AN1812 datasheet(6/34 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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6 / 34 page

3 Timing diagram

AN1812

6/34

Timing diagram

Figure 3 shows the overall operation of the ADC. Initially the capacitor is in the reset state (M1-

ON and M2- OFF), the op-amp output Vout is at V1 and so, the output of both comparators,

Comp1 and Comp2 is HIGH.

Capacitor charging can be started by switching M1 - OFF and M2 - ON. When the charging

starts, Vout rises. When Vout becomes greater than V2, a falling edge occurs on Comp1. This

causes an input capture at pin PB2 and software reads the timer value T2.

When Vout becomes greater than V3, a falling edge occurs on Comp2. Again this causes an

input capture at pin PB0 and software reads the timer value T3.

The capacitor is discharged by switching M1 - ON and M2- OFF. After this, the ADC can be kept

in reset condition by switching M1 - ON and M2 - OFF or we can continue repeating the same

process and make more measurements.

Figure 3.

Timing diagram

Charging

Time

Discharg.

Time

Settling

Time

Vout

Comp1

Comp2

Time (t)

AN1812 Datasheet(PDF) 6 Page - STMicroelectronics