LTC1864L Linear Technology, LTC1864L Datasheet - Page 9

• Manufacturer Part Number: LTC1864L
• Description: (LTC1864L / LTC1865L) 16-Bit 1/2-Channel 150ksps ADCs
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
LTC1864L OPERATION
Operating Sequence
The LTC1864L conversion cycle begins with the rising
edge of CONV. After a period equal to t
sion is finished. If CONV is left high after this time, the
LTC1864L goes into sleep mode drawing only leakage
current. On the falling edge of CONV, the LTC1864L goes
into sample mode and SDO is enabled. SCK synchronizes
the data transfer with each bit being transmitted from SDO
on the falling SCK edge. The receiving system should
capture the data from SDO on the rising edge of SCK. After
completing the data transfer, if further SCK clocks are
applied with CONV low, SDO will output zeros indefinitely.
See Figure 1.
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CONV
SDO
SCK
•
•
•
Figure 2. LTC1864L Transfer Curve
U
t
CONV
U
DON'T CARE
*V
W
IN
Hi-Z
= IN
+
CONV
Figure 1. LTC1864L Operating Sequence
– IN
–
, the conver-
SLEEP MODE
U
1864 F02
Analog Inputs
The LTC1864L has a unipolar differential analog input. The
converter will measure the voltage between the “IN
“IN
equals zero. Full scale occurs when IN
V
“IN
mode noise on the inputs is rejected by the ADC. If “IN
is grounded and V
will result on “IN
Reference Input
The voltage on the reference input of the LTC1864L
defines the full-scale range of the A/D converter. The
LTC1864L can operate with reference voltages from V
1V.
REF
V
IN
–
–
*
B15 B14
*AFTER COMPLETING THE DATA TRANSFER, IF FURTHER SCK CLOCKS ARE
” inputs. A zero code will occur when IN
” inputs are sampled at the same time, so common
APPLIED WITH CONV LOW, THE ADC WILL OUTPUT ZEROS INDEFINITELY
1
minus 1LSB. See Figure 2. Both the “IN
V
2
IN
B13
= 0V TO V
3
Figure 3. LTC1864L with Rail-to-Rail Input Span
B12
4
B11
5
CC
+
B10
REF
” as shown in Figure 3.
6
1
2
3
4
LTC1864L/LTC1865L
B9
V
IN
IN
GND
is tied to V
7
REF
t
+
–
LTC1864L
SMPL
B8
8
B7
9
CONV
SDO
SCK
V
B6
1 F
10
CC
B5
CC
11
8
7
6
5
1864 F03
, a rail-to-rail input span
B4
12
B3
13
V
+
CC
minus IN
B2
14
B1
15
SERIAL DATA LINK TO
ASIC, PLD, MPU, DSP
OR SHIFT REGISTERS
1854 F01
B0*
+
16
minus IN
Hi-Z
–
+
equals
+
” and
” and
18645Lf
CC
9
–
to
–
”