EVAL-AD7923CB Analog Devices Inc, EVAL-AD7923CB Datasheet - Page 19

• Manufacturer Part Number: EVAL-AD7923CB
• Description: BOARD EVAL FOR AD7923
• Manufacturer: Analog Devices Inc

Specifications of EVAL-AD7923CB

• Rohs Status: RoHS non-compliant
• Number Of Adc's: 1
• Number Of Bits: 12
• Sampling Rate (per Second): 200k
• Data Interface: Serial
• Inputs Per Adc: 4 Single Ended
• Input Range: 0 ~ 2.5 V
• Power (typ) @ Conditions: *
• Voltage Supply Source: Single
• Operating Temperature: -40°C ~ 125°C
• Utilized Ic / Part: AD7923

POWER vs. THROUGHPUT RATE
In auto shutdown mode, the average power consumption of the
ADC can be reduced at any given throughput rate. The power
saving depends on the SCLK frequency used, that is, conversion
time. In some cases where the conversion time is a large propor-
tion of the cycle time, the throughput rate needs to be reduced
to take advantage of the power-down modes. Assuming a
20 MHz SCLK is used, the conversion time is 800 ns, but the
DOUT
DOUT
SCLK
SCLK
DIN
DIN
CS
CS
PART IS IN
UNKNOWN MODE
AFTER POWER-ON
PART IS IN
UNKNOWN MODE
AFTER POWER-ON
1
1
DIN LINE HIGH FOR FIRST DUMMY CONVERSION
DIN LINE HIGH FOR FIRST DUMMY CONVERSION
Figure 25. Placing the AD7923 into Auto Shutdown Mode after Supplies are First Applied
INVALID DATA
Figure 24. Placing the AD7923 into Full Shutdown Mode after Supplies are First Applied
INVALID DATA
DOUT
SCLK
Figure 23. Placing the AD7923 into Normal Mode after Supplies are First Applied
DIN
CS
PART IS IN
UNKNOWN MODE
AFTER POWER-ON
IF IN SHUTDOWN AT POWER-ON
PART BEGINS TO POWER UP ON
CS RISING EDGE AS PM1 = PM0 = 1
CONTROL REGISTER IS LOADED ON
THE FIRST 12 CLOCKS. PM1 = 1, PM0 = 0
1
14
14
DATA INTO CONTROL REGISTER
Rev. B | Page 19 of 24
16
16
INVALID DATA
t
12
PART ENTERS SHUTDOWN ON
CS RISING EDGE AS PM1 = PM0 = 0
cycle time is 5 μs when the sampling rate is at a maximum of
200 kSPS. If the AD7923 is placed into shutdown for the
remainder of the cycle time, then on average far less power is
consumed in every cycle compared to leaving the device in
normal mode. Furthermore, Figure 26 shows how, as the
throughput rate is reduced, the part remains in its shutdown
longer and the average power consumption drops accordingly
over time.
ALLOW
TO KEEP THE PART IN NORMAL MODE, LOAD
PM1 = PM0 = 1 IN CONTROL REGISTER
CONTROL REGISTER IS LOADED ON THE
FIRST 12 CLOCKS. PM1 = 0, PM0 = 1
1
1
t
CHANNEL IDENTIFIER BITS + CONVERSION RESULT
POWER
14
TO ELAPSE
DATA INTO CONTROL REGISTER
16
DATA INTO CONTROL REGISTER
INVALID DATA
PART ENTERS AUTO SHUTDOWN ON
CS RISING EDGE AS PM1 = 0, PM0 = 1
14
14
16
16
AD7923