Datasheet

LTC2498
10
2498ff
GND (Pins 1, 3, 4, 5, 6, 31, 32, 33): Ground. Multiple
ground pins internally connected for optimum ground cur-
rent flow and V
CC
decoupling. Connect each one of these
pins to a common ground plane through a low impedance
connection. All eight pins must be connected to ground
for proper operation.
NC (Pin 2): No Connection. This pin can be left floating
or tied to GND.
COM (Pin 7): The Common Negative Input (IN
–
) for All
Single-Ended Multiplexer Configurations. The voltage on
CH0 to CH15 and COM pins can have any value between
GND – 0.3V to V
CC
+ 0.3V. Within these limits, the two
selected inputs (IN
+
and IN
–
) provide a bipolar input range
(V
IN
= IN
+
– IN
–
) from –0.5 • V
REF
to 0.5 • V
REF
. Outside
this input range, the converter produces unique over-range
and under-range output codes.
CH0 to CH15 (Pins 8 to 23): Analog Inputs. May be pro-
grammed for single-ended or differential mode.
MUXOUTP (Pin 24): Positive Multiplexer Output. Used
to drive an external buffer/amplifier or can be shorted
directly to ADCINP.
ADCINP (Pin 25): Positive ADC Input. Tie to the output
of a buffer/amplifier driven by MUXOUTP or tie directly
to MUXOUTP.
ADCINN (Pin 26): Negative ADC Input. Tie to
the output
of
a buffer/amplifier driven by MUXOUTN or tie directly
to MUXOUTN.
MUXOUTN (Pin 27): Negative Multiplexer Output. Used
to drive an external buffer/amplifier or can be shorted
directly to ADCINN.
V
CC
(Pin 28): Positive Supply Voltage. Bypass to GND with
a 10µF tantalum capacitor in parallel with a 0.1µF ceramic
capacitor as close to the part as possible.
REF
+
(Pin 29), REF
–
(Pin 30): Differential Reference Input.
The voltage on these pins can have any value between
GND and V
CC
as long as the reference positive input, REF
+
,
remains more positive than the negative reference input,
REF
–
, by at least 0.1V. The differential voltage (REF = REF
+
– REF
–
) sets the full-scale range for all input channels.
When performing an on-chip temperature measurement,
the minimum value of REF = 2V.
typical perForMance characteristics
PSRR vs Frequency at V
CC
(2x Speed Mode)
PSRR vs Frequency at V
CC
(2x Speed Mode)
FREQUENCY AT V
CC
(Hz)
0
–140
RREJECTION (dB)
–120
–80
–60
–40
0
20
100
140
2498 G37
–100
–20
80
180
220200
40
60
120 160
V
CC
= 4.1V DC ±1.4V
REF
+
= 2.5V
REF
–
= GND
IN
+
= GND
IN
–
= GND
f
O
= GND
T
A
= 25°C
FREQUENCY AT V
CC
(Hz)
30600
–60
–40
0
30750
2498 G38
–80
–100
30650 30700 30800
–120
–140
–20
REJECTION (dB)
V
CC
= 4.1V DC ±0.7V
REF
+
= 2.5V
REF
–
= GND
IN
+
= GND
IN
–
= GND
f
O
= GND
T
A
= 25°C
pin Functions