I7110 Datasheet, PDF (12/17 Pages) List of Unclassifed Manufacturers – 300 Mbps LED Drivers

i7110
LED Clamping, Laser Driving
Since most LEDs exhibit a longer ‘turn off’ time
than ‘turn on’ time, a clamping function is
included on the i7110 in order to reduce the ‘turn
off’ time. And the function is enabled by simply
connecting pin VDDC to VCC.
The disadvantage of clamping is that the LED’s
internal capacitance must be fully charged again
before the LED starts to emit light. This will
delay the turn on time of LED especially when
LED drive current is low. Use of peaking
function will reduce the ‘turn on’ delay. The
combination of peaking and clamping results in
very fast ‘turn on’ and ‘turn off’ speed for the
LED.
When driving lasers, it will often be helpful to
disable this clamping. This can be achieved by
leaving the VDDC connections floating.
Continuously over a –500ps to +500ps range.
The maximum difference between PWAP and
PWAN is ±1v. PWAP and PWAN will settle at a
voltage equal to (0.76*VCC) if left floating. It is
recommended that adjustment be implemented by
pull down resistors on PWAP and PWAN.
However it is common for one or other pin to be
tied to ground for maximum adjustment.
LED Drive Pulse Width Adjustment (PWA)
The input signal pulse width can be adjusted
before the output stage. The differential voltage
on the PWA pins shapes the input pulse
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© 2005 iCreate Technologies Corporation
APD-8011-001