Technical Reference Notes
ALD12/18/20/25 Series
(Single Output 16
th
Brick)
Basic Operation and Features
(continued)
OUTPUT ENABLE
(continued)
For Positive Enable, the converter is turned on when the Enable pin is at logic HIGH or left open. The unit turns off when the
Enable pin is at logic LOW or directly connected to -V
IN
. On the other hand, the Negative Enable version turns unit on when the
Enable pin is at logic LOW or directly connected to -V
IN
. The unit turns off when the Enable pin is at Logic HIGH.
OUTPUT OVER VOLTAGE PROTECTION (OVP)
The Over Voltage Protection circuit is non-latching - auto recovery mode. The converter will shut down and attempt to restart until
the fault is removed. There is a 20-50ms lockout period between restart attempts.
OVER CURRENT PROTECTION (OCP)
The Over Current Protection is non-latching - auto recovery mode. The converter shuts down once the output current reaches the
OCP range. The converter will attempt to restart until the fault is removed. There is a 20-50ms lockout period between restart
attempts. Note that the OCP threshold will be reduced proportionally with the output voltage trim up and/or remote sense
compensation. The percent rise in output voltage will be proportional to the reduction in OCP current inception.
OVER TEMPERATURE PROTECTION (OTP)
The Over Temperature Protection circuit will shutdown the converter once the average PCB temperature (See Figure 43A for OTP
reference sense point) reaches the OTP range. This feature prevents the unit from overheating and consequently going into thermal
runaway, which may further damage the converter and the end system. Such overheating may be an effect of operation outside the
given power thermal derating conditions. Restart is possible once the temperature of the sensed location drops to less than 110°C.
REMOTE SENSE
The remote sense pins can be used to compensate for any voltage drops (per indicated max limits) that may occur along the
connection between the output pins to the load. Pin 7 (+Sense) and Pin 5 (-Sense) should be connected to Pin 8 (+Vout) and Pin 4
(-Vout) respectively at the point where regulation is desired. The combination of remote sense and trim adjust cannot exceed 110%
of V
O
. When output voltage is trimmed up (through remote sensing and/or trim pin), output current must be derated and maximum
output power must not be exceeded.
TO SOURCE
+Vin
33uF
+Vo
0.1uF
10uF
L
O
A
D
-Vin
-Vo
Figure 5. Typical Application Circuit
MODEL: ALD12/18/20/25 SERIES
AUGUST 17, 2005 – REVISION C
SHEET 7 OF 20
ASTEC [ Astec America, Inc ]
