Maxim-integrated MAXQ7667 Manual de usuario descargar pdf (Pagina 250)

_________________________________________________________________________________________________________ 14-18

MAXQ7667 User’s Guide

In dual-edged conversions, it is up to the user to provide the required power-up and acquisition delay as explained in Table 14-5.

a) If ADC is in auto shutdown state, a minimum of 2.5µs power-up and acquisition delay is required followed by 13 ADC clock

cycles, for conversion, before the 12-bit result is available.

b) If ADC is not in auto shutdown state, a minimum of 1.5µs acquisition delay is required followed by 13 ADC clock cycles, for

conversion, before the 12-bit result is available.

Figure 14-10 shows dual-edge-controlled ADC conversion when the ADC is in auto shutdown state.

In dual-edge conversion, the power-up and acquisition is triggered by the rising edge of the ADC conversion start source signal

ADC_CNVST (ADC_CNVST is an internal signal generated from a combination of all the three conversion start sources described ear-

lier in this subsection). At the falling edge, the ADC starts conversion and a 12-bit result is written to the ADC result register in 13 ADC

clock cycles. The advantage of dual-edge mode is, depending on the analog input signal’s source impedance, the user can provide

additional acquisition time if required.

Figure 14-10. Dual-Edge ADC Conversion Timing; ADC Previously Off

SARBY

ADCDATA

ADCCLK

ADC_CNVST

DATA (n-1) DATA (n)

113

CONVERSION (n)

POWER-UP AND ACQUISITION

Figure 14-9. Single-Edge ADC Conversion Timing; ADC Previously On

SARBY

11713

ADCDATA

ADCCLK

ADC_CNVST

DATA (n-1) DATA (n)

ACQUISITION (n)

CONVERSION (n)

1 2 ... 245 246 247 248 249 250 251 252 253 254 255 ... 346 347

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Maxim-integrated MAXQ7667 Manual de usuario Pagina 250