AS3977-BQFU austriamicrosystems, AS3977-BQFU Datasheet - Page 34

• Manufacturer Part Number: AS3977-BQFU
• Description: IC RF TRANSMITTER FSK 16-QFN
• Manufacturer: austriamicrosystems

Specifications of AS3977-BQFU

• Frequency: 300MHz ~ 928MHz
• Applications: ISM
• Modulation Or Protocol: FSK
• Data Rate - Maximum: 100 kbps
• Power - Output: 10dBm
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Voltage - Supply: 2 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 16-VQFN Exposed Pad, 16-HVQFN, 16-SQFN, 16-DHVQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Memory Size: -
• Current - Transmitting: -

AS3977
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
The reference frequency should be in the range of 3 to 5, 75 MHz and can be calculated by:
The recommended setting of the divider is 4.
The next step is to calculate the Division ratio:
This division ration can be split into a part before the comma, called integer part and a part after the comma, also
called fractional part DR
The N-counter value of the Fractional N Synthesizer can be calculated with the formula:
The A-Counter is the rest of this Division and can be calculated by:
In case, the Value of the A-counter is zero, the value of the A-counter has to be increased by M and the value of N has
to be decreased by one
In case, the N-counter is in the range from 10 to 25 and the value of the A-counter is less than N-counter-7:
Note: In case, no solution can be found for the wanted center frequency, it may help to modify the reference fre-
Implementation
Starting from the equation,
The equation now rewritten by taking configuration registers and implementation details into account:
Reference frequency f
The reference frequency f
setting DIVR<2:0> and can be calculated with the help of:
www.austriamicrosystems.com
f
RF
quency or INT<8>
=
P
DIVR
f
XTAL
<
2
0 :
REF
>
+
FRAC
2
REF
⎝
(DIVR<2:0>)
⎜
⎛
(
INT
is determined by the crystal frequency f
<
9
N = whole numbered part of
>
f
RF
+
DR
4
)(
=
INT
AC
=
P f
<
----------------- -
P f
⋅
3
=
0 :
f
⋅
REF
f
f
REF
RF
INT < 7 : 4 > = AC - 1
REF
INT < 3 : 0 > = N - 10
(
>
REF
DR
+
=
⋅
INT
(
=
INT
M N
=
Revision 3.5
DIVR
<
N = N - 1
AC = M
------------------ -
divider
⋅
8
DR
–
f
⋅ >
XTAL
3
6
+
INT
) N
+
f
<
10
XTAL
–
AC
2
+
)
(
---------------------------- -
0 :
DR
+
DR
+
×
INT
>
M
FRAC
INT
+
M
FRAC
<
XTAL
2
7
4 :
–
>
3
)
and the reference divider division ratio
+
)
1
+
(
INT
<
8
>
+
1
)
⎝
⎜
⎛
3
+
FRAC
2
<
16
15
:
0
>
⎠
⎟
(EQ 10)
(EQ 11)
⎞
⎠
⎟
34 - 45
(EQ 3)
(EQ 4)
(EQ 5)
(EQ 6)
(EQ 7)
(EQ 8)
(EQ 9)
⎞