LTC1857/LTC1858/LTC1859
W U U
APPLICATIO S I FOR ATIO
U
DV
AV
DD
DD
MUX ADDRESS AND RANGE
CONVST
CH0
CH1
CONTROL
LOGIC
SDI
INTERNAL
CLOCK
BUSY
INPUT MUX
AND
RANGE
SELECT
•
•
•
SCK
RD
+
12-/14-/16-BIT
SAMPLING ADC
CH7
DATA OUT
SERIAL I/O
OV
DD
COM
–
SDO
4.096V
2.5V
REFERENCE
1.6384X
8k
–
+
+
–
1859 BD
MUXOUT
MUXOUT
ADC
ADC
AGND1
V
REFCOMP
AGND2 AGND3 DGND
REF
Figure 1. LTC1857/LTC1858/LTC1859 Simplified Equivalent Circuit
LT1792: Single, low noise JFET input op amp, ±5V
supplies.
+
–
A
A
CH0
CH1
IN
3000pF
IN
LT1793: Single, low noise JFET input op amp, 10pA bias
•
•
•
•
current, ±5V supplies.
+
–
MUXOUT
MUXOUT
LT1881/LT1882: Dual and quad, 200pA bias current, rail-
to-rail output op amps. Up to ±15V supplies.
+
ADC
–
ADC
LT1844/LT1885: Dual and quad, 400pA bias current, rail-
to-rail output op amps. Up to ±15V supplies. Faster
response and settling time.
1859 F02
Figure 2. Analog Input Filtering
INTERNAL VOLTAGE REFERENCE
LT1227: 140MHz video current feedback amplifier. 10mA
supply current. ±5V to ±15V supplies. Low noise and low
distortion.
The LTC1857/LTC1858/LTC1859 have an on-chip, tem-
perature compensated, curvature corrected, bandgap ref-
erence, which is factory trimmed to 2.50V. The full-scale
range of the LTC1857/LTC1858/LTC1859 is equal to ±5V,
0V to 5V, ±10V or 0V to 10V. The output of the reference
is connected to the input of a gain of 1.6384x buffer
through an 8k resistor (see Figure 3). The input to the
LT1468/LT1469: Single and dual 90MHz, 16-bit accurate
op amp. Good AC/DC specs.
LT1677: Single, low noise op amp. Rail-to-rail input and
output. Up to ±15V supplies.
185789f
11
Linear Systems [ Linear Systems ]
