LTC1605-1CG Linear Technology, LTC1605-1CG Datasheet - Page 8

• Manufacturer Part Number: LTC1605-1CG
• Description: IC A/D CONV 16BIT SAMPLNG 28SSOP
• Manufacturer: Linear Technology

Specifications of LTC1605-1CG

• Number Of Bits: 16
• Sampling Rate (per Second): 100k
• Data Interface: Parallel
• Number Of Converters: 1
• Power Dissipation (max): 80mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP (0.200", 5.30mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

LT
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LTC1605-1/LTC1605-2
Internal Voltage Reference
The LTC1605-1/LTC1605-2 has an on-chip, temperature
compensated, curvature corrected, bandgap reference,
which is factory trimmed to 2.50V. The full-scale range of
the ADC is equal to (1.6V
LTC1605-1 and ( 1.6V
LTC1605-2. The output of the reference is connected to
the input of a unity-gain buffer through a 4k resistor (see
Figure 3). The input to the buffer or the output of the
reference is available at REF (Pin 3). The internal refer-
ence can be overdriven with an external reference if more
accuracy is needed. The buffer output drives the internal
DAC and is available at CAP (Pin 4). The CAP pin can be
used to drive a steady DC load of less than 2mA. Driving
an AC load is not recommended because it can cause the
performance of the converter to degrade.
APPLICATIONS
8
®
1007 - Low noise precision amplifier. 2.7mA supply
A
IN
Figure 2. Analog Input Filtering
200
U
REF
REF
INFORMATION
1000pF
U
) or nominally 0V to 4V for the
) or nominally 4V for the
33.2k
W
1605-1/2 F02
V
CAP
IN
U
For minimum code transition noise the REF pin and the
CAP pin should each be decoupled with a capacitor to
filter wideband noise from the reference and the buffer
(2.2 F tantalum).
Offset and Gain Adjustments
The LTC1605-1/LTC1605-2 offset and full-scale errors
have been trimmed at the factory with the external
resistors shown in Figure 4. This allows for external
adjustment of offset and full scale in applications where
absolute accuracy is important. See Figure 5 for the offset
and gain trim circuit for the LTC1605-1/LTC1605-2.
First adjust the offset to zero by adjusting resistor R3.
Apply an input voltage of 30.5 V (0.5LSB) and adjust R3
so the code is changing between 0000 0000 0000 0001
and 0000 0000 0000 0000. The gain error is trimmed by
adjusting resistor R4. An input voltage of 3.999908V (FS
– 1.5LSB) is applied to V
output code is changing between 1111 1111 1111 1110
and 1111 1111 1111 1111. Figure 6a shows the unipolar
transfer characteristic of the LTC1605-1.
For the LTC1605-2, first adjust the offset to zero by
adjusting resistor R3. Apply an input voltage of – 61 V
(– 0.5LSB) and adjust R3 so the code is changing be-
tween 1111 1111 1111 1111 and 0000 0000 0000 0000.
The gain error is trimmed by adjusting resistor R4. An
input voltage of 3.999817V (+ FS – 1.5LSB) is applied to
V
between 0111 1111 1111 1110 and 0111 1111 1111
1111. Figure 6b shows the bipolar transfer characteris-
tics of the LTC1605-2.
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 conversions. For example, in Figure 7 the distribution
of output code is shown for a DC input that has been
digitized 10000 times. The distribution is Gaussian and
the RMS code transition is about 1LSB.
IN
and R4 is adjusted until the outut code is changing
IN
and R4 is adjusted until the