Application Notes
Output Over Voltage Protection:
The output voltage is constantly monitored by the
microprocessor and a redundant secondary-side crowbar
circuit that is set to a higher trip point than the
microprocessor protection. If the output voltage
exceeds the over-voltage specification, the
microprocessor will latch the converter off. To turn the
converter on requires either cycling the ON/OFF pin or
power to the converter. This advanced feature prevents
the converter from damaging the load if there is a
converter failure or application error. If non-latching is
required, consult factory.
Trim:
To trim the output voltage higher, connect the
required trim resistor from the Trim pin to the +Sense
pin. To trim the output voltage lower, connect the
required trim resistor from the Trim pin to the –Sense
pin. See diagram below.
Trim-down
Thermal Shutdown:
The printed circuit board temperature is measured
using a semiconductor sensor. If the maximum rated
temperature is exceeded, the converter is latched off.
To re-enable the converter requires cycling the ON/OFF
pin or power to the converter. If non-latching is
required, consult factory.
Trim-down (%)
Control Options:
As the behavior of the circuit is determined by
firmware in the microcontroller, specific customer
requirements such as
• non-latching thermal protection
• custom valid input voltage range
• controlled delay from initiating an ON/OFF
signal for power sequencing
can be accomplished with no change to hardware.
The standard behavior was chosen based on system
design experience but we understand that customers
often have their own requirements.
Please consult Galaxy Power for your special needs.
R
TRIM-DOWN
=
{
100
–2
∆%
}
5.11kΩ
Trim-up (for 3.3V)
Remote Sense:
The output voltage is regulated at the point where the
sense pins connect to the power output pins. Total
sense compensation should not exceed 0.4V or 10% of
Vout, whichever is greater.
R
TRIM-UP
=
{
Vo (100+∆%) (100+2∆%)
−
1.225∆%
∆%
}
5.11kΩ
Safety:
An external input fuse must always be used to meet
these safety requirements.
External Output Trimming
+ Sense
Trim
– Sense
Pisces Series, Page 4
WWW.GALAXYPWR.COM
Part No. 99-002 Rev. 4.0–093003
GALAXY [ GALAXY POWER, INC. ]
