Datasheet

24
LTC1197/LTC1197L
LTC1199/LTC1199L
A “Quick Look” Circuit for the LTC1197
Users can get a quick look at the function and timing of
the LTC1197 by using the following simple circuit (Figure
11). V
REF
is tied to V
CC
. V
IN
is applied to the +IN input and
the –IN input is tied to the ground. CS is driven at 1/16
the clock rate by the 74HC161 and D
OUT
outputs the data.
The output data from the D
OUT
pin can be viewed on an
oscilloscope that is set up to trigger on the falling edge
of CS (Figure 12). Note that after the LSB is clocked out,
the LTC1197 clocks out zeros until CS goes high. Also
note that with the resistor divider on D
OUT
the output
goes midway between V
CC
and ground when in the high
impedance mode.
Figure 11. “Quick Look” Circuit for the LTC1197
CLK
CS
D
OUT
FILL
ZEROES
HIGH
IMPEDANCE
2 NULL
BITS
MSB
(B9)
LSB
(B0)
VERTICAL: 5V/DIV
HORIZONTAL: 10µs/DIV
Figure 12. Scope Photo of the LTC1197 “Quick Look” Circuit
Waveforms Showing A/D Output 1001001001 (249
HEX
)
TYPICAL APPLICATIO S
U
CLR
CLK
A
B
C
D
P
GND
V
CC
RC
QA
QB
QC
QD
T
LOAD
74HC161
V
IN
TO OSCILLOSCOPE
D
OUT
CLK CS
1197/99 F11
V
CC
CLK
D
OUT
V
REF
LTC1197
CS
+IN
–IN
GND
1µF
5V
10k
CLK IN 7.2MHz MAX
10k
5V
+