MAX1204 Maxim, MAX1204 Datasheet - Page 9

• Manufacturer Part Number: MAX1204
• Description: 5v / 8-cHANNEL / sERIAL / 10-bIT adc WITH 3v dIGITAL iNTERFACE
• Manufacturer: Maxim

The T/H enters tracking mode on the falling clock edge
after the fifth bit of the 8-bit control word is shifted in. The
T/H enters hold mode on the falling clock edge after the
eighth bit of the control word is shifted in. IN- is connect-
ed to GND if the converter is set up for single-ended
inputs, and the converter samples the “+” input. IN- con-
nects to the “-” input if the converter is set up for differen-
tial inputs, and the difference of |N+ - IN- is sampled.
The positive input connects back to IN+ at the end of
the conversion, and C
The time required for the T/H to acquire an input signal is
a function of how quickly its input capacitance is
charged. If the input signal’s source impedance is high,
acquisition time increases and more time must be
allowed between conversions. The acquisition time,
t
the signal, and is also the minimum time needed for the
signal to be acquired. It is calculated by the following:
where R
input signal, and t
source impedances below 4k do not significantly affect
the ADC’s AC performance. Higher source impedances
Figure 5. Quick-Look Circuit
ACQ
FULL-SCALE ANALOG INPUT
0.01µF
, is the maximum time the device takes to acquire
ANALOG
C2
4.096V
INPUT
0V TO
IN
+3V
= 9kΩ, R
0.01µF
0.1µF
t
ACQ
C1
4.7µF
ACQ
_______________________________________________________________________________________
= 7 x (R
S
HOLD
is never less than 1.5µs. Note that
= the source impedance of the
REFADJ
REF
VL
CH7
S
charges to the input signal.
+ R
MAX1204
IN
) x 16pF
5V, 8-Channel, Serial, 10-Bit ADC
SSTRB
SHDN
DOUT
SCLK
GND
V
DIN
V
Track/Hold
CS
DD
SS
N.C.
+3V
with 3V Digital Interface
can be used if an input capacitor is connected to the
analog inputs, as shown in Figure 5. Note that the input
capacitor forms an RC filter with the input source imped-
ance, limiting the ADC’s signal bandwidth.
Figure 4. Equivalent Input Circuit
0.1µF
SINGLE-ENDED MODE:
DIFFERENTIAL MODE:
OSCILLATOR
GND
CH0
CH1
CH2
CH3
CH6
CH4
CH5
CH7
+5V
2MHz
REF
INPUT
MUX
CAPACITIVE DAC
C
SWITCH
–
CH1
C
IN+ = CHO–CH7, IN- = GND.
IN+ AND IN- SELECTED FROM PAIRS OF
CH0/CH1, CH2/CH3, CH4/CH5, CH6/CH7.
16pF
HOLD
TRACK
SWITCH
+
OSCILLOSCOPE
T/H
CH2
9k
R
IN
HOLD
ZERO
CH3
AT THE SAMPLING INSTANT,
THE MUX INPUT SWITCHES
FROM THE SELECTED IN+
CHANNEL TO THE SELECTED
IN– CHANNEL.
COMPARATOR
CH4
SCLK
SSTRB
DOUT
9