FEATURES DESCRIPTIONS (CON.)
Over-Temperature Protection
FEATURE DESCRIPTIONS (CON.)
Vo
The over-temperature protection consists of circuitry that
provides protection from thermal damage. If the
temperature exceeds the over-temperature threshold the
module will shut down. The module will try to restart after
shutdown. If the over-temperature condition still exists
during restart, the module will shut down again. This
restart trial will continue until the temperature is within
specification.
Vtrim
TRIM
GND
+
_
RLoad
Figure 31:
Circuit Configuration for programming output voltage
using external voltage source
Output Voltage Programming
The output voltage of the DNT can be programmed to any
voltage between 0.75Vdc and 3.3Vdc by connecting one
resistor (shown as Rtrim in Figure 30) between the TRIM
and GND pins of the module. Without this external
resistor, the output voltage of the module is 0.7525 Vdc.
To calculate the value of the resistor Rtrim for a particular
output voltage Vo, please use the following equation:
⎡
21070
⎤
Rtrim
= ⎢
−
5110
⎥ Ω
⎣
Vo
−
0.7525
⎦
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)
.
Voltage Margining
Output voltage margining can be implemented in the DNT
modules by connecting a resistor, R
margin-up
, from the Trim
pin to the ground pin for margining-up the output voltage
and by connecting a resistor, R
margin-down
, from the Trim pin
to the output pin for margining-down. Figure 32 shows the
circuit configuration for output voltage margining. If unused,
leave the trim pin unconnected. A calculation tool is
available from the evaluation procedure which computes
the values of R
margin-up
and R
margin-down
for a specific output
voltage and margin percentage.
Vin
Vo
For example, to program the output voltage of the DNS
module to 1.8Vdc, Rtrim is calculated as follows:
⎡
21070
⎤
Rtrim
= ⎢
−
5110
⎥ Ω =
15
K
Ω
⎣
1.8
−
0.7525
⎦
DNT can also be programmed by apply a voltage between
the TRIM and GND pins (Figure 31). The following
equation can be used to determine the value of Vtrim
needed for a desired output voltage Vo:
Vtrim
=
0.7
−
0.1698
×
(
Vo
−
0.7525
)
For example, to program the output voltage of a DNT
module to 3.3 Vdc, Vtrim is calculated as follows
Vtrim
=
0.7
−
0.1698
×
(
3.3
−
0.7525
)
=
0.267
V
Rmargin-down
Q1
Vo
On/Off Trim
Rmargin-up
RLoad
TRIM
Rtrim
GND
Rtrim
GND
Q2
Figure 30:
Circuit configuration for programming output voltage
using an external resistor
Figure 32:
Circuit configuration for output voltage margining
DS_DNT04SMD3A_01182007
9
DELTA [ DELTA ELECTRONICS, INC. ]
