Datasheet
LTC2450
10
2450fb
APPLICATIONS INFORMATION
Serial Clock Idle-High (CPOL = 1) Examples
In Figure 5, following a conversion cycle the LTC2450
automatically enters the low power sleep mode. The user
can monitor the conversion status at convenient intervals
using CS and SDO.
CS is pulled low to test whether or not the chip is in
the CONVERT state. While in the CONVERT state, SDO
is HIGH while CS is LOW. In the SLEEP state, SDO is
LOW while CS is LOW. These tests are not required op-
erational steps but may be useful for some applications.
When the data is available, the user applies 16 clock cycles
to transfer the result. The CS rising edge is then used to
initiate a new conversion.
The operation example of Figure 6 is identical to that of
Figure 5, except the new conversion cycle is triggered by
the falling edge of the serial clock (SCK). A 17th clock
pulse is used to trigger a new conversion cycle.
Serial Clock Idle-Low (CPOL = 0) Examples
In Figure 7, following a conversion cycle the LTC2450
automatically enters the low power sleep state. The user
determines data availability (and the end of conversion)
based upon external timing. The user then pulls CS low
(CS = ↓) and uses 16 clock cycles to transfer the result.
Following the 16th rising edge of the clock, CS is pulled high
(CS = ↑), which triggers a new conversion.
The timing diagram in Figure 8 is identical to that of Figure 7,
except in this case a new conversion is triggered by SCK.
The 16th SCK falling edge triggers a new conversion cycle
and the CS signal is subsequently pulled high.
Figure 5. Idle-High (CPOL = 1) Serial Clock Operation Example.
The Rising Edge of CS Starts a New Conversion
Figure 6. Idle-High (CPOL = 1) Clock Operation Example.
A 17th Clock Pulse is Used to Trigger a New Conversion Cycle
D
15
clk
1
clk
2
clk
3
clk
4
clk
15
clk
16
D
14
D
13
D
12
D
2
D
1
D
0
SD0
SCK
CONVERT CONVERTSLEEP
LOW I
CC
DATA OUTPUT
2450 F05
CS
D
15
D
14
D
13
D
12
D
2
D
1
D
0
SD0
clk
1
clk
2
clk
3
clk
4
clk
15
clk
16
clk
17
SCK
CONVERT CONVERTSLEEP
LOW I
CC
DATA OUTPUT
2450 F06
CS