Datasheet

12
LTC1594L/LTC1598L
15948lfb
after a delay of t
OFF
, all the channels are switched off to
ensure a break-before-make interval. After this interval,
the selected channel is switched on allowing signal
transmission. The selected channel remains on until the
next falling edge of CS and the process repeats itself with
the “EN” bit being logic high. If the “EN” bit is logic low,
all the channels are switched off simultaneously after a
delay of t
OFF
from CS being pulled low and all the
channels remain off until the next falling edge of CS.
Input Data Word
When CS is high, the LTC1594L/LTC1598L clock data
into the D
IN
inputs on the rising edge of the clock and
store the data into a 4-bit register. The input data words
are defined as follows:
D0EN D2 D1
CHANNEL SELECTION
1594L/98L AI02
“EN” Bit
The first bit in the 4-bit register is an “EN” bit. If the “EN”
bit is a logic high, as illustrated in Figure 1, it enables the
selected channel after a delay of t
ON
when the CS is pulled
low. If the “EN” bit is logic low, as illustrated in Figure 2,
it disables all channels after a delay of t
OFF
when the CS
is pulled low.
Multiplexer (MUX) Address
The 3 bits of input word following the “EN” bit select the
channel in the MUX for the requested conversion. For a
given channel selection, the converter will measure the
voltage of the selected channel with respect to the voltage
on the COM pin. Tables 1 and 2 show the various bit
combinations for the LTC1594L/LTC1598L channel
selection.
Table 1. Logic Table for the LTC1594L Channel Selection
CHANNEL STATUS EN D2 D1 DO
All Off 0 X X X
CH0 1 0 0 0
CH1 1 0 0 1
CH2 1 0 1 0
CH3 1 0 1 1
APPLICATIONS INFORMATION
WUU
U
Table 2. Logic Table for the LTC1598L Channel Selection
CHANNEL STATUS EN D2 D1 DO
All Off 0 X X X
CH0 1 0 0 0
CH1 1 0 0 1
CH2 1 0 1 0
CH3 1 0 1 1
CH4 1 1 0 0
CH5 1 1 0 1
CH6 1 1 1 0
CH7 1 1 1 1
Transfer Curve
The LTC1594L/LTC1598L are permanently configured
for unipolar only. The input span and code assignment
for this conversion type is illustrated below.
Transfer Curve
0V 1LSB
V
REF
–2LSB
V
REF
4096
V
REF
–1LSB
V
REF
V
IN
0 0 0 0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 0
•
•
•
1594L/98L • AI03
1LSB =
Output Code
OUTPUT CODE
•
•
•
1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 0
0 0 0 0 0 0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0
INPUT VOLTAGE
V
REF
– 1LSB
V
REF
– 2LSB
•
•
•
1LSB
0V
INPUT VOLTAGE
(V
REF
= 2.500V)
2.49939V
2.49878V
•
•
•
0.00061V
0V
1594L/98L • AI04