AN1812 datasheet(8/34 Pages) STMICROELECTRONICS

Part #	AN1812

Description	In general the ADC embedded in the ST7 microcontroller

PDF	34 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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8 / 34 page

5 Vout vs time diagram for different input voltages

AN1812

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Vout vs time diagram for different input voltages

In Figure 4, we can see the relationship between the Vout and time for different input voltages.

From the figure, it is clear that the conversion time for a negative input voltage is less than the

time taken for a positive input voltage.

Figure 4.

Vout Vs Time For Different Input Voltages

This ADC works for the range Vin <= V1 but if the input voltage is greater than V1 the direction of current I will

be inverted and the capacitor will start charging in the opposite direction and conversion will never take place.

For negative voltages current I, that depends on the difference V1 - Vin, will be high, so the charging time for

negative voltages will be less than the positive voltages.

Effective Time Tm = T - T’

Vin < 0

Vin =0

Vin > 0

(Vout)

T1’

T2’ T1

T3’

Time (t)

Here Tm1: for Vin < 0, Tm2: for Vin = 0 and Tm3: Vin>0

(Where Tin1 < Tin2 < Tin3)

AN1812 Datasheet(PDF) 8 Page - STMicroelectronics