doc.# dsfp-hv7801 a062813 hv7801 features ? supply voltage 8v to 450v ? voltage output device ? typical gain 5.01% ? max v sense 500mv ? fast rise and fall time, 700ns to 2.0s ? maximum quiescent current 50a applications ? smps current monitor ? battery current monitor ? motor control general description the hv7801 high side current monitor ic transfers a high- side current measurement voltage to its ground referenced output with a voltage gain of fve. the measurement voltage typically originates at a current sense resistor which is located in a high side circuit, such as the positive supply line. this monitor ic features a very wide input voltage range, high accuracy of transfer ratio, small size, low component count, low power consumption, ease of use, and low cost. offine, battery, and portable applications can be served equally well due to the wide input voltage range and the low quiescent current. typical application circuit high side current monitor 8.0 to 450v voltage gain of 5 8v to 450v input i sense v sense v out hv7801 in load gnd out v out = 5 ? v sense v r r sense r p (optional) supertex inc. supertex inc. www .supertex.com
2 doc.# dsfp-hv7801 a062813 hv7801 absolute maximum ratings parameter value v in , v load -0.5v to +460v v out -0.5v to +10v v sense -0.5v to +5.0v i load 10ma operating ambient temperature -40c to +85c operating junction temperature -40c to +125c storage temperature -65c to +150c absolute maximum ratings are those values beyond which damage to the device may occur. functional operation under these conditions is not implied. continuous operation of the device at the absolute rating level may affect device reliability. all voltages are referenced to device ground. sym parameter min typ max units conditions supply v in supply voltage 8.0 - 450 v * --- i q quiescent supply current - - 50 a - v in = 8v to 450v, v sense = 0mv input and output r out out pin output resistance - 16.5 - k - --- v out output voltage 0 - 65 mv - v sense = 0mv 420 - 580 v sense = 100mv 913 - 1087 v sense = 200mv 2395 - 2605 v sense = 500mv dynamic characteristics t rise output rise time, 10% to 90% - 0.7 - s - v sense step 5.0mv to 500mv - - 2.0 v sense step 0mv to 500mv t fall output fall time, 90% to 10% - 0.7 2.0 s - v sense step 500mv to 0mv electrical characteristics (t a = 25c unless otherwise specifed, v in = 8v to 450v) * values apply over the full temperature range. in load out gnd 1 5 4 2 3 nc pin confguration product marking y = last digit of year sealed w = code for week sealed = ?green? packaging 7byw 5-lead sot-23 package may or may not include the following marks: si or 5-lead sot-23 (top view) notes: 1. referenced to gnd 2. v sense = v in - v load ordering information part number package option packing HV7801K1-G 5-lead sot-23 2500/reel typical thermal resistance package ja 5-lead sot-23 253 o c/w -g denotes a lead (pb)-free / rohs compliant package note: thermal testboard per jedec jesd51-7 supertex inc. www .supertex.com
3 doc.# dsfp-hv7801 a062813 hv7801 block diagram application information general the hv7801 high side current monitor ic features accurate current sensing, small size, low component count, low power consumption, exceptional input voltage range, ease of use and low cost. typical use is measurement of line or load current for purpose of overcurrent protection, metering and current regulation. high side current sensing, as opposed to ground referenced or low side current sensing, is desirable or required when: ? the current to be measured does not fow in a circuit associated with ground. ? the measurement at ground level can lead to ambiguity due to changes in the grounding arrangement during feld use. ? introduction of a sense resistor in the system ground is undesirable due to issues with safety, emi, or signal degradation caused by common impedance coupling. principle of operation the operational amplifer and mosfet force the voltage across r a to track v sense within the limit of the offset voltage of the opamp, i.e. v ra = v sense . the current through r a returns to ground through r b . r a and r b are integrated, exhibiting tight matching and excellent tracking. by design, r b is fve times larger than r a . consequently, v rb is fve times larger than v ra , thus resulting in a voltage gain of 5. out pin loading effects note that the out pin has a typical output resistance of 16.5k. loading the output causes the voltage gain to drop and rise/fall time to increase. for example, assuming output resistance is 16.5k, the load resistance should exceed 16.5m in order to limit the drop in gain to 1 part in 1000. again assuming output resistance is 16.5k, capacitive loading of 6pf results in a response pole with a time constant of 100ns, not high enough to materially affect the output rise and fall time (about 700ns). sense resistor considerations limit the sense resistor voltage to 500mv during normal operating conditions. limit the power dissipation in the sense resistor to suit the application; a high sense voltage benefts accuracy, but increases power dissipation. consider the use of kelvin connections for applications where considerable voltage drops may occur in the pcb traces. a layout pattern which minimizes voltage across the sense lines is shown below. choose a low inductance type sense resistor if preservation of bandwidth is important. the use of kelvin connections helps by excluding the inductive voltage drop across the traces leading to the sense resistor. the inductive voltage drop may be substantial when operating at high frequencies. a trace or component inductance of just 10nh contributes an impedance of 6.2m at 100khz, which constitutes a 6% error when using a 100m sense resistor. r p (optional) i sense v sense r sense bias circuits hv780 1 in loa d gnd out v out r a r b + v sense - in load r sense supertex inc. www .supertex.com
4 doc.# dsfp-hv7801 a062813 hv7801 transient protection add a protection resistor (r p ) in series with the load pin if v sense can exceed 5v in a positive sense or 600mv in a negative sense, whether in a steady state or in transient conditions. a large v sense may occur during system startup or shutdown due to the charging and discharging of bulk storage capacitors. v sense may be large due to fault conditions, such as a short circuit condition, or a broken or missing sense resistor. an internal 5.0v zener diode with a current rating of 10ma protects the sense amplifer inputs. the block diagram shows the orientation of this diode. the zener diode provides clamping at 5v for a positive v sense and at 600mv for a negative v sense . under worst case conditions, limit the zener current to 10ma. a 100k resistor limits the maximum zener diode current to 4.5ma when v sense is 450v, whether positive or negative. note that the protection resistor may affect the bandwidth. the resistor forms a rc network with the trace and pin capacitance at the load pin. a capacitance of 5.0pf results in a time constant of 500ns. the protection resistor may cause an offset voltage due to bias current at the load input. under worst case bias current (1.0na), a 100k protection resistor could cause an offset of 100v or 0.2% of full scale. note that the bias current is nominally zero as the load is a high impedance cmos input. pin description pin # pin name description 1 load sense amplifer input. high impedance input with zener diode protection. add an external protection resistor in series with load if v sense exceeds the range of -600mv to +5.0v. 2 nc no connect. this pin must be left foating for proper operation. 3 in sense amplifer input and supply. 4 gnd supply return. 5 out output with a nominal output resistance of 16.5k. preservation of accuracy may require an external buffer amplifer to prevent excessive loading. supertex inc. www .supertex.com
5 hv7801 (the package drawing(s) in this data sheet may not refect the most current specifcations. for the latest package outline information go to http://www.supertex.com/packaging.html .) doc.# dsfp-hv7801 a062813 5-lead sot-23 package outline (k1) 2.90x1.60mm body, 1.45mm height (max), 0.95mm pitch symbol a a1 a2 b d e e1 e e1 l l1 l2 1 dimension (mm) min 0.90* 0.00 0.90 0.30 2.75* 2.60* 1.45* 0.95 bsc 1.90 bsc 0.30 0.60 ref 0.25 bsc 0 o 5 o nom - - 1.15 - 2.90 2.80 1.60 0.45 4 o 10 o max 1.45 0.15 1.30 0.50 3.05* 3.00* 1.75* 0.60 8 o 15 o jedec registration mo-178, variation aa, issue c, feb. 2000. * this dimension is not specifed in the jedec drawing. drawings not to scale. supertex doc. #: dspd-5sot23k1, version a041309. 1 5 d seating plane gauge plane l l1 l2 t op vi ew side v iew vi ew a - a vi ew b v iew b 1 e1 e a a2 a1 a a seating plane e b note 1 (index area d/2 x e/2) e1 note: 1. a pin 1 identifer must be located in the index area indicated. the pin 1 identifer can be: a molded mark/identifer; an embedded metal marker; or a printed indicator. supertex inc. does not recommend the use of its products in life support applications, and will not knowingly sell them for use in such appl ications unless it receives an adequate ?product liability indemnification insurance agreement.? supertex inc. does not assume responsibility for use of devices described, and limits its liabilit y to the replacement of the devices determined defective due to workmanship. no responsibility is assumed for possible omissions and inaccuracies. circuitry and specifications are subject to change without notice. for the latest product specifications refer to the supertex inc. (website: http//www .supertex.com) ?2013 supertex inc. all rights reserved. unauthorized use or reproduction is prohibited. supertex inc. 1235 bordeaux drive, sunnyvale, ca 94089 t el: 408-222-8888 www .supertex.com
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