SLAA412B June   2009  – August 2020 LFC789D25 , LM237 , LM317 , LM317L , LM317M , LM317MQ , LM337 , LP2950 , LP2951 , LP2981 , LP2981A , LP2985 , MC79L , REG101 , REG102 , REG103 , REG104 , REG1117 , REG1117A , REG1118 , REG113 , SN105125 , TL1963A , TL317 , TL5209 , TL720M05-Q1 , TL750L , TL750M , TL750M-Q1 , TL751L , TL760M33-Q1 , TL780 , TL783 , TLE4275-Q1 , TLV1117 , TLV1117LV , TLV2217 , TLV700-Q1 , TLV70012-Q1 , TPPM0110 , TPPM0111 , TPPM0301 , TPPM0302 , TPPM0303 , TPS51100 , TPS51103 , TPS51200 , TPS61100 , TPS61107 , TPS61120 , TPS61121 , TPS61122 , TPS65020 , TPS65021 , TPS65022 , TPS650231 , TPS65023B , TPS65050 , TPS657052 , TPS65708 , TPS657095 , TPS701 , TPS70175-Q1 , TPS702 , TPS703 , TPS70345-EP , TPS704 , TPS707 , TPS70751-EP , TPS708 , TPS71 , TPS71025 , TPS712 , TPS71202-EP , TPS713 , TPS715 , TPS715-Q1 , TPS71501-EP , TPS715A , TPS715A-NM , TPS718 , TPS719 , TPS71H01 , TPS72 , TPS720 , TPS721 , TPS72118-EP , TPS722 , TPS723 , TPS725 , TPS726 , TPS727 , TPS728 , TPS73 , TPS730 , TPS731 , TPS73101-EP , TPS731125-EP , TPS73115-EP , TPS73118-EP , TPS73125-EP , TPS73130-EP , TPS73132-EP , TPS73133-EP , TPS73150-EP , TPS732 , TPS732-Q1 , TPS73201-EP , TPS73215-EP , TPS73216-EP , TPS73218-EP , TPS73225-EP , TPS73230-EP , TPS73233-EP , TPS73250-EP , TPS734 , TPS735 , TPS736 , TPS73601-EP , TPS73615-EP , TPS73618-EP , TPS73625-EP , TPS73630-EP , TPS73632-EP , TPS73633-EP , TPS737 , TPS737-Q1 , TPS73HD3 , TPS74 , TPS74201 , TPS74301 , TPS74401 , TPS74701 , TPS74801 , TPS74901 , TPS751 , TPS75103 , TPS75105 , TPS75125-EP , TPS752 , TPS752-Q1 , TPS75201-EP , TPS75201M-EP , TPS75215-EP , TPS75218-EP , TPS75225-EP , TPS75233-EP , TPS753 , TPS75301-EP , TPS75318-EP , TPS75325-EP , TPS75333-EP , TPS754 , TPS755 , TPS756 , TPS757 , TPS758 , TPS759 , TPS760 , TPS76201 , TPS763-Q1 , TPS766 , TPS767 , TPS767-Q1 , TPS76701-EP , TPS76715-EP , TPS76718-EP , TPS76725-EP , TPS76733-EP , TPS767D3 , TPS767D3-Q1 , TPS767D301-EP , TPS768 , TPS768-Q1 , TPS76801-EP , TPS76815-EP , TPS76818-EP , TPS76825-EP , TPS76833-EP , TPS76850-EP , TPS769 , TPS769-Q1 , TPS76901-HT , TPS770 , TPS77101-Q1 , TPS773 , TPS774 , TPS77401-EP , TPS775 , TPS775-Q1 , TPS77501-EP , TPS77515-EP , TPS77518-EP , TPS77525-EP , TPS77533-EP , TPS776 , TPS776-Q1 , TPS77601-EP , TPS77615-EP , TPS77618-EP , TPS77625-EP , TPS77633-EP , TPS777 , TPS778 , TPS779 , TPS780 , TPS781 , TPS782 , TPS786 , TPS789 , TPS790 , TPS791-Q1 , TPS79101-EP , TPS79133-EP , TPS79147-EP , TPS793-Q1 , TPS79301-EP , TPS79318-EP , TPS79333-EP , TPS793475-EP , TPS794 , TPS797 , TPS797-Q1 , TPS79718-EP , TPS79730-EP , TPS799 , TPS799-Q1 , TPS7A45 , TPS7A47 , UA723 , UA78 , UA78L , UA78M , UA78M-Q1 , UA79 , UA79M , UC1832 , UC1832-SP , UC1834 , UC1834-SP , UC1836 , UC282 , UC2832 , UC2832-EP , UC2833 , UC2834 , UC2834M , UC2835 , UC2836 , UC285 , UC382 , UC3832 , UC3833 , UC3834 , UC3836 , UC385 , UCC281 , UCC283 , UCC2837 , UCC284 , UCC381 , UCC383 , UCC384

 

  1.   Trademarks
  2. 1LDO Noise and PSRR
  3. 2LDO Noise Types
  4. 3Noise Specifications in LDO Data Sheets
  5. 4Which Specification is for Your Application?
  6. 5How to Reduce the LDO Noise?
  7. 6Implications of the LDO Noise
  8. 7Revision History

2 LDO Noise Types

Noise is purely physical phenomenon that occurs with transistors and resistors. Transistors generate shot noise and flicker noise. The resistive element of MOSFETs also generates thermal noise like resistors. Thermal and shot noise is truly random in nature and its power is flat over frequency. It remains flat up to the bandwidth of the amplifier. Flicker noise is the noise due to trapped charges at the gate of the MOSFET. It follows Poisson’s Distribution with 1/f roll-off in power versus frequency hence it is higher at low frequencies. This noise dominates until it becomes smaller than thermal noise. (See Figure 2-1)

GUID-1CCE16F8-0478-4316-8AE3-5693EE76EBD8-low.gifFigure 2-1 LDO Noise (types)