PXAS30 Philips Semiconductors, PXAS30 Datasheet - Page 16

• Manufacturer Part Number: PXAS30
• Description: XA 16-bit microcontroller 32 K/1 K OTP/ROM/ROMless/ 8-channel 8-bit A/D/ low voltage 2.7 V.5.5 V/ I2C/ 2 UARTs/ 16 MB address range
• Manufacturer: Philips Semiconductors

Philips Semiconductors
Table 3. A/D Timing Configuration for 10-bit Mode
A/D Inputs
In order to obtain accurate measurements with the A/D Converter,
the source drive must be sufficient to adequately charge the
sampling capacitor during the sampling time. Figure 4 shows the
equivalent resistance and capacitance related to the A/D inputs.
A/D timing configurations indicated in Table 1 allow for full A/D
2000 Dec 01
0h (0000)
1h (0001)
2h (0010)
3h (0011)
4h (0100)
5h (0101)
6h (0110)
7h (0111)
8h (1000)
9h (1001)
Ah (1010)
Bh (1011)
Ch (1100)
Dh (1101)
Eh (1110)
Fh (1111)
XA 16-bit microcontroller
32 K/1 K OTP/ROM/ROMless, 8-channel 8-bit A/D, low voltage (2.7 V–5.5 V),
I
2
R
C
C
R
C, 2 UARTs, 16 MB address range
m
S
C
S
ADCFG 3 0
ADCFG.3–0
(pin capacitance)
(source resistance)
(sampling capacitor)
(multiplexer resistance)
R
S
+
Frequency (MHz)
Max. Oscillator
= 3 k maximum
= 10 pF maximum
= 2 pF maximum
= Recommended less than 20k for full specified accuracy. This allows time for the sampling
6.66
capacitor (C
causes the analog input to present a varying load to the pin.
12
12
12
12
12
13
13
13
13
13
16
20
20
V
8
8
ANALOG
INPUT
AD
AD
N+1
C
Figure 4. A/D Input: Equivalent Circuit
N
) to fully charge while the multiplexer switch is closed. Please note that sampling
Osc. Clocks
C
S
Sm
Sm
116
120
124
136
128
148
152
156
170
160
180
204
208
88
92
96
N
N+1
16
Multiplexer
Conversion Time
accuracy (according to the A/D specifications) assuming a source
resistance of less than or equal to 20k . Larger source resistances
may be accommodated by increasing the sampling time with a
different A/D timing configuration.
Rm
Rm
N+1
N
sec at max. Osc.
C
13.21
8.64
5.77
6.35
5.71
5.67
5.41
5.57
C
9.2
8.7
7.2
6.2
6.8
5.2
5.0
5.2
TO COMPARATOR
Preliminary specification
Sampling Time
(Osc. Clocks)
p
10
12
24
14
14
16
18
32
20
20
22
24
4
6
8
8
g
SU00948
XA-S3