U4256BM-R Datasheet, PDF (9/19 Pages) ATMEL Corporation – Frequency Synthesizer for Radio Tuning

SWO1, 2, 3 and 4
(Pin 7-10)
U4256BM-R
All switching outputs are ‘open drain’ and can be set and reset by software control.
Details are described in the data transfer protocol.
The switching output SWO1 to SWO4 can be controlled as following (Bits 30 to 33):
Switch Output
SWOx = ON (switch to GND)
SWOx = OFF
B30 + X
0
1
X = 0 to 3
Figure 10. Internal Components at SWO1, 2, 3 and 4
SWO1
SWO2
I
SWO3
SWO4
OSCIN, OSCOUT
(Pin 12 and Pin 13)
A crystal resonator (up to 15 MHz) is connected between OSCIN and OSCOUT in order
to generate the reference frequency. By using the U4256BM-R in connection with
U4255BM or T4258, the crystal frequency must be 10.25 MHz. The complete applica-
tion circuit is shown in Figure 15. If a reference is available, it can be applied at OSCIN.
The minimum voltage should be 100 mVrms. In this case, Pin OSCOUT has to be open.
The tuning capacity for the crystal oscillator has a range of 0.5 pF to 71.5 pF. The
values are coded binary. The tuning can be controlled by the Bits 78 to 85 as following:
B85 = 1
[pF]
0
0.5
1.0
1.5
...
63.0
63.5
B85 = 0
[pF]
8.0
8.5
9.0
19.5
...
71.0
71.5
B84 B83 B82 B81 B80 B79 B78
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
0
1
1
1
1
1
1
0
0
...
...
...
...
...
...
...
0
0
0
0
0
0
0
0
0
0
0
0
0
0
9
4562C–AUDR–08/04