Technical Reference Notes
ALD12/18/20/25 Series
(Single Output 16th Brick)
Basic Operation and Features
INPUT UNDER VOLTAGE LOCKOUT
To prevent any instability to the converter, which may affect the end system, the converter have been designed to turn-on once VIN
is in the voltage range of 34-36 VDC. Likewise, it has also been programmed to turn-off when VIN drops down to 31-33.5 VDC.
OUTPUT VOLTAGE ADJUST/TRIM
The converter comes with a TRIM pin (PIN 6), which is used to adjust the output by as much as 90% to 110% of its set point. This
is achieved by connecting an external resistor as described below.
To INCREASE the output, external Radj_up resistor
should be connected between TRIM PIN (Pin6) and
-Vout
-Vin
+SENSE PIN (Pin 7). Please refer to Equation (1) for the
-Sense
required external resistance and output adjust
relationship.
Rload
Vadj
+Sense
+Vout
Enable
+Vin
Radj_up
Equation (1a): 1.5V to 5V
(
)
5.1× Vo × 100 + ∆%
=
set
510
R
−
− 10.2 ΚΩ
adj_up
1.225× ∆%
∆%
Figure 3. External resistor configuration to increase the outputs
Equation (1b): 1.2V
(
)
5.1× Vo × 100 + ∆%
=
set
510
R
−
− 10.2 ΚΩ
adj_up
0.6× ∆%
∆%
To DECREASE the output, external Radj_down resistor
should be connected between TRIM pin (Pin 6) and
-SENSE PIN (Pin 5). Please refer to Equation (2) for the
required external resistance and output adjust
relationship.
-Vout
-Vin
-Sense
Radj_down
Rload
Vadj
+Sense
+Vout
Enable
+Vin
Equation (2):
510
Radj_down
− 10.2 kΩ
∆%
Where: ∆% = percent change in output voltage
Figure 4. External resistor configuration to increase the outputs
OUTPUT ENABLE
The converter comes with an Enable pin (PIN 2), which is primarily used to turn ON/OFF the converter. Both a Positive (no “N”
suffix required) and a Negative (suffix “N” required) Enable Logic options are being offered.
MODEL: ALD12/18/20/25 SERIES
AUGUST 17, 2005 – REVISION C
SHEET 6 OF 20
ASTEC [ Astec America, Inc ]
