ZXCT1107/1109/1110

LOW POWER HIGH-SIDE CURRENT MONITORS

ZXCT1107/1109/1110

Document number: DS35033 Rev. 1 - 2

14 of 17

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MARCH 2011

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Figure 4. Protection and EMC Filtering

EMC Susceptibility

In many applications, the circuit is required to operate in the presence of RF radiation. This radiation is coupled into the

circuit via the supply or load connections and will often cause significant bias shift due to rectification within the integrated

provides significant attenuation in the VHF and UHF regions. The value of C1 is recommended to be in the range of 10pF to

47pF, leadless ceramic type.

PCB Layout Considerations

create noticeable error at currents of the order of 1A and greater. The PCB must be designed to provide the maximum

possible copper carrying current via the sense resistor, and the traces from the S+ and S- pins must be connected only to the

resistor pads. In this way, the effect of the copper is minimized.

If used, the capacitor C1 should be placed very close the input pins S+ and S-.

Application: High Voltage Current Monitor

The schematic of Figure 5 shows how the current monitor may be used in a high voltage application such as a TV LED

backlight system. In this configuration the 500V PNP transistor Q1 drops a large proportion of the supply voltage. Diode D2

limits the differential input voltage to a safe level under overload conditions. The voltage across U1 is limited by the zener

therefore limited to a few volts. An additional output clamping diode may be required for higher gains. R1 is chosen to

give a suitable bias current in D1 for the given supply voltage range.