PI31XX-00-HVMZ Datasheet, PDF (23/26 Pages) Vicor Corporation – 28VIN, 3.3 to 15VOUT, ZVS Isolated Converter Module Family

Functional Description
DC-DC
Converter
MADE
IN
USA
U.S. PATS. LISTED ON PACKING MATERIALS & DATASHEETS
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 16V to 50V_DC.
Under surge conditions, the PI31xx-00-HVMZ can withstand up
to 55V_DC for 12.5ms 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 overvoltage trip point
(typically 53.5V) 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) 4.7µF 50V ceramic
capacitors of X7R dielectric in parallel with a low Q 100µF 63V
electrolytic capacitor. To reduce EMI and reflected ripple current,
a series inductor of 0.2 to 0.47µH 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 4.9V 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 3.3mA, minimum.
If the ENABLE pin is lower than 2.35V 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
28 Volt - M Grade
Page 23 of 26
Rev 1.6
02/2015
PI31xx-00-HVMZ
that a fault has occurred. Whenever the ENABLE pin is pulled
low, the TRIM/SS pin follows, resetting the internal and 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 1500pF.
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
500µs 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_nom + V_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
C_REF =
T_ssdesired – 230 • 10^−6
23000
vicorpower.com
800 927.9474