7
LTC1864L/LTC1865L
sn18645L 18645Lfs
V
REF
(Pin 1): Reference Input. The reference input defines
the span of the A/D converter and must be kept free of
noise with respect to GND.
IN
+
, IN
(Pins 2, 3): Analog Inputs. These inputs must be
free of noise with respect to GND.
GND (Pin 4): Analog Ground. GND should be tied directly
to an analog ground plane.
CONV (Pin 5): Convert Input. A logic high on this input
starts the A/D conversion process. If the CONV input is left
high after the A/D conversion is finished, the part powers
down. A logic low on this input enables the SDO pin,
allowing the data to be shifted out.
SDO (Pin 6): Digital Data Output. The A/D conversion
result is shifted out of this pin.
SCK (Pin 7): Shift Clock Input. This clock synchronizes the
serial data transfer.
V
CC
(Pin 8):
Positive Supply. This supply must be kept
free of noise and ripple by bypassing directly to the
analog ground plane.
UU
U
PI FU CTIO S
LTC1865L (MSOP Package)
CONV (Pin 1): Convert Input. A logic high on this input
starts the A/D conversion process. If the CONV input is left
high after the A/D conversion is finished, the part powers
down. A logic low on this input enables the SDO pin,
allowing the data to be shifted out.
CH0, CH1 (Pins 2, 3): Analog Inputs. These inputs must
be free of noise with respect to AGND.
AGND (Pin 4): Analog Ground. AGND should be tied
directly to an analog ground plane.
DGND (Pin 5): Digital Ground. DGND should be tied
directly to an analog ground plane.
SDI (Pin 6):
Digital Data Input. The A/D configuration
word is shifted into this input.
CONV (Pin 1): Convert Input. A logic high on this input
starts the A/D conversion process. If the CONV input is left
high after the A/D conversion is finished, the part powers
down. A logic low on this input enables the SDO pin,
allowing the data to be shifted out.
CH0, CH1 (Pins 2, 3): Analog Inputs. These inputs must
be free of noise with respect to GND.
GND (Pin 4): Analog Ground. GND should be tied directly
to an analog ground plane.
LTC1865L (SO-8 Package)
SDO (Pin 7): Digital Data Output. The A/D conversion
result is shifted out of this output.
SCK (Pin 8): Shift Clock Input. This clock synchronizes the
serial data transfer.
V
CC
(Pin 9):
Positive Supply. This supply must be kept
free of noise and ripple by bypassing directly to the
analog ground plane.
V
REF
(Pin 10): Reference Input. The reference input de-
fines the span of the A/D converter and must be kept free
of noise with respect to AGND.
SDI (Pin 5):
Digital Data Input. The A/D configuration
word is shifted into this input.
SDO (Pin 6): Digital Data Output. The A/D conversion
result is shifted out of this output.
SCK (Pin 7): Shift Clock Input. This clock synchronizes the
serial data transfer.
V
CC
(Pin 8):
Positive Supply. This supply must be kept
free of noise and ripple by bypassing directly to the
analog ground plane. V
REF
is tied internally to this pin.
LTC1864L
8
LTC1864L/LTC1865L
sn18645L 18645Lfs
Load Circuit for t
dDO
, t
r
, t
f
, t
dis
and t
en
Voltage Waveforms for SDO Rise and Fall Times, t
r
, t
f
Voltage Waveforms for SDO Delay Times, t
dDO
and
t
hDO
Voltage Waveforms for t
en
SDO
3k
20pF
TEST POINT
V
CC
t
dis
WAVEFORM 2, t
en
t
dis
WAVEFORM 1
1864 TC01
SCK
SDO
V
IL
t
dDO
t
hDO
V
OH
V
OL
1864 TC02
1864 TC03
CONV
SDO
t
en
SDO
t
r
t
f
1864 TC04
V
OH
V
OL
TEST CIRCUITS
Voltage Waveforms for t
dis
SDO
WAVEFORM 1
(SEE NOTE 1)
V
IH
t
dis
90%
10%
SDO
WAVEFORM 2
(SEE NOTE 2)
CONV
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
1864 TC05
FUNCTIONAL BLOCK DIAGRA
UU
W
1864/65 BD
16-BIT
SAMPLING
ADC
BIAS AND
SHUTDOWN
CONVERT
CLK
SERIAL
PORT
16 BITS
IN
+
(CH0)
IN
(CH1)
V
CC
V
REF
SDO
GND
CONV
(SDI) SCK
PIN NAMES IN
PARENTHESES
REFER TO LTC1865L
DATA OUT
DATA IN
+
9
LTC1864L/LTC1865L
sn18645L 18645Lfs
LTC1864L OPERATION
Operating Sequence
The LTC1864L conversion cycle begins with the rising
edge of CONV. After a period equal to t
CONV
, the conver-
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.
Analog Inputs
The LTC1864L has a unipolar differential analog input. The
converter will measure the voltage between the “IN
+
” and
“IN
” inputs. A zero code will occur when IN
+
minus IN
equals zero. Full scale occurs when IN
+
minus IN
equals
V
REF
minus 1LSB. See Figure 2. Both the “IN
+
” and
“IN
” inputs are sampled at the same time, so common
mode noise on the inputs is rejected by the ADC. If “IN
is grounded and V
REF
is tied to V
CC
, a rail-to-rail input span
will result on “IN
+
” as shown in Figure 3.
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
CC
to
1V.
CONV
t
CONV
SCK
SDO
16151413121110987654321
B15
B14 B12 B10 B8 B6 B4 B2 B0*
Hi-Z
1854 F01
Hi-Z
B13
B11 B9 B7 B5 B3 B1
SLEEP MODE
t
SMPL
*AFTER COMPLETING THE DATA TRANSFER, IF FURTHER SCK CLOCKS ARE
APPLIED WITH CONV LOW, THE ADC WILL OUTPUT ZEROS INDEFINITELY
DON'T CARE
1
2
3
4
8
7
6
5
V
REF
IN
+
IN
GND
V
CC
SCK
SDO
CONV
LTC1864L
1864 F03
V
IN
= 0V TO V
CC
V
CC
1µF
SERIAL DATA LINK TO
ASIC, PLD, MPU, DSP
OR SHIFT REGISTERS
Figure 1. LTC1864L Operating Sequence
Figure 3. LTC1864L with Rail-to-Rail Input SpanFigure 2. LTC1864L Transfer Curve
0V
1LSB
V
REF
– 2LSB
V
REF
– 1LSB
V
REF
V
IN
*
*V
IN
= IN
+
– IN
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
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
1864 F02
APPLICATIO S I FOR ATIO
WUUU

LTC1864LAIS8#TRPBF

Mfr. #:
Manufacturer:
Analog Devices Inc.
Description:
Analog to Digital Converters - ADC 16-bit, 3V, 150ksps ADC
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
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