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A Product Line of Diodes Incorporated
ZXCT1081
HIGH VOLTAGE HIGH-SIDE CURRENT MONITOR
Description
The ZXCT1081 is a high side current sense monitor with a gain of 10 and a voltage output. Using this device eliminates the need to disrupt the ground plane when sensing a load current. The wide input voltage range of 40V down to as low as 3V make it suitable for a range of applications; including systems operating from industrial 24-28V rails and power supplies.
Pin Assignments
VCC 1 GND 2 OUT 3
4 SENSE+ 5 SENSE-
Features
* * * * * 3V to 40V continuous high side voltage Accurate high-side current sensing Output voltage scaling x10 4.5V to 12V VCC range Low quiescent current: o 80 A supply pin o * * 30 A ISENSE+ SOT23-5 package -40C to 125C ambient temperature range
Applications
* * * * * * Automotive current measurement Industrial applications current measurement Battery management Over current monitor Power management Power adapters
Typical Application Circuit
VIN R SENSE
4 SENSE+
5 SENSE-
VCC
1
Vcc
ZXCT1081
OUT 3
GND 2
V OUT
ZXCT1081
Document number: DS32102 Rev. 1 - 2
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ZXCT1081 Pin Description
Pin 1 2 3 4 5 Name VCC GND OUT SENSE+ SENSEDescription This is the analogue 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 40V (60V transient) down to 3V. 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 40V (60V transient) down to 3V
Absolute Maximum Ratings
Parameter Continuous Voltage on SENSE+ and SENSETransient Voltage on SENSE+ and SENSEVoltage On All Other Pins Differential Sense Voltage, VSENSE Operating Temperature Storage Temperature Maximum Junction Temperature Package Power Dissipation Rating -0.6 and 45 -0.6 and 65 -0.6 and 14 800 -40 to 125 -55 to 150 125 300 @ TA= 25C
(de-rate to zero at 125C)
Unit V V V mV C C C mW
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
Symbol VIN VCC VSENSE VOUT TJ Parameter Common-Mode Sense+ Input Range Supply Voltage Range Differential Sense Input Voltage Range Output Voltage Range Ambient Temperature Range Min 3 4.5 0 0 -40 Max 40 12 0.15 1.5 125 Units V V V V C
ZXCT1081
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ZXCT1081 Electrical Characteristics (Test conditions: TA = 25C, VIN = 12V, VCC = 5V, VSENSE(a) = 100mV unless otherwise stated)
Symbol ICC ISENSE+ ISENSEVO(0) VO(10) Gain VOUTTC ACC IOH IOL PSRR CMRR BW
Notes:
(d)
Parameter VCC Supply Current SENSE+ Input Current SENSE- Input Current Zero VSENSE error (c) Output Offset Voltage VOUT/VSENSE VOUT Variation with Temperature Total Output Error Output Source Current Output Sink Current VCC Supply Rejection Ration Common-Mode Sense Rejection Ratio -3dB Small Signal Bandwidth
(a) (a) (b)
Condition VCC = 12V
VSENSE = 0V (a) VSENSE = 10mV (a) VSENSE = 10mV to 150mV
(a)
Min. 40 15 10 0 -30 9.95 -3
Typ. 80 30 40
10 30 1 20 60 75 50
Max. 120 60 80 35 +30 10.05 3
Unit A A nA mV mV ppm/C % mA A dB dB kHz
VOUT = 30mV VOUT = +30mV VCC = 4.5V to 12V VIN + 40V to 3V (a) VSENSE (AC) = 10mVpp
54 60
(a) VSENSE = "VSENSE+" - "VSENSE-" (b) The ZXCT1081 operates from a positive power rail and the internal voltage-current converter current flow is unidirectional; these result in the output offset voltage for VSENSE = 0V always being positive. (c) For VSENSE > 10mV, the internal voltage-current converter is fully linear. This enables a true offset to be defined and used. VO(10) is expressed as the variance about an output voltage of 100mV>. (d)Temperature dependent measurements are extracted from characterization and simulation results.
ZXCT1081
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ZXCT1081 Typical Operating Conditions (Test conditions: TA = 25C, VCC = 5V, VSENSE+ = 12V, VSENSE = 100mV)
ZXCT1081
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ZXCT1081 Typical Operating Conditions (Cont.)
ZXCT1081
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ZXCT1081 Typical Operating Conditions (Cont.)
ZXCT1081
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ZXCT1081 Typical Operating Conditions (Cont.)
ZXCT1081
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ZXCT1081 Application Information
The ZXCT1081 has been designed to allow it to operate with 5V supply rails while sensing common mode signals up to 40V. This makes it well suited to a wide range of industrial and power supply monitoring applications that require the interface to 5V systems while sensing much higher voltages. To allow this its VCC pin can be used independently of SENSE+. Figure 1 shows the basic configuration of the ZXCT1081.
Input
SENSE+
RSENSE
RSH
Load SENSE-
ZXCT1081
VCC M1 OUT
A2 +1
A1
RG
GND
Figure 1 Typical Configuration of ZXCT1081
Load current from the input is drawn through RSENSE developing a voltage VSENSE across the inputs of the ZXCT1081. The internal amplifier forces VSENSE across internal resistance RSH causing a current to flow through MOSFET M1. This current is then converted to a voltage by RG. A ratio of 10:1 between RG and RSH creates the fixed gain of 10. The output is then buffered by the unity gain buffer. The gain equation of the ZXCT1081 is: VOUT = IL RSENSE RG RSH x 1 = x RSENSE x 10
The maximum recommended differential input voltage, VSENSE, is 150mV; it will however withstand voltages up to 800m. This can be increased further by the inclusion of a resistor, RLIM, between SENSE- pin and the load; typical value is of the order of 10k .
ZXCT1081
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ZXCT1081
RSENSE RLIM CD
SENSE+
SENSE-
ZXCT1081
Figure 2 Protection/Error Sources for ZXCT1081
Capacitor CD provides high frequency transient decoupling when used with RLIM; typical values are of the order 10pF. For best performance RSENSE should be connected as close to the SENSE+ (and SENSE ) pins; minimizing any series resistance with RSENSE. 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 ZXCT1081 has been designed to operate with VSENSE of the order of 50mV to 150mV. Current monitors' basic configuration is that of a unipolar voltage to current to voltage converter powered from a single supply rail. The internal amplifier at the heart of the current monitor may well have a bipolar offset voltage but the output cannot go negative; this results in current monitors saturating at very low sense voltages. As a result of this phenomenon the ZXCT1081 has been specified 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. It is for this very reason that Zetex has specified an input offset voltage (VO(10)) at 10mV. The output voltage for any VSENSE voltage from 10mV to 150mV can be calculated as follows: VOUT = (VSENSE) xG + VO(10) Alternatively the load current can be expressed as: VOUT - VO(10) GxRSENSE
IL =
ZXCT1081
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ZXCT1081
Package Outline - 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 0.95 REF 1.90 REF 0.10 0 0.60 30 0.0039 0 Max 1.45 0.15 1.3 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
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
ZXCT1081
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ZXCT1081
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ZXCT1081
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