ZXCT1009 HIGH-SIDE CURRENT MONITOR Description Pin Assignments SOT23 Package Suffix - F 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. 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. VSENSE- 1 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 a SOT23 package make it a unique solution for portable battery equipment. The SM8 device offers an alternative package option. IOUT 2 VSENSE+ (Top View) SM8 Package Suffix - T8 Features * * * * * * * * 3 Low cost, accurate high-side current sensing Output voltage scaling Up to 2.5V sense voltage 2.5V to 20V supply range 4A quiescent current 1% typical accuracy SOT23 and SM8 packages AEC-Q100.3 qualified; ZXCT1009FTA only VSENSE- 1 8 N/C N/C 2 7 N/C VSENSE+ 3 6 N/C IOUT 4 5 N/C (Top View) Applications * * * * * * * * Battery chargers Smart battery packs DC motor control Over current monitor Power management Level translating Programmable current source Application Circuit RSENSE V IN 2 To load 3 V SENSE- V SENSE+ ZXCT1009 IOUT 1 VOUT ROUT ZXCT1009 Document number: DS33441 Rev. 12 - 2 1 of 8 www.diodes.com April 2011 (c) Diodes Incorporated ZXCT1009 HIGH-SIDE CURRENT MONITOR Pin Descriptions Pin Name VSENSE+ VSENSE- Pin Function Connection to supply voltage Connection to load IOUT Output current, proportional to measured current Absolute Maximum Ratings (TA = 25C) Description Voltage on any pin (relative to IOUT) Continous output current, IOUT Rating -0.6 to 20 Unit 25 mA V Continuous sense voltage, VSENSE -0.5 to +5 V Operating temperature, TA -40 to 85 C Storage temperature Package power SOT23 dissipation @ TA = 25C SM8 (Derate to zero @ 125C) -55 to 125 C 450 mW 2 W Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings for extended periods may reduce device reliability. Electrical Characteristics (TA = 25C, VIN = 5V, ROUT = 100) Symbol VIN Parameter Min VCC range 1 IOUT Output Current VSENSE Sense Voltage ISENSE- VSENSE Input Current ACC Transconductance, IOUT/VSENSE BW Bandwidth Limits Typ 2.5 VSENSE = 0V VSENSE = 10mV VSENSE = 100mV VSENSE = 200mV VSENSE = 1V 1 90 0.975 1.95 9.6 4 104 1.002 2.0 9.98 0 RSENSE = 0.1 VSENSE = 200mV Accuracy GM Notes: Conditions VSENSE(DC) = 10mv, RF PIN = -40dBm -2.5 VSENSE(DC) = 100mv, RF PIN = -20dBm Max Units 20 V 15 120 1.025 2.05 10.2 A A mA mA mA 2500 mV 100 nA 2.5 % 10000 A/V 300 2 kHz MHz 1. Includes input offset voltage contribution . VSENSE is defined as the differential voltage between VSENSE+ and VSENSE-. VSENSE = VSENSE+ - VSENSE= VIN - VLOAD = ILOAD x RSENSE -20dBm=63mVPP into 50 ZXCT1009 Document number: DS33441 Rev. 12 - 2 2 of 8 www.diodes.com April 2011 (c) Diodes Incorporated ZXCT1009 HIGH-SIDE CURRENT MONITOR Typical Characteristics ZXCT1009 Document number: DS33441 Rev. 12 - 2 3 of 8 www.diodes.com April 2011 (c) Diodes Incorporated ZXCT1009 HIGH-SIDE CURRENT MONITOR Typical Characteristics (cont.) Power Dissipation Application 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 text describes how to scale a load current to an output voltage. 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) W VSENSE = VIN - VLOAD 1 VOUT = 0.01 x VSENSE x ROUT 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 ZXCT1009 Document number: DS33441 Rev. 12 - 2 4 of 8 www.diodes.com April 2011 (c) Diodes Incorporated ZXCT1009 HIGH-SIDE CURRENT MONITOR Application Information (cont.) Li-Ion Charger Circuit Transient Protection An additional resistor, RLIM can be added in series with ROUT (as below), 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. RSENSE VIN 2 To load 3 VSENSE- VSENSE+ ZXCT1009 IOUT 1 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 Diodes 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. 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. Reference: DVS2954S1H Li-Ion Charger Development System. RLIM VOUT ROUT 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) = (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 ZXCT1009 Document number: DS33441 Rev. 12 - 2 5 of 8 www.diodes.com April 2011 (c) Diodes Incorporated ZXCT1009 HIGH-SIDE CURRENT MONITOR Application Information (cont.) 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 NTCof the device. 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 through Diodes applications group. Layout shows area of shunt resistor compared to SOT23 package. Not actual size. Effect of Sense Resisitor Material on Temperature Performance Ordering Information Device ZXCT1009FTA ZXCT1009F-7 ZXCT1009T8TA AEC-Q100 level Grade 3 None None ZXCT1009 Document number: DS33441 Rev. 12 - 2 Reel Size 7" 7" 7" Tape Width Quantity per Reel Part Marking Package 8mm 8mm 12mm 3000 Units 3000 Units 1000 Units 109 109 ZXCT1009 SOT23 SOT23 SM8 6 of 8 www.diodes.com April 2011 (c) Diodes Incorporated ZXCT1009 HIGH-SIDE CURRENT MONITOR Package Outline Dimensions (All Dimensions in mm) 1) SOT23 A B C H K M K1 D J 2) F L G SOT23 Dim Min Max Typ A 0.37 0.51 0.40 B 1.20 1.40 1.30 C 2.30 2.50 2.40 D 0.89 1.03 0.915 F 0.45 0.60 0.535 G 1.78 2.05 1.83 H 2.80 3.00 2.90 J 0.013 0.10 0.05 K 0.903 1.10 1.00 K1 0.400 L 0.45 0.61 0.55 M 0.085 0.18 0.11 0 8 All Dimensions in mm SM8 E A E1 A1 b D e 15 e1 45 SM-8 Dim Min Max Typ A 1.7 - - A1 0.02 0.1 - b 0.7 - - c 0.24 0.32 - D 6.3 6.7 - e 1.53 - - e1 4.59 - - E 6.7 7.3 - E1 3.3 3.7 - L 0.9 - - All Dimensions in mm c L ZXCT1009 Document number: DS33441 Rev. 12 - 2 7 of 8 www.diodes.com April 2011 (c) Diodes Incorporated ZXCT1009 HIGH-SIDE CURRENT MONITOR IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). 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