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-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

3 Noise Specifications in LDO Data Sheets

Typically noise in an LDO is specified by datasheets in two fashions. One is “Total (Integrated) output noise – in μVrms”, which is RMS value of the spectral noise density integrated over a finite frequency range. The second method is to show a “Spectral Noise density curve – in μV/√ Hz”, which is a plot of Noise density vs Frequency. Figure 3-1 shows both the specifications for TPS717xx series LDOs.

GUID-4C25BD29-36EF-4FF5-8763-14F0BBA663F8-low.gifFigure 3-1 Noise Specified in Two Ways (for TPS717xx LDOs)

Since the output noise voltage is specified by a single number, it is very useful for comparison purposes. When noise specifications of different LDOs are compared, it is imperative that the two regulators’ noise measurements be taken over the same frequency range and at the same output voltage and current values.