STM32F205ZG STMicroelectronics, STM32F205ZG Datasheet - Page 88

• Manufacturer Part Number: STM32F205ZG
• Description: High-performance ARM Cortex-M3 MCU with 1 Mbyte Flash, 120 MHz CPU, ART Accelerator
• Manufacturer: STMicroelectronics

Specifications of STM32F205ZG

• 10/100 Ethernet Mac With Dedicated Dma: supports IEEE 1588v2 hardware, MII/RMII

Electrical characteristics
5.3.11
Table 33.
1. Guaranteed by design, not tested in production.
88/170
MODEPER * INCSTEP
Symbol
f
md
Mod
PLL spread spectrum clock generation (SSCG) characteristics
The spread spectrum clock generation (SSCG) feature allows to reduce electromagnetic
interferences (see
SSCG parameters constraint
Equation 1
The frequency modulation period (MODEPER) is given by the equation below:
f
As an example:
If f
1:
Equation 2
Equation 2 allows to calculate the increment step (INCSTEP):
f
With a modulation depth (md) = ±2 % (4 % peak to peak), and f
An amplitude quantization error may be generated because the linear modulation profile is
obtained by taking the quantized values (rounded to the nearest integer) of MODPER and
INCSTEP. As a result, the achieved modulation depth is quantized. The percentage
quantized modulation depth is given by the following formula:
As a result:
The error in modulation depth is consequently: 2.0 - 1.99954 = 0.00046%.
PLL_IN
VCO_OUT
PLL_IN
INCSTEP
and f
= 1 MHz and f
must be expressed in MHz.
md
md
INCSTEP
Mod
quantized
quantized
must be expressed in Hz.
=
Table 39: EMI
round
%
%
=
MOD
=
[
round
=
(
Peak modulation depth
(
Modulation frequency
MODEPER
(
2
MODEPER
(
MODEPER INCSTEP
= 1 kHz, the modulation depth (MODEPER) is given by equation
25
15
[
–
×
Doc ID 15818 Rev 8
Parameter
(
(
1
1258
2
)
characteristics). It is available only on the main PLL.
15
×
–
2
×
1
×
=
) md
×
100
=
240
×
round 10
round f
×
)
⁄
5
(
×
100
)
[
[
f
⁄
VCO_OUT
(
PLL_IN
(
6
2
×
⁄
×
15
(
5
4
100
×
–
×
⁄
1
25
(
10
)
) 240
4
×
⁄
×
)
3
(
×
]
5
100 5
)
)
0.25
f
=
Min
]
Mod
⁄
STM32F205xx, STM32F207xx
-
-
(
=
1258md(quantitazed)%
(
)
×
2
25
)
VCO_OUT
=
15
]
×
1.99954%(peak)
–
MODEPER
1
Typ
) f
-
-
-
×
VCO_OUT
= 240 (in MHz):
Max
2
15
10
2
)
−1
]
(1)
)
Unit
KHz
%
-