator, a programmable output
regulator, or by connecting a fixed resistor between the adjustment and output, the LM337L can be
used as a precision current regulator. Supplies with electronic shutdown can be achieved by
clamping the adjustment pin to ground, which programs the output to 1.2 V, where most loads draw
The LM337L is available in a standard TO-92 transistor package and a standard SO-8
surface mount package. The LM337L is rated for operation over a –25°C to 125°C range.
For applications requiring output current in excess of 0.5 A and 1.5 A, The
LM137 series may be suitable.
For the positive complement, the LM117 and
LM317L series are