PI3545-00-LGIZ Datasheet, PDF (24/37 Pages) Vicor Corporation – 36 Vin to 60 Vin Cool-Power ZVS Buck Regulator & LED Driver

Functional Description
The PI354x-00 is a family of highly integrated ZVS-Buck
regulators. The PI354x-00 has an output voltage that can be
set within a prescribed range shown in Table 1. Performance
and maximum output current are characterized with a
specific external power inductor (see Table 2).
Vin
Cin
L1
VIN
PGND
VDR
PI354X
VS1
VOUT
VSN
VSP
SYNCO
VDIFF
SYNCI
LGH
PWRGD
EAIN
EN
EAO
TESTx
COMP
SGND
TRK
Vout
Cout
Figure 49 — ZVS-Buck with required components
For basic operation, Figure 49 shows the connections and
components required. No additional design or settings are
required.
ENABLE (EN)
EN is the enable pin of the converter. The EN Pin is
referenced to SGND and permits the user to turn the
regulator on or off. The EN default polarity is a positive logic
assertion. If the EN pin is left floating or asserted high, the
converter output is enabled. Pulling EN pin below 0.8 Vdc
with respect to SGND will disable the regulator output.
Remote Sensing
If remote sensing is required, the PI354x-00 product family is
equipped with an undedicated differential amplifier. This
amplifier can allow full differential remote sense by
configuring it as a differential follower and connecting the
VDIFF pin to the EAIN pin.
Switching Frequency Synchronization
The SYNCI input allows the user to synchronize the
controller switching frequency by an external clock
referenced to SGND. The external clock can synchronize the
unit between 50% and 110% of the preset switching
frequency (fS). The PI354x-00 syncs to the falling edge of the
applied clock, providing 180 degrees of phase shift with
respect to SYNCO.
This allows for the interleaved paralleling of two PI354x-00
devices. The SYNCI pin should be connected to SGND
through a zero Ohm resistor when not in use and should
never be left floating.
When using the internal oscillator, the SYNCO pin provides a
5 V clock that can be used to sync other regulators. Therefore,
one PI354x-00 can act as the lead regulator and have
additional PI354x-00s running in parallel and synchronized.
Cool-Power®
Page 24 of 37
Rev 1.3
2/2016
PI354x-00
Soft-Start
The PI354x-00 includes an internal soft-start capacitor to
control the rate of rise of the output voltage. See the
Electrical Characteristics Section for the default value.
Connecting an external capacitor from the TRK pin to SGND
will increase the start-up ramp period. See, “Soft Start
Adjustment and Track,” in the Applications Description
section for more details.
Output Voltage Selection
The PI354x-00 output voltage can be selected by connecting
a resistor from EAIN pin to SGND and a resistor from Vout to
the EAIN pin as shown in Figure 49. Table 1 defines the
allowable operational voltage ranges for the PI354x-00
family.
Device
PI3542-00-LGIZ
Output Voltage
Nom.
Range
2.5 V
2.2 V to 3.0 V
PI3543-00-LGIZ
3.3 V
2.6 V to 3.6 V
PI3545-00-LGIZ
5.0 V
4.0 V to 5.5 V
PI3546-00-LGIZ
12 V
6.5 V to 14.0 V
Table 1 — PI354x-00 family output voltage ranges
Output Current Limit Protection
PI354x-00 has two methods implemented to protect from
output short or over current condition.
Slow Current Limit protection: prevents the output from
sourcing current higher than the regulator’s maximum rated
current. If the output current exceeds the Current Limit
(I_{OUT_CL}) for 1024 μs, a slow current limit fault is initiated and
the regulator is shutdown which eliminates output current
flow. After Fault Restart Delay (t_{FR_DLY}), a soft-start cycle is
initiated. This restart cycle will be repeated indefinitely until
the excessive load is removed.
Fast Current Limit protection: PI354x-00 monitors the
regulator inductor current pulse-by-pulse to prevent the
output from supplying very high current due to sudden low
impedance short. If the regulator senses a high inductor
current pulse, it will initiate a fault and stop switching until
Fault Restart Delay ends and then initiate a soft-start cycle.
Input Undervoltage Lockout
If V_IN falls below the input Under Voltage Lockout (UVLO)
threshold, but remains high enough to power the internal
bias supply, the PI354x-00 will complete the current cycle
and stop switching. The system will soft start once the input
voltage is reestablished and after the Fault Restart Delay.
Input Overvoltage Lockout
If V_IN exceeds the input Over Voltage Lockout (OVLO)
threshold (V_OVLO), while the controller is running, the
PI354x-00 will complete the current cycle and stop
switching. The system will soft start once the input voltage is
reestablished and after the Fault Restart Delay.
vicorpower.com
800 927.9474