ZXCT1009 HIGH-SIDE CURRENT MONITOR DESCRIPTION The ZXCT1009 is a high side current sense monitor. Using this device eliminates the need to disrupt the ground plane when sensing a load current. APPLICATIONS It takes a high side voltage developed across a current shunt resistor and translates it into a proportional output current. * DC Motor control A user defined output resistor scales the output current into a ground-referenced voltage. * Power Management * Battery Chargers * Smart Battery Packs * Over current monitor * Level translating 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 its SOT23 package make it a unique solution for portable battery equipment. * Programmable current source APPLICATION CIRCUIT Vin FEATURES * Low cost, accurate high-side current sensing. To Load Rsense * Output voltage scaling. * Up to 2.5V sense voltage. ZXCT 1009 * 2.5V - 20V supply range. * 4A quiescent current. Vout * 1% typical accuracy. * SOT23 & SM8 packages. Rout ORDERING INFORMATION PART NUMBER PACKAGE PARTMARKING ZXCT1009F SOT23 109 ZXCT1009T8 SM8 ZXCT1009 8 leaded SOT223 ISSUE 4 - JULY 2003 1 SEMICONDUCTORS ZXCT1009 ABSOLUTE MAXIMUM RATINGS Voltage on any pin Continuous output current Continuous sense voltage Operating Temperature Storage Temperature Package Power Dissipation SOT23 SM8 -0.6V to 20V (relative to Iout) 25mA Vin + 0.5V > Vsense> Vin - 5V -40 to 85C -55 to 125C (TA = 25C) 450mW 2W ELECTRICAL CHARACTERISTICS Test Conditions TA = 25C, Vin = 5V, Rout = 100. SYMBOL PARAMETER CONDITIONS LIMITS Min V in I out V CC Range 1 Output current V sense =0V V sense =10mV Sense Voltage I sense Load pin Acc Accuracy Gm Transconductance, BW I out / V sense Bandwidth Max 20 V A 1 4 15 90 104 120 A V sense =100mV 0.975 1.002 1.025 mA V sense =200mV 1.95 2.0 2.05 mA 9.6 9.98 10.2 mA 2500 mV 100 nA V sense =1V V sense Typ 2.5 UNIT 0 input current R sense = 0.1 -2.5 V sense =200mV RF P in = -20dBm V sense = 10mV dc V sense = 100mV dc 2.5 % 10000 A/V 300 kHz 2 MHz 1 Includes input offset voltage contribution Vsense=Vin-Vload -20dBm=63mVp-p into 50 ISSUE 4 - JULY 2003 SEMICONDUCTORS 2 ZXCT1009 TYPICAL CHARACTERISTICS 5 VIN = 5V Tamb = 25C ROUT = 0W 1m Output Current Error (%) IOUT - Output Current (A) 10m 100 10 100 1m 10m 100m VIN = 5V Tamb = 25C ROUT = 0W 4 3 2 1 0 -1 Typical -2 1 10m 100m VSENSE (V) Error v Sense Voltage 3 VIN = 5V, Tamb = 25C, RF PIN = -20dBm VIN = 5V VSENSE = 1V ROUT = 0W 10.2 0 10.0 Gain (dB) IOUT - Output Current (mA) Typical Output v Sense Voltage 9.8 9.6 -3 DC VSENSE = 0.01V -6 DC VSENSE = 0.1V DC VSENSE = 1V -9 9.4 -40 -20 0 20 40 60 -12 0.01 80 0.1 Temperature (C) 1 10 Frequency (MHz) Frequency Response Output Current v Temperature 12 0 10 8 -10 VSENSE = 1V VIN = 5V Tamb = 25C ROUT = 0W VIN = 5V Tamb = 25C RF PIN = -20dBm -20 VSENSE = 0.8V Rejection (dB) IOUT - Output Current (mA) 1 VSENSE (V) VSENSE = 0.6V 6 VSENSE = 0.4V 4 VSENSE = 0.2V 2 VSENSE = 1V -30 VSENSE = 0.1V -40 -50 VSENSE = 0.01V -60 -70 -80 0 -90 0 1 2 3 4 5 1 VIN - Supply Voltage (V) 10 100 1k 10k 100k 1M 10M Frequency (Hz) Common Mode Rejection Transfer Characteristic ISSUE 4 - JULY 2003 3 SEMICONDUCTORS ZXCT1009 SCHEMATIC DIAGRAM TYPICAL CHARACTERISTICS (Cont.) Vin Load 100 + - Iout PIN DESCRIPTION Pin Name Pin Function V in Supply Voltage Load Connection to load/battery I out Output current, proportional to V in -V load CONNECTION DIAGRAMS SOT23 Package Suffix - F Load SM8 Package Suffix - T8 1 Vin 1 8 N/C N/C 2 7 N/C Vin 3 6 N/C Iout 4 5 N/C Load 3 Iout 2 Top View Top View ISSUE 4 - JULY 2003 SEMICONDUCTORS 4 ZXCT1009 POWER DISSIPATION APPLICATIONS INFORMATION 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: The following lines describe how to scale a load current to an output voltage. Vsense = Vin - Vload Vout = 0.01 x Vsense x Rout1 Pmax = (Tjmax - Tamb) / ja E.g. The device power dissipation, PD is given by the expression: A 1A current is to be represented by a 100mV output voltage: 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 ohms. 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 SM8 SOT23 TYPICAL CIRCUIT APPLICATION Vin Rsense ZXCT1009 Vin Load Rload Iout Vout Rout Where Rload 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. ISSUE 4 - JULY 2003 5 SEMICONDUCTORS ZXCT1009 APPLICATIONS INFORMATION (Continued) FZT789A 140H Charger Input FMMT3904 1k Transient Protection 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. To Battery + 0.2 ZHCS1000 Vin Load 100 FMMD914 10H + - 5V bq2954 MOD pin Vin ZXCT1009 To Load Rsense FMMT451 220 Iout SNS pin ZXCT 1009 100 support components omitted for clarity Rlim 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 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 maximum time out. Switching frequency of the PWM loop is approximately 120kHz. Vout R Figure 1.0 ZXCT1009 with additional current limiting Resistor Rlim. 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) = 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. R e fe r e nc e : D V S 2954S 1 H Li - I on C h a r g e r Development System. Vpk - Vmax Ipk Vpk = Peak transient voltage to be withstood Vmax = Maximum working Voltage = 20V Ipk = Peak output current = 40mA 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 4 - JULY 2003 SEMICONDUCTORS 6 ZXCT1009 APPLICATIONS INFORMATION (Continued) 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. ZXCT1009 ZXCT1009 Vout Vin Vout Load 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 Rout Rout Vin GND Actual Size Load GND Layout shows area of shunt resistor compared to SOT23 package. Not actual size Voltage across Copper Sense Resistor Normalised Voltage 1.4 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 4 - JULY 2003 7 SEMICONDUCTORS ZXCT1009 PACKAGE DIMENSIONS SOT23 N DIM Millimetres Inches Min Max Min Max A 2.67 3.05 0.105 0.120 B 1.20 1.40 0.047 0.055 C - 1.10 - 0.043 D 0.37 0.53 0.0145 0.021 F 0.085 0.15 0.0033 0.0059 G NOM 1.9 NOM 0.075 K 0.01 0.10 0.0004 0.004 L 2.10 2.50 0.0825 0.0985 NOM 0.95 N NOM 0.037 PACKAGE DIMENSIONS SM8 DIM Millimetres Min Typ Inches Max Min Typ Max A - - 1.7 - - 0.067 A1 0.02 - 0.1 0.0008 - 0.004 b - 0.7 - - 0.028 - c 0.24 - 0.32 0.009 - 0.013 D 6.3 - 6.7 0.248 - 0.264 E 3.3 - 3.7 0.130 - 0.145 e1 - 4.59 - - 0.180 - e2 - 1.53 - - 0.060 - He 6.7 - 7.3 0.264 - 0.287 Lp 0.9 - - 0.035 - - - - 15 - - 15 - 10 - - 10 - (c) Zetex plc 2003 Americas Asia Pacific Zetex GmbH Streitfeldstrae 19 D-81673 Munchen Zetex Inc 700 Veterans Memorial Hwy Hauppauge, NY 11788 Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 europe.sales@zetex.com USA Telephone: (1) 631 360 2222 Fax: (1) 631 360 8222 usa.sales@zetex.com 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 Europe Zetex plc Fields New Road Chadderton Oldham, OL9 8NP 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 4 - JULY 2003 SEMICONDUCTORS 8