Input:
Output:
Current:
Package:
35-75V
12V
17A (200W)
Quarter-brick
Product # PQ60120QEA17
Phone 1-888-567-9596
www.synqor.com
Doc.# 005-0005068 Rev. B
06/03/09
Page 12
Technical Specification
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 exami-
nation, 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 volt-
age, 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.
0
20
40
60
80
100
120
140
35
40
45
50
55
60
65
70
75
Vin (V)
V
o
u
t
S
te
p
S
ize
(m
V
)
= 12.0 Vout
= 10.0 Vout
≤ 8.75 Vout
Figure C: Output voltage resolution.
Figure D: Smallest possible Vout step at 48Vin and 12Vout.
* See Electrical Characteristics page.