oq2538u NXP Semiconductors, oq2538u Datasheet - Page 12

• Manufacturer Part Number: oq2538u
• Description: Sdh/sonet Stm16/oc48 Main Amplifiers
• Manufacturer: NXP Semiconductors

Philips Semiconductors
AGC and AGCDC level detection
When using rectifier A as an input signal level detector, the
AGC and 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
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.
2000 Sep 29
V AGC
AGC
LOS
SDH/SONET STM16/OC48 main amplifiers
(1) T
(2) T
(3) T
(mV)
V AGCDC
V
V
amb
amb
amb
LOSDC
AGCDC
Fig.11 AGC transfer characteristics.
= 20 C.
= +25 C.
= +85 C.
200
100
0
0
, can be used as a control input in an AGC
as a function of the input signal level
10
LOS
20
V
30
LOSDC
(1)
40
(2)
can be used as
(3)
V IN (mV p-p)
50
60
MGE746
80
12
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 minimize 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).
V LOS
(1) T
(2) T
(3) T
EE
pins (two at each corner) need to be connected to
amb
amb
amb
(mV)
V LOSDC
Fig.12 LOS detection characteristics.
= 20 C.
= +25 C.
= +85 C.
200
100
0
0
1
OQ2538HP; OQ2538U
2
3
4
(1)
5
(2)
6
(3)
Product specification
7
V IN (mV p-p)
8
9
10 11
MGE747