DS_DNS04SIP06A_07172008
10
FEATURES DESCRIPTIONS
(CON.)
Over-Temperature Protection
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.
Remote Sense
The DNS provide Vo remote sensing to achieve proper
regulation at the load points and reduce effects of
distribution losses on output line. In the event of an open
remote sense line, the module shall maintain local sense
regulation through an internal resistor. The module shall
correct for a total of 0.5V of loss. The remote sense line
impedance shall be < 10
Ω
.
Vo
Sense
Vin
GND
RL
Distribution Losses
Distribution Losses
Distribution
L
Distribution
Figure 36:
Effective circuit configuration for remote sense
operation
Output Voltage Programming
The output voltage of the DNS can be programmed to any
voltage between 0.75Vdc and 3.3Vdc by connecting one
resistor (shown as Rtrim in Figure 37) 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:
Ω
⎥⎦
⎤
⎢⎣
⎡
−
−
=
5110
7525
.
0
21070
Vo
Rtrim
For example, to program the output voltage of the DNS
module to 1.8Vdc, Rtrim is calculated as follows:
Ω
=
Ω
⎥⎦
⎤
⎢⎣
⎡
−
−
=
K
Rtrim
15
5110
7525
.
0
8
.
1
21070
DNS can also be programmed by apply a voltage between
the TRIM and GND pins (Figure 38). The following
equation can be used to determine the value of Vtrim
needed for a desired output voltage Vo:
(
)
7525
.
0
1698
.
0
7
.
0
−
×
−
=
Vo
Vtrim
For example, to program the output voltage of a DNS
module to 3.3 Vdc, Vtrim is calculated as follows
(
)
V
Vtrim
267
.
0
7525
.
0
3
.
3
1698
.
0
7
.
0
=
−
×
−
=
Vo
TRIM
GND
RLoad
Rtrim
Figure 37:
Circuit configuration for programming output voltage
using an external resistor
Vo
TRIM
GND
RLoad
Vtrim
+
_
Figure 38:
Circuit Configuration for programming output voltage
using external voltage source
Table 1 provides Rtrim values required for some common
output voltages, while Table 2 provides value of external
voltage source, Vtrim, for the same common output
voltages. By using a 1% tolerance trim resistor, set point
tolerance of ±2% can be achieved as specified in the
electrical specification.
Table 1
Vo(V)
Rtrim(K
Ω
)
0.7525
Open
1.2
41.97
1.5
23.08
1.8
15.00
2.5
6.95
3.3
3.16
Table 2
Vo(V)
Vtrim(V)
0.7525
Open
1.2
0.624
1.5
0.573
1.8
0.522
2.5
0.403
3.3
0.267