Datasheet

LTC2378-20
18
237820f
For more information www.linear.com/LTC2378-20
TiMing DiagraMs
Normal Mode, Multiple Devices
Figure 16 shows multiple LTC2378-20 devices operating
in normal mode (CHAIN = 0) sharing CNV, SCK and SDO.
By sharing CNV, SCK and SDO, the number of required
signals to operate multiple ADCs in parallel is reduced.
Since SDO is shared, the RDL/SDI input of each ADC must
be used to allow only one LTC2378-20 to drive SDO at a
time in order to avoid bus conflicts. As shown in Figure 16,
the RDL/SDI inputs idle high and are individually brought
low to read data out of each device between conversions.
When RDL/SDI is brought low, the MSB of the selected
device is output onto SDO.
237820 F16a
RDL
B
RDL
A
CONVERT
IRQ
DATA IN
DIGITAL HOST
CLK
CNV
LTC2378-20
SDO
A
SCK
RDL/SDI
CNV
LTC2378-20
SDO
B
SCK
RDL/SDI
CHAIN BUSY
CHAIN
237820 F16
D19
A
SDO
SCK
CNV
BUSY
CHAIN = 0
RDL/SDI
B
RDL/SDI
A
D19
B
D18
B
D1
B
D0
B
D17
B
D18
A
D17
A
D1
A
D0
A
Hi-Z
Hi-ZHi-Z
t
EN
t
HSDO
t
DSDO
t
DIS
t
SCKL
t
SCKH
t
CNVL
1 2 3 18 19 20 21 22 23 38 39 40
t
SCK
CONVERTCONVERT
t
QUIET
t
CONV
t
BUSYLH
POWER-DOWN AND ACQUIRE
POWER-DOWN
AND ACQUIRE
Figure 16. Normal Mode With Multiple Devices Sharing CNV, SCK and SDO