MAX1348BETX+T Maxim Integrated Products, MAX1348BETX+T Datasheet - Page 19

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MAX1348BETX+T

Manufacturer Part Number
MAX1348BETX+T
Description
IC ADC/DAC 12BIT W/FIFO 36WQFN
Manufacturer
Maxim Integrated Products
Type
ADC, DACr
Datasheet

Specifications of MAX1348BETX+T

Resolution (bits)
12 b
Sampling Rate (per Second)
225k
Data Interface
MICROWIRE™, QSPI™, Serial, SPI™
Voltage Supply Source
Analog and Digital
Voltage - Supply
4.75 V ~ 5.25 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
36-WQFN Exposed Pad, 36-HWQFN
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
The GPIOs can sink and source current. The
MAX1342/MAX1348 GPIOA0 and GPIOA1 can sink and
source up to 15mA. GPIOC0 and GPIOC1 can sink 4mA
and source 2mA. See Table 3.
The MAX1340/MAX1342/MAX1346/MAX1348 can oper-
ate from an internal oscillator. The internal oscillator is
active in clock modes 00, 01, and 10. Figures 6, 7, and
8 show how to start an ADC conversion in the three
internally timed conversion modes.
Read out the data at clock speeds up to 25MHz
through the SPI interface.
Set CKSEL1 and CKSEL0 in the setup register to 11 to
set up the interface for external clock mode 11. See
Table 5. Pulse SCLK at speeds from 0.1MHz to
3.6MHz. Write to SCLK with a 40% to 60% duty cycle.
The SCLK frequency controls the conversion timing.
See Figure 9 for clock mode 11 timing. See the ADC
Conversions in Clock Mode 11 section.
Address the reference through the setup register, bits 3
and 2. See Table 5. Following a wake-up delay, set
REFSEL[1:0] = 00 to program both the ADC and DAC
for internal reference use. Set REFSEL[1:0] = 10 to pro-
gram the ADC for internal reference use without a
wake-up delay. Set REFSEL[1:0] = 10 to program the
DAC for external reference, REF1. When using REF1 or
REF2/AIN_ in external reference, connect a 0.1µF
capacitor to AGND. Set REFSEL[1:0] = 01 to program
the ADC and DAC for external-reference mode. The
DAC uses REF1 as its external reference, while the
ADC uses REF2 as its external reference. Set
REFSEL[1:0] = 11 to program the ADC for external dif-
ferential reference mode. REF1 is the positive reference
Table 3. GPIO Maximum Sink/Source
Current
and REF2 is the negative reference in the ADC external
CURRENT
Source
Sink
12-Bit, Multichannel ADCs/DACs with FIFO,
______________________________________________________________________________________
GPIOA0, GPIOA1
Temperature Sensing, and GPIO Ports
(mA)
15
15
ADC/DAC References
MAX1342/MAX1348
Clock Modes
GPIOC0, GPIOC1
External Clock
Internal Clock
(mA)
4
2
differential mode.
When REFSEL[1:0] = 00 or 10, REF2/AIN_ functions as
an analog input channel. When REFSEL[1:0] = 01 or 11,
REF2/AIN_ functions as the device’s negative reference.
Issue a command byte setting bit 0 of the conversion
register to one to take a temperature measurement.
See Table 4. The MAX1340/MAX1342/MAX1346/
MAX1348 perform temperature measurements with an
internal diode-connected transistor. The diode bias cur-
rent changes from 68µA to 4µA to produce a tempera-
ture-dependent bias voltage difference. The second
conversion result at 4µA is subtracted from the first at
68µA to calculate a digital value that is proportional to
absolute temperature. The output data appearing at
DOUT is the digital code above, minus an offset to
adjust from Kelvin to Celsius.
The reference voltage used for the temperature mea-
surements is always derived from the internal reference
source to ensure that 1 LSB corresponds to 1/8 of a
degree Celsius. On every scan where a temperature
measurement is requested, the temperature conversion
is carried out first. The first 2 bytes of data read from
the FIFO contain the result of the temperature measure-
ment. If another temperature measurement is per-
formed before the first temperature result is read out,
the old measurement is overwritten by the new result.
Temperature results are in degrees Celsius (two’s com-
plement). See the Applications Information section for
information on how to perform temperature measure-
ments in each clock mode.
The MAX1340/MAX1342/MAX1346/MAX1348 communi-
cate between the internal registers and the external cir-
cuitry through the SPI-compatible serial interface. Table
1 details the command byte, the registers, and the bit
names. Tables 4–12 show the various functions within
the conversion register, setup register, unipolar-mode
register, bipolar-mode register, ADC averaging regis-
ter, DAC select register, reset register, and GPIO com-
mand register, respectively.
Select active analog input channels, scan modes, and a
single temperature measurement per scan by issuing a
command byte to the conversion register. Table 4
details channel selection, the four scan modes, and how
to request a temperature measurement. Start a scan by
writing to the conversion register when in clock mode 10
or 11, or by applying a low pulse to the CNVST pin when
in clock mode 00 or 01. See Figures 6 and 7 for timing
specifications for starting a scan with CNVST.
Temperature Measurements
Register Descriptions
Conversion Register
19

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