LTC1196/LTC1198
APPLICATI
OVERVIEW
The LTC1196/LTC1198 are 600ns sampling 8-bit A/D
converters packaged in tiny 8-pin SO packages and oper-
ating on 3V to 6V supplies. The ADCs draw only 10mW
from a 3V supply or 50mW from a 5V supply.
Both the LTC1196 and the LTC1198 contain an 8-bit,
switched-capacitor ADC, a sample-and-hold, and a serial
port (see Block Diagram). The on-chip sample-and-holds
have full-accuracy input bandwidths of 1MHz. Although
they share the same basic design, the LTC1196 and
LTC1198 differ in some respects. The LTC1196 has a
differential input and has an external reference input pin.
It can measure signals floating on a DC common-mode
voltage and can operate with reduced spans below 1V. The
S I FOR ATIO
CS
t
suCS
CLK
t
dDO
D
OUT
B0
t
SMPL
Hi-Z
NULL BITS
B7
B6
B5
B4
B3
B2
B1
B0*
t
SMPL
Hi-Z
NULL
BITS
*AFTER COMPLETING THE DATA TRANSFER, IF FURTHER CLOCKS ARE APPLIED WITH CS LOW, THE ADC WILL OUTPUT ZEROS INDEFINITELY.
1196/98 F01
Figure 1. LTC1196 Operating Sequence
CS
t
suCS
CLK
START
D
IN
SGL/
DIFF
D
OUT
HI-Z
t
SMPL
(2.5CLKs)
DUMMY
NULL BITS
B7
B6
B5
B4
ODD/
SIGN
DUMMY
DON’T CARE
t
dDO
B3
B2
B1
B0*
*AFTER COMPLETING THE DATA TRANSFER, IF FURTHER CLOCKS ARE APPLIED WITH CS LOW, THE ADC WILL OUTPUT ZEROS INDEFINITELY.
1196/98 F02
Figure 2. LTC1198 Operating Sequence Example: Differential Inputs (CH 1, CH 0)
14
U
LTC1198 has a 2-channel input multiplexer and can con-
vert either channel with respect to ground or the difference
between the two. It also automatically powers down when
not performing conversion, drawing only leakage current.
SERIAL INTERFACE
The LTC1196/LTC1198 will interface via three or four
wires to ASICs, PLDs, microprocessors, DSPs, or shift
registers (see Operating Sequence in Figures 1 and 2). To
run at their fastest conversion rates (600ns), they must be
clocked at 14.4MHz. HC logic families and any high speed
ASIC or PLD will easily interface to the ADCs at that speed
(see Data Transfer and Typical Application sections). Full
speed operation from a 3V supply can still be achieved with
3V ASICs, PLDs or HC logic circuits.
t
CYC
(12 CLKs)
t
CONV
(8.5 CLKs)
t
CYC
(16 CLKs)
POWER
DOWN
Hi-Z
t
CONV
(8.5CLKs)
W
U
UO
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