ZXCT1010_06 ZETEX | Alldatasheet
Document overview
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Technical content
Features
- 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 3 . 5 /H9262A quiescent current 1% typical accuracy SOT23-5 package
Applications
Battery chargers Smart battery packs D C m o t o r c o n t r o l Over current monitor Power management Programmable current source Pinout information Typical application circuit Device Package Device marking Reel size (inches) Tape width (mm) Quantity per reel ZXCT1010E5TA SOT23-5 101 7 8 3000 NC GND IOUT Load VIN Pinout - top view
Issue 9 - July 2006 2 www.zetex.com © Zetex Semiconductors plc 2006 Pin information Absolute maximum ratings Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for extended periods, may reduce device reliability. Pin Name Description
1 N/C Not connection
2 GND Ground connection
OUT Output current, proportional to VIN - VLOAD 4V SENSE+ Supply voltage 5V SENSE- Connection to load/battery Voltage on any pin (relative to GND pin) -0.6 to 20V (relative to GND) Continuous output current 25mA Continous sense voltage V IN + 0.5V > VSENSE > VIN - 5V Ambient operating temperature range -40 to 85°C Storage temperature -55 to 150°C Package power dissipation T amb= 25°C SOT23-5 300mW
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Electrical characteristics
Test conditions Tamb = 25°C, VIN = 5V, ROUT = 100/H9024 NOTES: (a) Includes input offset voltage contribution (b) VSENSE = VIN-VLOAD (c) -20dBm = 63mVp-p into 50/H9024 Symbol Parameter Conditions Limits Unit Min. Typ. Max. VIN VCC range 2.5 20 V IOUT (a) Output current V SENSE = 0V 0 0.3 10 /H9262A VSENSE = 10mV 85 100 115 /H9262A 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 IQ Ground pin current V SENSE = 0V 3.5 8 /H9262A VSENSE (b) Sense voltage 0 2500 mV ISENSE- VSENSE- input current 100 nA Acc Accuracy R SENSE = 0.1/H9024 VSENSE = 200mV -2.5 2.5 % Gm Transconductance, IOUT/VSENSE 10000 /H9262A/V BW Bandwidth RF PIN = -20dBm(c) VSENSE = 10mV DC 300 kHz VSENSE = 100mV DC 2 MHz
Issue 9 - July 2006 4 www.zetex.com © Zetex Semiconductors plc 2006 Typical characteristics
Issue 9 - July 2006 5 www.zetex.com © Zetex Semiconductors plc 2006 Power dissipation The maximum allowable power dissipation of the device for normal operation (P max), is a function of the package junction to ambient thermal resistance ( /H9052ja), maximum junction temperature (Tj max), and ambient temperature (Tamb), according to the expression: Pmax = (Tjmax – Tamb) / /H9052ja The device power dissipation, P D 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 R
SENSE to give 50mV > VSENSE > 500mV at full load. 2 Choose R OUT 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/H9024 Schematic diagram SENSE+ SENSE- GND 100/H9024 OUT
Issue 9 - July 2006 6 www.zetex.com © Zetex Semiconductors plc 2006 Typical circuit application Where RLOAD represents any load including DC motors, a charging battery or further circuitry that requires monitoring, R SENSE can be selected on specific re quirements 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-/H9252 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 maxi mum time out. Switching frequency of the PWM loop is approximately 120kHz. 100Ω 0.2Ω 100Ω FZT789A BC81725 1kΩ BAS16 10µH FMMT451 140µH ZHCS1000 220Ω SNS pin MOD pin Charger Input To Battery + bq2954 ZXCT1010 support components omitted for clarity + - Vin Load Iout
Issue 9 - July 2006 7 www.zetex.com © Zetex Semiconductors plc 2006 Bi-directional current sensing The ZXCT1010 can be used to measure current bi- directionally, if two device s are connected as shown opposite. If the voltage V1 is positive with respect to the voltage V2 the lower device will be ac tive, delivering a proportional output current to R OUT. 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 V SENSE due to offset current contribution. Devices can use separate output resistors if the current direction is to be monitored independently. Bi-directional transfer function -400 -200 0 200 400 Bidirectional Transfer Function Output Current (mA) Sense Voltage (mV) Output Current v Sense Voltage
Issue 9 - July 2006 8 www.zetex.com © Zetex Semiconductors plc 2006 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).
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Issue 9 - July 2006 10 www.zetex.com © Zetex Semiconductors plc 2006 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 whic h (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. Europe Zetex GmbH 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 Highway
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 Zetex Technology Park, Chadderton Oldham, OL9 9LL United Kingdom Telephone: (44) 161 622 4444 Fax: (44) 161 622 4446 hq@zetex.com Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches DIM Millimeters Inches Min. Max. Min. Max. A 0.90 1.45 0.0354 0.0570 A1 0.00 0.15 0.00 0.0059 A2 0.90 1.30 0.0354 0.0511 b 0.20 0.50 0.0078 0.0196 C 0.09 0.26 0.0035 0.0102 D 2.70 3.10 0.1062 0.1220 E 2.20 3.20 0.0866 0.1181 E1 1.30 1.80 0.0511 0.0708 e 0.95 REF 0.0374 REF e1 1.90 REF 0.0748 REF L 0.10 0.60 0.0039 0.0236 a° 0° 30° 0° 30°