LTC2450-1

13

24501fb

APPLICATIONS INFORMATION

24501 F12

SD0

SCK

CONVERT

CONVERT

SLEEP

DATA OUTPUT

CS = LOW

Figure 12. 2-Wire, Idle-High (CPOL = 1) Serial Clock, Operation Example

24501 F13

SD0

CS = LOW

SCK

CONVERT

CONVERT

DATA OUTPUT

Figure 13. 2-Wire, Idle-Low (CPOL = 0) Serial Clock Operation Example

2-Wire Operation

The 2-wire operation modes, while reducing the number

of required control signals, should be used only if the

LTC2450-1 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.

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 LTC2450-1 bypasses the SLEEP

state and immediately enters the DATA OUTPUT state. At

this moment the SDO pin outputs the most significant 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 LTC2450-1 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.