Datasheet

LTC2389-16
15
238916f
pin Functions
PD/FD (Pin 30): Pseudo-Differential/Fully-Differential
Input. This pin, in conjunction with Pin 6 (OB/2C), controls
the analog input range of the converter and the binary
format of the conversion result, as described in Table 2.
Logic levels are determined by OV
DD
.
CS (Pin 31): Chip Select Input. The data I/O bus is enabled
when CS is low and goes Hi-Z when CS is high. CS also
gates the external shift clock. Logic levels are determined
by OV
DD
.
RESET (Pin 32): Reset Input. When this pin is brought high,
the LTC2389-16 is reset. If this occurs during a conversion,
the conversion is halted and the data bus becomes Hi-Z.
Logic levels are determined by OV
DD
.
PD (Pin 33): Power-Down Input. When this pin is brought
high, the LTC2389-16 is powered down and subse-
quent conversion requests are ignored. Before enabling
power-down, the result of the last conversion result should
be read. Logic levels are determined by OV
DD
.
CNVST (Pin 34): Conversion Start Input. A falling edge on
this pin puts the internal sample-and-hold into the hold
mode and starts a conversion. CNVST is independent of
CS. Logic levels are
determined by V
DD
.
VCM (Pin 36): Common Mode Analog Output. Typically
the output voltage on this pin is 2.08V. Bypass to GND
with a 10μF capacitor.
REFOUT (Pin 37): Internal Reference Output. Connect
this pin to REFIN if using the internal reference, giving
a nominal reference voltage of 4.096V. If an external
reference is used, connect REFOUT to ground to power
down the internal reference.
REFIN (Pin 38): Reference Input. Connect this pin to
REFOUT if using the internal reference, giving a nominal
reference voltage of 4.096V. An external reference can be
applied to REFIN if a more accurate reference is required.
If an external reference is used tie REFOUT to ground to
power down the internal reference. For increased filtering
of reference noise, bypass this pin to REFSENSE using a
1μF, or larger, ceramic capacitor.
REFSENSE (Pin 39): Reference Input Sense. Do not connect
REFSENSE to ground when using the internal reference. If
an external reference is used, connect REFSENSE to the
ground pin of the external reference.
IN
–
, IN
+
(Pin 42, Pin 43): Negative and Positive Analog
Inputs. The analog input range depends on the levels
applied to Pin 30 (PD/FD) and Pin 6 (OB/2C), as described
in Table 2.
Table 2. Analog Input Range and Output Binary Format Configuration Table. Use Inputs PD/FD and OB/2C to Select Converter Analog
Input Range and Binary Format of Conversion Result.
PD/FD OB/2C ANALOG INPUT RANGE BINARY FORMAT OF CONVERSION RESULT
0 0 Fully-Differential Two’s Complement
0 1 Fully-Differential Offset Binary
1 0 Pseudo-Differential Bipolar Two’s Complement
1 1 Pseudo-Differential Unipolar Straight Binary