ZXCT1107Q/09Q/10Q

Document number: DS37002 Rev. 3 - 2

12 of 17

www.diodes.com

October 2018

© Diodes Incorporated

ZXCT1107Q/09Q/10Q

Design Example

A current monitor is required to provide an output voltage of 2V ±6% when the load current of a 12V supply is 2A. Resistors are available with 1%

tolerance.

The sense and output resistors will contribute a total possible error of 2%, so the ZXCT11xxQ error must not exceed 4%. From Table 1, the error of

ZXCT1107Q/09Q will be 3.4% if the sense voltage is 100mV. This satisfies the total error requirement of 6%.

Equation 5 gives:

Equation 6 gives:

1

.

0

*

004

.

0

2

= 5k

Ω

A suitable preferred value is 5.1k

Ω. This gives a systematic error of

+2%, which can be compensated elsewhere in the system if desired.

Figure 2 shows the resulting schematic.

S+

ZXCT1107

or

ZXCT1109

S-

50mΩ

OUT

LOAD

GND

5k1

OUTPUT

Figure 2 Example Circuit using ZXCT1107Q/09Q

Alternatively, the ZXCT1110Q may be used with a reduced sense voltage if desired. From Equation 4,

with ε=4%,

8

.

1

082

.

0







= 0.082/(4-1.8) = 37.2mV

Equation 5 gives:

A suitable preferred value is 20m

Ω. Then the sense voltage will be 2A * 20mΩ = 40mV.

Equation 6 gives:

04

.

0

*

004

.

0

2

= 12500

Ω

A suitable preferred value is 13k

Ω.

The alternative example circuit using the ZXCT1110Q with a sense

voltage of 40mV is shown in Figure 3, giving the required overall

accuracy of ±6%.

S+

ZXCT1110

S-

20mΩ

OUT

LOAD

GND

13k

GND

OUTPUT

Figure 3 Example Circuit using ZXCT1110Q