ZXCT1107Q/09Q/10Q

Document number: DS37002 Rev. 3 - 2

13 of 17

www.diodes.com

October 2018

© Diodes Incorporated

ZXCT1107Q/09Q/10Q

Protection against Load Short Circuit

In the event of a load short circuit or overload, a large proportion of the supply voltage may appear between the sense terminals. The supply may be

current limited, but there is normally a large reservoir capacitor which can deliver enough energy to damage the ZXCT11xx before the supply voltage

falls to a safe level due to current limit activation.

limits the current and therefore protects the current monitor device against load short circuit without introducing significant current measurement error.

S+

ZXCT1107

or

ZXCT1109

S-

OUT

LOAD

GND

OUTPUT

4.7k

C1

10pF

S+

ZXCT1110

S-

OUT

LOAD

GND

GND

OUTPUT

C1

10pF

4.7k

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 circuit. The bias shift may lead to erroneous operation of

recommended to be in the range of 10pF to 47pF, leadless ceramic type.

PCB Layout Considerations

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 an Electric Vehicle 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 diode D1. The output current of U1 is limited to about 3mA

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.

S+

ZXCT1107,

ZXCT1109

or

ZXCT1110

S-

200V to 450V

OUT

LOAD

GND

GND

LOW VOLTAGE

OUTPUT

C1

10pF

4.7k

12V

BAL99

2.2M

Q1

FMMT560

D1

D2

R1

U1

Figure 5 400V Current Monitor