EPC610 datasheet(32/34 Pages) EPC

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3.5.9. Cycle time calculation

The following example shows the estimation of the measurement cycle time tCYCLE.

Start &

init

Integration

DCS0

Conversion &

read-out DCS0

Integration

DCS1

Conversion &

read-out DCS1

Integration

DCS2

Conversion &

read-out DCS2

Integration

DCS3

Conversion &

read-out DCS3

Task

LED modulation

OFF

SYNCH

Total measurement cycle t

CYCLE

Integration time t

INT

Figure 31: Measurement cycle timing

The above timing diagram contains in detail the following tasks:

No. Task

Done by SPI data frame [bit]

Time used [μs]

Start measurement

μC

2 SPI commands x (16 SPI bits + 1 nSS pulse) = 34 bits

Init

epc610

8 rows x 18 SPI commands x (16 SPI bits + 1 nSS pulse) = 2'448 bits

Integration to acquire DCS0

epc610

Conversion

epc610

175

Readout DCS0

μC

8 rows x 18 SPI commands x (16 SPI bits + 1 nSS pulse) = 2'448 bits

245

Integration to acquire DCS1

epc610

Conversion

epc610

175

Readout DCS1

μC

8 rows x 18 SPI commands x (16 SPI bits + 1 nSS pulse) = 2'448 bits

245

Integration to acquire DCS2

epc610

10. Conversion

epc610

175

11. Readout DCS2

μC

8 rows x 18 SPI commands x (16 SPI bits + 1 nSS pulse) = 2'448 bits

245

12. Integration to acquire DCS3

epc610

13. Conversion

epc610

175

14. Readout DCS3

μC

8 rows x 18 SPI commands x (16 SPI bits + 1 nSS pulse) = 2'448 bits

245

Total measurement cycle

1'937

Table 16: Timing example of a measurement cycle

This example uses an integration time of 51μs and an SPI clock frequency of 10MHz.

*) Please note that an object or camera movement between task No. 3 and 12 may lead to false measurement data.

LED on-time and LED duty cycle

For the power dissipation estimation of the emitter LED (at pin LED), the LED on-time tLED_ON and the duty cycle DCLED-ON are of importance.

The following time periods have to be taken in consideration:

■ During the integration period tINT: the LED outputs are active for 50% of the time.

■ There are 4 integration periods tINT per measurement cycle tMEAS.

■ During the SPI communication, the LED outputs are not active.

The formula for the LED on-time is:

tLED−ON = 4⋅

INT

2 +

SYNCH

e.g.

LED-ON = 4 ∗

μ s

= 117μ s

The LED duty cycle DCLED-ON for the LED on-time versus the cycle time is

LED

−ON =

LED

−ON

CYCLE

e.g.

LED-ON =

117

μ s

1'937

μ s

= 6%

Characteristics subject to change without notice

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Datasheet epc610 - V1.7

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