ltc2450 Linear Technology Corporation, ltc2450 Datasheet - Page 13

• Manufacturer Part Number: ltc2450
• Description: Easy-to-use, Ultra-tiny 16-bit Delta Sigma Adc
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
2-Wire Operation
The 2-wire operation modes, while reducing the number of
required control signals, should be used only if the LTC2450
low power sleep capability is not required. In addition the
option to abort serial data transfers is no longer available.
Hardwire CS to GND for 2-wire operation.
Figure 12 shows a 2-wire operation sequence which uses
an idle-high (CPOL = 1) serial clock signal. The conversion
status can be monitored at the SDO output. Following a
conversion cycle, the ADC enters SLEEP state and the
SDO output transitions from HIGH to LOW. Subsequently
16 clock pulses are applied to the SCK input in order
to serially shift the 16 bit result. Finally, the 17th clock
pulse is applied to the SCK input in order to trigger a new
conversion cycle.
CS = LOW
SD0
CS = LOW
SCK
SCK
SD0
CONVERT
CONVERT
Figure 12. 2-Wire, Idle-High (CPOL = 1) Serial Clock, Operation Example
Figure 13. 2-Wire, Idle-Low (CPOL = 0) Serial Clock Operation Example
SLEEP
clk
clk
D
D
1
15
15
DATA OUTPUT
1
clk
2
clk
D
D
14
14
2
Figure 13 shows a 2-wire operation sequence which uses
an idle-low (CPOL = 0) serial clock signal. The conversion
status cannot be monitored at the SDO output. Following
a conversion cycle, the LTC2450 bypasses the SLEEP
state and immediately enters the DATA OUTPUT state. At
this moment the SDO pin outputs the most signifi cant bit
(D15) of the conversion result. The user must use external
timing in order to determine the end of conversion and
result availability. Subsequently 16 clock pulses are applied
to SCK in order to serially shift the 16-bit result. The 16th
clock falling edge triggers a new conversion cycle.
PRESERVING THE CONVERTER ACCURACY
The LTC2450 is designed to reduce as much as possible
the conversion result sensitivity to device decoupling,
PCB layout, antialiasing circuits, line and frequency
perturbations. Nevertheless, in order to preserve the
very high accuracy capability of this part, some simple
precautions are desirable.
clk
3
clk
D
D
13
DATA OUTPUT
13
3
clk
4
D
D
clk
12
12
4
clk
14
D
D
2
clk
2
15
clk
D
D
15
1
1
clk
16
clk
D
D
0
0
16
clk
17
CONVERT
CONVERT
LTC2450
2450 F13
2450 F12
13
2450fb