zxct1009 high-side current monitor zxct1009 document number: ds33441 rev. 12 - 2 1 of 8 www.diodes.com april 2011 ? diodes incorporated description the zxct1009 is a high side current sense monitor. using this device eliminates the n eed to disrupt the ground plane when sensing a load current. it takes a high side voltage developed across a current shunt resistor and translates it into a proportional output current. a user defined output resistor sca les the output current into a ground-referenced voltage. the wide input voltage range of 20v down to as low as 2.5v make it suitable for a range of applications. a minimum operating current of just 4a, combined with a sot23 package make it a unique solution for portable battery equipment. the sm8 device offers an alternative package option. features ? low cost, accurate high-side current sensing ? output voltage scaling ? up to 2.5v sense voltage ? 2.5v to 20v supply range ? 4 a quiescent current ? 1% typical accuracy ? sot23 and sm8 packages ? aec-q100.3 qualified; zxct1009fta only applications ? battery chargers ? smart battery packs ? dc motor control ? over current monitor ? power management ? level translating ? programmable current source ? pin assignments sot23 package suffix - f sm8 package suffix ? t8 application circuit i out v se ns e+ 3 v se ns e- (top view) 2 1 i out v se ns e+ 3 v se ns e- (top view) 2 1 i out n/c v se ns e - n/c (top view) 4 2 3 1 5 7 6 8 n/c v sense+ n/c n/c i out n/c v se ns e - n/c (top view) 4 2 3 1 5 7 6 8 n/c v sense+ n/c n/c v in r sense to load v out r out 1 2 3 zxct1009 v sense+ v sense- i out v in r sense to load v out r out 1 2 3 zxct1009 v sense+ v sense- i out
zxct1009 high-side current monitor zxct1009 document number: ds33441 rev. 12 - 2 2 of 8 www.diodes.com april 2011 ? diodes incorporated pin descriptions pin name pin function v sense+ connection to supply voltage v sense- connection to load i out output current, proportional to measured current absolute maximum ratings (t a = 25 c) description rating unit voltage on any pin (relative to i out ) -0.6 to 20 v continous output current, i out 25 ma continuous sense voltage, v sense ? -0.5 to +5 v operating temperature, t a -40 to 85 c storage temperature -55 to 125 c package power dissipation @ t a = 25c (derate to zero @ 125c) sot23 450 mw sm8 2 w operation above the absolute maximum rating may caus e device failure. operation at the absolute maximum ratings for extended periods may reduce device reliability. electrical characteristics (t a = 25 c, v in = 5v, r out = 100 ? ) symbol parameter conditions limits units min typ max v in v cc range 2.5 20 v i out 1 output current v sense = 0v v sense = 10mv v sense = 100mv v sense = 200mv v sense = 1v 1 90 0.975 1.95 9.6 4 104 1.002 2.0 9.98 15 120 1.025 2.05 10.2 a a ma ma ma v sense ? sense voltage 0 2500 mv i sense- v sense - input current 100 na a cc accuracy r sense = 0.1 ? v sense = 200mv -2.5 2.5 % g m transconductance, i out /v sense 10000 a/v bw bandwidth v sense(dc) = 10mv, rf p in = -40dbm ? v sense(dc) = 100mv, rf p in = -20dbm ? 300 2 khz mhz notes: 1. includes input offset voltage contribution ?. v sense is defined as the differential voltage between v sense+ and v sense- . v sense = v sense+ - v sense- = v in - v load = i load x r sense ? -20dbm=63mv pp into 50
zxct1009 high-side current monitor zxct1009 document number: ds33441 rev. 12 - 2 3 of 8 www.diodes.com april 2011 ? diodes incorporated typical characteristics
zxct1009 high-side current monitor zxct1009 document number: ds33441 rev. 12 - 2 4 of 8 www.diodes.com april 2011 ? diodes incorporated typical characteristics (cont.) power dissipation the maximum allowable power dissipation of the device for normal operation (p max ), is a function of the package junction to ambient thermal resistance ( ja ), maximum junction temperature (t jmax ), and ambient temperature (t amb ), according to the expression: p max = (t jmax ? t amb ) / ja the device power dissipation, p d is given by the expression: p d = i out (v in -v out ) w application information the following text describes how to scale a load current to an output voltage. v sense = v in - v load v out = 0.01 x v sense x r out 1 e.g. a 1a current is to be represented by a 100mv output voltage: 1) choose the value of r sense to give 50mv > v sense > 500mv at full load. for example v sense = 100mv at 1.0a. r sense = 0.1/1.0 => 0.1 ? . 2) choose r out to give v out = 100mv, when v sense = 100mv. rearranging 1 for rout gives: r out = v out /(v sense x 0.01) r out = 0.1 / (0.1 x 0.01) = 100 ?
zxct1009 high-side current monitor zxct1009 document number: ds33441 rev. 12 - 2 5 of 8 www.diodes.com april 2011 ? diodes incorporated application information (cont.) li-ion charger circuit the above figure shows the zxct1009 supporting the benchmarq bq2954 charge management ic. most of the support components for the bq2954 are omitted for clarity. this design also uses the diodes fzt789a high current super-? pnp as the switching transistor in the dc-dc step down converter and the fmmt451 as the drive npn for the fzt789a. the circuit can be configured to charge up to four li-ion cells at a charge curr ent of 1.25a. charge can be terminated on maximum voltage, selectable minimum current, or maximum time out. switching frequency of the pwm loop is approximately 120khz. the zxct1009 is intended as a direct functional replacement for the zds1009, which is featured in a complete design from unitrode/texas instruments on the li-ion charger circuit shown above. reference: dvs2954s1h li-ion charger development system. transient protection a n additional resistor, r lim can be added in series with r out (as below), to limit the current from i out . any circuit connected to v out will be protected from input voltage transients. this can be of particular use in automotive applications where load dump and other common transients need to be considered. zxct1009 with additional current limiting resistor r lim . a ssuming the worst case condition of v out = 0v; providing a low impedance to a transient, the minimum value of r lim is given by:- r lim(min) = (v pk ? v max )/i pk v pk = peak transient voltage to be withstood v max = maximum working voltage = 20v i pk = peak output current = 40ma the maximum value of r lim is set by v in(min) , v out(max) and the dropout voltage (see transfer characteristic on page 3) of the zxct1009 :- r lim(max) = r out [v in(min) ? (v dp + v out(max) )]/v out(max) v in(min) = minimum supply operating voltage v dp = dropout voltage v out(max) = maximum operating output voltage v in r sense to load v out r out 1 2 3 zxct1009 v sense+ v sense- i out r lim v in r sense to load v out r out 1 2 3 zxct1009 v sense+ v sense- i out r lim
zxct1009 high-side current monitor zxct1009 document number: ds33441 rev. 12 - 2 6 of 8 www.diodes.com april 2011 ? diodes incorporated application information (cont.) pcb trace shunt resistor for low cost solution the figure below shows output c haracteristics of the device when using a pcb resistive trace for a low cost solution in replacement for a conventional shunt resistor. the graph shows the linear rise in voltage across the resistor due to the ptc of the material and demonstrates how this rise in resistance value over temperature compensates for the ntcof the device. the figure opposite shows a pcb layout suggestion. the resistor section is 25mm x 0.25mm giving approximately 150m ? using 1oz copper. the data for the normalised graph was obtained using a 1a load current and a 100 ? output resistor. an electronic version of the pcb la yout is available through diodes applications group. effect of sense resisitor material on temperature performance layout shows area of shunt resistor compared to sot23 package. not actual size. ordering information device aec-q100 level reel size tape width quantity per reel part marking package zxct1009fta grade 3 7? 8mm 3000 units 109 sot23 ZXCT1009F-7 none 7? 8mm 3000 units 109 sot23 zxct1009t8ta none 7? 12mm 1000 units zxct1009 sm8
zxct1009 high-side current monitor zxct1009 document number: ds33441 rev. 12 - 2 7 of 8 www.diodes.com april 2011 ? diodes incorporated package outline dimensions (all dimensions in mm) 1) sot23 2) sm8 sot23 dim min max typ a 0.37 0.51 0.40 b 1.20 1.40 1.30 c 2.30 2.50 2.40 d 0.89 1.03 0.915 f 0.45 0.60 0.535 g 1.78 2.05 1.83 h 2.80 3.00 2.90 j 0.013 0.10 0.05 k 0.903 1.10 1.00 k1 - - 0.400 l 0.45 0.61 0.55 m 0.085 0.18 0.11 0 8 - all dimensions in mm sm-8 dim min max typ a ? 1.7 ? a1 0.02 0.1 ? b ? 0.7 ? c 0.24 0.32 ? d 6.3 6.7 ? e ? ? 1.53 e1 ? ? 4.59 e 6.7 7.3 ? e1 3.3 3.7 ? l 0.9 ? ? all dimensions in mm 15 45 l c e1 e d b ee1 a a1 a m j l d f b c h k g k1
zxct1009 high-side current monitor zxct1009 document number: ds33441 rev. 12 - 2 8 of 8 www.diodes.com april 2011 ? diodes incorporated important notice diodes incorporated makes no warranty of any kind, express or implied, with regards to this document, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose (and their equivalents under the laws of any jurisdiction). diodes incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or ot her changes without further notice to this document and any product described herein. diodes incorporated does not assume any liabi lity arising out of the application or use of this document or any product described herein; neither does diodes incorporated convey any license under its patent or trademark rights, nor the rights of others. any customer or user of this document or products desc ribed herein in such applications shall assume all risks of such use and will agree to hold diodes incorporated and all the companies whose products are represented on diodes incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthoriz ed sales channel. should customers purchase or use diodes incorporated products for any unintended or unauthorized application, customers shall indemnify and hold diodes incorporated and its representatives harmless against all claims, damages, expenses, and attorney fee s arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized a pplication. products described herein may be covered by one or more united states, international or foreign patents pending. product names and markings noted herein may also be covered by one or more united states, international or foreign trademarks. life support diodes incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the chief executive officer of diodes incorporated. as used herein: a. life support devices or systems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in significant injury to the user. b. a critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support dev ices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of diodes incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related information or support that may be provided by diodes incorporated. further, customers must fully indemnify diodes incorporated and its representatives against any damages arising out of the use of diodes incorporated products in such safety-critical, life support devices or systems. copyright ? 2011, diodes incorporated www.diodes.com
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