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MAX1304ECM+

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P37
MAX1304–MAX1306/MAX1308–MAX1310/MAX1312–MAX1314
8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs
with ±10V, ±5V, and 0 to +5V Analog Input Ranges
22 ______________________________________________________________________________________
Starting a Conversion
To start a conversion using internal clock mode, pull
CONVST low for the acquisition time (t
ACQ
). The T/H
acquires the signal while CONVST is low, and conver-
sion begins on the rising edge of CONVST. The end-of-
conversion signal (EOC) pulses low whenever a
conversion result becomes available for read. The end-
of-last-conversion signal (EOLC) goes low when the last
conversion result is available (Figure 7).
To start a conversion using external clock mode, pull
CONVST low for the acquisition time (t
ACQ
). The T/H
acquires the signal while CONVST is low. The rising
edge of CONVST is the sampling instant. Apply an
external clock to CLK to start the conversion. To avoid
T/H droop degrading the sampled analog input signals,
the first CLK pulse must occur within 10µs from the
rising edge of CONVST. Additionally, the external clock
frequency must be greater than 100kHz to avoid T/H
droop-degrading accuracy. The first conversion result
is available for read when EOC goes low on the rising
edge of the 13th clock cycle. Subsequent conversion
results are available after every third clock cycle there-
after (Figures 8 and 9).
In both internal and external clock modes, hold
CONVST high until the last conversion result is read. If
CONVST goes low in the middle of a conversion, the
current conversion is aborted and a new conversion is
initiated. Furthermore, there must be a period of bus
inactivity (t
QUIET
) for 50ns or longer before the falling
edge of CONVST for the specified ADC performance.
CONVST
CH0
TRACK
HOLD
D0–D11
SAMPLE
INSTANT
t
ACQ
t
EOC
t
ACC
t
CTR
t
RDH
t
RTC
t
RDL
t
REQ
TRACK
CH1
t
CONV
t
NEXT
EOC
t
CVEOLCD
t
QUIET
≥ 50ns
EOLC
CS*
RD
*CS CAN BE LOW AT ALL TIMES, LOW DURING THE RD CYCLES, OR THE SAME AS RD.
Figure 7. Read During Conversion—Channel 0 and Channel 1 Selected, Internal Clock
MAX1304–MAX1306/MAX1308–MAX1310/MAX1312–MAX1314
Reading a Conversion Result
Reading During a Conversion
Figures 7 and 8 show the interface signals to initiate a
read operation during a conversion cycle. These figures
show two channels selected for conversion. If more
channels are selected, the results are available succes-
sively at every EOC falling edge. CS can be low at all
times, low during the RD cycles, or the same as RD.
After initiating a conversion by bringing CONVST high,
wait for EOC to go low. In internal clock mode, EOC
goes low within 900ns. In external clock mode, EOC
goes low on the rising edge of the 13th CLK cycle. To
read the conversion result, drive CS and RD low to
latch data to the parallel digital output bus. Bring RD
high to release the digital bus. In internal clock mode,
the next EOC falling edge occurs within 225ns. In exter-
nal clock mode, the next EOC falling edge occurs in
three CLK cycles. When the last result is available
EOLC goes low.
Reading After Conversion
Figure 9 shows the interface signals for a read operation
after a conversion with all eight channels enabled. At
the falling of EOLC, driving CS and RD low places the
first conversion result onto the parallel bus. Successive
low pulses of RD place the successive conversion
results onto the bus. When the last conversion results in
the sequence are read, additional read pulses wrap the
pointer back to the first converted result.
CONVST
CLK
CH3
TRACK
HOLD
D0–D11
SAMPLE
INSTANT
t
ACQ
t
CNTC
t
CTR
t
RDH
t
RTC
t
ACC
t
RDL
t
REQ
TRACK
CH7
EOC
RD
1 2 3 12 13 14 15 16 17 18 19 1
t
CLK
t
EOCD
t
CONV
t
NEXT
t
EOC
t
EOCD
t
CLKH
t
EOLCD
t
CVEOLCD
t
QUIET
≥ 50ns
t
CLKL
EOLC
CS*
*CS CAN BE LOW AT ALL TIMES, LOW DURING THE RD CYCLES, OR THE SAME AS RD.
Figure 8. Read During Conversion—Channel 3 and Channel 7 Selected, External Clock
8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs
with ±10V, ±5V, and 0 to +5V Analog Input Ranges
______________________________________________________________________________________ 23
MAX1304–MAX1306/MAX1308–MAX1310/MAX1312–MAX1314
8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs
with ±10V, ±5V, and 0 to +5V Analog Input Ranges
24 ______________________________________________________________________________________
Power-Up Reset
At power-up, all channels are selected for conversion
(see the
Configuration Register
section). After applying
power, allow the 1ms wake-up time to elapse and then
initiate a dummy conversion and discard the results.
After the dummy conversion is complete, accurate con-
versions can be obtained.
Power-Saving Modes
Shutdown Mode
During shutdown the internal reference and analog
circuits in the device shutdown and the analog supply
current drops to 0.6µA (typ). Select shutdown mode
using the SHDN input. Set SHDN high to enter shut-
down mode. SHDN takes precedence over CHSHDN.
Entering and exiting shutdown mode does not change
the configuration byte. However, a new configuration
byte can be written while in shutdown mode by follow-
ing the standard write procedure shown in Figure 6.
EOC and EOLC are high when the MAX1304–MAX1306/
MAX1308–MAX1310/MAX1312–MAX1314 are shut down.
The state of the digital outputs D0–D11 is independent
of the state of SHDN. If CS and RD are low, the digital
outputs D0–D11 are active regardless of SHDN. The
digital outputs only go high impedance when CS or RD
is high. When the digital outputs are powered down, the
digital supply current drops to 20nA.
Exiting shutdown (falling edge of SHDN) starts a con-
version in the same way as the rising edge of CONVST.
After coming out of shutdown, initiate a dummy conver-
sion and discard the results. After the dummy conver-
sion, allow the 1ms wake-up time to expire before
initiating the first accurate conversion.
Channel Shutdown (
CCHHSSHHDDNN
)
The channel-shutdown feature allows analog input
channels to be powered down when they are not
selected for conversion. Powering down channels that
are not selected for conversion reduces the analog
supply current by 2.9mA per channel. To power down
channels that are not selected for conversion, pull
CHSHDN low. See the
Configuration Register
section
for information on selecting and deselecting channels
for conversion.
The drawback of powering down analog inputs that are
not selected for conversion is that it takes time to power
them up. Figure 10 shows how a dummy conversion is
used to power up an analog input in external clock
mode. After selecting a new channel in the configura-
tion register, initiate a dummy conversion and discard
the results. After the dummy conversion, allow the 1ms
wake-up time (t
WAKE
) to expire before initiating the first
accurate conversion.
D0–D11
CONVST
t
CTR
t
ACC
t
REQ
t
RDL
t
RDH
t
RTC
t
CVEOLCD
t
EOC
t
QUIET
= 50ns
CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7
ONLY LAST PULSE SHOWN
EOC
RD
CS*
EOLC
* CS CAN BE LOW AT ALL TIMES, LOW DURING THE RD CYCLES, OR THE SAME AS RD.
Figure 9. Read After Conversion—Eight Channels Selected, External Clock
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P37

MAX1304ECM+

Mfr. #:
Buy MAX1304ECM+
Manufacturer:
Maxim Integrated
Description:
Analog to Digital Converters - ADC 12-Bit 8Ch 1.075Msps 3V Precision ADC
Lifecycle:
New from this manufacturer.
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