PSA Series Extended Data Sheet

Positive Switching Regulator (Rugged)

REV. SEP 23, 2003

Page 5 of 13

Thermal Considerations

When a switching regulator is located in free, quasi-sta-

up phase, measured at the Measuring point of case tem-

Under practical operating conditions, the ambient tem-

ures (heat sink, fan, etc.) are taken to ensure that the case

95 °C.

≤ 95°C) at

full load ensures correct operation of the system.

1.2

1.0

0.8

0.6

0.4

0

0.2

0.4

1.0

1.2

0.2

0.6

0.8

1.4

05033

Fig. 5

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

50

60

70

80

90

100

0.9

1.0

Forced cooling

Convection cooling

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.

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 sup-

plies, in the event of a failure, do not result in an unsafe

condition (fail-safe).

Fig. 3

Dynamic load regulation.

1

t

0

t

≥10 µs

≥10 µs

05010