AN2859 datasheet(11/29 Pages) STMICROELECTRONICS

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DocID15255 Rev 2

11/29

AN2859

VSTATE level definition

According to the state of each AC switch, V0, V1, V2 and V3 levels are defined by equations

1, 2, 3 and 4 (see also Appendix B). In this document VAVF1_L and VAVF2_L are respectively

the STCCO81 and STCCO82 AVF output at the low level. The minimum and maximum

values of AVF at low level are respectively 0 V and 1 V.

Equation 1

ACS1 and ACS2 are on

Equation 2

ACS1 is on and ACS2 is off

Equation 3

ACS2 is on and ACS1 is off

Equation 4

ACS1 and ACS2 are off

The tolerance of the resistors (R1, R2, R3 and R4), the STCC08 output AVF signal electrical

dispersion and the DC power supply characteristics induce a dispersion on V0, V1, V2 and

V3 levels (see Table 2).

Knowing the previous equations 1, 2, 3 and 4, the resistors standard value and the

tolerance of the resistors, Vx_Max and Vx_Min (x = 0, 1, 2, or 3) values are defined

respectively by equations 5, 6, 7, 8, 9, 10, 11 and 12.

Table 2. Variation of the VSTATE signal according to the AC switch states

ACS1 state

ACS2 state

VSTATE status

V0_Min < VSTATE < V0_Max

OFF

V1_Min < VSTATE < V1_Max

OFF

V2_Min < VSTATE < V2_Max

OFF

V3_Max > VSTATE > V3_Min

()

AVF2_L

AVF1_L

·R

()

AVF1_L

·R

()

AVF2_L

·R

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