LTC1286 Linear Technology, LTC1286 Datasheet - Page 9

• Manufacturer Part Number: LTC1286
• Description: Micropower Sampling 12-Bit A/D Converters In S0-8 Packages
• Manufacturer: Linear Technology

APPLICATION INFORMATION
OVERVIEW
The LTC1286 and LTC1298 are micropower, 12-bit, suc-
cessive approximation sampling A/D converters. The
LTC1286 typically draws 250 A of supply current when
sampling at 12.5kHz while the LTC1298 nominally con-
sumes 350 A of supply current when sampling at
11.1 kHz. The extra 100 A of supply current on the
LTC1298 comes from the reference input which is inten-
tionally tied to the supply. Supply current drops linearly as
the sample rate is reduced (see Supply Current vs Sample
Rate). The ADCs automatically power down when not
performing conversions, drawing only leakage current.
They are packaged in 8-pin SO and DIP packages. The
LTC1286 operates on a single supply from 4.5V to 9V,
TEST CIRCUITS
WAVEFORM 1
WAVEFORM 2
(SEE NOTE 2)
(SEE NOTE 1)
NOTE 1: WAVEFORM 1 IS FOR AN OUTPUT WITH INTERNAL CONDITIONS SUCH
THAT THE OUTPUT IS HIGH UNLESS DISABLED BY THE OUTPUT CONTROL.
NOTE 2: WAVEFORM 2 IS FOR AN OUTPUT WITH INTERNAL CONDITIONS SUCH
THAT THE OUTPUT IS LOW UNLESS DISABLED BY THE OUTPUT CONTROL.
D
D
OUT
OUT
CS
D
CLK
D
OUT
CS
IN
Voltage Waveforms for t
LTC1298
U
U
W
t
dis
dis
START
1
V
IH
U
Voltage Waveforms for t
LTC1286/98 • TC05
10%
90%
2
CLK
CS
D
OUT
while the LTC1298 operates from a 4.5V to 5.5V supply.
Both the LTC1286 and the LTC1298 contain a 12-bit,
switched-capacitor ADC, a sample-and-hold, and a
serial port (see Block Diagram). Although they share
the same basic design, the LTC1286 and LTC1298
differ in some respects. The LTC1286 has a differential
input and has an external reference input pin. It can
measure signals floating on a DC common-mode volt-
age and can operate with reduced spans to 1V. Reduc-
ing the spans allows it to achieve 244 V resolution. The
LTC1298 has a two-channel input multiplexer and can
convert either channel with respect to ground or the
difference between the two. The reference input is tied
to the supply pin.
LTC1286
3
en
4
Voltage Waveforms for t
t
en
1
V
OL
LTC1286/LTC1298
B11
2
LTC1286/98 • TC07
t
en
en
V
OL
LTC1286/98 • TC06
B11
9