ZXCT1107/1109/1110

LOW POWER HIGH-SIDE CURRENT MONITORS

ZXCT1107/1109/1110

Document number: DS35033 Rev. 1 - 2

13 of 17

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MARCH 2011

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Alternatively, the ZXCT1110 may be used with a reduced sense voltage if desired. From Equation 3, with

ε=4%,

8

.

1

082

.

0

V

SENSE

−

ε

=

= 0.082/(4-1.8) = 37.2mV

Equation 4 gives

A suitable preferred value is 20m

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

Equation 5 gives

04

.

0

*

004

.

0

2

R

= 12500

Ω

A suitable preferred value is 13k

Ω.

The alternative example circuit using the ZXCT1110 with a sense voltage of 40mV is shown in Figure 3, giving the required

overall accuracy of ±6%.

S+

ZXCT1110

S-

20m

Ω

OUT

LOAD

GND

13k

GND

OUTPUT

Figure 3. Example Circuit using ZXCT1110

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.

The ZXCT11xx is rated for a maximum sense voltage of +0.8V, but is safe if the input current is limited to ±8.5mA. In Figure

introducing significant current measurement error.