Technical Specification
Quarter
48V 3.3/1.8V
77W
out
in
Brick Dual
Input Filtering and External Capacitance: Figure E pro-
vides a diagram showing the internal input filter components.
This filter dramatically reduces input terminal ripple current,
which otherwise could exceed the rating of an external elec-
trolytic input capacitor. The recommended external input
capacitance is specified in the “Input Characterisitcs” section.
More detailed information is available in the application note
titled “EMI Characteristics” on the SynQor website.
L
Vin(+)
C1
C2
_
Vin( )
Figure E: Internal Input Filter Diagram (values listed on page 3).
Figure F shows three turn-on scenarios, where a Startup Inhibit
Period is initiated at t0, t1, and t2:
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:
Before time t0, 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.
• Input Under-Voltage Lockout
• Input Over-Voltage Shutdown (not present in Quarter-brick)
• Output Over-Voltage Protection
• Over Temperature Shutdown
• Current Limit
At time t1, 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 t2, the Startup Inhibit
• Short Circuit Protection
Period has elapsed, and the output turns on within the typical
Turn-On Time.
• Turned off by the ON/OFF input
V
in
Under-Voltage
Lockout Turn-On
Threshold
ON/OFF
(pos logic)
ON
OFF
ON
OFF
ON
4ms (typical
turn on time)
V
out
200ms
(typical start-up
inhibit period)
200ms
200ms
t
t0
t1
t2
Figure F: Startup Inhibit Period (turn-on time not to scale)
Product # DQ63318QGL08
Phone 1-888-567-9596
Doc.# 005-2DQ638D Rev. B
10/7/03
Page 13
SYNQOR [ SYNQOR WORLDWIDE HEADQUARTERS ]
