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| ZXCT1008 AUTOMOTIVE HIGH-SIDE CURRENT MONITOR DESCRIPTION The ZXCT1008 is a high side current sense monitor. Using this device eliminates the need 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 scales 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. The ability to withstand high voltage transients and reverse polarity connection, makes this part very suitable for automotive and other transient rich environments. APPLICATIONS * Automotive current measurement * DC motor and solenoid control * Over current monitor * Power management FEATURES * Low cost, accurate high-side current sensing * -40 to +125C temperature range * Up to 500mV sense voltage * 2.5V - 20V supply range * 4A quiescent current * 1% typical accuracy * SOT23 APPLICATION CIRCUIT ORDERING INFORMATION DEVICE ZXCT1008FTA REEL SIZE 7" TAPE WIDTH 8mm QUANTITY PER REEL 3,000 units DEVICE MARKING * 108 ISSUE 2 - JULY 2004 1 ZXCT1008 ABSOLUTE MAXIMUM RATINGS Voltage on any pin Continuous output current Continuous sense voltage Operating temperature Storage temperature Package power dissipation (TA = 25C) -0.6V to 20V (relative to Iout) 10mA Vin + 0.5V > Vsense> Vin - 5V -40 to 125C -55 to 150C 450mW Derate to zero at 150C Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for extented periods, may reduce device reliability. ELECTRICAL CHARACTERISTICS Test Conditions TA = 25C, Vin = 5V, Rout = 100. SYMBOL V in I out 1 PARAMETER V CC range Output current CONDITIONS Min 2.5 V sense =0V V sense =10mV V sense =100mV V sense =200mV V sense =500mV 1 90 0.975 1.95 4.8 0 LIMITS Typ 4 104 1.0 2.0 5.0 UNIT Max 20 15 120 1.025 2.05 5.2 500 100 V A A mA mA mA mV nA V sense I sense Acc Gm BW Sense voltage V sense input current Accuracy Transconductance, I out / V sense Bandwidth RF P in = -20dBm V sense = 10mV dc V sense = 100mV dc R sense = 0.1 V sense =200mV -2.5 10000 2.5 % A/V 300 2 kHz MHz 1 Includes input offset voltage contribution Vsense=Vin-Vload -20dBm=63mVp-p into 50 ISSUE 2 - JULY 2004 2 ZXCT1008 TYPICAL CHARACTERISTICS ISSUE 2 - JULY 2004 3 ZXCT1008 TYPICAL CHARACTERISTICS (Cont.) SCHEMATIC DIAGRAM PIN DESCRIPTION Pin Name V sense + V sense I out Pin Function Supply voltage Connection to load/battery Output current, proportional to V in -V load CONNECTION DIAGRAM SOT23 Package Suffix - F Top View ISSUE 2 - JULY 2004 4 ZXCT1008 POWER DISSIPATION The maximum allowable power dissipation of the device for normal operation (Pmax), is a function of the package junction to ambient thermal resistance (ja), maximum junction temperature (Tjmax), and ambient temperature (Tamb), according to the expression: Pmax = (Tjmax - Tamb) / ja The device power dissipation, PD is given by the expression: PD=Iout.(Vin-Vout) Watts 1) Choose the value of Rsense to give 50mV > Vsense > 500mV at full load. For example Vsense = 100mV at 1.0A. Rsense = 0.1/1.0 => 0.1 2) Choose Rout to give Vout = 100mV, when Vsense = 100mV. Rearranging 1 for Rout gives: Rout = Vout /(Vsense x 0.01) Rout = 0.1 / (0.1 x 0.01) = 100 APPLICATIONS INFORMATION The following lines describe how to scale a load current to an output voltage. Vsense = Vin - Vload Vout = 0.01 x Vsense x Rout1 E.g. A 1A current is to be represented by a 100mV output voltage: ISSUE 2 - JULY 2004 5 ZXCT1008 Where Rload represents any load including DC motors, a charging battery or further circuitry that requires monitoring, Rsense can be selected on specific requirements of accuracy, size and power rating. An additional resistor, Rlim can be added in series with Rout (figure 1.0), to limit the current from Iout. Any circuit connected to Vout 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. The zener Z1 provides additional protection for local dump, reverse battery and high voltage transient incidents. Assuming the worst case condition of Vout = 0V; providing a low impedance to a transient, the minimum value of Rlim is given by:Rlim(min) = Vpk - Vmax Ipk TYPICAL AUTOMOTIVE CIRCUIT APPLICATION Vpk = Peak transient voltage to be withstood Vmax = Maximum working Voltage = 20V Ipk = Peak output current = 40mA Figure 1.0 ZXCT1009 with additional current limiting Resistor Rlim and zener Z1 The maximum value of Rlim is set by Vin(min), Vout(max) and the dropout voltage (see transfer characteristic on page 3) of the ZXCT1009 :Rlim(max) = Rout [Vin(min) - (Vdp + Vout (max))] Vout (max) Vin(min) = Minimum Supply Operating Voltage Vdp = Dropout Voltage Vout (max) = Maximum Operating Output Voltage ISSUE 2 - JULY 2004 6 APPLICATIONS INFORMATION ZXCT1008 PCB trace shunt resistor for low cost solution. The figure below 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 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 layout is available at www.zetex.com/isense ZXCT1009 Vout Vin ZXCT1009 Vout Vin Rout Load GND Rout Actual Size Load GND Layout shows area of shunt resistor compared to SOT23 package. Not actual size 1.4 Normalised Voltage Voltage across Copper Sense Resistor 1.2 VOUT with Copper Sense Resistor 1.0 VOUT with Ideal Sense Resistor 0.8 -40 -20 0 20 40 60 80 100 120 140 Temperature (C) Effect of Sense Resistor Material on Temperature Performance ISSUE 2 - JULY 2004 7 ZXCT1008 PACKAGE OUTLINE Controlling dimensions are in millimeters. Approximate conversions are given in inches PACKAGE DIMENSIONS Millimeters DIM A B C D F G 0.37 0.085 Min 2.67 1.20 Max 3.05 1.40 1.10 0.53 0.15 0.015 0.0034 Inches Min 0.105 0.047 Max 0.120 0.055 0.043 0.021 0.0059 DIM H K L M N Millimeters Min 0.33 0.01 2.10 0.45 Max 0.51 0.10 2.50 0.64 Inches Max 0.013 0.0004 0.083 0.018 Max 0.020 0.004 0.0985 0.025 0.95 NOM 0.0375 NOM 1.90 NOM 0.075 NOM (c) Zetex Semiconductors plc 2004 Europe Zetex GmbH Streitfeldstrae 19 D-81673 Munchen 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 Hwy 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 Lansdowne Road, Chadderton Oldham, OL9 9TY United Kingdom Telephone (44) 161 622 4444 Fax: (44) 161 622 4446 hq@zetex.com These offices are supported by agents and distributors in major countries world-wide. This publication is issued to provide outline information only which (unless agreed by the Company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating to the products or services concerned. The Company reserves the right to alter without notice the specification, design, price or conditions of supply of any product or service. For the latest product information, log on to www.zetex.com ISSUE 2 - JULY 2004 8 |
Price & Availability of ZXCT1008FT
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