ZXCT1009_07 Datasheet, PDF (7/9 Pages) Zetex Semiconductors – HIGH-SIDE CURRENT MONITOR

APPLICATIONS INFORMATION (Continued)
PCB trace shunt resistor for low
cost solution
The figure below shows output characteristics of the
device when using a PCB resistive trace for a low cost
solution in replacement for a conventional shunt
resistor. The graph shows the linear rise in voltage
across the resistor due to the PTC of the material and
demonstrates how this rise in resistance value over
temperature compensates for the NTC of the device.
The figure opposite shows a PCB layout suggestion.
The resistor section is 25mm x 0.25mm giving
approximately 150mΩ using 1oz copper. The data
for the normalised graph was obtained using a 1A
load current and a 100Ω output resistor. An
electronic version of the PCB layout is available at
www.zetex.com/isense.
ZXCT1009
Vout
Vin
GND
Load
Actual Size
ZXCT1009
ZXCT1009
Vout
Vin
GND
Load
1.4
1.2
1.0
Voltage across
Copper Sense
Resistor
V_OUT with Copper
Sense Resistor
0.8
V_OUT with Ideal
Sense Resistor
-40 -20 0 20 40 60 80 100 120 140
Temperature (°C)
Effect of Sense Resistor Material
on Temperature Performance
Layout shows area of shunt
resistor compared to SOT23
package. Not actual size
ISSUE 10 - JULY 2007
7
SEMICONDUCTORS