Agilent Technologies L4400 - Manual (Page 237)

L4451A 4-Channel Isolated D/A Converter with Waveform Memory 9
L4400 User’s Guide 225
The on- board memory provides storage for you to create up to 32 voltage
or current waveforms. You can apply a different waveform to each
channel to output. Or you can apply the same waveform to more than
one channel. For each channel you can designate the gain, frequency,
and/or offset for its output.
The waveforms are stored in instrument memory. Therefore, whenever
power is cycled, the volatile memory empties of data it has contained.
The waveform feature of the L4451A is not intended as a full- featured
substitute for a function generator, but as a means of storing
point- to- point updates.
Clock In
You can configure each DAC channel on the instrument to synchronize
off either an internally- generated 20 MHz clock or the positive edge of
an external user- supplied clock.
An external clock must be less than 10 MHz or indeterminate behavior
will result. Additionally, the maximum point- to- point update rate of the
DACs is 200 kHz. If you configure a DAC to run off an external clock,
you will need to ensure that the correct clock divisor is also configured
for that DAC. For example, if you supply a 10 MHz external clock, the
minimum clock divisor is 50 because the maximum update rate is 200
kHz. If a clock divisor less than the minimum is configured,
indeterminate behavior will results. Thresholds for the external clock
input are 5 V TTL tolerant.
Clock Out
There is one clock output on the DAC module, which you can configure to
output at frequencies up to 10 MHz. Since it uses a 16- bit clock divisor, the
available output frequencies range in steps of 20 MHz/2
16
with a minimum
output frequency of 305 Hz. The output impedance of the Clock Out is 50

The line between external Clock Out and external Clock In is
shared. Use the external Clock Out to provide the external Clock
In signal. However, both a user-supplied external clock and the
module’s Clock Out cannot drive the line at the same time.
Trigger In
You can configure each DAC on the module to trigger off an externally
provided ‘Trigger In’ that has a pulse width greater than 100 ns. The
Trigger In line is 5V TTL tolerant.
Trigger Out
The DAC module can source a TTL level Trigger Out. Trigger Out has a
pulse width between 5 and 10

s.
N O T E