PI352X-00 Datasheet, PDF (29/34 Pages) Vicor Corporation – 30VIN to 60VIN Cool-Power ZVS Buck Regulator

VDR Bias Regulator
The VDR internal bias regulator is a ZVS switching regulator that
resides internal to the PI352x-00 SIP. It is intended primarily to
power the internal controller and driver circuitry. The power
capability of this regulator is sized for the PI352x-00, with
adequate reserve for the application it was intended for.
It may be used for as a pullup source for open collector
applications and for other very low power uses with the
following restrictions:
1. The total external loading on VDR must be less than I_VDR.
2. No direct connection is allowed. Any noise source that can
disturb the VDR voltage can also affect the internal controller
operation. A series impedance is required between the VDR pin
and any external circuitry.
3. All loads must be locally de-coupled using a 0.1μF ceramic
capacitor. This capacitor must be connected to the VDR output
through a series resistor no smaller than 1kΩ, which forms a
low-pass filter.
PI352x-00
Additional System Design Considerations
1. Inductive loads: As with all power electronic applications,
consideration must be given to driving inductive loads that
may be exposed to a fault in the system which could result
in consequences beyond the scope of the power supply
primary protection mechanisms. An inductive load could be a
filter, fan motor or even excessively long cables. Consider an
instantaneous short circuit through an un-damped inductance
that occurs when the output capacitors are already at an
initial condition of fully charged. The only thing that limits the
current is the inductance of the short circuit and any series
resistance. Even if the power supply is off at the time of the
short circuit, the current could ramp up in the external inductor
and store considerable energy. The release of this energy will
result in considerable ringing, with the possibility of ringing
nodes connected to the output voltage below ground. The
system designer should plan for this by considering the use
of other external circuit protection such as load switches,
fuses, and transient voltage protectors. The inductive filters
should be critically damped to avoid excessive ringing or
damaging voltages. Adding a high current Schottky diode
from the output voltage to PGND close to the PI352x-00 is
recommended for these applications.
2. Low voltage operation: There is no isolation from an SELV
(Safety-Extra-Low-Voltage) power system. Powering low
voltage loads from input voltages as high as 60V may require
additional consideration to protect low voltage circuits from
excessive voltage in the event of a short circuit from input to
output. A fast TVS (transient voltage suppressor) gating an
external load switch is an example of such protection.
Manufacturer
Part Number
Murata
GRM32ER71A476KE15
Murata
GRM32ER72A225KA35
Murata
GRM32DR71E106MA12
Table 5 — Recommended input and output capacitor components
Value
47µF
2.2µF
10µF
Description
47μF 10V 1210 X7R
2.2μF 100V 1210 X7R
10µF 25V 1210 X7R
Product
Load
Current C_IN
(A)
C_OUT
C_IN
Ripple
Current
(I_RMS)
C_OUT
Ripple
Current
(I_RMS)
V_IN
Ripple
(mVpp)
V_OUT
Ripple
(mVpp)
Load
Step
(% Rating)
(1A/µs)
Transient
Deviation
Excluding
Ripple
(mVpk)
PI3525
20
10 x
2.2µF
12 x 47µF
8.0
14
960
75
50 – 100
160
PI3526
18
10 x
2.2µF
8 x 10µF
10.1
11
700
210
50 – 100
260
Table 6 — Recommended input and output capacitor quantity and performance at nominal line, nominal trim.
V_OUT
Recovery
Time (µs)
<80
<80
Cool-Power^® ZVS Switching Regulators
Page 29 of 34
Rev 1.3
06/2017
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