SP8854EKGHCAR Ver la hoja de datos (PDF) - Mitel Networks
Número de pieza
componentes Descripción
Fabricante
SP8854EKGHCAR Datasheet PDF : 13 Pages
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SP8854E
STROBE
CONTROL
MICRO
SP8854E
27 28
33p
100p
10MHZ
Application using
crystal reference
15V
15V
1n
1n
1n
1k
6 5 4 3 2 1 44 43 42 41 40
7
39
8
38
9
37
10
36
11
35
12
SP8854E
34
13
33
14
32
15
31
16
30
17
29
18 19 20 21 22 23 24 25 26 27 28
100p
LOOP FILTER
*
**
130V
15V
2·2k
1µ
10n
15V
1n
REF IN
FREF
FPD
VCO
OP27
ETC
* VALUES DEPEND
ON APPLICATION
Fig. 5 Typical application diagram
DESCRIPTION
Prescaler and AM counter The programmable divider
chain is of A and M counter construction and therefore
contains a dual modulus front end prescaler, an A counter
which controls the dual modulus ratio and an M counter which
performs the bulk multi-modulus division. A programmable
divider of this construction has a division ratio of MN1A and
a minimum integer steppable division ratio of N(N21), where
N is the prescaler value.
Data Entry and Storage
Data is loaded from the 16-bit bus into one of the internal
buffers by applying a positive pulse to the STROBE input. The
input bus can be driven from TTL or CMOS logic levels. When
STROBE is low, the inputs are isolated and the data can be
changed without affecting the programmed state.
When STROBE input is taken high, the A and M counters
are reset and the input data is applied to the internal storage
register. When the STROBE input is again taken low, the data
on the input bus is stored in the internal storage register and
the A and M counters released. The STROBE input is level
triggered so that if the data is changed whilst the input is high,
the final value before STROBE goes low will be stored.
In order to prevent disturbances on the VCO control voltage
when frequency changes are made, the STROBE input disables
6
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