SD16 Operation
27-6
SD16
27.2.6 Analog Input Characteristics
The SD16 uses a switched-capacitor input stage that appears as an
impedance to external circuitry as shown in Figure 27−2.
Figure 27−2. Analog Input Equivalent Circuit
R
S
1 k
V
S+
MSP430
C
S
V
S+
= Positive external source voltage
V
S−
= Negative external source voltage
R
S
= External source resistance
C
S
= Sampling capacitance
R
S
1 k
V
S−
C
S
AV
CC
/ 2
The maximum sampling frequency f
S
may be calculated from the minimum
settling time t
Settling
of the sampling circuit given by:
t
Settling
w
(
R
S
)
1
k
W
)
C
S
ln
ǒ
GAIN
2
17
V
Ax
V
REF
Ǔ
where
f
S
+
1
2
t
Settling
and
V
Ax
+
max
ǒŤ
AV
CC
2
*
V
S
)
Ť
,
Ť
AV
CC
2
*
V
S
*
ŤǓ
,
with V
S+
and V
S−
referenced to AV
SS
.
C
S
varies with the gain setting as shown in Table 27−1.
Table 27−1.Sampling Capacitance
PGA Gain
Sampling Capacitance C
S
1
1.25 pF
2, 4
2.5 pF
8
5 pF
16, 32
10 pF
Содержание MSP430x4xx Family
Страница 1: ...MSP430x4xx Family 2007 Mixed Signal Products User s Guide SLAU056G ...
Страница 2: ......
Страница 6: ...vi ...
Страница 114: ...3 76 RISC 16 Bit CPU ...
Страница 304: ...5 20 FLL Clock Module ...
Страница 340: ...7 8 Supply Voltage Supervisor ...
Страница 348: ...8 8 16 Bit Hardware Multiplier ...
Страница 372: ...9 24 32 Bit Hardware Multiplier ...
Страница 400: ...10 28 DMA Controller ...
Страница 428: ...13 10 Basic Timer1 ...
Страница 466: ...15 24 Timer_A ...
Страница 522: ...17 30 USART Peripheral Interface UART Mode ...
Страница 544: ...18 22 USART Peripheral Interface SPI Mode ...
Страница 672: ...23 12 Comparator_A ...
Страница 692: ...24 20 LCD Controller ...
Страница 746: ...26 28 ADC12 ...