XE8805AMI028LF Semtech, XE8805AMI028LF Datasheet - Page 127

• Manufacturer Part Number: XE8805AMI028LF
• Description: IC DAS 16BIT FLASH 8K MTP 64LQFP
• Manufacturer: Semtech

Specifications of XE8805AMI028LF

• Applications: Sensing Machine
• Core Processor: RISC
• Program Memory Type: FLASH (22 kB)
• Controller Series: XE8000
• Ram Size: 512 x 8
• Interface: UART, USRT
• Number Of I /o: 24
• Voltage - Supply: 2.4 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 64-LQFP
• Supply Voltage Range: 2.4V To 5.5V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: LQFP
• No. Of Pins: 64
• For Use With: XE8000MP - PROG BOARD AND PROSTART2 CARD
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

18.4.3.2
The calculation on the required low pass cut-off frequency given in 18.4.3.1 remains valid in this case. However,
the noise shaper allows using smaller PWM modulation for the same resolution. This increases the PWM
modulation frequency and as a consequence increases the output bandwidth.
An additional criterion however shows up: the filtering of the quantization noise. As can be seen from the examples
in 18.4.1, the interpolation between PWM codes generated by the noise shaper introduce sequences at
frequencies below the PWM modulation frequency. Assuming a low pass filter that has at least the same order as
the noise shaper, the resolution is given by (NsOrder≥1) :
The total resolution of the D/A is then the minimal of both criteria:
Table 18-6 and Table 18-7 show the signal bandwidth that can be obtained as a function of required resolution and
PWM modulation for first and second order noise shapers. It can be seen that these options are useful to obtain
high resolution using low PWM modulation m. For high PWM modulation m, the resolution is limited by the PWM
modulator and adding a noise shaper does not change anything.
© Semtech 2006
resolution (bit)
Table 18-6. Low pass cut-off frequency as a function of the selected PMW modulation and required resolution for a
NsOrder=1, f
Resolution
(bit)
Table 18-5. Signal bandwidth as a function of the required resolution for the PWM without noise shaper (Fin=0,
10
11
4
5
6
7
8
9
resolution
resolution =
Noise shaper of order 1 or 2
RC
10
11
12
13
14
15
16
8
9
=2MHz, Fin=0, LpOrder=2
PWM modulation m
quant
1596.4
min(
798.2
399.1
199.5
10
11
m
4
5
6
7
8
9
99.8
49.9
24.9
12.5
=
6.2
. 0
4
resolution
359
1596.4
+
798.2
399.1
199.5
99.8
49.9
24.9
12.5
m
6.2
f
+
5
c
quant
NsOrder
for LpOrder=1 (Hz)
,
resolution
1596.4
NsOrder=00, f
798.2
399.1
199.5
first order noise shaper.
7812
1953
99.8
49.9
24.9
12.5
0.48
488
122
7.6
1.9
30
6.2
6
⋅
⎛
⎜ ⎜
⎝
log
PWM
18-6
2
976.6
690.5
399.1
199.5
(
99.8
49.9
24.9
12.5
f
)
6.2
RC
PWM
f
7
c
=2MHz).
)
−
. 2
488.3
345.3
244.1
172.6
99.8
49.9
24.9
12.5
65
6.2
8
⎞
⎟ ⎟
⎠
f
c
for LpOrder=2 (Hz)
244.1
172.6
122.1
86.3
61.0
43.2
24.9
12.5
6.2
31250
11048
3906
1381
488
172
9
61
22
122.1
86.3
61.0
43.2
30.5
21.6
15.3
10.8
6.2
10
XE8805/05A
www.semtech.com
61.0
15.3
10.8
43.2
30.5
21.6
7.6
5.4
3.8
11