ZXCT1012

Document overview

  • Manufacturer or author: Diodes Incorporated
  • PDF pages: 9

Technical content

Features

  • 2.5V to 20V supply range
  • 3.5 μA quiescent current
  • Current output - user set gain
  • Thin package - TSOT25
  • Temperature range -40 to 85°C

Applications

  • Battery fuel gauge
  • Battery chargers
  • Overcurrent monitor
  • Power management Typical Application Circuit ZXCT1012 RSENSEVIN VOUT ROUT RLOAD SENSE+ SENSE- OUTGND

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR ZXCT1012 Document number: DS33444 Rev. 2 - 2 2 of 9 www.diodes.com September 2011 © Diodes Incorporated Pin Descriptions Pin Name Description

1 N/C No connection

2 GND Ground connection

3 OUT

Output current pin. Current generated due to a difference voltage between VSENSE+ and VSENSE- flows out of this pin. A suitable value resistor connected to ground creates an output voltage. The maximum voltage out of this pin will be VSENSE- - 1.5V.

4 SENSE+

This pin should be connected to the rail whose current is being measured and also provides power to internal circuitry. It is the positive input of the current monitor and has an input range from 20V down to 2.5V. The current through this pin varies with differential sense voltage.

5 SENSE- This is the negative input of the current monitor and has an input

range from 20V down to 2.5V. Absolute Maximum Ratings (TA = 25°C) Description Rating Unit VSENSE+ Max. 20 V Voltage on any pin(relative to GND pin) -0.6 and VSENSE+ +0.5 V VSENSE (Note 1) -0.15 to 3 V Ambient Operating Temperature Range -40 to 85 °C Storage Temperature -55 to 150 °C Maximum Junction Temperature 150 °C Power Dissipation (TA = 25°C) 300 (De-rate to 0 at 150°C) mW Package (Note 2) RθJA PDISS @ 25°C TSOT25 250°C/W 500mW Recommended Operating Conditions Symbol Parameter Min. Max. Units VIN Sense+ range 2.5 20 V TA Ambient temperature range differential -40 85 C VSENSE Sense voltage 10 2500 mV VOUT Output voltage swing 0 VSENSE- -15 V Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for extended periods, may reduce device reliability. Notes: 1. V SENSE is defined as the differential voltage between the SENSE+ and SENSE- pins. (VSENSE = VSENSE+ - VSENSE-) 2. Mounted on 30mm x 16mm x1.1mm FR4 board with 1oz copper.

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR ZXCT1012 Document number: DS33444 Rev. 2 - 2 3 of 9 www.diodes.com September 2011 © Diodes Incorporated Electrical Characteristics (TA = 25°C, VIN = VSENSE+ = 5V; unless otherwise specified) Symbol Parameter Conditions Limits Unit Min. Typ. Max. IOUT Output Current VSENSE = 0V VSENSE = 10mV VSENSE = 40mV VSENSE = 100mV VSENSE = 200mV 380 0.975 1.95 0.3 100 400 1.00 2.00 115 420 1.025 2.05 µA µA µA mA mA IQ Ground Pin Current VSENSE = 0V 3.5 8 µA ISENSE- SENSE- Pin Input Current 100 nA ACC Accuracy RSENSE = 0.1V VSENSE = 200mV -2.5 2.5 % Gm Transconductance,IOUT/VSENSE (Note 3) 10 mA/V TC Temperature Coefficient VSENSE = 200mV TA = 0 to 50°C (Note 3) 500 ppm/°C BW Bandwidth CL = 5pF ROUT = 1kΩ VSENSE = 10mV VSENSE = 100mV 300 2 kHz MHz CMRR (Note 4) Common Mode Rejection Ratio VSENSE = 100mV, ROUT = 1kΩ VIN = 2.5V to 20V 80 dB Notes: 3. Temperature dependent measurements are extracte d from characterisation and simulation results. 4. With the ZXCT1012 using SENSE+ as its power supply pin, comm on mode rejection cannot be distinguished from power supply rejection.

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR ZXCT1012 Document number: DS33444 Rev. 2 - 2 4 of 9 www.diodes.com September 2011 © Diodes Incorporated Typical Characteristics 100µ 1m 10m 100m 1 V ( V ) Typical Output vs. Sense Voltage SENSE 10m 100µ 10µ I, O U TPUT CURRENT (A)OUT V = 5 V T = 2 5 ° C R = 0 IN A OUT Ω 1m 10m 100m 1 V ( V ) Error vs. Sense Voltage SENSE 4OUTPUT CURRENT ERROR (%) Typical V = 5 V T = 2 5 ° C R = 0 IN A OUT Ω -40 TEMPERATURE (°C) Output Current vs. Temperature -20 0 20 40 60 80 -6% -4% -2% I, O U TPUT CURRENT (mA)OUT V = 5 V V = 0.2V R = 0 IN SENSE OUT Ω FREQUENCY (MHz) Frequency Response 0.01 0.1 1 10 -12 GAIN (dB) V = 5 V T = 2 5 C V = 63.2mVpp IN A SENSE(AC) DC V = 0.01VSENSE V = 0 . 1 VSENSE V = 1 VSENSE V , SUPPLY VOLTAGE (V) Transfer Characteristics IN 102 3 4 50 12I, OUTPUT CURRENT (mA)OUT V = 5 V T = 2 5 C R = 0 IN A OUT Ω V = 1 VSENSE V = 0.8VSENSE V = 0.4VSENSE V = 0 . 6 VSENSE V = 0.2VSENSE 1 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz) Common Mode Rejection -90 V = 5 V T = 2 5 C V = 6 3 . 2 V p p IN A SENSE(AC) -80 -70 -60 -50 -40 -30 -20 -10 REJECTION (dB) V = 0 . 0 1 VSENSE V = 1 VSENSE V = 0.1VSENSE

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR ZXCT1012 Document number: DS33444 Rev. 2 - 2 5 of 9 www.diodes.com September 2011 © Diodes Incorporated Applications Information The ZXCT1012 current monitor works by converting the voltage developed across a small sense resistor into a current on the out pin. In reality it is a voltage to cu rrent converter. This output current can be converted into a voltage simply by passing it through a resistor (ROUT) to ground. The current monitor has a transconductance of 10mA/V. But the overall amplifying conversion is affected by both the R SENSE and ROUT. The gain equation of the ZXCT1012 is: 100 OUTR SENSERLIOUTV × = For best performance RSENSE should be connected as close to the SENSE+ (and SENSE-) pins; which minimizes any series resistance with RSENSE and potential for interference pickup. When choosing appropriate values for R SENSE a compromise must be reached between in-line signal loss (including potential power dissipation effects) and small signal accuracy. Higher values for R SENSE gives better accuracy at low load currents by reducing the inaccuracies due to internal offsets. For best operation the ZXCT1012 has been designed to provide best performance with VSENSE of the order of 40mV to 200mV. Current monitors are single supply devices which means they tend to saturate at very low sense voltages. However it does mean the output can never go neg ative. Also the output can never change direct ion (monotonic). This is important if the current monitor is used in a control loop. As the sense voltage is reduced the output will tend to saturate as the input offset voltage starts to have greater effect. It is recommended to have a minimum sense voltage of 10mV to minimize linearity errors. Diodes has specified the output voltage at VSENSE of 10mV, 40mV, 100mV and 200mV; which is the recommended sense voltage range. The maximum differential input voltage, VSENSE, is 2.5V; however this will cause large output currents to flow increasing power dissipation in the chip. The sense voltage can be increased further, without damaging the ZXCT 1012, by the inclusion of a resistor, RLIM, between SENSE- pin and the load. Typical values around 10kΩ. See figure below. ZXCT1012 RSENSE RLIMCC If large reverse currents are expected then the resistor, RLIM, will provide protection from exceeding absolute maximum ratings. A suitable value for RLIM can be determined from: mA 5 V R ) REF ( SENSE LIM = Where VSENSE(REV) is the maximum expected reverse sense voltage generated.

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR ZXCT1012 Document number: DS33444 Rev. 2 - 2 6 of 9 www.diodes.com September 2011 © Diodes Incorporated Applications Information (cont.) The following lines describe how to scale a load current to an output voltage. VSENSE = RSENSE * ILOAD equation (1) I OUT = 10mA/V x VSENSE equation (2) V OUT = IOUT x ROUT equation (3) Design example In the circuit below a 1A current is to be represented by a 100mV output voltage (VOUT): A) To be within recommended values choose the value of R SENSE to give: 50mV > V SENSE > 200mV at full load. For example set V SENSE = 100mV at 1.0A. From equation (1) R SENSE = 0.1V/1.0A = 0.1Ω B) Now choose R OUT to give: V OUT = 100mV, when VSENSE = 100mV. From equation (2) I OUT = 10mA/V x 0.1 = 1mA Rearranging equation (3) for R OUT gives: R OUT = VOUT/IOUT = 0.1/0.001 = 100Ω ZXCT1012 RSENSEVIN VOUT ROUT RLOAD SENSE+ SENSE- OUTGND 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.

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR ZXCT1012 Document number: DS33444 Rev. 2 - 2 7 of 9 www.diodes.com September 2011 © Diodes Incorporated 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 ( θJA), maximum junction temperature (T JMAX), and ambient temperature (T A), according to the expression: PMAX = (TJMAX – TA) / θJA The device power dissipation, P D is given by the expression: P D = IOUT.(VIN-VOUT) watts Care must be taken when using this device at large input voltages and large sense voltages to prevent too much power dissipation. 100 200 300 400 500 600 T , AMBIENT TEMPERATURE ( C)A ° 0 2 5 5 0 7 51 0 0 1 2 51 5 0 VIN = 20V VSENSE = 2.5V ROUT = 100Ω I OUT = 2.5 x 0.01 = 25mA V OUT = IOUT x ROUT = 25mA x 100Ω = 2.5V = 438mW

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR ZXCT1012 Document number: DS33444 Rev. 2 - 2 8 of 9 www.diodes.com September 2011 © Diodes Incorporated

Ordering Information

Device Package Marking Reel Size Quantity ZXCT1012ET5TA TSOT25 1012 7 3000 Tape & Reel Package Outline Dimensions (All Dimensions in mm) Suggested Pad Layout TSOT25 Dim Min Max Typ A − 1.00 − A1 0.01 0.10 − A2 0.84 0.90 − D − − 2.90 E − − 2.80 E1 − − 1.60 b 0.30 0.45 − c 0.12 0.20 − e − − 0.95 e1 − − 1.90 L 0.30 0.50 L2 − − 0.25 θ 0° 8° 4° θ1 4° 12° − All Dimensions in mm Dimensions Value (in mm) C 0.950 X 0.700 Y 1.000 Y1 3.199 c L E1 E D e 5x b θ 4x 1 θ A C C X (5x) Y (5x)

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR ZXCT1012 Document number: DS33444 Rev. 2 - 2 9 of 9 www.diodes.com September 2011 © Diodes Incorporated 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). Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or ot her changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products desc ribed herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated website, harmless against all damages. Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthoriz ed sales channel. Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fee s arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application. Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings noted herein may also be covered by one or more United States, international or foreign trademarks. LIFE SUPPORT Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein: A. Life support devices or systems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in significant injury to the user. B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support dev ices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems. Copyright © 2011, Diodes Incorporated www.diodes.com