LTC1594L Datasheet, PDF (12/24 Pages) Linear Technology – 4- and 8-Channel, 3V Micropower Sampling 12-Bit Serial I/O A/D Converters

LTC1594L/LTC1598L
APPLICATIONS INFORMATION
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:
EN D2 D1 D0
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
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
111111111111
111111111110
•
•
•
000000000001
000000000000
1LSB = ^VREF
4096
Output Code
V_IN
1594L/98L • AI03
OUTPUT CODE
INPUT VOLTAGE
11111111111111
11111111111110
•
•
•
00000000000001
00000000000000
V_REF – 1LSB
V_REF – 2LSB
•
•
•
1LSB
0V
INPUT VOLTAGE
(V_REF = 2.500V)
2.49939V
2.49878V
•
•
•
0.00061V
0V
1594L/98L • AI04
12