000-0059H1007-100

Page 12 of 20

SLG59H1007V

Applications Information

HFET1 Safe Operating Area Explained

Silego’s HFET1 integrated power controllers incorporate a number of internal protection features that prevents them from

damaging themselves or any other circuit or subcircuit downstream of them. One particular protection feature is their Safe

Operation Area (SOA) protection. SOA protection is automatically activated under overpower and, in some cases, under

overcurrent conditions. Overpower SOA is activated if package power dissipation exceeds an internal 5W threshold longer than

2.5 ms. HFET1 devices will quickly switch off (open circuit) upon overpower detection and automatically resume (close) nominal

operation once overpower condition no longer exists.

One possible way to have an overpower condition trigger SOA protection is when HFET1 products are enabled into heavy output

resistive loads and/or into large load capacitors. It is under these conditions to follow carefully the “Safe Start-up Loading”

guidance in the Applications section of the datasheet. During an overcurrent condition, HFET1 devices will try to limit the output

current to the level set by the external RSET resistor. Limiting the output current, however, causes an increased voltage drop

dissipation also increases. If the resultant increase in package power dissipation is higher/equal than 5 W for longer than 2.5 ms,

internal SOA protection will be triggered and the FET will open circuit (switch off). Every time SOA protection is triggered, all

HFET1 devices will automatically attempt to resume nominal operation after 160 ms.

Safe Start-up Condition

SLG59H1007V has built-in protection to prevent over-heating during start-up into a heavy load. Overloading the VOUT pin with

a capacitor and a resistor may result in non-monotonic VOUT ramping. In general, under light loading on VOUT, VOUT ramping

where

When capacitor and resistor loading on VOUT during start up, the following tables will ensure VOUT ramping is monotonic without

triggering internal protection:

Slew Rate (V/ms)

0.5

66.7

500

80

1.0

33.3

250

80

1.5

22.2

160

80

2.0

16.7

120

80

2.5

13.3

100

80

x 5

μA x

20

3