issue 9 - july 2006 1 www.zetex.com ? zetex semiconductors plc 2006 zxct1010 enhanced high-side current monitor description ordering information the zxct1010 is a high side current sense monitor. using this device eliminates the need to disrupt the ground plane when sensing a load current. it is an enhanced version of the zxct1009 offering reduced typical output offset and improved accuracy at low sense 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 4 a, combined with its sot23-5 package make suitable for portable battery equipment. features ? low cost, accurate high-side current sensing output voltage scaling up to 2.5v sense voltage 2.5v ? 20v supply range 300na typical offset current 3.5 a quiescent current 1% typical accuracy sot23-5 package applications battery chargers smart battery packs dc motor control over current monitor power management programmable current source pinout information typical application circuit device package device marking reel size (inches) tape width (mm) quantity per reel zxct1010e5ta sot23-5 101 7 8 3000 nc gnd i out load v in pinout - top view 1 2 3 5 4
zxct1010 issue 9 - july 2006 2 www.zetex.com ? zetex semiconductors plc 2006 pin information absolute maximum ratings operation above the absolute maximum rating may cause device failure. operation at the absolute maximum ratings, for extended periods, may reduce device reliability. pin name description 1 n/c not connection 2 gnd ground connection 3i out output current, proportional to v in - v load 4v sense+ supply voltage 5v sense- connection to load/battery voltage on any pin (relative to gnd pin) -0.6 to 20v (relative to gnd) continuous output current 25ma continous sense voltage v in + 0.5v > v sense > v in - 5v ambient operating temperature range -40 to 85c storage temperature -55 to 150c package power dissipation t amb = 25c sot23-5 300mw
zxct1010 issue 9 - july 2006 3 www.zetex.com ? zetex semiconductors plc 2006 electrical characteristics test conditions t amb = 25c, v in = 5v, r out = 100 notes: (a) includes input offset voltage contribution (b) v sense = v in -v load (c) -20dbm = 63mvp-p into 50 symbol parameter conditions limits unit min. typ. max. v in v cc range 2.5 20 v i out (a) output current v sense = 0v 0 0.3 10 a v sense = 10mv 85 100 115 a v sense = 100mv 0.975 1.00 1.025 ma v sense = 200mv 1.95 2.00 2.05 ma v sense = 1v 9.7 10.0 10.3 ma i q ground pin current v sense = 0v 3.5 8 a v sense (b) sense voltage 0 2500 mv i sense- v sense- input current 100 na acc accuracy r sense = 0.1 v sense = 200mv -2.5 2.5 % gm transconductance, i out /v sense 10000 a/v bw bandwidth rf p in = -20dbm (c) v sense = 10mv dc 300 khz v sense = 100mv dc 2 mhz
zxct1010 issue 9 - july 2006 4 www.zetex.com ? zetex semiconductors plc 2006 typical characteristics
zxct1010 issue 9 - july 2006 5 www.zetex.com ? zetex semiconductors plc 2006 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 (tj max ), and ambient temperature (t amb ), according to the expression: pmax = (tj max ? t amb ) / ja the device power dissipation, p d is given by the expression: p d =i out .(v in -v out ) watts applications information the following lines describe 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) for example: 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 r out gives: r out = v out /(v sense x 0.01) r out = 0.1 / (0.1 x 0.01) = 100 schematic diagram sense+ sense- gnd 100 +- out
zxct1010 issue 9 - july 2006 6 www.zetex.com ? zetex semiconductors plc 2006 typical circuit application where r load represents any load including dc motors, a charging battery or further circuitry that requires monitoring, r sense can be selected on specific re quirements of accuracy, size and power rating. li-ion charger circuit the figure below shows the zxct1010 supporting the benchmarq bq2954 charge management ic. most of the support components for the bq2954 are omitted for clarity. this design also uses the zetex 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 current of 1.25a. charge can be terminated on maximum voltage, selectable minimum current, or maxi mum time out. switching frequency of the pwm loop is approximately 120khz. 100 ? 0.2 ? 100 ? fzt789a bc81725 1k ? bas16 10h fmmt451 140h zhcs1000 220 ? sns pin mod pin charger input to battery + bq2954 5v zxct1010 support components omitted for clarity + - v in load i out
zxct1010 issue 9 - july 2006 7 www.zetex.com ? zetex semiconductors plc 2006 bi-directional current sensing the zxct1010 can be used to measure current bi- directionally, if two device s are connected as shown opposite. if the voltage v1 is positive with respect to the voltage v2 the lower device will be ac tive, delivering a proportional output current to r out . due to the polarity of the voltage across rsense, the upper device will be inactive and will not contribute to the current delivered to r out . when v2 is more positive than v1, current will be flowing in the opposite direction, causing the upper de vice to be active instead. non-linearity will be apparent at small values of v sense due to offset current contribution. devices can use separate output resistors if the current direction is to be monitored independently. bi-directional tr ansfer function -400 -200 0 200 400 0 1 2 3 4 5 bidirectional transfer function output current (ma) sense voltage (mv) output current v sense voltage
zxct1010 issue 9 - july 2006 8 www.zetex.com ? zetex semiconductors plc 2006 pcb trace shunt resistor for low cost solution the figure opposite shows output characteristics 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 ntc of the device. the figure below shows a pcb layout suggestion. the resistor section is 25mm x 0.25mm giving approximately 150mw using 1oz copper. the data for the normalised graph was obtained using a 1a load current and a 100w output resistor. an electronic version of the pcb layout is available at www.zetex.com/isense layout shows area of shunt resistor compared to zsot23-5 package (not actual size).
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zxct1010 issue 9 - july 2006 10 www.zetex.com ? zetex semiconductors plc 2006 for international sales offices visit www.zetex.com/offices zetex products are distributed worldwide. for details, see www.zetex.com/salesnetwork this publication is issued to provide outline information only whic h (unless agreed by the company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contact or be regarded as a representation relating to the products or services concerned. the company reserves the right to alter without notice the specif ication, design, price or conditions of supply of any product or service. europe zetex gmbh streitfeldstra?e 19 d-81673 mnchen germany telefon: (49) 89 45 49 49 0 fax: (49) 89 45 49 49 49 europe.sales@zetex.com americas zetex inc 700 veterans memorial highway hauppauge, ny 11788 usa telephone: (1) 631 360 2222 fax: (1) 631 360 8222 usa.sales@zetex.com asia pacific zetex (asia ltd) 3701-04 metroplaza tower 1 hing fong road, kwai fong hong kong telephone: (852) 26100 611 fax: (852) 24250 494 asia.sales@zetex.com corporate headquarters zetex semiconductors plc zetex technology park, chadderton oldham, ol9 9ll united kingdom telephone: (44) 161 622 4444 fax: (44) 161 622 4446 hq@zetex.com package outline - sot23-5 note: controlling dimensions are in millimeters. ap proximate dimensions are provided in inches dim millimeters inches min. max. min. max. a 0.90 1.45 0.0354 0.0570 a1 0.00 0.15 0.00 0.0059 a2 0.90 1.30 0.0354 0.0511 b 0.20 0.50 0.0078 0.0196 c 0.09 0.26 0.0035 0.0102 d 2.70 3.10 0.1062 0.1220 e 2.20 3.20 0.0866 0.1181 e1 1.30 1.80 0.0511 0.0708 e 0.95 ref 0.0374 ref e1 1.90 ref 0.0748 ref l 0.10 0.60 0.0039 0.0236 a 0 30 0 30
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