View HEF4093BP_7156696.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

1. general description the hef4093b is a quad two-input nand gate. each input has a schmitt trigger circuit. the gate switches at different points for positive-going and negative-going signals. the difference between the positive voltage (v t+ ) and the negative voltage (v t ? ) is defined as hysteresis voltage (v h ). it operates over a recommended v dd power supply range of 3 v to 15 v referenced to v ss (usually ground). unused inputs must be connected to v dd , v ss , or another input. 2. features and benefits ? schmitt trigger input discrimination ? fully static operation ? 5 v, 10 v, and 15 v parametric ratings ? standardized symmetrical output characteristics ? specified from ?? 40 ? c to +85 ? c and ? 40 ? c to +125 ? c ? complies with jedec standard jesd 13-b 3. applications ? wave and pulse shapers ? astable multivibrators ? monostable multivibrators 4. ordering information hef4093b quad 2-input nand schmitt trigger rev. 8 ? 21 november 2011 product data sheet table 1. ordering information all types operate from ? 40 ? c to +125 ?c type number package name description version HEF4093BP dip14 plastic dual in-line package; 14 leads (300 mil) sot27-1 hef4093bt so14 plastic small outline package; 14 leads; body width 3.9 mm sot108-1
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 2 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger 5. functional diagram 6. pinning information 6.1 pinning fig 1. functional diagram fig 2. logic diagram (one gate) 001aag104 1 1a 2 1b 5 2a 6 2b 8 3a 9 3b 12 4a 13 4b 3 4 10 11 1y 2y 3y 4y 001aag105 na nb ny fig 3. pin configuration hef4093b 1a v dd 1b 4b 1y 4a 2y 4y 2a 3y 2b 3b v ss 3a 001aag106 1 2 3 4 5 6 7 8 10 9 12 11 14 13
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 3 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger 6.2 pin description 7. functional description [1] h = high voltage level; l = low voltage level. 8. limiting values [1] for dip14 packages: above t amb = 70 ? c, p tot derates linearly with 12 mw/k. [2] for so14 packages: above t amb = 70 ? c, p tot derates linearly with 8 mw/k. table 2. pin description symbol pin description 1a to 4a 1, 5, 8, 12 input 1b to 4b 2, 6, 9, 13 input 1y to 4y 3, 4, 10, 11 output v dd 14 supply voltage v ss 7 ground (0 v) table 3. function table [1] input output na nb ny llh lhh hl h hhl table 4. limiting values in accordance with the absolute maximum rating system (iec 60134). voltages are referenced to v ss = 0 v (ground). symbol parameter conditions min max unit v dd supply voltage ? 0.5 +18 v i ik input clamping current v i < ? 0.5 v or v i >v dd + 0.5 v - ? 10 ma v i input voltage ? 0.5 v dd + 0.5 v i ok output clamping current v o < ? 0.5 v or v o >v dd + 0.5 v - ? 10 ma i i/o input/output current - ? 10 ma i dd supply current - 50 ma t stg storage temperature ? 65 +150 ?c t amb ambient temperature ? 40 +125 ?c p tot total power dissipation t amb = ? 40 ? c to +125 ?c dip14 [1] - 750 mw so14 [2] - 500 mw p power dissipation per output - 100 mw
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 4 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger 9. recommended operating conditions 10. static characteristics table 5. recommended operating conditions symbol parameter conditions min max unit v dd supply voltage 3 15 v v i input voltage 0 v dd v t amb ambient temperature in free air ? 40 +125 ?c table 6. static characteristics v ss = 0 v; v i =v ss or v dd ; unless otherwise specified. symbol parameter conditions v dd t amb = ? 40 ?c t amb = +25 ?c t amb = +85 ?c t amb = +125 ?c unit min max min max min max min max v oh high-level output voltage ?i o ? < 1 ? a 5 v 4.95 - 4.95 - 4.95 - 4.95 - v 10 v 9.95 - 9.95 - 9.95 - 9.95 - v 15 v 14.95 - 14.95 - 14.95 - 14.95 - v v ol low-level output voltage ?i o ? < 1 ? a 5 v - 0.05 - 0.05 - 0.05 - 0.05 v 10 v - 0.05 - 0.05 - 0.05 - 0.05 v 15 v - 0.05 - 0.05 - 0.05 - 0.05 v i oh high-level output current v o = 2.5 v 5 v - ? 1.7 - ? 1.4 - ? 1.1 - ? 1.1 ma v o = 4.6 v 5 v - ? 0.64 - ? 0.5 - ? 0.36 - ? 0.36 ma v o = 9.5 v 10 v - ? 1.6 - ? 1.3 - ? 0.9 - ? 0.9 ma v o = 13.5 v 15 v - ? 4.2 - ? 3.4 - ? 2.4 - ? 2.4 ma i ol low-level output current v o = 0.4 v 5 v 0.64 - 0.5 - 0.36 - 0.36 - ma v o = 0.5 v 10 v 1.6 - 1.3 - 0.9 - 0.9 - ma v o = 1.5 v 15 v 4.2 - 3.4 - 2.4 - 2.4 - ma i i input leakage current 15 v - ? 0.1 - ? 0.1 - ? 1.0 - ? 1.0 ? a i dd supply current all valid input combinations; i o =0a 5 v - 0.25 - 0.25 - 7.5 - 7.5 ? a 10 v - 0.5 - 0.5 - 15.0 - 15.0 ? a 15 v - 1.0 - 1.0 - 30.0 - 30.0 ? a c i input capacitance ---7.5-- - -pf
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 5 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger 11. dynamic characteristics [1] typical value of the propagation delay and output transition time can be calculated with the extrapolation formula (c l in pf). table 7. dynamic characteristics t amb = 25 ?c; c l = 50 pf; t r = t f ? 20 ns; wave forms see figure 4 ; test circuit see figure 5 ; unless otherwise specified. symbol parameter conditions v dd extrapolation formula [1] min typ max unit t phl high to low propagation delay na or nb to ny 5 v 63 ns + (0.55 ns/pf)c l - 90 185 ns 10 v 29 ns + (0.23 ns/pf)c l -4080ns 15 v 22 ns + (0.16 ns/pf)c l -3060ns t plh low to high propagation delay na or nb to ny 5 v 58 ns + (0.55 ns/pf)c l - 85 170 ns 10 v 29 ns + (0.23 ns/pf)c l -4080ns 15 v 22 ns + (0.16 ns/pf)c l -3060ns t thl high to low output transition time ny to low 5 v 10 ns + (1.00 ns/pf)c l - 60 120 ns 10 v 9 ns + (0.42 ns/pf)c l -3060ns 15 v 6 ns + (0.28 ns/pf)c l -2040ns t tlh low to high output transition time na or nb to high 5 v 10 ns + (1.00 ns/pf)c l - 60 120 ns 10 v 9 ns + (0.42 ns/pf)c l -3060ns 15 v 6 ns + (0.28 ns/pf)c l -2040ns table 8. dynamic power dissipation v ss = 0 v; t r = t f ? 20 ns; t amb = 25 ? c. symbol parameter v dd typical formula where: p d dynamic power dissipation 5v p d = 1300 ? f i + ? (f o ? c l ) ? v dd 2 ( ? w) f i = input frequency in mhz; f o = output frequency in mhz; c l = output load capacitance in pf; ? (f o ? c l ) = sum of the outputs; v dd = supply voltage in v. 10 v p d = 6400 ? f i + ? (f o ? c l ) ? v dd 2 ( ? w) 15 v p d = 18700 ? f i + ? (f o ? c l ) ? v dd 2 ( ? w)
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 6 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger 12. waveforms measurement points are given in table 9 . logic levels: v ol and v oh are typical output voltage levels that occur with the output load. t r , t f = input rise and fall times. fig 4. propagation delay and output transition time 001aag197 input output t plh t phl 0 v v i v m v m v oh v ol t tlh t thl 90 % 10 % 10 % 90 % t r t f table 9. measurement points supply voltage input output v dd v m v m 5 v to 15 v 0.5v dd 0.5v dd test data given in table 10 . definitions for test circuit: dut = device under test. c l = load capacitance including jig and probe capacitance. r t = termination resistance should be equal to the output impedance z o of the pulse generator. fig 5. test circuit v dd v i v o 001aag182 dut c l r t g table 10. test data supply voltage input load v dd v i t r , t f c l 5 v to 15 v v ss or v dd ? 20 ns 50 pf
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 7 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger 13. transfer characteristics table 11. transfer characteristics v ss =0v; t amb = 25 ? c; see figure 6 and figure 7 . symbol parameter conditions v dd min typ max unit v t+ positive-going threshold voltage 5 v 1.9 2.9 3.5 v 10 v 3.6 5.2 7 v 15 v 4.7 7.3 11 v v t ? negative-going threshold voltage 5 v 1.5 2.2 3.1 v 10 v 3 4.2 6.4 v 15 v 4 6.0 10.3 v v h hysteresis voltage 5 v 0.4 0.7 - v 10 v 0.6 1.0 - v 15 v 0.7 1.3 - v fig 6. transfer characteristic fig 7. waveforms showing definition of v t+ and v t ? (between limits at 30 % and 70 %) and v h 001aag107 v o v i v h v t+ v t? 001aag108 v o v i v h v t+ v t?
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 8 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger a. v dd = 5 v; t amb = 25 ?cb . v dd = 10 v; t amb = 25 ? c c. v dd = 15 v; t amb = 25 ?c fig 8. typical drain current as a function of input v i (v) 05 2.5 001aag109 200 100 i dd (a) 0 v i (v) 010 5 001aag110 1000 500 i dd (a) 0 v i (v) 020 10 001aag111 2000 1000 i dd (a) 0
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 9 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger 14. application information some examples of applications for the hef4093b are: ? wave and pulse shapers ? astable multivibrators ? monostable multivibrators if a schmitt trigger is driven via a high-impedance (r > 1 k ? ), then it is necessary to incorporate a capacitor c with a value of ; otherwise oscillation can occur on the edges of a pulse. c p is the external parasitic capacitance between inputs and output; the value depends on the circuit board layout. remark: the two inputs may be connected togethe r, but this will result in a larger through-current at the moment of switching. t amb = 25 ? c. fig 9. typical switching levels as a function of supply voltage v dd (v) 2.5 17.5 12.5 7.5 515 10 001aag112 5 10 v i (v) 0 v t+ v t? fig 10. astable multivibrator fig 11. schmitt trigger driven via a high-impedance input 001aag113 v dd v dd 1 2 3 7 14 c p r c 001aag114 v dd v dd 1 2 3 7 14 c c p ------ v dd v ss ? v h ------------------------- >
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 10 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger 15. package outline fig 12. package outline sot27-1 (dip14) unit a max. 1 2 (1) (1) b 1 cd (1) z ee m h l references outline version european projection issue date iec jedec jeita mm inches dimensions (inch dimensions are derived from the original mm dimensions) sot27-1 99-12-27 03-02-13 a min. a max. b max. w m e e 1 1.73 1.13 0.53 0.38 0.36 0.23 19.50 18.55 6.48 6.20 3.60 3.05 0.254 2.54 7.62 8.25 7.80 10.0 8.3 2.2 4.2 0.51 3.2 0.068 0.044 0.021 0.015 0.77 0.73 0.014 0.009 0.26 0.24 0.14 0.12 0.01 0.1 0.3 0.32 0.31 0.39 0.33 0.087 0.17 0.02 0.13 050g04 mo-001 sc-501-14 m h c (e ) 1 m e a l seating plane a 1 w m b 1 e d a 2 z 14 1 8 7 b e pin 1 index 0 5 10 mm scale note 1. plastic or metal protrusions of 0.25 mm (0.01 inch) maximum per side are not included. dip14: plastic dual in-line package; 14 leads (300 mil) sot27-1
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 11 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger fig 13. package outline sot108-1 (so14) unit a max. a 1 a 2 a 3 b p cd (1) e (1) (1) eh e ll p qz ywv references outline version european projection issue date iec jedec jeita mm inches 1.75 0.25 0.10 1.45 1.25 0.25 0.49 0.36 0.25 0.19 8.75 8.55 4.0 3.8 1.27 6.2 5.8 0.7 0.6 0.7 0.3 8 0 o o 0.25 0.1 dimensions (inch dimensions are derived from the original mm dimensions) note 1. plastic or metal protrusions of 0.15 mm (0.006 inch) maximum per side are not included. 1.0 0.4 sot108-1 x w m a a 1 a 2 b p d h e l p q detail x e z e c l v m a (a ) 3 a 7 8 1 14 y 076e06 ms-012 pin 1 index 0.069 0.010 0.004 0.057 0.049 0.01 0.019 0.014 0.0100 0.0075 0.35 0.34 0.16 0.15 0.05 1.05 0.041 0.244 0.228 0.028 0.024 0.028 0.012 0.01 0.25 0.01 0.004 0.039 0.016 99-12-27 03-02-19 0 2.5 5 mm scale so14: plastic small outline package; 14 leads; body width 3.9 mm sot108-1
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 12 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger 16. revision history table 12. revision history document id release date data sheet status change notice supersedes hef4093b v.8 20111121 product data sheet - hef4093b v.7 modifications: ? table 6 : i oh minimum values changed to maximum hef4093b v.7 20100901 product data sheet - hef4093b v.6 hef4093b v.6 20091202 product data sheet - hef4093b v.5 hef4093b v.5 20090728 product data sheet - hef4093b v.4 hef4093b v.4 20080612 product data sheet - hef4093b_cnv v.3 hef4093b_cnv v.3 19950101 product specification - hef4093b_cnv v.2 hef4093b_cnv v.2 19950101 product specification - -
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 13 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger 17. legal information 17.1 data sheet status [1] please consult the most recently issued document before initiating or completing a design. [2] the term ?short data sheet? is explained in section ?definitions?. [3] the product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple device s. the latest product status information is available on the internet at url http://www.nxp.com . 17.2 definitions draft ? the document is a draft versi on only. the content is still under internal review and subject to formal approval, which may result in modifications or additions. nxp semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall hav e no liability for the consequences of use of such information. short data sheet ? a short data sheet is an extract from a full data sheet with the same product type number(s) and title. a short data sheet is intended for quick reference only and should not be relied upon to contain detailed and full information. for detailed and full information see the relevant full data sheet, which is available on request vi a the local nxp semiconductors sales office. in case of any inconsistency or conflict with the short data sheet, the full data sheet shall prevail. product specification ? the information and data provided in a product data sheet shall define the specification of the product as agreed between nxp semiconductors and its customer , unless nxp semiconductors and customer have explicitly agreed otherwis e in writing. in no event however, shall an agreement be valid in which the nxp semiconductors product is deemed to offer functions and qualities beyond those described in the product data sheet. 17.3 disclaimers limited warranty and liability ? information in this document is believed to be accurate and reliable. however, nxp semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. in no event shall nxp semiconductors be liable for any indirect, incidental, punitive, special or consequential damages (including - without limitation - lost profits, lost savings, business interruption, costs related to the removal or replacement of any products or rework charges) whether or not such damages are based on tort (including negligence), warranty, breach of contract or any other legal theory. notwithstanding any damages that customer might incur for any reason whatsoever, nxp semiconductors? aggregate and cumulative liability towards customer for the products described herein shall be limited in accordance with the terms and conditions of commercial sale of nxp semiconductors. right to make changes ? nxp semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. this document supersedes and replaces all information supplied prior to the publication hereof. suitability for use ? nxp semiconductors products are not designed, authorized or warranted to be suitable for use in life support, life-critical or safety-critical systems or equipment, nor in applications where failure or malfunction of an nxp semiconductors product can reasonably be expected to result in personal injury, death or severe property or environmental damage. nxp semiconductors accepts no liability for inclusion and/or use of nxp semiconductors products in such equipment or applications and therefore such inclusion and/or use is at the customer?s own risk. applications ? applications that are described herein for any of these products are for illustrative purpos es only. nxp semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification. customers are responsible for the design and operation of their applications and products using nxp semiconductors products, and nxp semiconductors accepts no liability for any assistance with applications or customer product design. it is customer?s sole responsibility to determine whether the nxp semiconductors product is suitable and fit for the customer?s applications and products planned, as well as fo r the planned application and use of customer?s third party customer(s). customers should provide appropriate design and operating safeguards to minimize the risks associated with their applications and products. nxp semiconductors does not accept any liability related to any default, damage, costs or problem which is based on any weakness or default in the customer?s applications or products, or the application or use by customer?s third party customer(s). customer is responsible for doing all necessary testing for the customer?s applic ations and products using nxp semiconductors products in order to av oid a default of the applications and the products or of the application or use by customer?s third party customer(s). nxp does not accept any liability in this respect. limiting values ? stress above one or more limiting values (as defined in the absolute maximum ratings system of iec 60134) will cause permanent damage to the device. limiting values are stress ratings only and (proper) operation of the device at these or any other conditions above those given in the recommended operating conditions section (if present) or the characteristics sections of this document is not warranted. constant or repeated exposure to limiting values will permanently and irreversibly affect the quality and reliability of the device. terms and conditions of commercial sale ? nxp semiconductors products are sold subject to the gener al terms and conditions of commercial sale, as published at http://www.nxp.com/profile/terms , unless otherwise agreed in a valid written individual agreement. in case an individual agreement is concluded only the terms and conditions of the respective agreement shall apply. nxp semiconductors hereby expressly objects to applying the customer?s general terms and conditions with regard to the purchase of nxp semiconducto rs products by customer. no offer to sell or license ? nothing in this document may be interpreted or construed as an offer to sell products t hat is open for acceptance or the grant, conveyance or implication of any lic ense under any copyrights, patents or other industrial or intellectual property rights. export control ? this document as well as the item(s) described herein may be subject to export control regulations. export might require a prior authorization from competent authorities. document status [1] [2] product status [3] definition objective [short] data sheet development this document contains data from the objecti ve specification for product development. preliminary [short] data sheet qualification this document contains data from the preliminary specification. product [short] data sheet production this document contains the product specification.
hef4093b all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2011. all rights reserved. product data sheet rev. 8 ? 21 november 2011 14 of 15 nxp semiconductors hef4093b quad 2-input nand schmitt trigger non-automotive qualified products ? unless this data sheet expressly states that this specific nxp semicon ductors product is automotive qualified, the product is not suitable for automotive use. it is neither qualified nor tested in accordance with automotive testing or application requirements. nxp semiconductors accepts no liabili ty for inclusion and/or use of non-automotive qualified products in automotive equipment or applications. in the event that customer uses t he product for design-in and use in automotive applications to automotive specifications and standards, customer (a) shall use the product without nxp semiconductors? warranty of the product for such automotive applicat ions, use and specifications, and (b) whenever customer uses the product for automotive applications beyond nxp semiconductors? specifications such use shall be solely at customer?s own risk, and (c) customer fully indemnifies nxp semiconductors for any liability, damages or failed product claims resulting from customer design and use of the product for automotive app lications beyond nxp semiconductors? standard warranty and nxp semiconduct ors? product specifications. 17.4 trademarks notice: all referenced brands, produc t names, service names and trademarks are the property of their respective owners. 18. contact information for more information, please visit: http://www.nxp.com for sales office addresses, please send an email to: salesaddresses@nxp.com
nxp semiconductors hef4093b quad 2-input nand schmitt trigger ? nxp b.v. 2011. all rights reserved. for more information, please visit: http://www.nxp.com for sales office addresses, please se nd an email to: salesaddresses@nxp.com date of release: 21 november 2011 document identifier: hef4093b please be aware that important notices concerning this document and the product(s) described herein, have been included in section ?legal information?. 19. contents 1 general description . . . . . . . . . . . . . . . . . . . . . . 1 2 features and benefits . . . . . . . . . . . . . . . . . . . . 1 3 applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 4 ordering information . . . . . . . . . . . . . . . . . . . . . 1 5 functional diagram . . . . . . . . . . . . . . . . . . . . . . 2 6 pinning information . . . . . . . . . . . . . . . . . . . . . . 2 6.1 pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 6.2 pin description . . . . . . . . . . . . . . . . . . . . . . . . . 3 7 functional description . . . . . . . . . . . . . . . . . . . 3 8 limiting values. . . . . . . . . . . . . . . . . . . . . . . . . . 3 9 recommended operating conditions. . . . . . . . 4 10 static characteristics. . . . . . . . . . . . . . . . . . . . . 4 11 dynamic characteristics . . . . . . . . . . . . . . . . . . 5 12 waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 13 transfer characteristics . . . . . . . . . . . . . . . . . . 7 14 application information. . . . . . . . . . . . . . . . . . . 9 15 package outline . . . . . . . . . . . . . . . . . . . . . . . . 10 16 revision history . . . . . . . . . . . . . . . . . . . . . . . . 12 17 legal information. . . . . . . . . . . . . . . . . . . . . . . 13 17.1 data sheet status . . . . . . . . . . . . . . . . . . . . . . 13 17.2 definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 17.3 disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 17.4 trademarks. . . . . . . . . . . . . . . . . . . . . . . . . . . 14 18 contact information. . . . . . . . . . . . . . . . . . . . . 14 19 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

▲Up To Search▲

Price & Availability of HEF4093BP

	To Download HEF4093BP Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .