Technical Specification
Half
48V 2.5V
60A
out
in
Brick
the primary-side ground, Vin(-).
Good" signal. This pin is referenced to the secondary-side
ground, Vsense(-). The voltage at this pin tracks the output volt-
age but has a value several times higher. For example, during
normal operation the OR Drive voltage is at least high enough
to fully gate on a standard MOSFET, whose source voltage is
equal to the output voltage of the converter. With nominal out-
put voltage, the OR Drive signals are listed in the table below
for each output voltage. An internal 2.7 KΩ source resistance
will limit the current drawn from this pin. However, the user is
responsible for the overvoltage protection of the MOSFET or
other external circuitry driven by this voltage. It is recom-
mended that the user include a zener diode between the gate
and source of the external MOSFET(s) driven by the OR Drive
pin. For more information, refer to the Full Feature Application
Note found on the SynQor web site (www.synqor.com).
Start Sync (pin B): The Start Synchronization pin will allow
a more consistent start-up sequence. To operate this feature,
connect together the Start-Sync pins of multiple current-sharing
units. This will permit immediate start-up with loads greater than
the current limit of a single unit. Without this connection, any
set of converters attempting to asynchronously start (or re-start)
with a load greater than the current limit of a single unit will
"hiccup". This “hiccup” mode will continue until one converter
attempts a start at the same time as the minimum number of
additional units necessary to sustain the load condition. For
example, three 50 amp units starting into a 90 amp load would
require two units to simultaneously attempt a start. The Start
Sync connection synchronizes these starting attempts and pro-
vides a more consistent and reliable start-up sequence. For
details about the "hiccup mode" or repeated startup attempts,
please see the "Startup Inhibit Period" note in this Technical
Specification.
OR-Drive Voltages
Vout
1.2
1.5
1.8
2.0
2.5
3.3
5.0
12
No Load
Full Load
TBD
9
TBD
12
14
16
21
16
20
26
28
11
11
13
13
19
24
26
Clock Sync (pin A): The External Clock Synchronization pin
provides the ability for the user to control the EMI signature and
synchronize sensitive circuitry to quiet periods in the converter
operation. With this option, the converter can be synchronized
to an external clock signal whose frequency is greater than that
of the free-running internal clock. However, substantially raising
the converter’s frequency will reduce its efficiency. Therefore,
the recommended frequency range for the external clock syn-
chronization signal applied to this pin would be the lowest
value possible without dropping below the minimum frequen-
cies listed below:
15
275 KHz for the 1.5V and 3.3V units
225 KHz for the 1.8V and 2.0V units
255 KHz for the 2.5V, 5V, 12V and 15V units
The following requirements should also be met:
• The external clock signal should be referenced to the
negative input voltage, Vin(-).
• The high level of the signal should be between 3.5V
and 5.0V.
• The low level should be between -0.5V and +1.2V.
• Do not apply a clock signal lower than the specified
frequency.
OR Drive (pin C): This pin provides a signal which can be
used to drive an OR-ing FET and/or an auxiliary external con-
trol circuitry. This pin may also be used as a basic "Power-
Product # PQ48025HTA60
Phone 1-888-567-9596
Doc.# 005-2HT425F Rev. Q
11/19/02
Page 13
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