© 2013
PAGE 10
WTC3293
www.teamwavelength.com
WTC3293-00400-I
Troubleshooting
If the PGAIN or I TERM are turned all the way
counterclockwise (CCW), the WTC3293 will
not produce current.
If using HSET and the setpoint is 1 V higher
than it should be, the VSET SOURCE jumper
is not removed.
DAC Protection -- Change Defaults
If the voltage set by the external input drops
below 0.3 V, the failsafe circuit is triggered
and the setpoint defaults to 1 V. This
prevents overheating of the load if the input
signal fails. The 1 V default is designed
for 10 k
Ω
thermistors (1 V = 25 °C). This
default is only used with RSET.
To override the failsafe default, remove D1,
use the HSET input, or the onboard trimpot.
To change the failsafe trip point, change
the voltage divider between D1 & D2.
Use the following formula to calculate the
appropriate value:
V
TRIP
= 6.6 D2
D1 + D2
D1 default is 100 k
Ω
.
D2 default is 4.99 k
Ω
.
D1 should not go below 100 k
Ω
.
To change the default once tripped, change
the voltage divider between D3 & D4.
Use the following formula to calculate the
appropriate value:
V
DEFAULT
= 6.6 D4
D3
+
D4
D3 default is 49.9 k
Ω
.
D4 default is 9.76 k
Ω
.
D3 should not go below 49.9 k
Ω
.
D1, D2, D3, and D4 are 0805 size resistors.
To simplify set up or to minimize thermal drift, Wavelength recommends that you eliminate
trimpots in circuitry. The following details how to use
fi
xed resistances in place of trimpots.
Wavelength can load boards at the factory to your speci
fi
c requirements. Contact Sales to
request a Product Variation.
APPLICATION NOTES
Figure 10
DAC Protection Circuit Settings