FX803 Datasheet, PDF (9/17 Pages) Sanyo Semicon Device – DC-DC Converter

Controlling Protocol ......
Frequency Measurement Formulæ
To assist in the production of ‘look-up’ tables and limit-values in the µController and provide guidance upon the determination
of N and R from a measured frequency, the following formulæ show the derivation of the Rx frequency, S , from the
INPUT
measured data bytes (N and R), Figure 6.
High Band Measurement
S – High Band
INPUT
In the measurement period of 9.125ms, there are Nh
cycles at 2S_INPUT and Rh clock cycles at 56.000kHz.
so
Nh + Rh =
9.125ms
2xS
INPUT
56000
From which S
= 28000 x Nh Hz
[1]
INPUT
(511 – Rh)
Nh and Rh – High Band
The measurement period
=
9.125ms
Clock Frequency
=
56.000kHz
The measured frequency
=
2 x S_INPUT c/s
In the measurement period there are:
2 x S x 9.125 x 10-3 cycles
INPUT
Nh is the lower integer value of this decimal number:
Nh
= INT (9.125 x 10^-3 x 2 x S )
[4]
INPUT
Rh is rounded to the nearest integer of this decimal number:
Rh
=
(9.125 x 10^-3 – Nh ) x 56000
[5]
2xS
INPUT
Mid Band Measurements
S_INPUT – Mid Band
In the measurement period of 18.250ms, there are Nm
cycles at 2S and Rm clock cycles at 28.000kHz.
INPUT
so
Nm + Rm =
18.250ms
2 x S_INPUT
28000
From which S_INPUT = 14000 x Nm Hz
[2]
(511 – Rm)
Nm and Rm – Mid Band
The measurement period
=
18.250ms
Clock Frequency
=
28.000kHz
The measured frequency
= 2 x S c/s
INPUT
In the measurement period there are:
2 x S x 18.250 x 10-3 cycles
INPUT
Nm is the lower integer value of this decimal number:
Nm
= INT (18.250 x 10^-3 x 2 x S_INPUT)
[6]
Rm is rounded to the nearest integer of this decimal number:
Rm =
(18.250 x 10^-3 – Nm ) x 28000
[7]
2 x S_INPUT
Extended Band Measurements
S_INPUT – Extended Band
In the measurement period of 9.125ms, there are Ne
cycles at S and Re clock cycles at 56.000kHz.
INPUT
so
Ne + Re =
9.125ms
S
INPUT
56000
From which S
= 56000 x Ne Hz
[3]
INPUT
(511 – Re)
Ne and Re – Extended Band
The measurement period
=
Clock Frequency
=
The measured frequency
=
In the measurement period there are:
S x 9.125 x 10-3 cycles
INPUT
9.125ms
56.000kHz
S c/s
INPUT
Ne is the lower integer value of this decimal number:
Ne
= INT (9.125 x 10^-3 x S_INPUT)
[8]
Re is rounded to the nearest integer of this decimal number:
Re
=
(9.125 x 10^-3 – Ne ) x 56000
[9]
S_INPUT
9