CS30 datasheet(12/18 Pages) STMICROELECTRONICS

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Parameter definitions

CS30

12/18

DocID026040 Rev 1

Parameter definitions

4.1

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:

4.2

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:

4.3

Gain (Av) and input offset voltage (Vos)

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

Vout versus Vsense curve with the X-axis (see Figure 20). If Vout1 is the output voltage with

Vsense=Vsense1=50mV and Vout2 is the output voltage with Vsense=Vsense2=5mV, then Vos

can be calculated with the following formula:

The amplification gain Av is defined as the ratio between output voltage and input differential

voltage:

CMR

–

ΔVout

ΔVicm Av

⋅

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

log

⋅

SVR

–

ΔVout

ΔVCC Av

⋅

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

log

⋅

Vos

Vsense1

Vsense1 Vsense2

–

Vout1 Vout2

–

------------------------------------------------ Vout1

⋅





–

Vout

Vsense

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

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