參數(shù)資料
型號: TC3400VOA
元件分類: ADC
英文描述: 2-CH 16-BIT DELTA-SIGMA ADC, SERIAL ACCESS, PDSO8
封裝: SOIC-8
文件頁數(shù): 7/11頁
文件大?。?/td> 61K
代理商: TC3400VOA
5
TC3400
+1.8V, Low Power , 16-Bit Sigma -
Delta A/D Converter
TC3400-1 6/29/00
GENERAL THEORY OF OPERATION
The TC3400 is a 16-bit sigma-delta A/D converter with
one differential input. The detailed description of the key
components of the TC3400 is outlined below. (Also refer to
the
A/D Operational Flowchart on page 9 and the Timing
Diagrams in Figures 2 through 4).
A/D Converter Operation
When the TC3400 is not converting, it is in sleep mode
with both the SCLK and SDAT lines high. An A/D conversion
is initiated by a high to low transition on the SCLK line at
which time the internal clock of the TC3400 is started. Each
additional high to low transition of SCLK (following the initial
SCLK falling edge) and during the time interval t4 will
decrement the conversion accuracy by one bit and reduce
the conversion time by one half. The time interval t4 is
referred to as the resolution reduction window. The mini-
mum conversion resolution is 10 bits so any more than 6
SCLK transitions during t4 will be ignored.
After each high to low transition of SCLK, in the t4
interval, the SDAT output is driven high by the TC3400 to
acknowledge that the conversion has been decremented.
When the SCLK returns high or the t4 interval ends, the
SDAT line returns low (see Figure 2). When the conversion
is complete SDAT is driven high. The 3400 now enters sleep
mode and the conversion value can be read as a serial data
word on the SDAT line.
Reading the Data Word
After the conversion is complete and SDAT goes high,
the conversion value can be clocked serially onto the SDAT
line by high to low transitions of the SCLK. The data word is
in two’s compliment format with the sign bit clocked onto the
SDAT line first followed by the MSB and ending in the LSB.
For a 16 bit conversion the data word would consist of a sign
bit followed by 15 magnitude bits, Table 1 shows the data
word versus input voltage for a 16 bit conversion. Note that
the full scale input voltage range is
±(2 REFIN– 1LSB). When
REFOUT is fed back directly to REFIN, an LSB is 73V for a
16 bit convertion, as REFOUT is typically 1.193V.
Figure 3 shows typical SCLK and SDAT waveforms for
16, 12 and 10 bit conversions. Note that any complete
convert and read cycle requires 17 negative edge clock
pulses. The first is the convert command. Then, up to six of
these can occur in the resolution reduction window, t4, to
decrement accuracy. The remaining pulses clock out the
conversion data word.
Table 1. Data Conversion Word vs. Voltage Input
(REFIN = 1.193V)
Data Word
INn+ – INn(Volts)
0111 1111 1111 1111
2.38596 (Positive Full Scale)
0000 0000 0000 0001
72.8 E – 6
0000 0000 0000 0000
0
1111 1111 1111 1111
–72.8 E – 6
1000 0000 0000 0001
–2.38596 (Negative Full Scale)
1000 0000 0000 0000
Reserved Code
The SCLK input has a filter which rejects any positive or
negative pulse of width less than 50nsec to reduce noise.
The rejection width of this pulse can vary between 50nsec
and 750nsec depending on processing parameters and
supply voltage.
Figure 3 shows a truth table for determining the mode of
operation for the TC3400 part by recording the value of
SDAT for SCLK in a high, then low, then high state. For
example, if SCLK goes through a 1-0-1 transition and the
corresponding values of SDAT are 1-1-0, then the SCLK
falling edge started a new data conversion. A 0-1-0 for SDAT
would have indicated a resolution reduction had occurred.
This is useful if the microcontroller has a watchdog reset or
otherwise loses track of where the TC3400 part is in the
conversion and data readout sequence. The microcontroller
can simply transition SCLK until it “finds” a Start Conversion
condition.
相關(guān)PDF資料
PDF描述
TC3400VOART 1-CH 16-BIT DELTA-SIGMA ADC, SERIAL ACCESS, PDSO8
TC3400VOATR 1-CH 16-BIT DELTA-SIGMA ADC, SERIAL ACCESS, PDSO8
TC3400VOA 1-CH 16-BIT DELTA-SIGMA ADC, SERIAL ACCESS, PDSO8
TC3400VPA 1-CH 16-BIT DELTA-SIGMA ADC, SERIAL ACCESS, PDIP8
TC3401EQR 2-CH 16-BIT DELTA-SIGMA ADC, SERIAL ACCESS, PDSO16
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