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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 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 ZXCT1051 provides a fixed gain of 10 thereby removing the need for an additional resistor.
Features
* * * * * * * Accurate down to end current sensing Output voltage scaling x10 0 to VCC-2V sense input range 2.7 to 20V supply range 50 A quiescent current 1% typical accuracy SOT23-5 package
Applications
* * * * * * Power supply DC motor and solenoid control Battery management Over current monitor Power management Short circuit detection
Pin connections
Typical application circuit
VSENSE+ RSENSE VSENSE-
VCC GND VOUT
VSENSEVSENSE+ VSENSEVCC ZXCT1051 GND VOUT
VSENSE+
VOUT
Ordering information
Order code ZXCT1051E5TA Package SOT23-5 Partmark 1051 Reel size (inches) 7 Tape width (mm) 8 Quantity per reel 3,000
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ZXCT1051
Absolute maximum ratings
VCC max. Voltage on VSENSE- and VSENSE+ Voltage on all other pins VSENSE "(VSENSE+) - (VSENSE-) Operating temperature, TA Storage temperature Maximum junction temperature Package power dissipation 20V -0.6 to VCC -0.6V and VCC +0.6V 500 mV -40 to 125C -55 to 150C 150C 300mW at TA = 25C (de-rate to zero at 150C)
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 VSENSE+ VCC VSENSE VOUT TA Common-mode sense input range Supply voltage range Differential sense input voltage range Output voltage range Ambient temperature range Min. 0 2.7 0 0 -40 Max. VCC-2 20 0.3 VCC - 2 125 Units V V V V C
Pin function table
PIN 1 2 3 4 Name VCC GND OUT VSENSE+ Description This is the analog supply and provides power to internal circuitry Ground pin Output voltage pin. NMOS source follower with 20A bias to ground This is the positive 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 This is the negative input of the current monitor and has an input range from 0V up to VCC - 2V
5
VSENSE-
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ZXCT1051
Electrical characteristics
Test conditions TA = 25C, VSENSE+ = 10V, VCC = 12V, VSENSE = 100mV Symbol IQ VOUT Parameter VCC pin current Output voltage Conditions VSENSE = 0V VSENSE = 0V =30mV =100mV =150mV 0 291 0.98 1.45 Min. Typ. 45 3 300 1.00 1.50 TBD 15 Max. 70 10 309 1.02 1.55 TBD 150 300 2.5 3.75 10 -2 VSENSE(DC) VSENSE(AC) = 10mV = 10mVPP CL = 5pF, VSENSE(DC) = 100mV VCC = 2.7V to 20V VSENSE+ = 0.7V VCC = 20V VSENSE+ = 0 to 18V TBD 300 1 TBD 2 % kHz MHz dB 5 Units A mV mV V V A nA ppm/C k
ISENSE+ ISENSEVOUT TC ROUT Gain Accuracy BW
VSENSE+ input current VSENSE = 0V VSENSE- input current VSENSE = 0V VOUT variation with temperature Output resistance VOUT/VSENSE Total output error Bandwidth See note (b)
PSRR
Power supply rejection ratio Common mode rejection ratio
CMRR
TBD
TBD
dB
NOTES: (a) VSENSE = "VSENSE+" - "VSENSE-" (b) Temperature dependent measurements are extracted from characterization and simulation results.
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Typical characteristics
Test conditions unless otherwise stated: TA = 25C, VCC = 12V, VSENSE+ =10V, VSENSE = 100mV DC characteristics Y-axis ICC X-axis VCC (0 to 20V) VCC (2 to 20V) ISENSE+ ISENSE+ ISENSEVOUT VOUT VOH VOL Differential gain VOUT VOUT VSENSE+ (0 to 18V) TA VSENSE+ (0 to 18V) VSENSE TA IOH source IOL sink VSENSE VSENSE+ (0 to 18V) VCC (0 to 20V) Variables TA = -40, 25, 85, 125C, VSENSE = 0V VSENSE+ = 0V TA = -40, 25, 85, 125C, VSENSE = 0V VSENSE+ = VCC - 2V TA=25C, VSENSE = 0V, VCC = 20V VSENSE = 0V, VSENSE+ = 18V VCC = 20V TA=25C, VSENSE = 0V, VCC = 20V TA = -40C, 0C, 25C, 85C, 125C. VSENSE = 10mV, 50mV, 100mV. Output source current swept TA = -40C, 25C, 125C. Differential sense voltage swept and differential gain calculated VSENSE = 10mV, 50mV, 100mV, 150mV TA = -40C, 0C, 25C, 85C, 125C. VSENSE = 10mV, 50mV, 100mV, 150mV TA = -40C, 0C, 25C, 85C, 125C.
AC and transient characteristics Small signal bandwidth Large signal response Small signal response PSRR CMRR Frequency Time Time Frequency Frequency VSENSE(DC) = 10mV, VSENSE(AC) = 10mVPP VSENSE(DC) = 100mV, VSENSE(AC) = 10mVPP VSENSE+ = 12V, VSENSE- = 0V to -0.2V to +0.2V to 0V VSENSE+ = 12V, VSENSE- = 0V to -0.01V to +0.1V to 0V VCC(AC) = 10mVPP VSENSE+(AC) = 10mVPP
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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 (<1A) 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+ VCC Load VSENSE-
Q1
RSH RG
VOUT
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 ---------- x 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.
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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)
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Packaging details - SOT23-5
DIM A A1 A2 b C D E E1 e e1 L a Min. 0.90 0.00 0.90 0.20 0.09 2.70 2.20 1.30
Millimeters Max. 1.45 0.15 1.30 0.50 0.26 3.10 3.20 1.80 0.95 REF 1.90 REF 0.10 0 0.60 30 0.0039 0 Min. 0.0354 0.00 0.0354 0.0078 0.0035 0.1062 0.0866 0.0511
Inches Max. 0.0570 0.0059 0.0511 0.0196 0.0102 0.1220 0.1181 0.0708 0.0374 REF 0.0748 REF 0.0236 30
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
Europe Zetex GmbH Streitfeldstrae 19 D-81673 Munchen 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
For international sales offices, agents and distributors please go to www.zetex.com/salesnetwork This publication is issued to provide outline information only which (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.
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