LM117HV, LM317HV

www.ti.com

SNVS773D – APRIL 2000 – REVISED SEPTEMBER 2015

10 Power Supply Recommendations

Normally, no capacitors are needed unless the device is situated more than six inches from the input filter

capacitors, in which case an input bypass is needed. An optional output capacitor can be added to improve

transient response. The adjustment terminal can be bypassed to achieve very high ripple rejections ratios, which

are difficult to achieve with standard 3-terminal regulators. For information regarding capacitor selection, refer to

External Capacitors.

11 Layout

11.1 Layout Guidelines

Some layout guidelines should be followed to ensure proper regulation of the output voltage with minimum noise.

Traces carrying the load current should be wide to reduce the amount of parasitic trace inductance and the

feedback loop from V2 to ADJ should be kept as short as possible. To improve PSRR, a bypass capacitor can be

placed at the ADJ pin and should be located as close as possible to the IC. In cases when VIN shorts to ground,

an external diode should be placed from VOUT to VIN to divert the surge current from the output capacitor and

protect the IC. Similarly, in cases when a large bypass capacitor is placed at the ADJ pin and VOUT shorts to

ground, an external diode should be placed from ADJ to VOUT to provide a path for the bypass capacitor to

discharge. These diodes should be placed close to the corresponding IC pins to increase their effectiveness.

11.2 Layout Example

Figure 33. Layout Example (TO-220 Package)

Copyright © 2000–2015, Texas Instruments Incorporated

Submit Documentation Feedback

21

Product Folder Links: LM117HV LM317HV