GS9015ACPJ View Datasheet(PDF) - Gennum -> Semtech
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Description
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GS9015ACPJ Datasheet PDF : 13 Pages
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0.1µ
-5V
0.1µ
-5V
4 3 2 1 28 27 26
ECL
DATA
INPUTS
5
DDI
6
DDI
7 VCC1
8 VEE1
9 VEE1
10 ƒ/2
11 VEE3
GS9015A
25
SDO
24
SDO
23
SCO
22
SCO
SS1 21
20
SS0
19
CD
12 13 14 15 16 17 18
5.6p
910
10n
0.1µ
-5V
390
390
100
100
100
100
390
390
10k
-5V
DATA
DATA
CLOCK
CLOCK
CARRIER
DETECT
OUTPUT
÷2
÷1
-5V
STAR
ROUTED
-5V
See Figure 15
LOOP
VOLTAGE
-5V
All resistors in ohms, all capacitors in microfarads unless otherwise stated.
Fig. 14 GS9015A Typical Test Circuit Using -5V Supply
VCO Frequency Setting Resistors
There are two modes of VCO operation available in the
GS9015A depending on the state of the ÷ 2 block. The ÷ 2
block is enabled according to : ÷ 2 ENABLE = ƒ/2 • SS1. When
the ƒ/2 ENABLE (pin 10) is LOW, any of the four VCO
frequency setting resistors, RVCO0 through RVCO3, (pins
13, 14, 15 and 17) may be used for any data r a t e f r o m 100
Mb/s t o 4 0 0 M b / s . F o r e x a m p l e , f o r 143 Mb/s data
rate, the value of the total RVCO resistance is approximately
6k8 and for 270 Mb/s operation, the value is
approximately 3k5. The 5k potentiometers will then tune
the desired data rate near their mid-points.
Jitter performance at the lower data rates (143, 177 Mb/s) is
improved by operating the VCO at twice the normal frequency.
This is accomplished by enabling the divide by two block in
the PLL section of the GS9015A.
When ƒ/2 (Pin 10) is HIGH, two of the RVCO pins are assigned
to data rates below 200 Mb/s and two are assigned to data
rates over 200 Mb/s. The selection is dependent upon the
level of STANDARD SELECT BIT, SS1 (pin 21). When SS1
is LOW, RVCO0 and RVCO1 (pins 13 and 14) are used for the
higher data rates. When SS1 is HIGH, the VCO frequency is
now twice the bit rate and its frequency is set by RVCO2 and
RVCO3 (pins 15 and 17).
For 143 Mb/s and 270 Mb/s operation, (the VCO is at
286 MHz and 270 MHz respectively) the total resistance
required is approximately the same for both data rates. This
also applies for 177 Mb/s and 360 Mb/s operation (the VCO
is tuned to 354 MHz and 360 MHz respectively). This means
that one potentiometer may be used for each frequency pair
with only a small variation of the fixed resistor value. This
halves the number of adjustments required.
520 - 99 - 05
10
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