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参数资料
| 型号： | MAX1221BETX+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 16/44页 |
| 文件大小： | 0K |
| 描述： | IC ADC/DAC 12BIT W/FIFO 36TQFNEP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 类型： | ADC，DAC |
| 分辨率（位）： | 12 b |
| 采样率（每秒）： | 225k |
| 数据接口： | MICROWIRE?，QSPI?，串行，SPI? |
| 电压电源： | 模拟和数字 |
| 电源电压： | 2.7 V ~ 5.25 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 36-WFQFN 裸露焊盘 |
| 供应商设备封装： | 36-TQFN 裸露焊盘（6x6） |
| 包装： | 带卷 (TR) |
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MAX1221/MAX1223/MAX1343
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________
23
Clock Modes
Internal Clock
The MAX1221/MAX1223/MAX1343 can operate 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.
External Clock
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.
ADC/DAC References
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 mode, connect a 0.1F
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
and REF2 is the negative reference in the ADC external
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.
Temperature Measurements
Issue a command byte setting bit 0 of the conversion
register to one to take a temperature measurement.
See Table 4. The MAX1221/MAX1223/MAX1343 perform
temperature measurements with an internal diode-con-
nected transistor. The diode bias current changes from
68A to 4A to produce a temperature-dependent bias
voltage difference. The second conversion result at 4A
is subtracted from the first at 68A 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.
Register Descriptions
The MAX1221/MAX1223/MAX1343 communicate
between the internal registers and the external circuitry
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.
Conversion Register
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.
A conversion is not performed if it is requested on a
channel or one of the channel pairs that has been con-
figured as
CNVST or REF2. For channels configured as
differential pairs, the CHSEL0 bit is ignored and the two
pins are treated as a single differential channel. For the
MAX1221/MAX1343, the CHSEL3 bit must be zero.
MAX1221/MAX1343
CURRENT
GPIOA0, GPIOA1
(mA)
GPIOC0, GPIOC1
(mA)
Sink
15
4
Source
15
2
Table 3. GPIO Maximum Sink/Source
Current
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