Description ZXCT1009 is a high-side current detection monitor. With this device, there is no need to interrupt the ground plane when inducing load currents. It generates a high side voltage through a current shunt resistor and converts it to a proportional output current. AuserDefinedOutputresStorscales input the output current to the ground reference voltage. A wide input voltage range of 20 volts to slo is 2.5 volts, making it suitable for a range of applications. The minimum operating current is only 4A, which, coupled with its SOT23 package, makes it a unique solution for portable battery devices.
Features, Low Cost, Accurate High Side Current Sensing, Output Voltage Scaling, Up to 2.5V Sense Voltage, 2.5V– 20V Supply Range, 4µA Quiescent Current, 1% Typical Accuracy, SOT2 3 and SM8 Package Applications, Battery Charger, Smart Battery Pack, DC Motor Control, Over Current Monitor, Power Management, Level Shifting, Programmable Current Source
ZXCT1009

Absolute Maximum Ratings Voltage on Any Pin
-0.6V to 20V (relative to Iout)
Continuous output current
25mA continuous induced voltage VIN+0.5V>VIN>VIN-5V 8224 ;
Operating temperature
-40 to 85 degrees Celsius storage temperature
-55 to 125 °C
Package power consumption (TA=25 degrees Celsius)
Salt 23
450 MW - derate to zero at 125°C
Operation at 2 watts above the absolute maximum rating may cause device failure. Extended operating hours at Absolute Maximum Ratings can reduce device reliability.
Electrical characteristics test conditions TA=25°C, Vin=5V, Rout=100Ω.

If Rload represents any load, including DC motors, rechargeable batteries, or other circuits that need to be monitored, Rsense can be selected based on specific requirements for accuracy, size, and power rating.
Application Information (continued)

Li-Ion Charger Circuit The above diagram shows the ZXCT1009 supporting the benchmark bq2954 charge management IC. Most of the bq2954's supporting components are omitted for clarity. The design also uses the ZETEX FZT789A high current super PNP as the switching transistor in the DC-DC buck converter and the FZMT451 as the driving NPN for the FZT789A, the circuit can be configured to charge four Li-Ion batteries with a current of 1.25A, charging can be done at Termination at maximum voltage, selectable minimum current, or maximum pause time. The switching frequency of the PWM loop is approximately
120 kHz.
The ZXCT1009 is intended to be a drop-in functional replacement for the ZDS1009, which incorporates a complete design by Unitrode/Texas Instruments on the above-mentioned Li-Ion charger circuit. Reference: DVS2954S1H Li-ion Charger Development System.
Transient protection An additional resistor, Rlim can be connected in series with Rout to limit the current of Iout. Any circuits connected to the output will be protected from input voltage transients. This is especially useful in automotive applications where load shedding and other common transients need to be considered.

Application Information (continued)
PCB Tracking Parallel Resistors for Low Cost Solutions
Output characteristics of the device when PCB resistors replace traditional parallel resistors. The graph shows the linear rise in voltage applied to the resistance of the material and illustrates how the rise in resistance value exceeds the temperature compensation of the device.
The diagram opposite shows a PCB layout recommendation. The resistance part is 25mm x 0.25mm, about 150μm, using 1OZ copper.