ZXCT1051 Precision wide input range current monitor Description The ZXCT1051 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 ZXCT1051 can be used on the high or low side of the load. The ZXCT1051 provides a fixed gain of 10 thereby removing the need for an additional resistor. 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. 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 • 50 µA quiescent current • Power management • 1% typical accuracy • Short circuit detection • SOT23-5 package Pin connections Typical application circuit VCC VSENSEVSENSE+ VSENSE- GND VOUT VSENSE- RSENSE VSENSE+ VCC VSENSE+ ZXCT1051 GND VOUT VOUT Ordering information Order code Package Partmark Reel size (inches) Tape width (mm) Quantity per reel ZXCT1051E5TA SOT23-5 1051 7 8 3,000 Issue 2 - November 2006 © Zetex Semiconductors plc 2006 1 www.zetex.com ZXCT1051 Absolute maximum ratings VCC max. 20V Voltage on VSENSE- and VSENSE+ -0.6 to VCC Voltage on all other pins -0.6V and VCC +0.6V VSENSE "(VSENSE+) - (VSENSE-) 500mV Operating temperature, Tamb -40 to 125°C Storage temperature -55 to 150°C Maximum junction temperature 150°C Package power dissipation 300mW at Tamb = 25°C (de-rate to zero at 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 Parameter Min. Max. Units 0 VCC-2 V 2.7 20 V VSENSE+ Common-mode sense input range VCC Supply voltage range VSENSE Differential sense input voltage range 0 0.3 V VOUT Output voltage range 0 VCC - 2 V Tamb Ambient temperature range -40 125 °C Pin function table Pin Name Description 1 VCC This is the analog supply and provides power to internal circuitry 2 GND Ground pin 3 OUT Output voltage pin. 4 VSENSE+ This is the positive input of the current monitor and has an input range from 0V up to VCC – 2V. 5 VSENSE- 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. Issue 2 - November 2006 © Zetex Semiconductors plc 2006 2 www.zetex.com ZXCT1051 Electrical characteristics Test conditions Tamb = 25°C, VSENSE+ = 10V, VCC = 12V, VSENSE = 100mV Symbol Parameter Conditions Min. Typ. Max. IQ VCC pin current VSENSE = 0V VOUT Output voltage VSENSE = 0V =30mV =100mV =150mV 45 70 µA 6 300 1.00 1.50 15 309 1.02 1.55 mV mV V V ISENSE+ VSENSE+ input current VSENSE = 0V 10 150 nA ISENSE- VSENSE- input current VSENSE = 0V 60 150 nA VOUT TC VOUT variation with temperature 300 ppm/°C ROUT Output resistance Gain VOUT/VSENSE Accuracy Total output error BW Bandwidth 0 291 0.98 1.45 See note (b) 2.5 3.75 Units 5 k⍀ 2 % 10 -2 VSENSE(DC) VSENSE(AC) = 10mV = 10mVPP CL = 5pF, VSENSE(DC) = 100mV 300 kHz 1 MHz PSRR Power supply VCC = 2.7V to 20V rejection ratio refered VSENSE- = 0V to output 58 dB CMRR Common mode VCC = 20V rejection ratio refered VSENSE+ = 0 to 18V to output 66 dB NOTES: (a) VSENSE = "VSENSE+" - "VSENSE-" (b) Temperature dependent measurements are extracted from characterization and simulation results. Issue 2 - November 2006 © Zetex Semiconductors plc 2006 3 www.zetex.com ZXCT1051 ICC Supply Current (A) ICC Supply Current (A) Typical characteristics 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 2 - November 2006 © Zetex Semiconductors plc 2006 Sense- Current v Sense Voltage 4 www.zetex.com ZXCT1051 10 1 ∆VOUT Output Voltage (mV) VOUT - Output Voltage (V) Typical characteristics 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 10.0 9.9 -15 -10 -5 0 5 10 µ 15 20 0 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 2 - November 2006 © Zetex Semiconductors plc 2006 100m 150m Incremental Gain v Sense Voltage ∆VOUT - Output Voltage (mV) ∆VOUT - Output Voltage (mV) VOUT v Load Current 50m 12 8 4 0 -4 -8 -12 0 5 10 15 20 Supply Characteristic 5 www.zetex.com ZXCT1051 Typical characteristics 70 Supply Rejection (dB) 20 Gain (dB) 10 0 -10 -20 -30 -40 -50 -60 100 1k 10k 100k 1M 60 50 40 30 20 10 0 10M 1000 10000 100000 1E7 PSRR 1.2 90 VOUT - Output Voltage (V) Common Mode Rejection (dB) Bandwidth 1000000 80 70 60 50 40 30 20 10 0 100 1k 10k 100k 1.0 0.8 0.6 0.4 0.2 0.0 0 1M CMRR 2 4 µ 6 8 10 Large Signal Pulse Response 12 VOUT - Output Voltage (V) VOUT - Output Voltage (V) 1.02 1.00 10 0.98 0.96 0.94 0.92 0.90 0.88 0 2 4 µ 6 8 10 © Zetex Semiconductors plc 2006 6 4 2 0 0 Small Signal Pulse Response Issue 2 - November 2006 8 5 10 15 20 25 µ 30 35 40 Turn on/off Characteristic 6 www.zetex.com ZXCT1051 Application information The ZXCT1051 is Zetex’ first current monitor with 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 ZXCT1051 draws very little current (<1µA) from the lines being sensed. The separate VCC pin enables the ZXCT1051 to be operated at sense line voltages down to 0V, where the ZXCT1021 would switch off. This feature enables the ZXCT1051 to be used to sense the currents flowing through lines that have been shorted to ground and is Zetex’ first current monitor to do this. RSENSE VRAIL VSENSE+ VSENSE- VCC Load Q1 RSH VOUT RG GND GND Basic operation Load current from VIN is drawn through RSENSE developing a voltage VSENSE across the ZXCT1051. The internal amplifier forces VSENSE across internal resistance RSH causing a current to flow through transistor Q1. This current is then converted to a voltage by RG. A ratio of 10:1 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 gain equation of the ZXCT1051 is: RG V SENSE = I L R SENSE ----------- × 1 R SH 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 VSENSE- pin and the load. For best performance RSENSE should be connected as close to the VSENSE+ and VSENSE- pins thus minimizing any series resistance with RSENSE. Issue 2 - November 2006 © Zetex Semiconductors plc 2006 7 www.zetex.com ZXCT1051 The ZXCT1051 has been designed to allow it to operate from supplies (VCC) ranging from 2.7V to 20V while sensing common mode signals from 0V up to VCC -2V. When choosing appropriate values for RSENSE a compromise must be reached between in-line signal loss (including potential power dissipation effects) and small signal accuracy. Higher values for RSENSE gives better accuracy at low load currents by reducing the inaccuracies due to internal offsets. For best operation the ZXCT1051 has been designed to operate with VSENSE of the order of 50mV to 150mV. Due to the very nature of current monitors they tend to saturate at very low sense voltages. This is due to them being operated from single supply and that the basic configuration is that of a unipolar voltage to current to voltage converter. The internal amplifiers at the heart of the current monitor may well have a bipolar offset voltage but the output cannot go negative. For this reason the ZXCT1051 has been designed to operate in a linear manner over a VSENSE range of 10mV to 150mV range, however it will still be monotonic down to VSENSE of 0V. The device has a fixed DC voltage gain of 10; no external scaling resistors are required for the output. Output voltage is simply defined as: VOUT = gain x VSENSE (V) Issue 2 - November 2006 © Zetex Semiconductors plc 2006 8 www.zetex.com ZXCT1051 Packaging details - SOT23-5 DIM A A1 A2 b C D E E1 e e1 L a° Millimeters Min. 0.90 0.00 0.90 0.20 0.09 2.70 2.20 1.30 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 Issue 2 - November 2006 © Zetex Semiconductors plc 2006 9 www.zetex.com ZXCT1051 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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