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| MAX1115 Datasheet, PDF (7/12 Pages) Maxim Integrated Products – Single-Supply, Low-Power, Serial 8-Bit ADCs | |||
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Single-Supply, Low-Power, Serial 8-Bit ADCs
ANALOG
INPUTS
CH0
VDD
0.1µF
GND
MAX1115
MAX1116
CONVST
SCLK
DOUT
VDD
VDD
1µF
CPU
I/O
SCK (SK)
MISO (SI)
GND
Figure 3. Typical Operating Circuit
GND
CH0
VDD
2
CAPACITIVE DAC
CHOLD
16pF
HOLD
RIN
6.5kâ¦
TRACK
Figure 4. Equivalent Input Circuit
COMPARATOR
AUTO-ZERO
RAIL
Input Voltage Range
Internal protection diodes that clamp the analog input
to VDD and GND allow the input pin (CH0) to swing
from (GND - 0.3V) to (VDD + 0.3V) without damage.
However, for accurate conversions, the inputs must not
exceed (VDD + 50mV) or be less than (GND - 50mV).
Input Bandwidth
The ADCâs input tracking circuitry has a 4MHz small-
signal bandwidth, so it is possible to digitize high-
speed transient events and measure periodic signals
with bandwidths exceeding the ADCâs sampling rate by
using undersampling techniques. Anti-alias filtering is
recommended to avoid high-frequency signals being
aliased into the frequency band of interest.
Serial Interface
The MAX1115/MAX1116 have a 3-wire serial interface.
The CNVST and SCLK inputs are used to control the
device, while the three-state DOUT pin is used to
access the conversion results.
The serial interface provides connection to microcon-
trollers (µCs) with SPI, QSPI, and MICROWIRE serial
interfaces at clock rates up to 5MHz. The interface sup-
ports either an idle high or low SCLK format. For SPI
and QSPI, set CPOL = CPHA = 0 or CPOL = CPHA = 1
in the SPI control registers of the µC. Figure 5 shows
the MAX1115/MAX1116 common serial-interface con-
nections. See Figures 6aâ6d for details on the serial-
interface timing and protocol.
I/O
SCK
MISO
+3V
SS
a) SPI
CS
SCK
MISO
+3V
SS
b) QSPI
I/O
SK
SI
CONVST
SCLK
DOUT
MAX1115
MAX1116
CONVST
SCLK
DOUT
MAX1115
MAX1116
CONVST
SCLK
DOUT
MAX1115
MAX1116
c) MICROWIRE
Figure 5. Common Serial-Interface Connections
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