PM9109BF
The formula for f
P,
as shown in the data sheet can be simplified if:
FOSC = 3.5795MHz
I
I
= 16µA
I
V
= 14µA
I
R
= 50µA
recommended crystal with this frequency is used
by choice of correct values for RSH, R1 and R2 (STEP 1)
by choice of correct values for R3, R6 and R4 (STEP 2)
recommended reference setting with value of 24K for
resistor R7
If these values are substituted into the original formula:
f
P
= 40062.5/Ks
(1)
Ks
is an integer constant which can be programmed into the device.
Range is 1025 ... 16384.
Display increment frequency is 64 times lower (refer to diagram “Programmable
slope divider” in the datasheet).
Display increment = 40062.5/(Ks*64) = 626/Ks
(2)
Substituting Ks into each of these two formulae gives ranges for f
P
and Display
increment:
f
P
= 39.0854Hz ... 3.6659Hz
Display increment = 0.6107Hz ... 0.0573Hz
(3)
(4)
These values are min and max for f
p
at all rated conditions because of properly
adjusted resistor values (chosen in STEP 1 and STEP 2) to ensure that I
I
= 16µA
and I
V
= 14µA.
How much energy is now represented by one pulse on SDO?
In this example the rated power is 24000W which gives energy 24000Ws for 1
second. Energy for 1 pulse on SDO is then 24000Ws/f
P
. Now substitute ranges
given in statement (3) above:
Energy for 1 pulse on SDO
= (24000/39.0854)Ws ... (24000/3.6659)Ws
= 614.04Ws ... 6546.82Ws
sames
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SAMES [ SAMES ]
