User`s manual
XP8600 I/O Configurations s 25
Current Output
A current output is selected by connecting pins 12 on jumper block J1 or
J2. (It is possible to operate one channel with a voltage output and the
other channel with a current output.) The current output can be calculated
using Equation (3-3).
I1 = (OUT1/R2) × (RP2/RP1)
I2 = (OUT2/R3) × (RP2/RP1)
where OUT1 and OUT2 are the outputs of the D/A converter chips. The
output values can be changed by changing resistor packs RP1 and RP2.
The maximum output current is limited by the op-amp to 20 mA.
The op-amps U1C (Channel 1) and U1D (Channel 2) can carry a maxi-
mum of 20 mA. The output channels can each put out a maximum of 14 V,
and so an output load must be less than 700 Ω if the maximum current is to
be delivered.
Reset and Power-Up Delay
The XP8600 has a reset device, U12, to monitor VCC. Whenever VCC is
interrupted, U12 pulls /RST low. The /RST line remains low until
~350ms after VCC has been restored, allowing time for the power supply
and the D/A circuits to stabilize. U12 also monitors the /RST line. When
it detects a low-going edge, U12 pulls /RST low for at least 350 ms. Thus,
the board may be reset with either software or a pushbutton. Software
must allow a 350 ms delay after each reset or power-up cycle.
(3-3)