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. It is an enhanced version of the ZXCT1009 offering reduced typical output offset and improved accuracy at low sense voltage. 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 SOT23-5 package make suitable for portable battery equipment. Features Applications • Low cost, accurate high-side current sensing • Battery chargers • Smart battery packs • Output voltage scaling • DC motor control • Up to 2.5V sense voltage • Over current monitor • 2.5V – 20V supply range • Power management • 300nA typical offset current • Programmable current source • 3.5A quiescent current • 1% typical accuracy • SOT23-5 package Pinout information NC 1 Typical application circuit 5 Load GND 2 IOUT 3 4 VIN Pinout - top view Ordering information Device Package Device marking Reel size (inches) Tape width (mm) Quantity per reel ZXCT1010E5TA SOT23-5 101 7 8 3000 Issue 9 - July 2006 © Zetex Semiconductors plc 2006 1 www.zetex.com ZXCT1010 Pin information Pin Name Description 1 N/C Not connection 2 GND Ground connection 3 IOUT Output current, proportional to VIN - VLOAD 4 VSENSE+ Supply voltage 5 VSENSE- Connection to load/battery Absolute maximum ratings Voltage on any pin (relative to GND pin) -0.6 to 20V (relative to GND) Continuous output current 25mA Continous sense voltage VIN + 0.5V > VSENSE > VIN - 5V Ambient operating temperature range -40 to 85°C Storage temperature -55 to 150°C Package power dissipation Tamb= 25°C SOT23-5 300mW Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for extended periods, may reduce device reliability. Issue 9 - July 2006 © Zetex Semiconductors plc 2006 2 www.zetex.com ZXCT1010 Electrical characteristics Test conditions Tamb = 25°C, VIN = 5V, ROUT = 100⍀ Symbol Parameter VIN VCC range IOUT(a) Output current IQ Conditions Min. 2.5 Acc Gm Transconductance, IOUT/VSENSE BW Bandwidth Max. 20 V 0 0.3 10 A VSENSE = 10mV 85 100 115 A VSENSE = 100mV 0.975 1.00 1.025 mA VSENSE = 200mV 1.95 2.00 2.05 mA VSENSE = 1V 9.7 10.0 10.3 mA 3.5 8 A 2500 mV 100 nA 2.5 % Ground pin current VSENSE = 0V VSENSE- input current Accuracy Unit VSENSE = 0V VSENSE(b) Sense voltage ISENSE- Limits Typ. 0 RSENSE = 0.1⍀ VSENSE = 200mV -2.5 10000 A/V RF PIN = -20dBm(c) VSENSE = 10mV DC 300 kHz VSENSE = 100mV DC 2 MHz NOTES: (a) Includes input offset voltage contribution (b) VSENSE = VIN-VLOAD (c) -20dBm = 63mVp-p into 50⍀ Issue 9 - July 2006 © Zetex Semiconductors plc 2006 3 www.zetex.com ZXCT1010 Typical characteristics Issue 9 - July 2006 © Zetex Semiconductors plc 2006 4 www.zetex.com ZXCT1010 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 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 ROUT(1) For example: A 1A current is to be represented by a 100mV output voltage: 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⍀ Schematic diagram SENSE+ SENSE- 100⍀ + GND OUT Issue 9 - July 2006 © Zetex Semiconductors plc 2006 5 www.zetex.com ZXCT1010 Typical circuit application 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. Li-Ion charger circuit The figure below 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. FZT789A 140µH Charger Input BC81725 1kΩ To Battery + 0.2Ω ZHCS1000 Vin Load 100Ω BAS16 10µH + - 5V bq2954 MOD pin ZXCT1010 FMMT451 220Ω Iout SNS pin 100Ω support components omitted for clarity Issue 9 - July 2006 © Zetex Semiconductors plc 2006 6 www.zetex.com ZXCT1010 Bi-directional current sensing The ZXCT1010 can be used to measure current bidirectionally, if two devices are connected as shown opposite. 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 Bidirectional 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 9 - July 2006 © Zetex Semiconductors plc 2006 7 www.zetex.com ZXCT1010 PCB trace shunt resistor for low cost solution The figure opposite 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 below shows a PCB layout suggestion. The resistor section is 25mm x 0.25mm giving approximately 150mW using 1oz copper. The data for the normalised graph was obtained using a 1A load current and a 100W output resistor. An electronic version of the PCB layout is available at www.zetex.com/isense Layout shows area of shunt resistor compared to ZSOT23-5 package (not actual size). Issue 9 - July 2006 © Zetex Semiconductors plc 2006 8 www.zetex.com ZXCT1010 Intentionally left blank Issue 9 - July 2006 © Zetex Semiconductors plc 2006 9 www.zetex.com ZXCT1010 Package outline - SOT23-5 DIM Millimeters Min. 0.90 0.00 0.90 0.20 0.09 2.70 2.20 1.30 A A1 A2 b C D E E1 e e1 L a° Inches Max. 1.45 0.15 1.30 0.50 0.26 3.10 3.20 1.80 Min. 0.0354 0.00 0.0354 0.0078 0.0035 0.1062 0.0866 0.0511 0.95 REF 1.90 REF 0.10 0° Max. 0.0570 0.0059 0.0511 0.0196 0.0102 0.1220 0.1181 0.0708 0.0374 REF 0.0748 REF 0.60 30° 0.0039 0° 0.0236 30° Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches Europe Americas Asia Pacific Corporate Headquarters Zetex GmbH Streitfeldstraße 19 D-81673 München Germany Zetex Inc 700 Veterans Memorial Highway Hauppauge, NY 11788 USA Zetex (Asia Ltd) 3701-04 Metroplaza Tower 1 Hing Fong Road, Kwai Fong Hong Kong Zetex Semiconductors plc Zetex Technology Park, Chadderton Oldham, OL9 9LL United Kingdom Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 [email protected] Telephone: (1) 631 360 2222 Fax: (1) 631 360 8222 [email protected] Telephone: (852) 26100 611 Fax: (852) 24250 494 [email protected] Telephone: (44) 161 622 4444 Fax: (44) 161 622 4446 [email protected] For international sales offices visit www.zetex.com/offices Zetex products are distributed worldwide. For details, see www.zetex.com/salesnetwork 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 contact 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. Issue 9 - July 2006 © Zetex Semiconductors plc 2006 10 www.zetex.com