Delta Electronics DNQ12 - Manual (Page 8)

DS_DNQ12SIP25_07172008
8
FEATURES DESCRIPTIONS (CON.)
Over-Temperature Protection
The overtemperature protection consists of circuitry that
provides protection from thermal damage. If the
temperature exceeds the overtemperature threshold,
the module will shut down. The module will try to restart
after shutdown. If the overtemperature condition still
exists during restart, the module will shut down again.
This restart trial will continue until the temperature is
within specification
Output Voltage Programming
The output voltage of the DNQ can be programmed to
any voltage from 0.8Vdc to 5.5Vdc by connecting one
resistor (shown as Rtrim in Figure 22) in the Sense(+) pin
of the module. Without this external resistor (Sense(+) pin
is shorted to Vo), the output voltage of the module is
0.7887Vdc. With Sense(+) not connected to Vo, the
output of the module will reach overvoltage shutdown. A
1µF multilayer ceramic capacitor is required from Rtrim to
Sense(-) pin to minimize noise. To calculate the value of
the resistor Rtrim for a particular output voltage Vo,
please use the following equation:
775 ( 1)
0.7887
Vo
Rtrim
= × −
Where Rtrim is the external resistor in Ω and Vo is the
desired output voltage.
Vin Vo
GND
LOAD
Sense(+)
Sense(-)
Share
SEQ/
ENA
Rtrim
1µF
Figure 22: Circuit configuration for programming output voltage
For example, to program the output voltage of the DNQ
module to 3.3Vdc, Rtrim is calculated as follows:
3.3
775 ( 1)
0.7887
Rtrim
= × −
Rtrim = 2468 Ω
Table 1 provides Rtrim values required for some common
output voltages. By using 0.1% thick metal film resistor,
the output voltage tolerance in the electrical specification
can be achieved over all operating input voltage, resistive
load and temperature conditions.
Table 1
VO,set (V) Rtrim (Ω)
0.8 11
1.0 208
1.2 404
1.5 699
1.8 994
2.0 1190
2.5 1682
3.3 2468
5.0 4138
Overvoltage Shutdown Open
The amount of power delivered by the module is the
voltage at the output terminals multiplied by the output
current. When using the trim feature, the output voltage
of the module can be increased, which at the same
output current would increase the power output of the
module. Care should be taken to ensure that the
maximum output power of the module must not exceed
the maximum rated power (
Vo.set x Io.max ≤ P max ).