PI3106-00-HVMZ_16 Datasheet, PDF (23/26 Pages) Vicor Corporation – Cool-Power ZVS Isolated DC-DC Converter Modules

Functional Description
Figure 41 — Picor PI31xx-00-HVMZ Shown With System Fuse, Filter,
Decoupling And Extended Soft Start
Input Power Pins IN(+) and IN(-)
The input power pins on the PI31xx-00-HVMZ are connected to the
input power source which can range from 16 V to 50 V DC. Under
surge conditions, the PI31xx-00-HVMZ can withstand up to 55 V DC
for 12.5 ms without incurring damage. The user should take care to
avoid driving the input rails above the specified ratings. Since the
PI31xx-00-HVMZ is designed with high reliability in mind, the input
pins are continuously monitored. If the applied voltage exceeds the
input over-voltage trip point (typically 53.5 V) the conversion
process shall be terminated immediately. The converter initiates soft-
start automatically within 80ms after the input voltage is reduced
back to the appropriate value. The input pins do not have reverse
polarity protection. If the PI31xx-00-HVMZ is operated in an
environment where reverse polarity is a concern, the user should
consider using a polarity protection device such as a suitably rated
diode. To avoid the high losses of using a diode, the user should
consider the much higher efficiency Picor family of intelligent
Cool-ORing® solutions that can be used in reverse polarity
applications. Information is available at vicorpower.com.
The PI31xx-00-HVMZ will draw nearly zero current until the input
voltage reaches the internal start up threshold. If the ENABLE pin is
not pulled low by external circuitry, the output voltage will begin
rising to its final output value about 80ms after the input UV lockout
releases. This will occur automatically even if the ENABLE
pin is floating.
To help keep the source impedance low, the input to the
PI31xx-00-HVMZ should be bypassed with (2) 4.7uF 50 V ceramic
capacitors of X7R dielectric in parallel with a low Q 100uF 63 V
electrolytic capacitor. To reduce EMI and reflected ripple current, a
series inductor of 0.2 to 0.47 uH can be added. The input traces to the
module should be low impedance configured in such a manner as to
keep stray inductance minimized.
ENABLE
The ENABLE pin serves as a multi-function pin for the
PI31xx-00-HVMZ. During normal operation, it outputs the on-board
4.9 V regulator which can be used for trimming the module up. The
ENABLE pin can also be used as a remote enable pin either from the
secondary via an optocoupler and an external isolated bias supply or
from the primary side through a small signal transistor, FET, or any
device that sinks 3.3 mA, minimum. If the ENABLE pin is lower than
2.35 V typical, the converter will be held off or shut down if already
operating. A third feature is offered in that during a fault condition,
such as output OVP, input UV or OV, or output current limit, the
ENABLE pin is pulled low internally. This can be used as a signal to
the user that a fault has occurred. Whenever the ENABLE pin is
pulled low, the TRIM/SS pin follows, resetting the internal and
PI31xx-00-HVMZ
external soft-start circuitry. All faults will pull ENABLE low including
over temperature. If increased turn on delay is desired, the ENABLE
pin can be bypassed with a small capacitor up to a maximum
of 1500 pF.
TRIM/SS Pin
The TRIM/SS pin serves as another multi-purpose pin. First, it is used
as the reference for the internal error amplifier. Connecting a resistor
from TRIM/SS to SGND allows the reference to be margined down by
as much as -20%. Connecting a resistor from TRIM/SS to ENABLE
will allow the reference and output voltage to be margined up by
10%. If the user wishes a longer start up time, a small ceramic
capacitor can be added to TRIM/SS to increase it. It is critical to
connect any device between TRIM/SS and SGND and not -IN,
otherwise high frequency noise will be introduced to the reference
and possibly cause erratic operation. Referring to the figures below,
the appropriate trim up or trim down resistor can be calculated using
the equivalent circuit diagram and the equations. When trimming
up, the trim down resistor is not populated. When trimming down,
the trim up resistor is not populated. The soft start time is adjustable
within the limits defined by the data tables and has a default value of
500us to reach steady state. The internal soft start capacitor value is
10nF.
ENABLE
PI31xx
VERO
10k
RSS
TRIM/SS
Vref
•
SGND
Rhigh
•
Rlow
•
( ) ^{R =}
( ) ^low
–V
desired
•
R_INT
–Vout + V
nom
desired
( ) ⁽ _[( ⁾ _{) + ]} R_high =
–RSS
•
–Vout
nom
•
V+
ERO
V
desired
•
V
ref
V_ref –Vout_nom
V
desired
Figure 42 — Trim Equations And Equivalent Circuit
T
– 230 • 10^−6
C = ^ssdesired
REF
23000
Cool-Power®
Page 23 of 26
Rev 1.6
02/2015
vicorpower.com
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