Datasheet

LTC2487
11
2487fd
PIN FUNCTIONS
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
/Gain to 0.5 • V
REF
/Gain.
Outside this input range, the converter produces unique
over-range and under-range output codes.
CH0 to CH3 (Pin 8-Pin 11): Analog Inputs. May be pro-
grammed for single-ended or differential mode.
V
CC
(Pin 12): 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
+
, REF
–
(Pin 13, Pin 14): 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 (V
REF
= REF
+
– REF
–
) sets the full-scale range (–0.5 • V
REF
/Gain to 0.5
• V
REF
/Gain) for all input channels. When performing an
on-chip temperature measurement, the minimum value
of REF = 2V.
Exposed Pad (Pin 15): Ground. This pin is ground and
must be soldered to the PCB ground plane. For prototyping
purposes, this pin may remain fl oating.
FUNCTIONAL BLOCK DIAGRAM
AUTOCALIBRATION
AND CONTROL
DIFFERENTIAL
3RD ORDER
Δ3 MODULATOR
DECIMATING FIR
ADDRESS
INTERNAL
OSCILLATOR
I
2
C
INTERFACE
GND
V
CC
CH0
CH1
CH2
CH3
COM
MUX
IN
+
IN
–
CA0
SCL
REF
+
REF
–
CA1
SDA
f
O
(INT/EXT)
2487 BD
+
–
1.7k
TEMP
SENSOR