MAX1266AEEI Maxim Integrated, MAX1266AEEI Datasheet - Page 15

• Manufacturer Part Number: MAX1266AEEI
• Description: Analog to Digital Converters - ADC
• Manufacturer: Maxim Integrated

Specifications of MAX1266AEEI

• Number Of Channels: 6/3
• Architecture: SAR
• Conversion Rate: 420 KSPs
• Resolution: 12 bit
• Input Type: Single-Ended/Pseudo-Differential
• Snr: 70 dB
• Interface Type: Parallel
• Operating Supply Voltage: 4.5 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Package / Case: QSOP-28
• Maximum Power Dissipation: 667 mW
• Minimum Operating Temperature: - 40 C
• Number Of Converters: 1
• Voltage Reference: 2.5 V

Table 5. Full Scale and Zero Scale for Unipolar and Bipolar Operation
Figure 8. Unipolar Transfer Functions
Shutdown mode turns off all chip functions that draw
quiescent current, reducing the typical supply current
to 2µA immediately after the current conversion is com-
pleted. A rising edge on WR causes the MAX1266/
MAX1268 to exit shutdown mode and return to normal
operation. To achieve full 12-bit accuracy with a 4.7µF
reference bypass capacitor, 500µs is required after
power-up. Waiting 500µs in standby mode, instead of
in full-power mode, can reduce power consumption by
a factor of 3 or more. When using an external refer-
ence, only 50µs is required after power-up. Enter
standby mode by performing a dummy conversion with
the control byte specifying standby mode.
Note: Bypass capacitors larger than 4.7µF between
REF and GND result in longer power-up delays.
Table 5 shows the full-scale voltage ranges for unipolar
and bipolar modes. Figures 8 depicts the nominal
111 . . . 111
111 . . . 110
100 . . . 010
100 . . . 001
100 . . . 000
011 . . . 111
011 . . . 110
000 . . . 000
011 . . . 101
000 . . . 001
OUTPUT CODE
(COM)
with +2.5V Reference and Parallel Interface
Zero scale
0
Full scale
1 LSB =
FS = REF + COM
ZS = COM
1
—
2
4096
REF
______________________________________________________________________________________
420ksps, +5V, 6-/2-Channel, 12-Bit ADCs
UNIPOLAR MODE
INPUT VOLTAGE (LSB)
2048
FULL-SCALE
TRANSITION
Transfer Function
V
Shutdown Mode
REF
FS - 3/2 LSB
COM
—
+ COM
FS
unipolar input/output (I/O) transfer function, and Figure 9
shows the bipolar I/O transfer function. Code transitions
occur halfway between successive-integer LSB values.
Output coding is binary, with 1 LSB = (V
When running at the maximum clock frequency of
7.6MHz, the specified throughput of 420ksps is
achieved by completing a conversion every 18 clock
cycles: 1 write cycle, 3 acquisition cycles, 13 conver-
sion cycles, and 1 read cycle. This assumes that the
results of the last conversion are read before the next
control byte is written. It is possible to achieve higher
throughputs, up to 475ksps, by first writing a control
byte to begin the acquisition cycle of the next conver-
sion, then reading the results of the previous conver-
sion from the bus. This technique (Figure 10) allows a
conversion to be completed every 16 clock cycles.
Note that the switching of the data bus during acquisi-
Figure 9. Bipolar Transfer Functions
*COM ≥ V
Negative full scale
011 . . . 111
011 . . . 110
000 . . . 010
000 . . . 001
000 . . . 000
111 . . . 111
111 . . . 110
100 . . . 000
111 . . . 101
100 . . . 001
Positive full scale
Zero scale
OUTPUT CODE
REF
/ 2
- FS
1 LSB =
FS = REF
ZS = COM
-FS =
BIPOLAR MODE
-REF
2
2
4096
REF
+ COM
+ COM
Maximum Sampling Rate/
INPUT VOLTAGE (LSB)
COM*
Achieving 475ksps
-V
V
REF
REF
COM
/2 + COM
/2 + COM
REF
+FS - 1 LSB
/ 4096).
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