ltc1867l Linear Technology Corporation, ltc1867l Datasheet - Page 8

• Manufacturer Part Number: ltc1867l
• Description: Ltc1863l - Micropower, 3v, 12-bit, 8-channel 175ksps Adcs
• Manufacturer: Linear Technology Corporation

LTC1863L/LTC1867L
APPLICATIO S I FOR ATIO
Overview
The LTC1863L/LTC1867L are complete, low power, multi-
plexed ADCs. They consist of a 12-/16-bit, 175ksps capaci-
tive successive approximation A/D converter, a precision
internal reference, a configurable 8-channel analog input
multiplexer (MUX) and a serial port for data transfer.
Conversions are started by a rising edge on the CS/CONV
input. Once a conversion cycle has begun, it cannot be
restarted. Between conversions, the ADCs receive an input
word for channel selection and output the conversion
result, and the analog input is acquired in preparation for
the next conversion. In the acquire phase, a minimum time
of 2.01µs will provide enough time for the sample-and-
hold capacitors to acquire the analog signal.
8
TI I G DIAGRA S
CS/CONV
CS/CONV
CS/CONV
W U
SDO
SCK
Hi-Z
t
t
7
4
(SLEEP Mode Wake-Up Time)
50%
t 1
(SDO Valid After CS/CONV↓)
(For Short Pulse Mode)
50%
SLEEP BIT (SLP = 0)
READ-IN
U
0.45V
U
t
1
W
t
4
t
7
W
50%
1.9V
0.45V
U
50%
CS/CONV
During the conversion, the internal differential 16-bit
capacitive DAC output is sequenced by the SAR from the
most significant bit (MSB) to the least significant bit
(LSB). The input is sucessively compared with the binary
weighted charges supplied by the differential capacitive
DAC. Bit decisions are made by a low power, differential
comparator that rejects common mode noise. At the end
of a conversion, the DAC output balances the analog input.
The SAR content (a 12-/16-bit data word) that represents
the analog input is loaded into the 12-/16-bit output
latches.
SDO
SCK
SDI
SDO
SCK
t
3
t
5
(SDO Valid Hold Time After SCK↓)
t
(SDI Setup Time Before SCK↑),
1.9V
6
0.45V
t
1.9V
2
t
(SDI Hold Time After SCK↑)
8
(SDO Valid After SCK↓),
(BUS Relinquish Time)
t
8
t
5
90%
10%
1.9V
t
6
0.45V
0.45V
1.9V
t
t
3
2
Hi-Z
1.9V
0.45V
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1863L7L TD