ZXCT1050 Precision wide input range current monitor Description The ZXCT1050 is a wide input range current monitor, which operates over a range of input voltages from ground up to VCC-2V. As a result the ZXCT1050 can be used on the high or low side of the load. The very low offset voltage enables a typical accuracy of 1% for sense voltages of only 30mV, giving better tolerances for small sense resistors necessary at higher currents. The ZXCT1050 provides variable gain by using two external resistors. The first of which sets the transconductance and the second setting the overall gain. Features Applications • Accurate down to end current sensing • Power supply • Output voltage scaling x10 • DC motor and solenoid control • 0 to VCC-2V sense input range • Battery management • 2.7 to 20V supply range • Over current monitor • 50µA quiescent current • Power management • SOT23-5 package • Short circuit detection Pin connections VCC 1 Typical application circuit 5 RSENSE IN SENSE- RSHUNT GND 2 SENSE+ OUT 3 4 SENSE+ VCC SENSE- ZXCT1050 Load OUT OUT RGAIN Ordering information Order code ZXCT1050E5TA Pack Part mark Reel size (inches) Tape width (mm) Quantity per reel SOT23-5 1050 7 8 3000 Issue 1 - June 2007 © Zetex Semiconductors plc 2007 1 www.zetex.com ZXCT1050 Absolute maximum ratings VCC max. 20V Voltage on SENSE- and SENSE+ -0.6 to VCC Voltage on all other pins -0.6V and VCC +0.6V VSENSE = ‘(VSENSE+) - (VSENSE-)’ 500mV Operating temperature -40 to 125°C Storage temperature -55 to 150°C Maximum junction temperature 150°C Package power dissipation 300mW* at TA = 25°C (De-rate to zero for TJ = 150°C) Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for extended periods, may reduce device reliability. Recommended operating conditions VSENSE+ Parameter Common-mode sense input range Min. 0 Max. VCC-2 VCC Supply voltage range 2.7 20 Units V V VSENSE Differential sense input voltage range 10 300 mV VOUT Output voltage range 0 VCC-2 V TA Ambient temperature range -40 125 °C Recommended resistor gain setting combinations Gain RSH RG 10 20 50 100 20 50 100 7.5k⍀ 7.5k⍀ 7.5k⍀ 7.5k⍀ 3.75k⍀ 1.5k⍀ 750⍀ 3.75k⍀ 7.5k⍀ 18.7k⍀ 37.5k⍀ 3.75k⍀ 3.75k⍀ 3.75k⍀ Pin function table PIN 1 Name VCC Description This is the analog supply and provides power to internal circuitry. 2 3 GND OUT 4 SENSE+ Ground pin. Output pin. A resistor, RGAIN, connected from this pin pin down to ground develops an output voltage. This is the positive input of the current monitor and has an input range from 0V up to VCC – 2V. 5 SENSE- This is the negative input of the current monitor and has an input range from 0V up to VCC – 2V. The current through this pin varies with differential sense voltage. A resistor, RSHUNT, from this pin to the rail being sensed set the transconductance of the current monitor. Issue 1 - June 2007 © Zetex Semiconductors plc 2007 2 www.zetex.com ZXCT1050 Electrical characteristics Test conditions TA = 25°C, VSENSE+ = 10V, VCC = 12V, VSENSE = 100mV, RSH = 7.5k⍀, RG = 3.75k⍀. Symbol Parameter Conditions Min. Typ. Max. IQ VCC pin current VSENSE = 0V VOUT Output voltage VSENSE = 0V =30mV =100mV =150mV 45 70 µA 3 300 1.00 1.50 15 315 1.03 1.55 mV mV V V ISENSE+ VSENSE+ input current VSENSE = 0V 60 150 nA ISENSE- VSENSE- input current VSENSE = 0V 15 150 nA VOUT TC VOUT variation with temperature 300 ppm/°C Gain VOUT/VSENSE Accuracy Total output error BW Bandwidth 0 285 0.97 1.45 See note (*) Units 10 -3 VSENSE(DC) = 10mV VSENSE(AC) = 10mVPP CL = 5pF, VSENSE(DC) = 100mV 3 % 300 kHz 0.8 MHz PSRR Power supply rejection ratio VCC = 2.7V to 20V VSENSE+ = 0.7V 60 dB CMRR Common mode rejection ratio VCC = 20V VSENSE+ = 0 to 18V 70 dB NOTES: (*) Temperature dependent measurements are extracted from characterisation and simulation results. Issue 1 - June 2007 © Zetex Semiconductors plc 2007 3 www.zetex.com ZXCT1050 Typical characteristics ICC Supply Current (A) ICC Supply Current (A) RG = 3.75k⍀, RSH = 7.5k⍀ unless otherwise stated. Supply Current v Input Voltage IS- Sense Current (A) ICC Supply Current (A) Supply Current v Supply Voltage Sense- Current v Supply Voltage IS- Sense Current (A) Percentage Change IS- (%) Supply Current v Sense Voltage Sense- Current v Temperature Issue 1 - June 2007 © Zetex Semiconductors plc 2007 Sense- Current v Sense Voltage 4 www.zetex.com ZXCT1050 Typical characteristics 10 1 ΔVOUT Output Voltage (mV) VOUT - Output Voltage (V) RG = 3.75k⍀, RSH = 7.5k⍀ unless otherwise stated. 100m 10m 1E-3 0.01 0.1 5 0 -5 -40 -20 0 20 40 60 80 100 120 Temperature Characteristic 10.1 Incremental Gain VOUT - Output Voltage (mV) 1100 1050 1000 950 900 -20 -15 -10 -5 0 5 10 μ 15 10.0 9.9 20 18 16 14 12 10 8 6 4 2 0 -2 -4 -6 -8 0 2 4 6 8 10 12 14 16 18 20 Common Mode Characteristic Issue 1 - June 2007 © Zetex Semiconductors plc 2007 50m 100m 150m Incremental Gain v Sense Voltage ΔVOUT - Output Voltage (mV) ΔVOUT - Output Voltage (mV) VOUT v Load Current 0 12 8 4 0 -4 -8 -12 0 5 10 15 20 Supply Characteristic 5 www.zetex.com ZXCT1050 Typical characteristics RG = 3.75k⍀, RSH = 7.5k⍀ unless otherwise stated. Referred to 1V Issue 1 - June 2007 © Zetex Semiconductors plc 2007 6 www.zetex.com ZXCT1050 Applications information The ZXCT1050 is a current output version of the ZXCT1051 and as such uses a separate power supply pin. All biasing for the internal amplifiers comes from its separate VCC input and is not ‘line powered’, unlike the ZXCT1021. This means that at very small sense voltages the ZXCT1050 draws very little current (<1A) from the lines being sensed. The separate VCC pin enables the ZXCT1050 to be operated at sense line voltages down to 0V, where the ZXCT1021 would switch off. This feature enables the ZXCT1050 to be used to sense the currents flowing through lines that have been shorted to ground. VRAIL R SH R SENSE IL SENSE+ (4) (5) SENSE- VCC (1) Load Q1 Out (3) ZXCT1050 GND RG GND (2) Basic operation Load current, IL, from VRAIL is drawn through RSENSE developing a voltage VSENSE across the sense inputs of the ZXCT1050. The internal amplifier forces VSENSE across external resistance RSH (internal on the ZXCT1051) causing a current to flow through transistor Q1 and out of the output pin, OUT. This current is then converted to a voltage by a resistor, RG, between OUT and GND. The overall gain of the ZXCT1050 is determined by the following expression: RG GAIN = 20 × ---------R SH A ratio of 1:2 between RSH and RG creates the fixed gain of 10 with an output impedance equal to RG (see electrical characteristics for output current-voltage characteristics). The ZXCT1050 has both RG and RSH external. This allows RG and RSH to be varied so that the required gain can be achieved at the required output impedance. For low power applications both RG and RSH can be increased whereas for driving low impedance RG and RSH can be decreased. The maximum recommended value for RG is 40k⍀ and the maximum recommended value for RSH is 10k⍀. Large values of RSH start increasing the effective input offset error, while large values of RG can created load errors and reduce bandwidths. The maximum differential input voltage, VSENSE, is 150mV (IL * RSENSE); however voltages up to 500mV will not damage it. This can be increased further by the inclusion of a resistor, RLIM, between the SENSE+ pin and the rail being sensed, VRAIL. For best performance RSENSE should be connected as close to the SENSE+ and SENSE- pins thus minimizing any series resistance with RSENSE. Issue 1 - June 2007 © Zetex Semiconductors plc 2007 7 www.zetex.com ZXCT1050 Intentionally left blank Issue 1 - June 2007 © Zetex Semiconductors plc 2007 8 www.zetex.com ZXCT1050 Package outline - SOT23-5 DIM A A1 A2 b c D E E1 e e1 L L2 a° Millimeters Min. 0.01 0.84 0.30 0.12 Inches Max. 1.00 0.10 0.90 0.45 0.20 Min. 0.0003 0.0330 0.0118 0.0047 2.90 BSC 2.80 BSC 1.60 BSC 0.95 BSC 1.90 BSC 0.30 0.114 BSC 0.110 BSC 0.062 BSC 0.0374 BSC 0.0748 BSC 0.50 0.0118 0.25 BSC 4° Max. 0.0393 0.0039 0.0354 0.0177 0.0078 0.0196 0.010 BSC 12° 4° 12° Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches Issue 1 - June 2007 © Zetex Semiconductors plc 2007 9 www.zetex.com ZXCT1050 Definitions Product change Zetex Semiconductors reserves the right to alter, without notice, specifications, design, price or conditions of supply of any product or service. Customers are solely responsible for obtaining the latest relevant information before placing orders. Applications disclaimer The circuits in this design/application note are offered as design ideas. It is the responsibility of the user to ensure that the circuit is fit for the user’s application and meets with the user’s requirements. No representation or warranty is given and no liability whatsoever is assumed by Zetex with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights arising from such use or otherwise. Zetex does not assume any legal responsibility or will not be held legally liable (whether in contract, tort (including negligence), breach of statutory duty, restriction or otherwise) for any damages, loss of profit, business, contract, opportunity or consequential loss in the use of these circuit applications, under any circumstances. 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Samples may be available “Active” Product status recommended for new designs “Last time buy (LTB)” Device will be discontinued and last time buy period and delivery is in effect “Not recommended for new designs” Device is still in production to support existing designs and production “Obsolete” Production has been discontinued Datasheet status key: “Draft version” This term denotes a very early datasheet version and contains highly provisional information, which may change in any manner without notice. “Provisional version” This term denotes a pre-release datasheet. It provides a clear indication of anticipated performance. However, changes to the test conditions and specifications may occur, at any time and without notice. “Issue” This term denotes an issued datasheet containing finalized specifications. However, changes to specifications may occur, at any time and without notice. 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