PQ60120HZX50 Datasheet, PDF (11/13 Pages) SynQor Worldwide Headquarters – Half-brick DC/DC Converter

Technical Specification
Input: 35-75 V
Output: 12 V
Current: 50 A (600W)
Package: Half-brick
APPLICATION CONSIDERATIONS
Limited Output Voltage Resolution: The internal voltage
control feedback loop has limited resolution. Therefore, the output
voltage will exhibit discrete steps as the loop responds to changes
in line, load, trim, or remote sense. For instance, on close
examination, the startup ramp has a “stair-step” shape.Likewise,
a load transient response will be composed of multiple discrete
steps. The size of each step is well determined, and is shown in
Figure C.A close-up picture of a single step is shown in Figure D.
Stepping will not occur under steady state conditions.
Current share and active trim not recommended: It is
important to note that external feedback control using the sense
or trim pins will cause sustained stepping. External current
share or active trim circuits contain a separate reference voltage.
After this external feedback has taken control, the actual output
voltage can still differ from the external reference voltage by as
much as the step size.If the external feedback loop integrates
this error voltage, it will cause a limit cycle oscillation.For this
reason, external feedback using the sense and trim pins is not
recommended.
Input System Instability: This condition can occur because
any DC/DC converter appears incrementally as a negative
resistance load. A detailed application note titled “Input System
Instability” is available on the SynQor website which provides
an understanding of why this instability arises, and shows the
preferred solution for correcting it.
140
120
100
80
60
40
20
0
35
40
45
50
55
60
Vin (V)
Figure C: Output voltage resolution.
= 12.0 Vout
= 10.0 Vout
£_{≤ 8.75 Vout}
65
70
75
Figure D: Smallest possible Vout step at 48Vin and 12Vout.
* See Electrical Characteristics page.
Product # PQ60120HZx50
Phone [phone]
www.synqor.com
Doc.# 005-2HZ612J Rev. D
06/12/09
Page 11