ADE7978 datasheet(34/125 Pages) AD

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ADE7978/ADE7933/ADE7932/ADE7923

Data Sheet

Rev. D | Page 34 of 125

Gain Error

Gain error in the ADE7933/ADE7932 and ADE7923 represents

the difference between the measured ADC output code (minus

the offset) and the ideal output code (see the Current Channel

ADC and Voltage Channel ADCs sections). The difference is

expressed as a percentage of the ideal code and represents the

overall gain error of one current or voltage channel.

Gain Drift over Temperature

Gain drift is the change in gain over temperature. The gain

temperature coefficient includes the temperature variation of the

ADC gain and of the internal voltage reference. Gain drift over

temperature represents the overall temperature coefficient of one

current or voltage channel. With the internal voltage reference

in use, the ADC gain is measured at −40°C, +25°C, and +85°C.

The temperature coefficient is computed as follows:

Drift =

(

)

(

)

(

) (

)

(

)

(

)

(

) (

)









−

max

Gain

Gain drift is measured in ppm of FS/°C.

Power Supply Rejection (PSR)

PSR quantifies the ADE7978 and ADE7933/ADE7932/

ADE7923 chipset measurement error as a percentage of reading

when the power supplies are varied. For the ac PSR measurement,

a reading at nominal supplies (3.3 V) is taken when the voltage

at the input pins is 0 V. A second reading is obtained with the

same input signal levels when an ac signal (120 mV rms at 50 Hz

or 100 Hz) is introduced onto the supplies. Any error introduced

by this ac signal is expressed as a percentage of reading (power

supply rejection ratio, PSRR). PSR = 20 log10 (PSRR).

For the dc PSR measurement, a reading at nominal supplies

(3.3 V) is taken when the voltage between the IP and IM pins is

6.25 mV rms, and the voltages between the V1P, V2P, and VM

pins are 100 mV rms. A second reading is obtained with the

same input signal levels when the power supplies are varied by

±10%. Any error introduced is expressed as a percentage of the

reading (PSRR). PSR = 20 log10 (PSRR).

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