psa242.5-2iry Power-One, psa242.5-2iry Datasheet - Page 5

• Manufacturer Part Number: psa242.5-2iry
• Description: Psa Series Extended Positive Switching Regulators Benign
• Manufacturer: Power-One

Thermal Considerations
When a switching regulator is located in free, quasi-sta-
tionary air (convection cooling) at a temperature T
and is operated at its nominal output current I
case temperature T
up phase, measured at the Measuring point of case tem-
perature T
Under practical operating conditions, the ambient tem-
perature T
ures (heat sink, fan, etc.) are taken to ensure that the case
temperature T
80°C.
Example: Sufficient forced cooling allows T
simple check of the case temperature T
load ensures correct operation of the system.
Fig. 4
Output current derating versus temperature
Output Protection
A voltage suppressor diode which in worst case conditions
fails into a short circuit, protects the output against an in-
ternally generated overvoltage. Such an overvoltage could
occur due to a failure of either the control circuit or the
switching transistor. The output protection is not designed
to withstand externally applied overvoltages. The user
should ensure that systems with Power-One power
supplies, in the event of a failure, do not result in an unsafe
condition (fail-safe).
I
Fig. 3
Dynamic load regulation.
REV. SEP 17, 2003
U
o
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
1
0
/I
o
0
o nom
I
o
T
/I
A min
o nom
u
Convection cooling
od
C
A
(see: Mechanical Data).
may exceed 50°C, provided additional meas-
40
C
does not exceed its maximum value of
10 µs
t
d
C
50
will not exceed 80°C after the warm-
DU
Forced cooling
60
o I
u
od
70
C
(T
10 µs
C
A max
80
t
d
80°C) at full
= 65°C. A
T
o nom
A
C max
= 50°C
T
, the
A
Page 5 of 11
DU
[ C]
05010
o I
t
t
Positive Switching Regulator
Parallel and Series Connection
Outputs of equal nominal voltages can be parallel-con-
nected. However, the use of a single unit with higher out-
put power, because of its power dissipation, is always a
better solution.
In parallel-connected operation, one or several outputs
may operate continuously at their current limit knee-point,
which will cause an increase of the heat generation. Con-
sequently, the max. ambient temperature should be re-
duced by 10 K.
Outputs can be series-connected with any other module.
In series-connection the maximum output current is limited
by the lowest current limitation. Electrically separated
source voltages are needed for each module!
Short Circuit Behaviour
A constant current limitation circuit holds the output cur-
rent almost constant whenever an overload or a short cir-
cuit is applied to the regulator's output. It acts self-protect-
ing and recovers – in contrary to the fold back method –
automatically after removal of the overload or short circuit
condition.
1.2
0.8
0.6
0.2
Fig. 5
Overload, short-circuit behaviour U
1.0
0.4
U
0
o
/U
o nom
0.2
PSA Series Extended Datasheet
0.4
0.6
0.8
1.0
o
versus I
I
o L
1.2
s (Benign)
o
05033
.
1.4
I
o
/I
o nom