Datasheet
10
LTC1606
1606fa
changing between 1111 1111 1111 1111 and 0000 0000
0000 0000. The gain error is trimmed by adjusting resistor
R4. An input voltage of 9.999542V (+FS – 1.5LSB) is
applied to V
IN
and R4 is adjusted until the output code is
changing between 0111 1111 1111 1110 and 0111 1111
1111 1111. Figure 6 shows the bipolar transfer character-
istic of the LTC1606.
If the external resistors are not used, the resulting offset
and gain error ranges are shown in Table 1.
DC Performance
One way of measuring the transition noise associated with
a high resolution ADC is to use a technique where a DC
signal is applied to the input of the ADC and the resulting
output codes are collected over a large number of conver-
sions. For example in Figure 7, the distribution of output
code is shown for a DC input that has been digitized 4096
times. The distribution is Gaussian and the RMS code
transition is about 0.65LSB.
DIGITAL INTERFACE
Internal Clock
The ADC has an internal clock that is trimmed to achieve
a typical conversion time of 2.3µs. No external adjust-
ments are required and, with the typical acquisition time of
1µs, throughput performance of 250ksps is assured.
+
5
4
3
2
1
10µF
+
2.2µF
33.2k
1%
100k
±10V INPUT
200Ω
1%
V
IN
AGND1
REF
CAP
AGND2
LTC1606
1606 • F05
392k
R4
50k
R3
50k
5V
Figure 5. ±10V Input with Offset and Gain Trim
INPUT VOLTAGE (V)
0V
OUTPUT CODE
–1
LSB
1606 • F06
011...111
011...110
000...001
000...000
100...000
100...001
111...110
1
LSB
BIPOLAR
ZERO
111...111
FS/2 – 1LSB–FS/2
FS = 20V
1LSB = FS/65536
Figure 6. LTC1606 Bipolar Transfer Characteristics
Table 1
WITH BOTH EXTERNAL WITHOUT THE EXTERNAL WITHOUT EITHER EXTERNAL
ERROR TERM RESISTORS INCLUDED 33.2k RESISTOR RESISTOR INCLUDED
Offset Error – 10mV < Error < 10mV 10mV < Error< 55mV 54mV < Error < 155mV
+Full-Scale Error –0.25% < Error < 0.25%
–0.50% < Error < 0.50% –1.3% < Error < –0.10% –3.40% < Error < –0.85%
–Full-Scale Error –0.25% < Error < 0.25%
–0.50% < Error < 0.50% 0.25% < Error < 1.40% 2.10% < Error < 6.15%
APPLICATIO S I FOR ATIO
WUUU
Figure 7. Histogram for 4096 Conversions
2500
2000
1500
1000
500
0
–3 –2 –1 0 1 2 3 4
COUNTS
CODE
1606 • F07