Datasheet

LTC2309
7
2309fd
pIn FunCtIOns
CH3-CH7 (Pins 1-5): Channel 3 to Channel 7 Analog
Inputs. CH3-CH7 can be configured as single-ended
or differential input channels. See the Analog Input
Multiplexer section.
COM (Pin 6): Common Input. This is the reference
point for all single-ended inputs. It must be free of
noise and should be connected to ground for unipolar
conversions and midway between GND and REFCOMP
for bipolar conversions.
V
REF
(Pin 7): 2.5V Reference Output. Bypass to GND
with a minimum 2.2µF ceramic capacitor. The internal
reference may be overdriven by an external 2.5V refer-
ence at this pin.
REFCOMP (Pin 8): Reference Buffer Output. Bypass
to GND with 10µF and 0.1µF ceramic capacitors in
parallel. Nominal output voltage is 4.096V. The internal
reference buffer driving this pin is disabled by ground-
ing V
REF
, allowing REFCOMP to be overdriven by an
external source.
GND (Pins 9-11, 18-20): Ground. All GND pins must
be connected to a solid ground plane.
V
DD
(Pins 12, 13, 21): 5V Supply. The range of V
DD
is
4.75V to 5.25V. Bypass V
DD
to GND with a 10µF ceramic
capacitor in parallel with three 0.1µF ceramic capacitors,
one located as close as possible to each pin.
AD0 (Pin 14): Chip Address Control Pin. This pin is
configured as a three-state (LOW, HIGH, floating) ad-
dress control bit for the device I
2
C address. See Table 2
for address selection.
AD1 (Pin 15): Chip Address Control Pin. This pin is
configured as a three-state (LOW, HIGH, floating)
address control bit for the device I
2
C address. See
Table 2 for address selection.
SCL (Pin 16): Serial Clock Pin of the I
2
C Interface. The
LTC2309 can only act as a slave and the SCL pin only
accepts an external serial clock. Data is shifted into
the SDA pin on the rising edges of the SCL clock and
output through the SDA pin on the falling edges of the
SCL clock.
SDA (Pin 17): Bidirectional Serial Data Line of the I
2
C
Interface. In transmitter mode (read), the conversion
result is output at the SDA pin, while in receiver mode
(write), the D
IN
word is input at the SDA pin to con-
figure the ADC. The pin is high impedance during the
data input mode and is an open-drain output (requires
an appropriate pull-up device to V
DD
) during the data
output mode.
CH0-CH2 (Pins 22-24): Channel 0 to Channel 2 Analog
Inputs. CH0-CH2 can be configured as single-ended
or differential input channels. See the Analog Input
Multiplexer section.
Exposed Pad (Pin 25): Ground. Must be soldered
directly to ground plane.
(QFN)