AD7280 데이터 시트보기 (PDF) - Analog Devices
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AD7280 Datasheet PDF : 33 Pages
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AD7280
CNVST
Preliminary Technical Data
TOTAL CONVERSION TIME
= ((tACQ + tCONV) x #conversions per part) - tACQ+ (#parts x tDELAY)
INTERNAL ADC
CONVERSIONS
PART 1
INTERNAL ADC
CONVERSIONS
PART 2
INTERNAL ADC
CONVERSIONS
PART 3
tCONV
VOLT 1
VOLT 2
tACQ + tCONV
VOLT 3
TEMP 6
tDELAY
tDELAY
VOLT 7
VOLT 8
VOLT 9
tACQ + tCONV
tDELAY
tDELAY
VOLT 13 VOLT 14
VOLT 15
tACQ + tCONV
Figure 14. ADC conversions & Readback on a chain of 3 AD7280s
TEMP 12
TEMP 18
Suggested External Component Configurations on
Analog Inputs
As outlined in the Track-and –Hold section the acquisition time
of the AD7280 is selected by the status of bits D6 and D5 in the
CONTROL register. This provides flexibility in selecting external
components on the analog inputs. Included below are two
suggested configurations for placing external components on the
analog inputs to the AD7280.
Combined LP filter and Current Limiting Resistors
Please refer to Figure 15.
the 10kΩ resistor. The cut off frequency of the low pass filter is
318Hz. Using these external components the default acquisition
time of 400 ns may be used, which will allow a combined
acquisition and conversion time of 1µs.
Current Limiting Resistors
Please refer to Figure 16.
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
100nF
100nF
100nF
100nF
100nF
100nF
AD7280
Vin6
Vin5
Vin4
Vin3
Vin2
Vin1
Vin0
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
AD7280
Vin6
Vin5
Vin4
Vin3
Vin2
Vin1
Vin0
Figure 16. External Series Resistance
Figure 15. External Series Resistance & Shunt Capacitance
The 10kΩ resistor in series with the inputs provides protection
to the analog inputs in the event of an over-voltage or under-
voltage on those inputs. The 100nF capacitor across the pseudo
differential inputs acts as a low pass filter in conjunction with
The 10kΩ resistor in series with the inputs provides protection
to the analog inputs in the event of an over-voltage or under-
voltage on those inputs. Using these external components an
acquisition time of 1.6 µs should be used, which will allow a
combined acquisition and conversion time of 2.2µs.
Rev. PrD | Page 16 of 33
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