SA8025A Ver la hoja de datos (PDF) - Philips Electronics
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SA8025A Datasheet PDF : 23 Pages
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Philips Semiconductors
1.8GHz low-voltage Fractional-N synthesizer
Product specification
SA8025A
Table 1. Function Table
Symbol
Bits
Function
NM1
12
Number of main divider cycles when prescaler modulus = 64*
NM2
8 if PR = “01”
4 if PR = “10”
Number of main divider cycles when prescaler modulus = 65*
NM3
4 if PR = “10” Number of main divider cycles when prescaler modulus = 68*
NM4
PR
4 if PR = “11” or
“00”
2
Number of main divider cycles when prescaler modulus = 73*
Prescaler type in use
PR = “01”: modulus 2 prescaler (64/65)
PR = “10”: modulus 3 prescaler (64/65/68)
PR = “11”: modulus 4 prescaler (64/65/68/73)
PR = “00”: modulus 3 prescaler (64/65/73)
NF
FMOD
3
Fractional-N increment
1
Fractional-N modulus selection flag
“1”: modulo 8
“0”: modulo 5
LONG
1
A word format selection flag
“0”: 24 bit A0 format
“1”: 32 bit A1 format
CN
8
Binary current setting factor for main charge pumps
CL
2
Binary acceleration factor for proportional charge pump current
CK
4
Binary acceleration factor for integral charge pump current
EM
1
Main divider enable flag
EA
1
Auxiliary divider enable flag
SM
2
Reference select for main phase detector
SA
2
Reference select for auxiliary phase detector
NR
12
Reference divider ratio
NA
12
Auxiliary divider ratio
Auxiliary prescaler mode:
PA
1
PA = “0”: divide by 4
PA = “1”: divide by 1
*Not including reset cycles and Fractional-N effects.
Table 2. Prescaler Ratio
The total division ratio from prescaler to the phase detector may be expressed as:
if PR = “01”
N = (NM1 + 2) x 64 + NM2 x 65
N’ = (NM1 + 1) x 64 + (NM2 + 1) x 65 (*)
if PR = “10”
N = (NM1 + 2) x 64 + NM2 x 65 + (NM3 + 1) x 68
N’ = (NM1 + 1) x 64 + (NM2 + 1) x 65 + (NM3 + 1) x 68 (*)
if PR = “11”
N = (NM1 + 2) x 64 + NM2 x 65 + (NM3 + 1) x 68 + (NM4 + 1) x 73
N’ = (NM1 + 1) x 64 + (NM2 + 1) x 65 + (NM3 + 1) x 68 + (NM4 + 1) x 73 (*)
if PR = “00”
N = (NM1 + 2) x 64 + NM2 x 65 + (NM4 + 1) x 73
N’ = (NM1 + 1) x 64 + (NM2 + 1) x 65 + (NM4 + 1) x 73 (*)
(*) When the fractional accumulator overflows the prescaler ratio = 65 (64 + 1) and the total division ratio N’ = N + 1
Table 3. PR Modulus
PR Modulus Prescaler
01
2
10
3
11
4
00
3
NM1
12
12
12
12
Bit Capacity
NM2 NM3
8
–
4
4
4
4
8
–
NM4
–
–
4
4
1996 Oct 15
12
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