ZXCT1010 ENHANCED HIGH-SIDE CURRENT MONITOR DESCRIPTION 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. APPLICATIONS • Battery Chargers • Smart Battery Packs • DC Motor control It is an enhanced version of the ZXCT1009 offering reduced typical output offset and improved accuracy at low sense voltage. • Over current monitor • Power Management • 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 4µA, combined with its SOT23-5 package make suitable for portable battery equipment. • Programmable current source FEATURES Vin • 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. • 4µA quiescent current. • 1% typical accuracy. • SOT23 -5 package. APPLICATION CIRCUIT To Load Rsense Vin Load ZXCT1010 GND I out Vout Rout ORDERING INFORMATION ISSUE 4 - DECEMBER 2001 1 PART NUMBER PACKAGE PARTMARKING ZXCT1010E5 SOT23-5 1010 ZXCT1010 ABSOLUTE MAXIMUM RATINGS Voltage on any pin Continuous output current Continuous sense voltage Operating Temperature Storage Temperature Package Power Dissipation SOT23-5 -0.6V to 20V (relative to GND) 25mA Vin + 0.5V > Vsense†> Vin – 5V -40 to 85°C -55 to 125°C (TA = 25°C) 500mW ELECTRICAL CHARACTERISTICS Test Conditions TA = 25°C, Vin = 5V, Rout = 100Ω. SYMBOL PARAMETER CONDITIONS LIMITS Min V in V CC Range I out 1 Output current Iq Ground pin current V sense 2 Sense Voltage I sense Load pin UNIT Typ 2.5 Max 20 V V sense = 0V 0 0.3 10 µA V sense = 10mV 85 100 115 µA 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 V sense = 0V 1 4 8 µA 0 2500 mV 100 nA input current Acc Accuracy Gm Transconductance, BW Bandwidth R sense = 0.1Ω -2.5 V sense = 200mV 2.5 % 10000 µA/V RF P in = -20dBm 3 V sense = 10mV dc 300 kHz V sense = 100mV dc 2 MHz I out / V sense 1 Includes input offset voltage contribution Vsense=Vin-Vload 3 -20dBm=63mVp-p into 50Ω 2 ISSUE 4 - DECEMBER 2001 2 ZXCT1010 TYPICAL CHARACTERISTICS ISSUE 4 - DECEMBER 2001 3 ZXCT1010 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 GND Ground CONNECTION DIAGRAM SOT23-5 Package Suffix – E5 NC 1 GND 2 Iout 3 5 Load 4 VIN Top View SCHEMATIC DIAGRAM Vin Load 100Ω + - Iout ISSUE 4 - DECEMBER 2001 4 ZXCT1010 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 (θja), 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) / θja 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 Ω TYPICAL CIRCUIT APPLICATION Vin Rsense V in Load ZXCT1010 GND I out Vout Rload 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 - DECEMBER 2001 5 ZXCT1010 Bi-Directional Current Sensing APPLICATIONS INFORMATION (Continued) FZT789A 140µH 1kΩ 3 BC81725 To Battery + 0.2Ω ZHCS1000 Vin Iout Charger Input The ZXCT1010 can be used to measure current bi-directionally, if two devices are connected as shown below. Load 100Ω BAS16 5 Load Vin 4 10µH + - 5V MOD pin V1 V2 R sense ZXCT1010 FMMT451 220Ω 4 Iout Vin Load 5 Vout 3 SNS pin Iout bq2954 100Ω support components omitted for clarity R out Li-Ion Charger Circuit The above figure 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 maximum time out. Switching frequency of the PWM loop is approximately 120kHz. If the voltage V1 is positive with respect to the voltage V2 the lower device will be active, delivering a proportional output current to Rout. Due to the polarity of the voltage across Rsense, the upper device will be inactive and will not contribute to the current delivered to Rout. When V2 is more positive than V1, current will be flowing in the opposite direction, causing the upper device to be active instead. Non-linearity will be apparent at small values of Vsense due to offset current contribution. Devices can use separate output resistors if the current direction is to be monitored independently. Bi-directional Transfer Function Output Current (mA) 5 4 3 2 1 0 -400 -200 0 200 400 Sense Voltage (mV) Output Current v Sense Voltage ISSUE 4 - DECEMBER 2001 6 ZXCT1010 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. 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 100Ω output resistor. An electronic version of the PCB layout is available at www.zetex.com/isense Actual Size Layout shows area of shunt resistor compared to SOT23-5 package. Not actual size ISSUE 4 - DECEMBER 2001 7 ZXCT1010 PACKAGE DIMENSIONS SOT23-5 DIM Millimetres Inches MIN MAX MIN MAX A 0.90 1.45 0.035 0.057 A1 0.00 0.15 0.00 0.006 A2 0.90 1.3 0.035 0.051 b 0.35 0.50 0.014 0.020 C 0.09 0.20 0.0035 0.008 D 2.80 3.00 0.110 0.118 E 2.60 3.00 0.102 0.118 E1 1.50 1.75 0.059 0.069 e 0.95 REF 0.037 REF e1 1.90 REF 0.075 REF L 0.10 0.60 0.004 0.024 a° 0 10 0 10 © Zetex plc 2001 Zetex plc Fields New Road Chadderton Oldham, OL9 8NP United Kingdom Telephone (44) 161 622 4422 Fax: (44) 161 622 4420 Zetex GmbH Streitfeldstraße 19 D-81673 München Zetex Inc 700 Veterans Memorial Hwy Hauppauge, NY11788 Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 USA Telephone: (631) 360 2222 Fax: (631) 360 8222 Zetex (Asia) Ltd 3701-04 Metroplaza, Tower 1 Hing Fong Road Kwai Fong Hong Kong Telephone: (852) 26100 611 Fax: (852) 24250 494 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 - DECEMBER 2001 8