ADC1225 datasheet(5/18 Pages) NSC

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AC Electrical Characteristics (Continued)

Note 4

Two on-chip diodes are tied to each analog input as shown below

TLH5676 – 4

Errors in the AD conversion can occur if these diodes are forward biased more than 50 mV This means that if AVCC and DVCC are minimum (475 VDC) and Vb is

minimum (b475VDC) full-scale must be s 48VDC

Note 5

A diode exists between analog VCC and digital VC

TLH5676 – 20

To guarantee accuracy it is required that the AVCC and DVCC be connected together to a power supply with separate bypass filters at each VCC pin

Note 6

A diode exists between analog ground and digital ground

TLH5676 – 21

To guarantee accuracy it is required that the analog ground and digital ground be connected together externally

Note 7

Accuracy is guaranteed at fCLKe10 MHz At higher clock frequencies accuracy may degrade

Note 8

Typicals are at 25 C and represent most likely parametric norm

Note 9

Tested and guaranteed to National’s AOQL (Average Outgoing Quality Level)

Note 10

Guaranteed but not 100% production tested These limits are not used to calculate outgoing quality levels

Note 11

Linearity error is defined as the deviation of the analog value expressed in LSBs from the straight line which passes through positive full scale and zero

after adjusting zero error (See

Figures 1b and 1c )

Note 12

Human body model 100 pF discharged through a 15 kX resistor

TLH5676 – 8

FIGURE 1a Transfer Characteristic

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