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july 2006 rev. 12 1/22 22 ld2981 series ultra low drop voltage regulators with inhibit low esr output capacitors compatible feature summary stable with low esr ceramic capacitors ultra low dropout voltage (0.17v typ. at 100ma load, 7mv typ. at 1ma load) very low quiescent current (80a typ. at no load in on mode; max 1a in off mode) guaranteed output current up to 100ma logic-controlled electronic shutdown output voltage of 1.5; 1.8; 2.5; 3.0; 3.3; 3.6; 3.8; 5.0v internal current and thermal limit 0.75% tolerance output voltage available (a version) output low noise voltage 160vrms temperature range: -40 to 125c smallest package sot23-5l and sot-89 fast dynamic response to line and load changes description the ld2981 series are 100ma fixed-output voltage regulator. the low drop-voltage and the ultra low quiescent current make them suitable for low noise, low power applications and in battery powered systems. the quiescent current in sleep mode is less than 1a when inhibit pin is pulled low. shutdown logic control function is available on pin n.3 (ttl compatible). this means that when the device is used as local regulator, it is possible to put a part of the board in standby, decreasing the total power consumption. the ld2981 is designed to work with low esr ceramic capacitor. typical applications are in cellular phone, palmtop/laptop computer, personal digital assistant (pda), personal stereo, camcorder and camera. sot-89 sot23-5l www.st.com schematic diagram
ld2981 series 2/22 contents 1 pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6 application notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.1 external capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.2 input capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.3 output capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.4 important . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.5 inhibit input operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.6 reverse current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7 package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8 order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 9 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
ld2981 series pin configuration 3/22 1 pin configuration figure 1. pin connections (top view) to-92 sot23-5l table 1. pin description pin n sot23-5l pin n sot-89 symbol name and function 13v in input port 2 2 gnd ground pin 3 inhibit control switch on/off. inhibit is not internally pulled-up; it cannot be left floating. disable the device when connected to gnd or to a positive voltage less than 0.18v 4 nc not connected 51v out output port table 2. thermal data symbol parameter sot23-5l sot-89 unit r thjc thermal resistance junction-case 81 15 c/w r thja thermal resistance junction-ambient 255 110 c/w
maximum ratings ld2981 series 4/22 2 maximum ratings note: absolute maximum ratings are those values beyond which damage to the device may occur. functional operation under these condition is not implied. table 3. absolute maximum ratings symbol parameter value unit v i dc input voltage -0.3 to 16 v v inh inhibit input voltage -0.3 to 16 v i o output current internally limited p d power dissipation internally limited t stg storage temperature range -55 to 150 c t op operating junction temperature range -40 to 125 c
ld2981 series typical application 5/22 3 typical application note: inhibit pin is not internally pulled-up then it must not be left floating. disable the device when connected to gnd or to a positive voltage less than 0.18v. figure 2. application circuit
electrical characteristics ld2981 series 6/22 4 electrical characteristics table 4. electrical characteristics for ld2981ab (t j = 25 c, v i = v o(nom) +1v, c i = 1f(x7r), c o = 2.2f(x7r), i o = 1ma, v inh = 2v, unless otherwise specified). symbol parameter test conditions min. typ. max. unit v op operating input voltage 2.5 16 v v o output voltage i o = 1 ma 2.481 2.5 2.518 v i o = 1 to 100 ma 2.475 2.525 i o = 1 to 100 ma, t j = -40 to 125c 2.437 2.562 v o output voltage i o = 1 ma 2.828 2.85 2.872 v i o = 1 to 100 ma 2.822 2.878 i o = 1 to 100 ma, t j = -40 to 125c 2.779 2.921 v o output voltage i o = 1 ma 2.977 3 3.023 v i o = 1 to 100 ma 2.970 3.030 i o = 1 to 100 ma, t j = -40 to 125c 2.925 3.075 v o output voltage i o = 1 ma 3.176 3.2 3.224 v i o = 1 to 100 ma 3.168 3.232 i o = 1 to 100 ma, t j = -40 to 125c 3.12 3.28 v o output voltage i o = 1 ma 3.275 3.3 3.325 v i o = 1 to 100 ma 3.267 3.333 i o = 1 to 100 ma, t j = -40 to 125c 3.217 3.383 v o output voltage i o = 1 ma 3.573 3.6 3.627 v i o = 1 to 100 ma 3.564 3.636 i o = 1 to 100 ma, t j = -40 to 125c 3.510 3.690 v o output voltage i o = 1 ma 3.771 3.8 3.829 v i o = 1 to 100 ma 3.762 3.838 i o = 1 to 100 ma, t j = -40 to 125c 3.705 3.895 v o output voltage i o = 1 ma 3.97 4 4.03 v i o = 1 to 100 ma 3.96 4.04 i o = 1 to 100 ma, t j = -40 to 125c 3.9 4.1 v o output voltage i o = 1 ma 4.664 4.7 4.735 v i o = 1 to 100 ma 4.653 4.747 i o = 1 to 100 ma, t j = -40 to 125c 4.582 4.817 v o output voltage i o = 1 ma 4.813 4.85 4.887 v i o = 1 to 100 ma 4.801 4.899 i o = 1 to 100 ma, t j = -40 to 125c 4.729 4.971 v o output voltage i o = 1 ma 4.962 5 5.038 v i o = 1 to 100 ma 4.950 5.050 i o = 1 to 100 ma, t j = -40 to 125c 4.875 5.125 ? v o line regulation v o(nom) + 1 < v in < 16 v, i o = 1 ma 0.003 0.014 %/v t j = -40 to 125c 0.032
ld2981 series electrical characteristics 7/22 note: 1 for v o < 2.5v dropout voltage can be calculated according to the minimum input voltage in full temperature range. i q quiescent current on mode i o = 0 80 100 a i o = 0, t j = -40 to 125c 150 i o = 1 ma 100 150 i o = 1 ma, t j = -40 to 125c 200 i o = 25 ma 250 400 i o = 25 ma, t j = -40 to 125c 800 i o = 100 ma 1000 1300 i o = 100 ma, t j = -40 to 125c 2600 off mode v inh < 0.3 v 0.8 v inh < 0.15 v, t j = -40 to 125c 2 v drop dropout voltage ( note: 1 ) i o = 0 1 3 mv i o = 0, t j = -40 to 125c 5 i o = 1ma 7 10 i o = 1ma, t j = -40 to 125c 15 i o = 25ma 70 100 i o = 25ma, t j = -40 to 125c 150 i o = 100ma 180 250 i o = 100ma, t j = -40 to 125c 375 i sc short circuit current r l = 0 150 ma svr supply voltage rejection c o = 10f, f = 1khz 63 db v inh inhibit input logic low low = output off, t j = -40 to 125c 0.18 v v inl inhibit input logic high high = output on, t j = -40 to 125c 1.6 v i inh inhibit input current v inh = 0v, t j = -40 to 125c 0 -1 a v inh = 5v, t j = -40 to 125c 5 15 e n output noise voltage b w = 300 hz to 50 khz, c o = 10f 160 v rms t shdn thermal shutdown 170 c table 4. electrical characteristics for ld2981ab (t j = 25 c, v i = v o(nom) +1v, c i = 1f(x7r), c o = 2.2f(x7r), i o = 1ma, v inh = 2v, unless otherwise specified). symbol parameter test conditions min. typ. max. unit
electrical characteristics ld2981 series 8/22 table 5. electrical characteristics for ld2981c (t j = 25c, v i = v o(nom) +1v, c i = 1f(x7r), c o = 2.2f(x7r), i o = 1ma, v inh = 2v, unless otherwise specified) symbol parameter test conditions min. typ. max. unit v op operating input voltage 2.5 16 v v o output voltage i o = 1 ma 1.478 1.5 1.522 v i o = 1 to 100 ma 1.470 1.530 i o = 1 to 100 ma, t j = -40 to 125c 1.445 1.555 v o output voltage i o = 1 ma 1.777 1.8 1.822 v i o = 1 to 100 ma 1.764 1.836 i o = 1 to 100 ma, t j = -40 to 125c 1.737 1.863 v o output voltage i o = 1 ma 2.468 2.5 2.531 v i o = 1 to 100 ma 2.45 2.55 i o = 1 to 100 ma, t j = -40 to 125c 2.412 2.587 v o output voltage i o = 1 ma 2.814 2.85 2.885 v i o = 1 to 100 ma 2.793 2.907 i o = 1 to 100 ma, t j = -40 to 125c 2.75 2.949 v o output voltage i o = 1 ma 2.962 3 3.037 v i o = 1 to 100 ma 2.94 3.06 i o = 1 to 100 ma, t j = -40 to 125c 2.895 3.105 v o output voltage i o = 1 ma 3.16 3.2 3.24 v i o = 1 to 100 ma 3.136 3.264 i o = 1 to 100 ma, t j = -40 to 125c 3.088 3.312 v o output voltage i o = 1 ma 3.258 3.3 3.341 v i o = 1 to 100 ma 3.234 3.366 i o = 1 to 100 ma, t j = -40 to 125c 3.184 3.415 v o output voltage i o = 1 ma 3.555 3.6 3.645 v i o = 1 to 100 ma 3.528 3.672 i o = 1 to 100 ma, t j = -40 to 125c 3.474 3.726 v o output voltage i o = 1 ma 3.752 3.8 3.847 v i o = 1 to 100 ma 3.724 3.876 i o = 1 to 100 ma, t j = -40 to 125c 3.667 3.933 v o output voltage i o = 1 ma 3.95 4 4.05 v i o = 1 to 100 ma 3.92 4.08 i o = 1 to 100 ma, t j = -40 to 125c 3.86 4.14 v o output voltage i o = 1 ma 4.641 4.7 4.758 v i o = 1 to 100 ma 4.606 4.794 i o = 1 to 100 ma, t j = -40 to 125c 4.535 4.864 v o output voltage i o = 1 ma 4.789 4.85 4.91 v i o = 1 to 100 ma 4.753 4.947 i o = 1 to 100 ma, t j = -40 to 125c 4.68 5.019
ld2981 series electrical characteristics 9/22 note: 1 for v o < 2.5v dropout voltage can be calculated according to the minimum input voltage in full temperature range. v o output voltage i o = 1 ma 4.937 5 5.062 v i o = 1 to 100 ma 4.9 5.1 i o = 1 to 100 ma, t j = -40 to 125c 4.825 5.175 ? v o line regulation v o(nom) + 1 < v in < 16 v, i o = 1 ma 0.003 0.014 %/v t j = -40 to 125c 0.032 i q quiescent current on mode i o = 0 80 100 a i o = 0, t j = -40 to 125c 150 i o = 1 ma 100 150 i o = 1 ma, t j = -40 to 125c 200 i o = 25 ma 250 400 i o = 25 ma, t j = -40 to 125c 800 i o = 100 ma 1000 1300 i o = 100 ma, t j = -40 to 125c 2600 off mode v inh < 0.3 v 0.8 v inh < 0.15 v, t j = -40 to 125c 2 v drop dropout voltage ( note: 1 ) i o = 0 1 3 mv i o = 0, t j = -40 to 125c 5 i o = 1 ma 7 10 i o = 1 ma, t j = -40 to 125c 15 i o = 25 ma 70 100 i o = 25 ma, t j = -40 to 125c 150 i o = 100 ma 180 250 i o = 100 ma, t j = -40 to 125c 375 i sc short circuit current r l = 0 150 ma svr supply voltage rejection c o = 10f, f = 1khz 63 db v inh inhibit input logic low low = output off, t j = -40 to 125c 0.18 v v inl inhibit input logic high high = output on, t j = -40 to 125c 1.6 v i inh inhibit input current v inh = 0v, t j = -40 to 125c 0 -1 f v inh = 5v, t j = -40 to 125c 5 15 e n output noise voltage b w = 300 hz to 50 khz, c o = 10f 160 v rms t shdn thermal shutdown 170 c table 5. electrical characteristics for ld2981c (t j = 25c, v i = v o(nom) +1v, c i = 1f(x7r), c o = 2.2f(x7r), i o = 1ma, v inh = 2v, unless otherwise specified) symbol parameter test conditions min. typ. max. unit
typical performance characteristics ld2981 series 10/22 5 typical performance characteristics (t j = 25c, v i = v o(nom) +1v, c i = 1f(x7r), c o = 2.2f(x7r), v inh = 2v, unless otherwise specified). figure 3. output voltage vs temperature figure 4. output voltage vs temperature figure 5. line regulation vs temperature figure 6. load regulation vs temperature figure 7. dropout voltage vs temperature figure 8. quiescent current vs temperature
ld2981 series typical performance characteristics 11/22 . . figure 9. quiescent current vs output current figure 10. off mode quiescent current vs temperature figure 11. quiescent current vs input voltage figure 12. dropout voltage vs output current figure 13. inhibit input current vs temperature figure 14. inhibit voltage vs temperature
typical performance characteristics ld2981 series 12/22 figure 15. supply voltage rejection vs frequency figure 16. noise voltage vs frequency figure 17. best case: highest output version figure 18. worst case: lowest output version figure 19. load transient response v o = 4.7v, i o = 1 to 100ma, c o = 4.7f (x7r) figure 20. line transient response v i = [v o(nom) +1v], v o = 4.7v, i o = 100ma, c o = 4.7f (x7r)
ld2981 series application notes 13/22 6 application notes 6.1 external capacitors like any low-dropout regulator, the ld2981 requires external capacitors for regulator stability. this capacitor must be selected to meet the requirements of minimum capacitance and equivalent series resistance. we suggest to solder input and output capacitors as close as possible to the relative pins. 6.2 input capacitor an input capacitor whose value is 1f is required with the ld2981 (amount of capacitance can be increased without limit). this capacitor must be located a distance of not more than 0.5" from the input pin of the device and returned to a clean analog ground. any good quality ceramic, tantalum or film capacitors can be used for this capacitor. 6.3 output capacitor the ld2981 is designed specifically to work with ceramic output capacitors. it may also be possible to use tantalum capacitors, but these are not as attractive for reasons of size and cost. by the way, the output capacitor must meet both the requirement for minimum amount of capacitance and esr (equivalent series resistance) value. the figure 3. and figure 4. show the allowable esr range as a function of the output capacitance. these curves represent the stability region over the full temperature and i o range. due to the different loop gain, the stability improves for higher output versions and so the suggested minimum output capacitor value, if low esr ceramic type is used, is 1f for output voltages equal or major than 3.8v, 2.2f for output voltages from 2.85 to 3.3v, and 3.3f for the other versions. however, if an output capacitor lower than the suggested one is used, it?s possible to make stable the regulator adding a resistor in series to the capacitor (see figure1 & figure2 to choose the right value according to the used version and keeping in account that the esr of ceramic capacitors has been measured @ 100khz). 6.4 important the output capacitor must maintain its esr in the stable region over the full operating temperature to assure stability. also, capacitor tolerance and variation with temperature must be considered to assure the minimum amount of capacitance is provided at all times. this capacitor should be located not more than 0.5" from the output pin of the device and returned to a clean analog ground. 6.5 inhibit input operation the inhibit pin can be used to turn off the regulator when pulled low, so drastically reducing the current consumption down to less than 1a. when the inhibit feature is not used, this pin must be tied to v i to keep the regulator output on at all times. to assure proper operation, the signal source used to drive the inhibit pin must be able to swing above and below the specified thresholds listed in the electrical characteristics section under v ih v il . any slew rate can be used to drive the inhibit.
application notes ld2981 series 14/22 6.6 reverse current the power transistor used in the ld2981 has not an inherent diode connected between the regulator input and output. if the output is forced above the input, no current will flow from the output to the input across the series pass transistor. when a v rev voltage is applied on the output, the reverse current measured, according to the test circuit in figure 21. , flows to the gnd across the two feedback resistors. this current typical value is 160a. r 1 and r 2 resistors are implanted type; typical values are, respectively, 42.6 k ? and 51.150 k ? . figure 21. reverse current test circuit
ld2981 series package mechanical data 15/22 7 package mechanical data in order to meet environmental requirements, st offers these devices in ecopack ? packages. these packages have a lead-free second level interconnect. the category of second level interconnect is marked on the package and on the inner box label, in compliance with jedec standard jesd97. the maximum ratings related to soldering conditions are also marked on the inner box label. ecopack is an st trademark. ecopack specifications are available at: www.st.com.
package mechanical data ld2981 series 16/22 dim. mm. mils min. typ max. min. typ. max. a 1.4 1.6 55.1 63.0 b 0.44 0.56 17.3 22.0 b1 0.36 0.48 14.2 18.9 c 0.35 0.44 13.8 17.3 c1 0.35 0.44 13.8 17.3 d 4.4 4.6 173.2 181.1 d1 1.62 1.83 63.8 72.0 e 2.29 2.6 90.2 102.4 e 1.42 1.57 55.9 61.8 e1 2.92 3.07 115.0 120.9 h 3.94 4.25 155.1 167.3 l 0.89 1.2 35.0 47.2 sot-89 mechanical data p025h
ld2981 series package mechanical data 17/22 dim. mm. mils min. typ max. min. typ. max. a 0.90 1.45 35.4 57.1 a1 0.00 0.10 0.0 3.9 a2 0.90 1.30 35.4 51.2 b 0.35 0.50 13.7 19.7 c 0.09 0.20 3.5 7.8 d 2.80 3.00 110.2 118.1 e 1.50 1.75 59.0 68.8 e0.95 37.4 h 2.60 3.00 102.3 118.1 l 0.10 0.60 3.9 23.6 sot23-5l mechanical data 7049676c .
package mechanical data ld2981 series 18/22 dim. mm. inch min. typ max. min. typ. max. a 180 7.086 c 12.8 13.0 13.2 0.504 0.512 0.519 d 20.2 0.795 n 60 2.362 t 14.4 0.567 ao 3.13 3.23 3.33 0.123 0.127 0.131 bo 3.07 3.17 3.27 0.120 0.124 0.128 ko 1.27 1.37 1.47 0.050 0.054 0.0.58 po 3.9 4.0 4.1 0.153 0.157 0.161 p 3.9 4.0 4.1 0.153 0.157 0.161 tape & reel sot23-xl mechanical data
ld2981 series package mechanical data 19/22 dim. mm. inch min. typ max. min. typ. max. a 180 7.086 c 12.8 13.0 13.2 0.504 0.512 0.519 d 20.2 0.795 n 60 2.362 t 14.4 0.567 ao 4.70 4.80 4.90 0.185 0.189 0.193 bo 4.30 4.40 4.50 0.169 0.173 0.177 ko 1.70 1.80 1.90 0.067 0.071 0.075 po 3.9 4.0 4.1 0.153 0.157 0.161 p 7.9 8.0 8.1 0.311 0.315 0.319 tape & reel sot89 mechanical data
order code ld2981 series 20/22 8 order code table 6. order code part number output voltage ab version c version sot23-5l sot-89 sot23-5l sot-89 ld2981cm15tr 1.5 v ld2981cm18tr ld2981cu18tr 1.8 v ld2981abm25tr ld2981abu25tr (1) 1. available on request. ld2981cm25tr ld2981cu25tr (1) 2.5 v ld2981abm30tr ld2981abu30tr (1) ld2981cm30tr ld2981cu30tr (1) 3.0 v ld2981abm33tr ld2981abu33tr ld2981cm33tr ld2981cu33tr 3.3 v ld2981abm36tr ld2981abu36tr (1) ld2981cm36tr LD2981CU36TR (1) 3.6 v ld2981abm38tr ld2981abu38tr (1) ld2981cm38tr ld2981cu38tr (1) 3.8 v ld2981abm50tr ld2981abu50tr ld2981cm50tr ld2981cu50tr 5.0 v
ld2981 series revision history 21/22 9 revision history table 7. revision history date revision changes 25-jul-2006 12 order codes has been updated and new template.
ld2981 series 22/22 please read carefully: information in this document is provided solely in connection with st products. stmicroelectronics nv and its subsidiaries (?st ?) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described he rein at any time, without notice. all st products are sold pursuant to st?s terms and conditions of sale. purchasers are solely responsible for the choice, selection and use of the st products and services described herein, and st as sumes no liability whatsoever relating to the choice, selection or use of the st products and services described herein. no license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. i f any part of this document refers to any third party products or services it shall not be deemed a license grant by st for the use of such third party products or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoev er of such third party products or services or any intellectual property contained therein. unless otherwise set forth in st?s terms and conditions of sale st disclaims any express or implied warranty with respect to the use and/or sale of st products including without limitation implied warranties of merchantability, fitness for a particular purpose (and their equivalents under the laws of any jurisdiction), or infringement of any patent, copyright or other intellectual property right. unless expressly approved in writing by an authorized st representative, st products are not recommended, authorized or warranted for use in military, air craft, space, life saving, or life sustaining applications, nor in products or systems where failure or malfunction may result in personal injury, death, or severe property or environmental damage. st products which are not specified as "automotive grade" may only be used in automotive applications at user?s own risk. resale of st products with provisions different from the statements and/or technical features set forth in this document shall immediately void any warranty granted by st for the st product or service described herein and shall not create or extend in any manner whatsoev er, any liability of st. st and the st logo are trademarks or register ed trademarks of st in various countries. information in this document supersedes and replaces all information previously supplied. the st logo is a registered trademark of stmicroelectronics. all other names are the property of their respective owners. ? 2006 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - belgium - brazil - canada - china - czech republic - finland - france - germany - hong kong - india - israel - ital y - japan - malaysia - malta - morocco - singapore - spain - sweden - switzerland - united kingdom - united states of america www.st.com

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