CY7B991
CY7B992
Pin Definitions
Signal
Name
I/O
Description
REF
I
Reference frequency input. This input supplies the frequency and timing against which allfunctional
variation is measured.
FB
I
PLL feedback input (typically connected to one of the eight outputs).
Three-level frequency range select. See Table 1.
Three-level function select inputs for output pair 1 (1Q0, 1Q1). See Table 2.
Three-level function select inputs for output pair 2 (2Q0, 2Q1). See Table 2.
Three-level function select inputs for output pair 3 (3Q0, 3Q1). See Table 2.
Three-level function select inputs for output pair 4 (4Q0, 4Q1). See Table 2.
Three-level select. See test mode section under the block diagram descriptions.
Output pair 1. See Table 2.
FS
I
1F0, 1F1
2F0, 2F1
3F0, 3F1
4F0, 4F1
TEST
I
I
I
I
I
1Q0, 1Q1
2Q0, 2Q1
3Q0, 3Q1
4Q0, 4Q1
O
O
Output pair 2. See Table 2.
O
Output pair 3. See Table 2.
O
Output pair 4. See Table 2.
V
V
PWR
PWR
PWR
Power supply for output drivers.
CCN
CCQ
Power supply for internal circuitry.
GND
Ground.
(xF0, xF1) inputs. Table 2 below shows the nine possible out-
Block Diagram Description
put 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
Phase Frequency Detector and Filter
These two blocks accept inputs from the reference frequency
(REF) input and the feedback (FB) input and generate correc-
tion information to control the frequency of the Voltage-Con-
trolled Oscillator (VCO). These blocks, along with the VCO,
form a Phase-Locked Loop (PLL) that tracks the incoming
REF signal.
0t selected.
U
[1]
Table 2. Programmable Skew Configurations
Function Selects
Output Functions
1F1,2F1, 1F0,2F0, 1Q0,1Q1,
3F1, 4F1 3F0, 4F0 2Q0, 2Q1 3Q0, 3Q1 4Q0, 4Q1
VCO and Time Unit Generator
LOW
LOW
LOW
MID
LOW
MID
–4t
–3t
–2t
–1t
Divide by 2 Divide by 2
U
U
U
U
The VCO accepts analog control inputs from the PLL filter
block and generates a frequency that is used by the time unit
generator to create discrete time units that are selected in the
skew select matrix. The operational range of the VCO is de-
–6t
–4t
–2t
–6t
–4t
–2t
U
U
U
U
U
U
HIGH
LOW
MID
termined by the FS control pin. The time unit (t ) is determined
U
by the operating frequency of the device and the level of the
FS pin as shown in Table 1.
MID
0t
0t
0t
U
U
U
MID
HIGH
LOW
MID
+1t
+2t
+3t
+4t
+2t
+4t
+6t
+2t
+4t
+6t
U
U
U
U
U
U
U
U
U
U
[1]
Table 1. Frequency Range Select and t Calculation
HIGH
HIGH
U
f
(MHz)
NOM
1
tU = -----------------------
NOM × N
Approximate
HIGH
HIGH
Divide by 4 Inverted
f
Frequency(MHz)At
[2, 3]
Notes:
FS
Min. Max.
where N =
Which t = 1.0 ns
U
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 fre-
quency (fNOM) of the VCO 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 fNOM
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.
3. When the FS pin is selected HIGH, the REF input must not transition
upon power-up until VCC has reached 4.3V.
LOW
MID
15
25
40
30
50
80
44
26
16
22.7
38.5
62.5
HIGH
Skew Select Matrix
The skew select matrix is comprised of four independent sec-
tions. Each section has two low-skew, high-fanout drivers
(xQ0, xQ1), and two corresponding three-level function select
2
CYPRESS [ CYPRESS ]
