PI3420-00-LGIZ Datasheet, PDF (22/30 Pages) Vicor Corporation – 8 V to 18 Vin, 15 A Cool-Power ZVS Buck Regulator

Functional Description
The PI34xx-00 is a family of highly integrated ZVS-Buck
regulators. The PI34xx-00 has a set output voltage that is
trimmable within a prescribed range shown in Table 1.
Performance and maximum output current are characterized
with a specific external power inductor
(see Table 4).
L1
V_IN
V_IN
VS1
C_IN
PI34xx
PGND
V_OUT
REM
SYNCI
SYNCO
EN
TRK
ADJ
EAO
V_OUT
C_OUT
Figure 36 — ZVS-Buck with required components
For basic operation, Figure 36 shows the connections and
components required. No additional design or settings are
required.
ENABLE (EN)
EN is the enable pin of the regulator. The EN Pin is referenced
to SGND and permits the user to turn the regulator on or off.
The EN polarity is a positive logic assertion. If the EN pin is
left floating or asserted high, the regulator output is enabled.
Pulling EN pin below 0.8 Vdc with respect to SGND will
disable the regulator output.
Remote Sensing
An internal 100 Ω resistor is connected between REM pin and
VOUT pin to provide regulation when the REM connection is
broken. Referring to Figure 36, it is important to note that L1
and Cout are the output filter and the local sense point for
the power supply output. As such, the REM pin should be
connected at Cout as the default local sense connection
unless remote sensing to compensate additional distribution
losses in the system. The REM pin should not be left floating.
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 PI34xx-00 syncs to the falling edge of the applied clock
providing 180° phase shift from SYNCO. This allows for the
paralleling of two PI34xx-00 devices. When using the
internal oscillator, the SYNCO pin provides a 5 V clock that
can be used to sync other regulators. Therefore, one PI34xx-
00 can act as the lead regulator and have additional
PI34xx-00s running in parallel and interleaved.
Cool-Power®
Page 22 of 30
Rev 1.3
12/2015
PI34xx-00
Soft-Start
The PI34xx-00 includes an internal soft-start capacitor to
ramp the output voltage in 2ms from 0 V to full output
voltage. 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 Trim
The PI34xx-00 output voltage can be trimmed up from the
preset output by connecting a resistor from ADJ pin to SGND
and can be trimmed down by connecting a resistor from ADJ
pin to V_OUT. The Table 1 defines the voltage ranges for the
PI34xx-00 family.
Device
PI3420-00-LGIZ
PI3421-00-LGIZ
PI3422-00-LGIZ
PI3423-00-LGIZ
PI3424-00-LGIZ
Output Voltage
Set
Range
1.0 V
1.0 to 1.4 V
1.8 V
1.4 to 2.0 V
2.5 V
2.0 to 3.1 V
3.3 V
2.3 to 4.1 V
5.0 V
3.3 to 6.5 V
Table 1 — PI34xx-00 family output voltage ranges
Output Current Limit Protection
PI34xx-00 has two methods implemented to protect from
output short or over current condition.
Slow Current Limit protection: prevents the output load from
sourcing current higher than the regulator’s maximum rated
current. If the output current exceeds the Current Limit
(I_{OUT_CL}) for 1024 us, 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: PI34xx-00 monitors the
regulator inductor current pulse-by-pulse to prevent the
output from supplying very high current due to sudden low
impedance short
(50 A Typical). 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 Undervoltage Lockout (UVLO)
threshold, the regulator will enter a low power state and
initiate a fault. The system will restart once the input voltage
is reestablished and after the Fault Restart Delay.
Input Overvoltage Lockout
If VIN exceeds the input Overvoltage Lockout (OVLO)
threshold (VOVLO), while the regulator is running, the
PI34xx-00 will complete the current cycle and stop
switching. The system will resume operation after the Fault
Restart Delay.
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