SD16_A Operation
28-5
SD16_A
28.2 SD16_A Operation
The SD16_A module is configured with user software. The setup and
operation of the SD16_A is discussed in the following sections.
28.2.1 ADC Core
The analog-to-digital conversion is performed by a 1-bit, second-order
sigma-delta modulator. A single-bit comparator within the modulator quantizes
the input signal with the modulator frequency f
M
. The resulting 1-bit data
stream is averaged by the digital filter for the conversion result.
28.2.2 Analog Input Range and PGA
The full-scale input voltage range for each analog input pair is dependent on
the gain setting of the programmable gain amplifier of each channel. The
maximum full-scale range is
±
V
FSR
where V
FSR
is defined by:
V
FSR
+
V
REF
ń
2
GAIN
PGA
For a 1.2V reference, the maximum full-scale input range for a gain of 1 is:
"
V
FSR
+
1.2
V
ń
2
1
+"
0.6
V
See the device-specific data sheet for full-scale input specifications.
28.2.3 Voltage Reference Generator
The SD16_A module has a built-in 1.2V reference. It can be used for each
SD16_A channel and is enabled by the SD16REFON bit. When using the
internal reference an external 100nF capacitor connected from V
REF
to AV
SS
is recommended to reduce noise. The internal reference voltage can be used
off-chip when SD16VMIDON = 1. The buffered output can provide up to 1mA
of drive. When using the internal reference off-chip, a 470nF capacitor
connected from V
REF
to AV
SS
is required. See device-specific data sheet for
parameters.
An external voltage reference can be applied to the V
REF
input when
SD16REFON and SD16VMIDON are both reset.
28.2.4 Auto Power-Down
The SD16_A is designed for low power applications. When the SD16_A is not
actively converting, it is automatically disabled and automatically re-enabled
when a conversion is started. The reference is not automatically disabled, but
can be disabled by setting SD16REFON = 0. When the SD16_A or reference
are disabled, they consume no current.
Summary of Contents for MSP430x4xx Family
Page 1: ...MSP430x4xx Family 2007 Mixed Signal Products User s Guide SLAU056G ...
Page 2: ......
Page 6: ...vi ...
Page 114: ...3 76 RISC 16 Bit CPU ...
Page 304: ...5 20 FLL Clock Module ...
Page 340: ...7 8 Supply Voltage Supervisor ...
Page 348: ...8 8 16 Bit Hardware Multiplier ...
Page 372: ...9 24 32 Bit Hardware Multiplier ...
Page 400: ...10 28 DMA Controller ...
Page 428: ...13 10 Basic Timer1 ...
Page 466: ...15 24 Timer_A ...
Page 522: ...17 30 USART Peripheral Interface UART Mode ...
Page 544: ...18 22 USART Peripheral Interface SPI Mode ...
Page 672: ...23 12 Comparator_A ...
Page 692: ...24 20 LCD Controller ...
Page 746: ...26 28 ADC12 ...