LTC1606 Linear Technology, LTC1606 Datasheet - Page 9

• Manufacturer Part Number: LTC1606
• Description: 16-Bit/ 250ksps/ Single Supply ADC
• Manufacturer: Linear Technology

APPLICATIONS
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 2.3 s. No external adjust-
ments are required and, with the typical acquisition time of
1 s, throughput performance of 250ksps is assured.
DATA MODE
Figure 7. Histogram for 4096 Conversions
MODE
BUSY
2500
2000
1500
1000
500
R/C
0
–3
DATA VALID
PREVIOUS
ACQUIRE
U
–2
t
6
Figure 8. Conversion Timing with Outputs Enabled After Conversion (CS Tied Low)
INFORMATION
–1
U
CODE
t
t
3
7
0
t
1
1
W
Hi-Z
2
3
t
9
1606 • F07
CONVERT
4
t
DATA VALID
U
CONV
PREVIOUS
t
2
t
4
t
11
NOT VALID
Timing and Control
Conversion start and data read are controlled by two
digital inputs: CS and R/C. To start a conversion and put
the sample-and-hold into the hold mode, bring CS and
R/C low for no less than 40ns. Once initiated, it cannot be
restarted until the conversion is complete. Converter
status is indicated by the BUSY output and this is low while
the conversion is in progress.
There are two modes of operation. The first mode is shown
in Figure 8. The digital input R/C is used to control the start
of conversion. CS is tied low. When R/C goes low, the
sample-and-hold goes into the hold mode and a conver-
sion is started. BUSY goes low and stays low during the
conversion and will go back high after the conversion has
been completed and the internal output shift registers
have been updated. R/C should remain low for no less than
40ns. During the time R/C is low, the digital outputs are in
a Hi-Z state. R/C should be brought back high within 1 s
after the start of the conversion to ensure that no errors
occur in the digitized result. The second mode, shown in
Figure 9, uses the CS signal to control the start of a
conversion and the reading of the digital output. In this
mode the R/C input signal should be brought low no less
than 10ns before the falling edge of CS. The minimum
pulse width for CS is 40ns. When CS falls, BUSY goes low
and will stay low until the end of the conversion. BUSY will
go high after the conversion has been completed. The new
data is valid when CS is brought back low again to initiate
a read. Again, it is recommended that both R/C and CS
return high within 1 s after the start of the conversion.
ACQUIRE
t
5
t
8
t
ACQ
VALID
DATA
CONVERT
Hi-Z
LTC1606
VALID
DATA
1606 • F08
9