DocID16873 Rev 3

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TSC103

Parameter definitions

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5

Parameter definitions

5.1

Common-mode rejection ratio (CMR)

The common-mode rejection ratio (CMR) measures the ability of the current-sensing

amplifier to reject any DC voltage applied on both inputs Vp and Vm. The CMR is referred

back to the input so that its effect can be compared with the applied differential signal. The

CMR is defined by the formula:

5.2

Supply voltage rejection ratio (SVR)

The supply-voltage rejection ratio (SVR) measures the ability of the current-sensing

amplifier to reject any variation of the supply voltage VCC. The SVR is referred back to the

input so that its effect can be compared with the applied differential signal. The SVR is

defined by the formula:

5.3

Gain (Av) and input offset voltage (Vos)

The input offset voltage is defined as the intersection between the linear regression of the

Vout vs. Vsense curve with the X-axis (see Figure 17). If Vout1 is the output voltage with

Vsense = Vsense1 and Vout2 is the output voltage with Vsense = Vsense2, then Vos can be

calculated with the following formula.

CMR

20

–

ΔVout

ΔVicm Av

⋅

------------------------------

log

⋅

=

SVR

20

–

ΔVout

ΔVCC Av

⋅

------------------------------

log

⋅

=

Vos

Vsense1

Vsense1 Vsense2

–

Vout1 Vout2

–

------------------------------------------------

Vout1

⋅

⎝⎠

⎛⎞

–

=