MAX1020_12 Datasheet, PDF (22/44 Pages) Maxim Integrated Products – 10-Bit, Multichannel ADCs/DACs with FIFO, Temperature Sensing, and GPIO Ports

10-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
The first 2 bytes of data read out after a temperature
measurement always contain the 12-bit temperature
result, preceded by four leading zeros, MSB first. If
another temperature measurement is performed before
the first temperature result is read out, the old measure-
ment is overwritten by the new result. Temperature
results are in degrees Celsius (two’s complement), at a
resolution of 8 LSB per degree. See the Temperature
Measurements section for details on converting the dig-
ital code to a temperature.
10-Bit DAC
In addition to the 10-bit ADC, the MAX1020/MAX1022/
MAX1057/MAX1058 also include eight voltage-output,
10-bit, monotonic DACs with less than 4 LSB integral
nonlinearity error and less than 1 LSB differential nonlin-
earity error. Each DAC has a 2µs settling time and ultra-
low glitch energy (4nV•s). The 10-bit DAC code is
unipolar binary with 1 LSB = V_REF / 4096.
DAC Digital Interface
Figure 1 shows the functional diagram of the MAX1057/
MAX1058. The shift register converts a serial 16-bit word
to parallel data for each input register operating with a
clock rate up to 25MHz. The SPI-compatible digital inter-
face to the shift register consists of CS, SCLK, DIN, and
DOUT. Serial data at DIN is loaded on the falling edge
of SCLK. Pull CS low to begin a write sequence. Begin a
write to the DAC by writing 0001XXXX as a command
byte. The last 4 bits of the DAC select register are don’t-
care bits. See Table 10. Write another 2 bytes to the
DAC interface register following the command byte to
select the appropriate DAC and the data to be written to
it. See Tables 20 and 21.
The eight double-buffered DACs include an input and a
DAC register. The input registers are directly connect-
ed to the shift register and hold the result of the most
recent write operation. The eight 10-bit DAC registers
hold the current output code for the respective DAC.
Data can be transferred from the input registers to the
DAC registers by pulling LDAC low or by writing the
appropriate DAC command sequence at DIN. See
Table 20. The outputs of the DACs are buffered through
eight rail-to-rail op amps.
The MAX1020/MAX1022/MAX1057/MAX1058 DAC out-
put-voltage range is based on the internal reference or
an external reference. Write to the setup register (see
Table 5) to program the reference. If using an external
voltage reference, bypass REF1 with a 0.1µF capacitor
to AGND. The MAX1057 internal reference is 2.5V. The
MAX1020/MAX1022/MAX1058 internal reference is
4.096V. When using an external reference on any of
these devices, the voltage range is 0.7V to V_AVDD.
DAC Transfer Function
See Table 2 for various analog outputs from the DAC.
DAC Power-On Wake-Up Modes
The state of the RES_SEL input determines the wake-up
state of the DAC outputs. Connect RES_SEL to AVDD
or AGND upon power-up to be sure the DAC outputs
wake up to a known state. Connect RES_SEL to AGND
to wake up all DAC outputs at 000h. While RES_SEL is
low, the 100kΩ internal resistor pulls the DAC outputs to
AGND and the output buffers are powered down.
Connect RES_SEL to AVDD to wake up all DAC outputs
at 3FFh. While RES_SEL is high, the 100kΩ pullup
resistor pulls the DAC outputs to V_REF1 and the output
buffers are powered down.
DAC Power-Up Modes
See Table 21 for a description of the DAC power-up
and power-down modes.
GPIOs
In addition to the internal ADC and DAC, the
MAX1057/MAX1058 also provide 12 general-purpose
input/output channels, GPIOA0–GPIOA3, GPIOB0–
GPIOB3, and GPIOC0–GPIOC3. The MAX1020 includes
four GPIO channels (GPIOA0, GPIOA1, GPIOC0,
Table 2. DAC Output Code Table
DAC CONTENTS
MSB
LSB
11
1111 1111
ANALOG OUTPUT
+V_REF
⎛ 1023⎞
⎝⎜ 1024⎠⎟
10
0000 0001
+V_REF
⎛ 513 ⎞
⎝⎜ 1024⎠⎟
10
0000
0000
+V_REF
⎛ 512 ⎞
⎝⎜ 1024⎠⎟
=
⎛
⎝⎜
+V_REF
2
⎞
⎠⎟
01
0111 0111
+V_REF
⎛ 511 ⎞
⎝⎜ 1024⎠⎟
00
0000 0001
00
0000 0000
+V_REF
⎛ 1⎞
⎝⎜ 1024⎠⎟
0
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