cy7b991v-5jit Cypress Semiconductor Corporation., cy7b991v-5jit Datasheet - Page 3

• Manufacturer Part Number: cy7b991v-5jit
• Description: Low Voltage Programmable Skew Clock Buffer
• Manufacturer: Cypress Semiconductor Corporation.

Block Diagram Description
Phase Frequency Detector and Filter
The Phase Frequency Detector and Filter blocks accept inputs
from the reference frequency (REF) input and the feedback (FB)
input. They generate correction information to control the
frequency of the Voltage Controlled Oscillator (VCO). These
blocks, along with the VCO, form a Phase Locked Loop (PLL)
that tracks the incoming REF signal.
VCO and Time Unit Generator
The VCO accepts analog control inputs from the PLL filter block.
It generates a frequency that is used by the time unit generator
to create discrete time units, selected in the skew select matrix.
The operational range of the VCO is determined by the FS
control pin. The time unit (t
frequency of the device and the level of the FS pin as shown in
Table
Table 1. Frequency Range Select and t
Document Number: 38-07141 Rev. *C
Notes
FS
LOW
MID
HIGH
1. For all three state inputs, HIGH indicates a connection to V
2. The level to be set on FS is determined by the “normal” operating frequency (f
3. When the FS pin is selected HIGH, the REF input must not transition upon power up until V
[2, 3]
circuitry holds an unconnected input to V
appears at 1Q0 and the other outputs when they are operated in their undivided modes (see
when the output connected to FB is undivided. The frequency of the REF and FB inputs is f
using a divided output as the FB input.
1.
f
Min
NOM
15
25
40
(MHz)
Max
30
50
80
t
U
where N =
=
U
----------------------- -
f
44
26
16
) is determined by the operating
NOM
1
×
N
CC
/2.
Frequency (MHz) At
Which t
U
Approximate
Calculation
22.7
38.5
62.5
U
CC
= 1.0 ns
, LOW indicates a connection to GND, and MID indicates an open connection. Internal termination
[1]
NOM
Skew Select Matrix
The skew select matrix is comprised of four independent
sections. Each section has two low skew, high fanout drivers
(xQ0, xQ1), and two corresponding three level function select
(xF0, xF1) inputs.
functions for each section as determined by the function select
inputs. All times are measured with respect to the REF input
assuming that the output connected to the FB input has 0t
selected.
Table 2. Programmable Skew Configurations
) of the V
LOW
LOW
LOW
MID
MID
MID
HIGH
HIGH
HIGH
1F1, 2F1,
3F1, 4F1
Function Selects
NOM
CO
CC
Table
/2 or f
and Time Unit Generator (see ). Nominal frequency (f
has reached 2.8V.
1F0, 2F0,
LOW
MID
HIGH
LOW
MID
HIGH
LOW
MID
HIGH
3F0, 4F0
2). The frequency appearing at the REF and FB inputs is f
NOM
/4 when the part is configured for a frequency multiplication
Table 2
1Q0, 1Q1,
2Q0, 2Q1
–4t
–3t
–2t
–1t
+1t
+2t
+3t
+4t
0t
shows the nine possible output
U
U
U
U
U
U
U
U
U
Output Functions
3.3V RoboClock
Divide by 2 Divide by 2
Divide by 4
3Q0, 3Q1
–6t
–4t
–2t
+2t
+4t
+6t
0t
U
U
U
U
U
U
U
CY7B991V
[1]
4Q0, 4Q1
Page 3 of 14
Inverted
NOM
–6t
–4t
–2t
+2t
+4t
+6t
0t
) always
U
U
U
U
U
U
U
NOM
®
U
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