PI6C3991-2 Просмотр технического описания (PDF) - Pericom Semiconductor
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PI6C3991-2
Pericom Semiconductor
PI6C3991-2 Datasheet PDF : 11 Pages
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PI6C3991
3.3V High-Speed, Low-Voltage Programmable
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Pin Descriptions
Signal Name I/O
Description
REF
I Reference frequency input. This input supplies the frequency and timing against which all functional variation is measured.
FB
I PLL feedback input (typically connected to one of the eight outputs)
FS
I Three-level frequency range select. see Table 1.
1F0, 1F1
I Three-level function select inputs for output pair 1 (1Q0, 1Q1). See Table 2.
2F0, 2F1
I Three-level function select inputs for output pair 2 (2Q0, 2Q1). See Table 2.
3F0, 3F1
I Three-level function select inputs for output pair 3 (3Q0, 3Q1). See Table 2.
4F0, 4F1
I Three-level function select inputs for output pair 4 (4Q0, 4Q1). See Table 2.
TEST
I Three-level select. See test mode section under the block diagram descriptions
1Q0, 1Q1 O Output pair 1. See Table 2
2Q0, 2Q1 O Output pair 2. See Table 2
3Q0, 3Q1 O Output pair 3. See Table 2
4Q0, 4Q1 O Output pair 4. See Table 2
VCCN
PWR Power supply for output drivers
VCCQ
PWR Power supply for internal circuitry
GND
PWR Ground
Table 1. Frequency Range Select and tU Calculation(1) Table 2. Programmable Skew Configurations(1)
FS(1,2)
LOW
MID
HIGH
FNOM (MHz)
Min.
15
25
40
Max.
30
50
80
tU =
1
fNOM
×
N
where N=
44
26
16
Approximate
Freq. (MHz) at
which tU= 1.0ns
22.7
38.5
62.5
Function Selects
1F1, 2F1, 1F0, 2F0,
3F1, 4F1 3F0, 4F0
LOW
LOW
LOW
MID
LOW
HIGH
MID
LOW
MID
MID
MID
HIGH
HIGH
LOW
HIGH
MID
HIGH
HIGH
Output Functions
1Q0, 1Q1,
2Q0, 2Q1
3Q0, 3Q1
4Q0, 4Q1
4tU
Divide by 2 Divide by 2
3tU
6tU
6tU
2tU
4tU
4tU
1tU
2tU
2tU
0tU
0tU
0tU
+1tU
+2tU
+2tU
+2tU
+4tU
+4tU
+3tU
+6tU
+6tU
+4tU
Divide by 4 Inverted
Notes:
1. For all three-state inputs, HIGH indicates a connection to VCC, LOW indicates a connection to GND, and MID indicates an
open connection. Internal termination circuitry holds an unconnected input to VCC/2.
2. The level to be set on FS is determined by the normal operating frequency (fNOM) and Time Unit Generator
(see Logic Block Diagram). Nominal frequency (fNOM) always appears at 1Q0 and the other outputs when they are operated in
their undivided modes (see Table 2). The frequency appearing at the REF and FB inputs will be f NOM when the output connected
to FB is undivided. The frequency of the REF and FB inputs will be fNOM/2 or fNOM/4 when the part is configured for a frequency
multiplication by using a divided output as the FB input.
2
PS8450B 04/09/01
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