MAX1295 Maxim, MAX1295 Datasheet - Page 9

• Manufacturer Part Number: MAX1295
• Description: 265ksps / +3V / 6-/2-Channel / 12-Bit ADCs with +2.5V Reference and Parallel Interface
• Manufacturer: Maxim

Table 1. Control-Byte Functional Description
the analog inputs. This configuration is pseudo-differ-
ential in that only the signal at IN+ is sampled. The
return side (IN-) must remain stable within ±0.5LSB
(±0.1LSB for best performance) with respect to GND
during a conversion. To accomplish this, connect a
0.1µF capacitor from IN- (the selected input) to GND.
During the acquisition interval, the channel selected as
the positive input (IN+) charges capacitor C
Figure 3a. MAX1295 Simplified Input Structure
D2, D1, D0
D7, D6
SINGLE-ENDED MODE: IN+ = CH0–CH5, IN- = COM
DIFFERENTIAL MODE: IN+ AND IN- SELECTED FROM PAIRS OF
BIT
COM
CH0
D5
D4
D3
CH1
CH2
CH3
CH4
CH5
V
REF
INPUT
MUX
with +2.5V Reference and Parallel Interface
ACQMOD
PD1, PD0
SGL/DIF
UNI/BIP
A2, A1, A0
12-BIT CAPACITIVE DAC
NAME
C
CH0/CH1 AND CH2/CH3, AND CH4/CH5
SWITCH
–
_______________________________________________________________________________________
12pF
C
HOLD
TRACK
SWITCH
+
265ksps, +3V, 6-/2-Channel, 12-Bit ADCs
T/H
PD1 and PD0 select the various clock and power-down modes.
R
800
ACQMOD = 0: Internal Acquisition Mode
ACQMOD = 1: External Acquisition Mode
SGL/DIF = 0: Pseudo-Differential Analog Input Mode
SGL/DIF = 1: Single-Ended Analog Input Mode
In single-ended mode, input signals are referred to COM. In differential mode, the voltage difference
between two channels is measured (Tables 2, 4).
UNI/BIP = 0: Bipolar Mode
UNI/BIP = 1: Unipolar Mode
In unipolar mode, an analog input signal from 0V to V
signal can range from -V
Address bits A2, A1, A0 select which of the 6/2 (MAX1295/MAX1297) channels is to be converted
(Tables 2, 3).
IN
0
0
1
1
HOLD
ZERO
AT THE SAMPLING INSTANT,
THE MUX INPUT SWITCHES
FROM THE SELECTED IN+
CHANNEL TO THE SELECTED
IN- CHANNEL.
0
1
0
1
COMPARATOR
Full Power-Down Mode. Clock mode is unaffected.
Standby Power-Down Mode. Clock mode is unaffected.
Normal Operation Mode. Internal clock mode selected.
Normal Operation Mode. External clock mode selected.
HOLD
REF
. At the
/2 to +V
FUNCTIONAL DESCRIPTION
REF
end of the acquisition interval, the T/H switch opens,
retaining charge on C
at IN+.
The conversion interval begins with the input multiplex-
er switching C
negative input (IN-). This unbalances node ZERO at
the comparator’s positive input. The capacitive digital-
to-analog converter (DAC) adjusts during the remain-
Figure 3b. MAX1297 Simplified Input Structure
/2.
SINGLE-ENDED MODE: IN+ = CH0–CH1, IN- = COM
DIFFERENTIAL MODE: IN+ AND IN- SELECTED FROM PAIR
COM
CH0
CH1
V
REF
REF
INPUT
MUX
HOLD
12-BIT CAPACITIVE DAC
can be converted; in bipolar mode, the
C
CH0/CH1
SWITCH
–
12pF
C
HOLD
from the positive input (IN+) to the
TRACK
SWITCH
HOLD
+
T/H
R
800
IN
HOLD
as a sample of the signal
ZERO
AT THE SAMPLING INSTANT,
THE MUX INPUT SWITCHES
FROM THE SELECTED IN+
CHANNEL TO THE SELECTED
IN- CHANNEL.
COMPARATOR
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