Philips Semiconductors
SDH/SONET data and clock recovery unit
STM1/4/16 OC3/12/48 GE
Product specification
OQ2541HP; OQ2541U
handbook, full pagewidth
BAND GAP
REFERENCE
100 nF VEE
PC
2Ω
β > 100
GND
on chip
off chip
1 kΩ
R1 1
2 Ω kΩ
3.3
nF
1 µF
L1(1)
−4.5 V
MGL732
(1) L1 = RF choke type Murata BLM21 or equivalent.
Fig.6 Schematic diagram of OQ2541 power control loop.
handbook, halfpage
500 Ω
16 kΩ
on chip
GND
AREF VAREF
RAREF
VEE
off chip
MGL667
Fig.7 Functionality of pin AREF.
If the outputs are AC-coupled, the formulae for calculating
the required voltage on pin AREF and the value of the
resistor connected between pins AREF and VEE as
follows:
VAREF = –R-----L--R--+---L--R-----o × 0.5Vswing
(1)
and:
R
1
×
V----V-A---ER---E-E---F-
–
1
RAREF
=
----------------------------------------------------------------
1
–
RR-----12--
×
V----V-A---ER---E-E---F-
–
1
(2)
where R1 = 500 Ω, R2 = 16 kΩ and VEE = −3.3 V.
To maintain a single-ended swing of 200 mV (p-p) across
a 50 Ω AC-coupled load, the voltage on pin AREF must be
–100 mV × -(---5---0-----5+---0---1--Ω-0---0----)---Ω--- = –300 mV
This can be achieved by connecting a 7.3 kΩ resistor
between pins AREF and VEE.
1999 May 27
8