LTC1594_15 Datasheet, PDF (15/24 Pages) Linear Technology – 4- and 8-Channel, Micropower Sampling 12-Bit Serial I/O A/D Converters

LTC1594/LTC1598
APPLICATIONS INFORMATION
BOARD LAYOUT CONSIDERATIONS
Grounding and Bypassing
The LTC1594/LTC1598 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 LTC1594/LTC1598 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 LTC1594/LTC1598 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 LTC1594/LTC1598 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
CSADC = CSMUX = CS
SAMPLE
HOLD
“ANALOG” INPUT MUST
t_ON
SETTLE DURING
THIS TIME
t_SMPL
t_CONV
CLK
D_IN
EN
D2
D1
D0
DON‘T CARE
D_OUT
MUXOUT = ADCIN
B11
1ST BIT TEST “COM” INPUT MUST
SETTLE DURING THIS TIME
CH0 TO CH7
COM
Figure 7. LTC1594/LTC1598 ADCIN and COM Input Settling Windows
1594/98 F07
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