Datasheet
CONVST_x
ADC CH_x
ACQ
CONV
Power-Down
ACQ
ASLEEP
BUSY
CONV
Power-Down
6t
CCLK
ADS8528
ADS8548
ADS8568
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SBAS543A –AUGUST 2011– REVISED OCTOBER 2011
The auto-sleep mode is enabled by pulling pin 36 (ASLEEP) high. If the auto-sleep mode is enabled, the
ADS8528/48/68 automatically reduce the current requirement to 7mA (IAVDD) after finishing a conversion; thus,
the end of conversion actually activates this power-down mode. Triggering a new conversion by applying a
positive CONVST_x edge puts the device back into normal operation, starts the acquisition of the analog input,
and automatically starts a new conversion 6 to 7 conversion clock cycles later, as shown in Figure 42. Therefore,
a complete conversion process takes 25 to 26 conversion clock cycles; thus, the maximum throughput rate in
auto-sleep mode is reduced to a maximum of 400kSPS for the ADS8528, 375kSPS for the ADS8548, and
330kSPS for the ADS8568 in serial interface mode. In parallel mode, the maximum data rates are 510kSPS for
the ADS8528, 470kSPS for the ADS8548 and 400kSPS for the ADS8568. If enabled, the internal reference
remains active during auto-sleep mode. Table 8 compares the analog current requirements of the device in
different modes.
Figure 42. Auto-Sleep Power-Down Mode
Table 8. Maximum Analog Current (IAVDD) Demand of the ADS85x8
NORMAL
POWER-UP POWER-UP
ANALOG OPERATION
OPERATIONA ENABLED/DIS ACTIVATED TO NORMAL TO NEXT
CURRENT TO RESUMED BY
L MODE ABLED BY BY OPERATION CONVERSION
(IAVDD) POWER-
DELAY START TIME
DOWN DELAY
12.5mA/ch pair Power on
Normal
at maximum CONVST_x — — — —
operation
Power off
data rate
ASLEEP = 1
Each end of At falling edge
Auto-sleep 1.75mA/ch pair CONVST_x Immediate 7 × t
CCLK
max
conversion of BUSY
ASLEEP = 0
HW/SW = 1 Immediate after
Power-down of 16µA PD_x = 1 PD_x = 0 completing
Immediate 10ms
channel pair X (channel pair X) (CONFIG bit) (CONFIG bit) CONFIG
HW/SW = 0
update
Power on
Power-down
30µA STBY = 0 Immediate STBY = 1 Immediate 10ms
(entire device)
Power off
Copyright © 2011, Texas Instruments Incorporated 37
Product Folder Link(s): ADS8528 ADS8548 ADS8568