OQ2538HP_97 PHILIPS [NXP Semiconductors], OQ2538HP_97 Datasheet - Page 12

• Manufacturer Part Number: OQ2538HP_97
• Description: SDH/SONET main amplifier
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
AGC and AGCDC level detection
When using rectifier A as an input signal level detector, the
AGC and the AGCDC pins must be decoupled to ground
with 100 nF capacitors. The AGCDC output is intended as
a reference voltage against which the actual AGC output
voltage can be compared. This voltage difference,
V
loop. A graph depicting output voltage difference as a
function of the input signal level (typical) is shown in
Fig.11. Note that an input signal with the specified
peak-to-peak value is applied to both IN and INQ inputs,
but with complementary phase.
LOS and LOSDC level detection
The output of rectifier B can be used for LOS detection.
The LOSDC output provides a reference voltage against
which the voltage at the LOS output can be compared.
The voltage difference V
input to a LOS detection circuit. Both outputs need to be
decoupled using 100 nF capacitors. A graph depicting
1997 Nov 26
AGC
V AGC
SDH/SONET main amplifier
(1) T
(2) T
(3) T
(mV)
V
amb
amb
amb
V AGCDC
AGCDC
Fig.11 AGC transfer characteristics.
= 20 C.
= +25 C.
= +85 C.
200
100
0
, can be used as a control input in an AGC
0
10
LOS
expected
20
max
V
LOSDC
30
(1)
expected
40
min
can be used as
(2)
(3)
V IN (mV p-p)
50
60
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80
12
V
(typical) is shown in Fig.12. Note that an input signal with
the specified peak-to-peak value is applied to both IN and
INQ inputs, but with complementary phase.
Grounding and power supply decoupling
The ground connection on the PCB needs to be a large
copper area fill connected to a common ground plane with
as low inductance as possible, preferably positioned
directly underneath the LQFP48 package. The large area
fill will improve heat transfer to the PCB and thus aid IC
cooling.
All V
a common supply plane with as low inductance as
possible. This plane should be decoupled to ground.
To avoid high frequency resonance, multiple bypass
capacitors should not be mounted at the same location.
To minimise low frequency switching noise in the vicinity of
the OQ2538HP, the power supply line should be filtered
once using an LC-circuit with a low cut-off frequency
(see Fig.14).
LOS
V LOS
(1) T
(2) T
(3) T
EE
V
pins (two at each corner) need to be connected to
amb
amb
amb
(mV)
LOSDC
V LOSDC
Fig.12 LOS detection characteristics.
= 20 C.
= +25 C.
= +85 C.
200
100
as a function of the input signal level
0
0
1
2
3
expected
max
4
(1)
5
Preliminary specification
(2)
expected
6
(3)
min
7
V IN (mV p-p)
OQ2538HP
8
9
10 11
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