ZXCT1008 ZETEX | Alldatasheet

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Technical content

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.

FEATURES

  • Low cost, accurate high-side current sensing
  • -40 to +125°C temperature range
  • Up to 500mV sense voltage
  • 2.5V – 20V supply range
  • 4µA quiescent current
  • 1% typical accuracy
  • SOT23 DEVICE MARKING
  • 108

APPLICATIONS

  • Automotive current measurement
  • DC motor and solenoid control
  • Over current monitor
  • Power management APPLICATION CIRCUIT DEVICE REEL SIZE TAPE WIDTH QUANTITY PER REEL ZXCT1008FTA 7” 8mm 3,000 units

ORDERING INFORMATION

Voltage on any pin -0.6V to 20V (relative to I out) Continuous output current 10mA Continuous sense voltage V in + 0.5V > Vsense†> Vin – 5V Operating temperature -40 to 125 °C Storage temperature -55 to 150 °C Package power dissipation (TA = 25°C) 450mW Derate to zero at 150 °C 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 = 25°C, Vin = 5V, Rout = 100Ω. SYMBOL PARAMETER CONDITIONS LIMITS UNIT Min Typ Max Vin VCC range 2.5 20 V Iout

1 Output current V sense =0V

Vsense =10mV Vsense =100mV Vsense =200mV Vsense =500mV 0.975 1.95 4.8 104 1.0 2.0 5.0 120 1.025 2.05 5.2 µA µA mA mA mA V sense † Sense voltage 0 500 mV Isense -V sense - input current 100 nA Acc Accuracy Rsense = 0.1 Ω Vsense =200mV -2.5 2.5 % Gm Transconductance, Iout /V sense 10000 µA/V BW Bandwidth RF P in= -20dBm‡ Vsense = 10mV dc Vsense = 100mV dc 300 kHz MHz

1 Includes input offset voltage contribution†Vsense=Vin-Vload

‡ -20dBm=63mVp-p into 50Ω

Vsense - Connection to load/battery Iout Output current, proportional to V in-Vload SOT23 Package Suffix – F Top View CONNECTION DIAGRAM SCHEMATIC DIAGRAM TYPICAL CHARACTERISTICS (Cont.)

The following lines describe how to scale a load current to an output voltage. Vsense = Vin -V load Vout = 0.01 x Vsense x Rout1 E.g. A 1A current is to be represented by a 100mV output voltage: 1) Choose the value of R sense to give 50mV > Vsense > 500mV at full load. For example Vsense = 100mV at 1.0A. Rsense = 0.1/1.0 => 0.1 Ω 2) Choose R out to give Vout = 100mV, when Vsense = 100mV. Rearranging 1 for Rout gives: Rout =V out /(Vsense x 0.01) Rout = 0.1 / (0.1 x 0.01) = 100 Ω 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 (θja), maximum junction temperature (Tjmax), and ambient temperature (Tamb), according to the expression: P max = (Tjmax – Tamb) / θja The device power dissipation, P D is given by the expression: PD=Iout.(Vin-Vout) Watts APPLICATIONS INFORMATION

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 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 I out. 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 V out = 0V; providing a low impedance to a transient, the minimum value of Rlim is given by:- R( m i n ) VV Ilim pk max pk Vpk = Peak transient voltage to be withstood Vmax = Maximum working Voltage = 20V Ipk = Peak output current = 40mA The maximum value of R lim is set by V in(min), Vout(max) and the dropout voltage (see transfer characteristic on page 3) of the ZXCT1009 :- R R [V V V (max) Vlim out in dp out out (max) (min) ( )] (max)= Vin(min) = Minimum Supply Operating Voltage Vdp = Dropout Voltage Vout (max) =Maximum Operating Output Voltage Figure 1.0 ZXCT1009 with additional current limiting Resistor R lim and zener Z1 TYPICAL AUTOMOTIVE CIRCUIT APPLICATION

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 150mΩ using 1oz copper. The data for the normalised graph was obtained using a 1A load current and a 100 Ω output resistor. An electronic version of the PCB layout is available at www.zetex.com/isense -40 -20 0 20 40 60 80 100 120 140 0.8 1.0 1.2 1.4 Effect of Sense Resistor Material on Temperature Performance VOUT with Ideal Sense Resistor VOUT with Copper Sense Resistor Voltage across Copper Sense Resistor Normalised Voltage Temperature (°C) Vout Vin GND Load Rout ZXCT1009 APPLICATIONS INFORMATION Layout shows area of shunt resistor compared to SOT23 package. Not actual size Vout Vin GND Load Rout ZXCT1009 Actual Size

Streitfeldstraße 19 D-81673 München 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 © Zetex Semiconductors plc 2004 PACKAGE OUTLINE DIM Millimeters Inches DIM Millimeters Inches Min Max Min Max Min Max Max Max G 1.90 NOM 0.075 NOM /H5007/H5007 /H5007 PACKAGE DIMENSIONS Controlling dimensions are in millimeters. Approximate conversions are given in inches