LMX3305 National Semiconductor, LMX3305 Datasheet - Page 22

• Manufacturer Part Number: LMX3305
• Description: Triple Phase Locked Loop for RF Personal Communications
• Manufacturer: National Semiconductor

www.national.com
2.0 Programming Description
2.6.3 FRAC_D (RF_N[9]-[6])
These four bits, the fractional accumulator modulus denominator, set the fractional denominator from 1/2 to 1/16 resolution.
MODULUS NUMERATOR (FRAC_N) AND DENOMINATOR (FRAC_D) PROGRAMMING
Remark: The
1/2 can be represented by 8/16.
2.6.4 FBPS (RF_N[5])
This bit when set to one will bypass the delay line calculation used in the fractional circuitry. This will improve the phase noise
while sacrificing performance on reference spurs. When the bit is set to zero, the delay line circuit is in effect to reduce reference
spur.
2.6.5 PCS (RF_N[4])
This bit will determine whether the RF PLL should operate in PCS frequency range or cellular frequency range. When the bit is
set to one, the RF PLL will operate in the PCS mode and when it is set to zero, the cellular mode.
2.6.6 RF_PWDN (RF_N[3])
This bit will asynchronously powerdown the RF PLL when set to one. For normal operation, it should be set to zero.
2.6.7 Test (RF_N[2]-[0])
These bits are the internal factory testing only. They should be set to zero for normal operation.
RF_N[13]-[10]
Numerator
Fractional
(FRAC_N)
10=1010
11=1011
12=1100
13=1101
14=1110
15=1111
0=0000
1=0001
2=0010
3=0011
4=0100
5=0101
6=0110
7=0111
8=1000
9=1001
Modulus Denominator
*
(FRAC_N / FRAC_D) denotes that the fraction number can be represented by (FRAC_N / FRAC_D) as indicated in the parenthesis. For example,
0001
10-14
1-8
15
16
1
9
*
(8/16)
0010
FRAC_D values between 1 to 8 are not allowed.
2
*
(10/15)
*
(5/15)
0011
3
*
(12/16)
*
*
(4/16)
(8/16)
0100
4
*
Functions like an integer-N PLL as fractional component is set to 0.
(12/15)
*
*
*
(3/15)
(6/15)
(9/15)
0101
5
*
(10/12)
(Continued)
1
1
0
*
*
*
*
•
(2/12)
(4/12)
(6/12)
(8/12)
0110
6
Fractional Denominator, (FRAC_D)
*
*
(10/14)
(12/14)
*
*
*
*
(2/14)
(4/14)
(6/14)
(8/14)
0111
7
22
*
*
*
(10/16)
(12/16)
(14/16)
*
*
*
*
RF_N[9]-[6]
(2/16)
(4/16)
(6/16)
(8/16)
1000
8
0
1
0
•
1001
1/9
2/9
3/9
4/9
5/9
6/9
7/9
8/9
9
FRAC_D [3:0]
Not Allowed
1010
1/10
2/10
3/10
4/10
5/10
6/10
7/10
9/10
8/10
10
10/11 10/12 10/13 10/14 10/15
1011
1/11
2/11
3/11
4/11
5/11
6/11
7/11
8/11
9/11
11
11/12 11/13 11/14 11/15
1100
1/12
2/12
3/12
4/12
5/12
6/12
7/12
8/12
9/12
12
0
1
0
•
12/13 12/14 12/15
1101
1/13
2/13
3/13
4/13
5/13
6/13
7/13
8/13
9/13
13
13/14 13/15
1110
1/14
2/14
3/14
4/14
5/14
6/14
7/14
8/14
9/14
14
14/15
1111
1/15
2/15
3/15
4/15
5/15
6/15
7/15
8/15
9/15
15
1
1
0
•
10/16
11/16
12/16
13/16
14/16
15/16
0000
1/16
2/16
3/16
4/16
5/16
6/16
7/16
8/16
9/16
16