ZXCT1107/1109/1110

LOW POWER HIGH-SIDE CURRENT MONITORS

ZXCT1107/1109/1110

Document number: DS35033 Rev. 1 - 2

10 of 17

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MARCH 2011

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Application Information

Description

The current monitor ICs ZXCT1107, ZXCT1109 and ZXCT1110 all use a similar application circuit topology for high-side

current sensing, with small differences. The ZXCT1110 has a separate ground pin whereas the ZXCT1107 and ZXCT1109

do not. The use of ZXCT1110 allows reduction of the absolute current measurement error in some applications by providing

a reduced output offset current. The ZXCT1107 provides a mirror image pin assignment of the ZXCT1109 to ease PCB

layout in very small equipment designs.

convenient processing by a further device, such as a comparator, amplifier or analog-to-digital converter within a

microcontroller system.

The current monitor output current is defined through the nominal transconductance of 4mA/V.

Amp

Equation 1

Then the resistors determine the output voltage as described below.

S+

ZXCT1110

S-

OUT

LOAD

GND

GND

OUTPUT

Figure 1. Basic Application Circuit

Calculation of Resistor Values

and accuracy for the given temperature range. The resistor must be small enough to avoid excessive volt drop between the

power supply and the load. However, the resistor must be large enough to avoid excessive current measurement error,

particularly random errors.

In a typical application, a digital system, perhaps a microcontroller, is set up to monitor the current. At a certain threshold

At this current level, the current

measurement error must be limited to a known value.

The total percentage error comprises the inherent error in the

The ZXCT1107/ZXCT1109 absolute

error is shown in Table 1 with error limits drawn from the table of Electrical Characteristics above. This error varies with