sp8126b Exar Corporation, sp8126b Datasheet - Page 5

• Manufacturer Part Number: sp8126b
• Description: High Speed Differential Apc Amplifier
• Manufacturer: Exar Corporation

A major consideration in developing the optical
pick-up head system is the extremely small form
factor, which is additionally aggravated by the
physical locations required by the light path.
Special care must be taken when designing the
Flex or PCB for this part. The output peak
current requirement is in the order of 12.5mA
when driving 50pF of capacitive load with a
slew rate of 250V/µs Therefore care must be
taken to provide low inductance, low resistance
paths for power and ground and output traces.
Supply coupling is also very important. Good
supply decoupling is important to ensure the
high frequency performance of the system by
eliminating supply lead inductance effects. The
decoupling capacitor C1, as shown in Figure 5,
should be as close to the part as possible. This
Rev:B Date: 3/18/04
Figure 4. Test and Evaluation PCB Layout for COB 8 Lead Package
Top
SP8126B High Speed Differential APC Amplifier
LAYOUT AND ROUTING CONSIDERATIONS
5
capacitor should be 0.1µF ceramic. C2 is op-
tional to improve decoupling and is recom-
mended to be 1µF tantalum. The layout of the
PCB is pictured here. Note the wide and short
traces on the supply lines.
The traces for the gain resistors R
R
excessive parasitics. Any parasitics on these
nodes will limit the performance of the system.
R
eters in the application. This is a single layer
board using FR4 material.
In order to minimize coupling capacitance into
the gain setting resistor nodes, it is also critical
that V
traces associated with the gain-setting resistors.
GAIN2
GAIN1
OUT
and R
are kept as short as possible to avoid
+ and V
GAIN2
Bottom
OUT
are subminiature potentiom-
- are routed away from the
© Copyright 2004 Sipex Corporation
GAIN1
and