LTC2414 LINER [Linear Technology], LTC2414 Datasheet - Page 18

• Manufacturer Part Number: LTC2414
• Description: 8-/16-Channel 24-Bit No Latency TM ADCs
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
LTC2414/LTC2418
Table 5. LTC2414/LTC2418 State Duration
State
CONVERT
SLEEP
DATA OUTPUT
Serial Clock Input/Output (SCK)
The serial clock signal present on SCK (Pin 18) is used to
synchronize the data transfer. Each bit of data is shifted out
the SDO pin on the falling edge of the serial clock and each
input bit is shifted in the SDI pin on the rising edge of the
serial clock.
In the Internal SCK mode of operation, the SCK pin is an
output and the LTC2414/LTC2418 create their own serial
clock by dividing the internal conversion clock by 8. In the
External SCK mode of operation, the SCK pin is used as
input. The internal or external SCK mode is selected on
power-up and then reselected every time a HIGH-to-LOW
transition is detected at the CS pin. If SCK is HIGH or float-
ing at power-up or during this transition, the converter
enters the internal SCK mode. If SCK is LOW at power-up
or during this transition, the converter enters the external
SCK mode.
Serial Data Input (SDI)
The serial data input pin, SDI (Pin 20), is used to shift in the
channel control bits during the data output state to prepare
the channel selection for the following conversion.
When CS (Pin 16) is HIGH or the converter is in the con-
version state, the SDI input is ignored and may be driven
HIGH or LOW. When CS goes LOW and the conversion is
complete, SDO goes low and then SDI starts to shift in bits
on the rising edge of SCK.
18
Operating Mode
Internal Oscillator
External Oscillator
Internal Serial Clock
External Serial Clock with
Frequency f
U
SCK
U
kHz
W
F
(60Hz Rejection)
F
(50Hz Rejection)
F
with Frequency f
(f
F
(Internal Oscillator)
F
Frequency f
O
O
O
O
O
EOSC
= LOW
= HIGH
= External Oscillator
= LOW/HIGH
= External Oscillator with
/2560 Rejection)
U
EOSC
EOSC
kHz
kHz
Serial Data Output (SDO)
The serial data output pin, SDO (Pin 17), provides the
result of the last conversion as a serial bit stream (MSB
first) during the data output state. In addition, the SDO pin
is used as an end of conversion indicator during the
conversion and sleep states.
When CS (Pin 16) is HIGH, the SDO driver is switched to
a high impedance state. This allows sharing the serial
interface with other devices. If CS is LOW during the
convert or sleep state, SDO will output EOC. If CS is LOW
during the conversion phase, the EOC bit appears HIGH on
the SDO pin. Once the conversion is complete, EOC goes
LOW. The device remains in the sleep state until the first
rising edge of SCK occurs while CS = LOW.
Chip Select Input (CS)
The active LOW chip select, CS (Pin 16), is used to test the
conversion status and to enable the data input/output
transfer as described in the previous sections.
In addition, the CS signal can be used to trigger a new
conversion cycle before the entire serial data transfer has
been completed. The LTC2414/LTC2418 will abort any
serial data transfer in progress and start a new conversion
cycle anytime a LOW-to-HIGH transition is detected at the
CS pin after the converter has entered the data input/
output state (i.e., after the first rising edge of SCK occurs
with CS = LOW). If the device has not finished loading the
Duration
133ms, Output Data Rate ≤ 7.5 Readings/s
160ms, Output Data Rate ≤ 6.2 Readings/s
20510/f
As Long As CS = HIGH Until CS = LOW and SCK
As Long As CS = LOW But Not Longer Than 1.67ms
(32 SCK cycles)
As Long As CS = LOW But Not Longer Than 256/f
(32 SCK cycles)
As Long As CS = LOW But Not Longer Than 32/f
(32 SCK cycles)
EOSC
s, Output Data Rate ≤ f
EOSC
/20510 Readings/s
SCK
EOSC
ms
ms
241418fa