Technical Specification
Eighth
Brick
Startup Inhibit Period:
The Startup Inhibit Period ensures
that the converter will remain off for at least 200ms when it is
shut down for any reason. When an output short is present,
this generates a 5Hz "hiccup mode," which prevents the con-
verter from overheating. In all, there are seven ways that the
converter can be shut down, initiating a Startup Inhibit Period:
• Input Under-Voltage Lockout
• Input Over-Voltage Shutdown (not present in Eighth-brick)
• Output Over-Voltage Protection
• Over Temperature Shutdown
• Current Limit
• Short Circuit Protection
• Turned off by the ON/OFF input
Figure F shows three turn-on scenarios, where a Startup Inhibit
Period is initiated at t
0
, t
1
, and t
2
:
48Vin 1.5Vout 15A
Before time t
0
, when the input voltage is below the UVL thresh-
old, the unit is disabled by the Input Under-Voltage Lockout fea-
ture. When the input voltage rises above the UVL threshold, the
Input Under-Voltage Lockout is released, and a Startup Inhibit
Period is initiated. At the end of this delay, the ON/OFF pin is
evaluated, and since it is active, the unit turns on.
At time t
1
, the unit is disabled by the ON/OFF pin, and it can-
not be enabled again until the Startup Inhibit Period has
elapsed.
When the ON/OFF pin goes high after t
2
, the Startup Inhibit
Period has elapsed, and the output turns on within the typical
Turn-On Time.
Vin
Under-Voltage
Lockout Turn-On
Threshold
ON/OFF
(pos logic)
ON
OFF
ON
OFF
ON
Vout
14ms
(typical
200ms
(typical start-up
inhibit period)
turn on time)
200ms
200ms
t
0
t
1
t
2
t
Figure F:
Startup Inhibit Period (turn-on time not to scale)
Product # PQ60015EML15
Phone 1-888-567-9596
Doc.# 005-2EM651E Rev. B
9/3/03
Page 12
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