ZXCT1081 datasheet(9/11 Pages) DIODES

9 / 11 page

ZXCT1081

Document number: DS32102 Rev. 1 - 2

9 of 11

www.diodes.com

March 2010

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RSENSE

RLIM

ZXCT1081

SENSE+

SENSE-

Figure 2 Protection/Error Sources for ZXCT1081

Capacitor CD provides high frequency transient decoupling when used with RLIM; typical values are of the order 10pF.

For best performance RSENSE should be connected as close to the SENSE+ (and SENSE ) pins; minimizing any series

resistance with RSENSE.

When choosing appropriate values for RSENSE a compromise must be reached between in-line signal loss (including

potential power dissipation effects) and small signal accuracy.

Higher values for RSENSE gives better accuracy at low load currents by reducing the inaccuracies due to internal offsets. For

best operation the ZXCT1081 has been designed to operate with VSENSE of the order of 50mV to 150mV.

Current monitors' basic configuration is that of a unipolar voltage to current to voltage converter powered from a single

supply rail. The internal amplifier at the heart of the current monitor may well have a bipolar offset voltage but the output

cannot go negative; this results in current monitors saturating at very low sense voltages.

As a result of this phenomenon the ZXCT1081 has been specified to operate in a linear manner over a VSENSE range of

10mV to 150mV range, however it will still be monotonic down to VSENSE of 0V.

It is for this very reason that Zetex has specified an input offset voltage (VO(10)) at 10mV. The output voltage for any VSENSE

voltage from 10mV to 150mV can be calculated as follows:

VOUT = (VSENSE) xG + VO(10)

Alternatively the load current can be expressed as:

IL =

VOUT – VO(10)

GxRSENSE

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