LTC1604CG View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1604CG' PDF : 20 Pages View PDF
LTC1604
APPLICATIONS INFORMATION
LTC1450
ANALOG INPUT
2V TO 2.7V
DIFFERENTIAL
2V TO 2.7V
1 AIN+
2 AIN–
LTC1604
3
VREF
47µF
4
REFCOMP
5
AGND
1604 F13
Figure 13. Driving VREF with a DAC
±2.5V
ANALOG INPUT
0V TO
5V
1 AIN+
2 AIN–
3 VREF
LTC1604
10µF
4 REFCOMP
5 AGND
1604 F14b
Figure 14b. Selectable 0V to 5V or ±2.5V Input Range
80
70
60
50
40
30
20
10
0
1k
10k
100k
1M
INPUT FREQUENCY (Hz)
1604 G14a
Figure 14a. CMRR vs Input Frequency
Full-Scale and Offset Adjustment
Figure 15a shows the ideal input/output characteristics
for the LTC1604. The code transitions occur midway
between successive integer LSB values (i.e., – FS +
0.5LSB, – FS + 1.5LSB, – FS + 2.5LSB,... FS – 1.5LSB,
FS – 0.5LSB). The output is two’s complement binary with
1LSB = FS – (– FS)/65536 = 5V/65536 = 76.3µV.
In applications where absolute accuracy is important,
offset and full-scale errors can be adjusted to zero. Offset
error must be adjusted before full-scale error. Figure 15b
shows the extra components required for full-scale error
adjustment. Zero offset is achieved by adjusting the offset
applied to the AIN– input. For zero offset error apply
can not exceed the AVDD or VSS power supply voltages.
Integral nonlinearity errors (INL) and differential nonlin-
earity errors (DNL) are independent of the common mode
voltage, however, the bipolar zero error (BZE) will vary.
The change in BZE is typically less than 0.1% of the
common mode voltage. Dynamic performance is also
affected by the common mode voltage. THD will degrade
as the inputs approach either power supply rail, from 96dB
with a common mode of 0V to 86dB with a common mode
of 2.5V or – 2.5V.
Differential inputs allow greater flexibility for accepting
different input ranges. Figure 14b shows a circuit that
converts a 0V to 5V analog input signal with only an
additional buffer that is not in the signal path.
011...111
011...110
000...001
000...000
111...111
111...110
100...001
100...000
– (FS – 1LSB)
FS – 1LSB
INPUT VOLTAGE (AIN+ – AIN–)
1604 F15a
Figure 15a. LTC1604 Transfer Characteristics
14
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