Datasheet

15
LTC1594L/LTC1598L
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APPLICATIONS INFORMATION
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BOARD LAYOUT CONSIDERATIONS
Grounding and Bypassing
The LTC1594L/LTC1598L are easy to use if some care is
taken. They should be used with an analog ground plane
and single point grounding techniques. The GND pin
should be tied directly to the ground plane.
The V
CC
pin should be bypassed to the ground plane with
a 10µF tantalum capacitor with leads as short as possible.
If the power supply is clean, the LTC1594L/LTC1598L
can also operate with smaller 1µF or less surface mount
or ceramic bypass capacitors. All analog inputs should
be referenced directly to the single point ground. Digital
inputs and outputs should be shielded from and/or
routed away from the reference and analog circuitry.
SAMPLE-AND-HOLD
Both the LTC1594L/LTC1598L provide a built-in sample-
and-hold (S&H) function to acquire signals through the
selected channel, assuming the ADCIN and MUXOUT
pins are tied together. The S & H of these parts acquire
input signals through the selected channel relative to
COM input during the t
SMPL
time (see Figure 7).
Single-Ended Inputs
The sample-and-hold of the LTC1594L/LTC1598L allows
conversion of rapidly varying signals. The input voltage
is sampled during the t
SMPL
time as shown in Figure 7.
The sampling interval begins after t
ON
time once the CS
is pulled low and continues until the second falling CLK
edge after the CS is low (see Figure 7). On this falling CLK
Figure 7. LTC1594L/LTC1598L ADCIN and COM Input Settling Windows
CLK
D
IN
D
OUT
MUXOUT = ADCIN
CH0 TO CH7
SAMPLE HOLD
“ANALOG” INPUT MUST
SETTLE DURING
THIS TIME
t
SMPL
t
ON
t
CONV
CSADC = CSMUX = CS
D2 D1EN D0
DON‘T CARE
1ST BIT TEST “COM” INPUT MUST
SETTLE DURING THIS TIME
B11
COM
1594L/98L F07