Datasheet

LTC2412
17
2412f
APPLICATIO S I FOR ATIO
WUU
U
anytime a LOW-to-HIGH transition is detected at the CS
pin after the converter has entered the data output state
(i.e., after the first rising edge of SCK occurs with
CS␣=␣LOW).
Finally, CS can be used to control the free-running modes
of operation, see Serial Interface Timing Modes section.
Grounding CS will force the ADC to continuously convert
at the maximum output rate selected by F
O
.
SERIAL INTERFACE TIMING MODES
The LTC2412’s 3-wire interface is SPI and MICROWIRE
compatible. This interface offers several flexible modes of
operation. These include internal/external serial clock,
2- or 3-wire I/O, single cycle conversion and autostart. The
following sections describe each of these serial interface
timing modes in detail. In all these cases, the converter
can use the internal oscillator (F
O
= LOW or F
O
= HIGH) or
an external oscillator connected to the F
O
pin. Refer to
Table␣ 4 for a summary.
External Serial Clock, Single Cycle Operation
(SPI/MICROWIRE Compatible)
This timing mode uses an external serial clock to shift out
the conversion result and a CS signal to monitor and
control the state of the conversion cycle, see Figure 5.
The serial clock mode is selected on the falling edge of CS.
To select the external serial clock mode, the serial clock pin
(SCK) must be LOW during each CS falling edge.
Figure 5. External Serial Clock, Single Cycle Operation
Table 4. LTC2412 Interface Timing Modes
Conversion Data Connection
SCK Cycle Output and
Configuration Source Control Control Waveforms
External SCK, Single Cycle Conversion External CS and SCK CS and SCK Figures 5, 6
External SCK, 2-Wire I/O External SCK SCK Figure 7
Internal SCK, Single Cycle Conversion Internal CS ↓ CS ↓ Figures 8, 9
Internal SCK, 2-Wire I/O, Continuous Conversion Internal Continuous Internal Figure 10
EOC
BIT 31
SDO
SCK
(EXTERNAL)
CS
TEST EOC
SUB LSBMSBSIGCH0/CH1
BIT 0
LSB
BIT 5BIT 27 BIT 26BIT 28BIT 29BIT 30
SLEEP
SLEEP
TEST EOC
(OPTIONAL)
DATA OUTPUT CONVERSION
2412 F05
CONVERSION
Hi-ZHi-ZHi-Z
TEST EOC
= 50Hz REJECTION
= EXTERNAL OSCILLATOR
= 60Hz REJECTION
V
CC
V
CC
F
O
REF
+
SCK
CH1
+
CH1
–
SDO
GND
CS
114
2
3
13
6
7
12
8, 9, 10, 15, 16
11
REFERENCE
VOLTAGE
0.1V TO V
CC
CH0
+
CH0
–
4
5
ANALOG INPUT RANGE
–0.5V
REF
TO 0.5V
REF
1µF
2.7V TO 5.5V
LTC2412
3-WIRE
SPI INTERFACE
REF
–