MAX1227_12 Datasheet, PDF (15/22 Pages) Maxim Integrated Products – 12-Bit 300ksps ADCs with FIFO,Temp Sensor, Internal Reference

12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Temperature Measurements
The MAX1227/MAX1229/MAX1231 perform tempera-
ture measurements with an internal diode-connected
transistor. The diode bias current changes from 68µA
to 4µA to produce a temperature-dependent bias volt-
age 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 above digital
code minus an offset to adjust from Kelvin to Celsius.
The reference voltage used for the temperature mea-
surements is derived from the internal reference source
to ensure that 1 LSB corresponds to 1/8 of a degree.
Output Data Format
Figures 4–7 illustrate the conversion timing for the
MAX1227/MAX1229/MAX1231. The 12-bit conversion
result is output in MSB-first format with four leading
zeros. DIN data is latched into the serial interface on
the rising edge of SCLK. Data on DOUT transitions on
the falling edge of SCLK. Conversions in clock modes 00
and 01 are initiated by CNVST. Conversions in clock
modes 10 and 11 are initiated by writing an input data
byte to the conversion register. Data is binary for unipo-
lar mode and two’s complement for bipolar mode.
Table 4. Unipolar Mode Register (Addressed Through Setup Register)
BIT NAME
UCH0/1
UCH2/3
UCH4/5
UCH6/7
UCH8/9
UCH10/11
UCH12/13
UCH14/15
BIT
7 (MSB)
6
5
4
3
2
1
0 (LSB)
FUNCTION
Set to 1 to configure AIN0 and AIN1 for unipolar differential conversion.
Set to 1 to configure AIN2 and AIN3 for unipolar differential conversion.
Set to 1 to configure AIN4 and AIN5 for unipolar differential conversion.
Set to 1 to configure AIN6 and AIN7 for unipolar differential conversion.
Set to 1 to configure AIN8 and AIN9 for unipolar differential conversion (MAX1229/MAX1231 only).
Set to 1 to configure AIN10 and AIN11 for unipolar differential conversion (MAX1229/MAX1231 only).
Set to 1 to configure AIN12 and AIN13 for unipolar differential conversion (MAX1231 only).
Set to 1 to configure AIN14 and AIN15 for unipolar differential conversion (MAX1231 only).
Table 5. Bipolar Mode Register (Addressed Through Setup Register)
BIT NAME
BCH0/1
BCH2/3
BCH4/5
BCH6/7
BCH8/9
BCH10/11
BCH12/13
BCH14/15
BIT
7 (MSB)
6
5
4
3
2
1
0 (LSB)
FUNCTION
Set to 1 to configure AIN0 and AIN1 for bipolar differential conversion.
Set to 1 to configure AIN2 and AIN3 for bipolar differential conversion.
Set to 1 to configure AIN4 and AIN5 for bipolar differential conversion.
Set to 1 to configure AIN6 and AIN7 for bipolar differential conversion.
Set to 1 to configure AIN8 and AIN9 for bipolar differential conversion (MAX1229/MAX1231 only).
Set to 1 to configure AIN10 and AIN11 for bipolar differential conversion (MAX1229/MAX1231 only).
Set to 1 to configure AIN12 and AIN13 for bipolar differential conversion (MAX1231 only).
Set to 1 to configure AIN14 and AIN15 for bipolar differential conversion (MAX1231only).
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