MAX9690
Ultra-Fast ECL-Output Comparator
_______________________________________________________________________________________ 3
__________Applications Information
Layout
Because of the MAX9690’s large gain-bandwidth characteristic, special precautions need to be taken if its highspeed capabilities are to be used. A PC board with a
ground plane is mandatory. Mount all decoupling capacitors as close to the power-supply pins as possible, and
process the ECL outputs in microstrip fashion, consistent
with the load termination of 50Ω to 120Ω. For low-impedance applications, microstrip layout at the input may also
be helpful. Pay close attention to the bandwidth of the
decoupling and terminating components. Chip components can be used to minimize lead inductance.
Input Slew-Rate Requirements
As with all high-speed comparators, the high gain-bandwidth product of these devices creates oscillation problems when the input traverses through the linear region.
For clean switching without oscillation or steps in the output waveform, the input must meet certain minimum slewrate requirements. The tendency of the part to oscillate is
a function of the layout and source impedance of the circuit employed. Both poor layout and larger source impedance increase the minimum slew-rate requirement.
____________________Timing Diagram
The timing diagram illustrates the series of events that
completes the compare function, under worst-case
conditions. The leading edge of the input signal (illustrated as a large-amplitude, small-overdrive pulse)
switches the comparator. Outputs –Q–and Q are similar
in timing.
Definition of Terms
V
OS
Input Offset Voltage—The voltage required
between the input terminals to obtain 0V differential at the output.
V
IN
Input Voltage Pulse Amplitude
V
OD
Input Voltage Overdrive
t
pd+
Input to Output High Delay—The propagation
delay measured from the time the input signal
crosses the input offset voltage to the 50% point
of an output low-to-high transition.
t
pd-
Input to Output Low Delay—The propagation
delay measured from the time the input signal
crosses the input offset voltage to the 50% point
of an output high-to-low transition.
SWITCHING CHARACTERISTICS
(V+ = +5V, V- = -5.2V, RL= 50Ω, VT= -2V, TA= +25°C, unless otherwise noted.)
Note 1: Not tested, guaranteed by design.
Note 2: V
IN
= 100mV, VOD= 10mV.
PARAMETER
SYMBOL
MAX9690C/E
MIN TYP MAX
MAX9690M
MIN TYP MAX
UNITS
1.3 1.8 1.3 1.8
1.5 2.0
Input to Output High
(Notes 1, 2)
t
pd+
1.7 2.4
ns
1.3 1.8 1.3 1.8
1.5 2.0
CONDITIONS
TA= +25°C
TA= 0°C to +70°C
TA= -55°C to +125°C
TA= +25°C
TA= 0°C to +70°C
Input to Output Low
(Notes 1, 2)
t
pd-
1.7 2.4
ns
TA= -55°C to +125°C