Rainbow Electronics MAX1425 - Manual (Page 11)

MAX1425
10-Bit, 20Msps ADC
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and REFN. In this mode, the voltages at these pins
are set to their nominal values (see Electrical
Characteristics). The reference voltage levels can be
adjusted externally by applying a voltage at REFIN.
This allows other input levels to be used as well. The
full external reference mode is entered when REFIN =
AGND. External voltages can be applied to REFP,
CML, and REFN. In this mode, the internal reference
shuts down, resulting in less overall power consump-
tion.
Clock Input (CLK)
CLK is TTL/CMOS-compatible. Since the interstage
conversion of the device depends on the rising and
falling edges of the external clock, use a clock with low
jitter and fast rise and fall times (<2ns). Low clock jitter
improves SNR performance. The MAX1425 operates
with a 50% duty cycle. If the clock has a duty cycle
other than 50%, the clock must meet the specifications
for high and low periods as stated in the Electrical
Characteristics.
Output Enable/Power-Down Function
(
OE
/PD) and Output Data
All data outputs, D0 through D9, are TTL/CMOS-logic
compatible. There is a 5.5 clock-cycle latency between
the start convert signal and the valid output data. The
output coding for the MAX1425 is in binary two’s com-
plement format, which has the MSB inverted (Table 1).
The digital output goes into a high-impedance state
and the device into a low-power mode when OE/PD
goes high. For normal operation, drive OE low. The out-
puts are not designed to drive high capacitances or
n - 6
n
n - 5
n + 1
n - 4
n + 2
n - 3
n + 3
n - 2
n + 4
n - 1
n + 5
n
n + 6
n + 1
n + 7
5.5 CLOCK-CYCLE LATENCY
ANALOG INPUT
CLOCK INPUT
DATA OUTPUT
Figure 3. System Timing Diagram
Figure 4. Output Timing Diagram
DATA 0
INPUT
CLK
OUTPUT
DATA
t OD
t CLK
t CH
t CI
DATA 1 DATA 2
1 1 1 1 1 1 1 1 1 1 -1 LSB
1 1 1 0 0 0 0 0 0 0 -1/4 Full Scale
1 1 0 0 0 0 0 0 0 0 -1/2 Full Scale
0 1 0 0 0 0 0 0 0 0 +1/2 Full Scale
0 0 1 0 0 0 0 0 0 0 +1/4 Full Scale
0 0 0 0 0 0 0 0 0 1 +1 LSB
0 0 0 0 0 0 0 0 0 0 Bipolar Zero
0 1 1 0 0 0 0 0 0 0 +3/4 Full Scale
0 1 1 1 1 1 1 1 0 1 +Full Scale 2LSB
0 1 1 1 1 1 1 1 1 0 +Full Scale 1LSB
0 1 1 1 1 1 1 1 1 1 +Full Scale
OUTPUT CODE
(TWO’S COMPLEMENT)
DIFFERENTIAL INPUT
Table 1. MAX1425 Output Code
1 0 1 0 0 0 0 0 0 0 -3/4 Full Scale
1 0 0 0 0 0 0 0 0 1 -Full Scale + 1LSB
1 0 0 0 0 0 0 0 0 0 -Full Scale