ADCMP580_05 AD [Analog Devices], ADCMP580_05 Datasheet - Page 11

• Manufacturer Part Number: ADCMP580_05
• Description: Ultrafast SiGe Voltage Comparators
• Manufacturer: AD [Analog Devices]

APPLICATION INFORMATION
POWER/GROUND LAYOUT AND BYPASSING
The ADCMP58x family of comparators is designed for very
high speed applications. Consequently, high speed design
techniques must be used to achieve the specified performance.
It is critically important to use low impedance supply planes,
particularly for the negative supply (V
plane (V
planes are recommended as part of a multilayer board. Provid-
ing the lowest inductance return path for the switching currents
ensures the best possible performance in the target application.
It is also important to adequately bypass the input and output
supplies. A 1 μF electrolytic bypass capacitor should be placed
within several inches of each power supply pin to ground. In
addition, multiple high quality 0.1 μF bypass capacitors should
be placed as close as possible to each of the V
supply pins and should be connected to the GND plane with
redundant vias. High frequency bypass capacitors should be
carefully selected for minimum inductance and ESR. Parasitic
layout inductance should be strictly avoided to maximize the
effectiveness of the bypass at high frequencies.
ADCMP58x FAMILY OF OUTPUT STAGES
Specified propagation delay dispersion performance is achieved
by using proper transmission line terminations. The outputs of
the ADCMP580 family comparators are designed to directly
drive 400 mV into 50 Ω cable or microstrip/stripline transmis-
sion lines terminated with 50 Ω referenced to the proper return.
The CML output stage is shown in the simplified schematic
diagram in Figure 24. Each output is back-terminated with
50 Ω for best transmission line matching. The outputs of the
ADCMP581/ADCMP582 are illustrated in Figure 25; they
should be terminated to −2 V for ECL outputs of ADCMP581
and V
native, Thevenin equivalent termination networks may also be
used. If these high speed signals must be routed more than a
centimeter, then either microstrip or stripline techniques are
required to ensure proper transition times and to prevent
excessive output ringing and pulse width-dependent
propagation delay dispersion.
CCO
CCO
− 2 V for PECL outputs of ADCMP582. As an alter-
), and the ground plane (GND). Individual supply
EE
), the output supply
EE
, V
CCI
, and V
CCO
Rev. 0 | Page 11 of 16
USING/DISABLING THE LATCH FEATURE
The latch inputs (LE/ LE ) are active low for latch mode and are
internally terminated with 50 Ω resistors to the V
using the ADCMP580, V
When using the ADCMP581, V
−2 V. When using the ADCMP582, V
externally to V
plane.
When using the ADCMP580/ADCMP582, the latch function
can be disabled by connecting the LE pin to V
external pull-down resistor and leaving the LE pin discon-
nected. To prevent excessive power dissipation, the resistor
should be 1.5 kΩ for the ADCMP580 and 1 kΩ for the
ADCMP582. When using the ADCMP581 comparators, the
latch can be disabled by connecting the LE pin to GND with
an external 450 Ω resistor and leaving the LE pin disconnected.
The idea is to create an approximate 0.5 V offset using the
internal resistor as half of the voltage divider. The V
should be connected as recommended.
ADCMP580/ADCMP581/ADCMP582
ADCMP581/ADCMP582 ECL/PECL Output Stage
Figure 25. Simplified Schematic Diagram of the
CCO
Figure 24. Simplified Schematic Diagram
of the ADCMP580 CML Output Stage
− 2 V, preferably with its own low inductance
V
EE
TT
16mA
should be connected to ground.
GND / Vcco
50Ω
GND
V
EE
TT
should be connected to
50Ω
TT
should be connected
Q
Q
EE
Q
Q
with an
TT
pin. When
TT
pin