PI354X-00 Datasheet, PDF (25/39 Pages) –

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).
V_IN
C_IN
L1
VIN
VS1
PGND _PI354X VOUT
VDR
VSN
VSP
SYNCO
VDIFF
SYNCI
LGH
PWRGD
EAIN
EN
EAO
TESTx
COMP
SGND
TRK
V_OUT
C_OUT
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 0.8V_DC 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 SYNCO pin provides a 5V level clock that can be used to
monitor the internal clock of the regulator, or synchronize other
regulators to it. The start of the switching cycles will coincide with
the rising edge of SYNCO, and SYNCO will remain high for ½ the
period of the preset switching frequency (f_S), or T1, whichever
is longer. The SYNCI input allows the controller to synchronize
its internal clock to an external clock source. The SYNCI pin
should be connected to SGND through a 0Ω resistor when
not in use and should never be left floating. The controller can
synchronize to frequencies between 50% and 110% of the preset
switching frequency (f_S). When using SYNCI, the PI354x-00 phase
synchronizes to the falling edge of the applied clock on SYNCI.
When SYNCI is driven from a second module’s SYNCO, there is
an effective 180 degrees of phase shift between the start of the
switching cycles, provided the modules are switching at the preset
switching frequency. At higher loads when pulse stretching occurs
and the operating frequency is lowered, the phase shift is
Cool-Power^® ZVS Switching Regulators
Page 25 of 39
Rev 1.6
03/2017
PI354x-00
no longer 180 degrees. Also when the switching frequency of a
module is reduced due to an external clock source driving SYNCI,
the current limit threshold may be significantly reduced.
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
Output Voltage
Nom.
Range
PI3542-00-LGIZ
2.5V
2.2V to 3.0V
PI3543-00-LGIZ
3.3V
2.6V to 3.6V
PI3545-00-LGIZ
5.0V
4.0V to 5.5V
PI3546-00-LGIZ
12V
6.5V to 14.0V
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 1024µs, 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 Undervoltage 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.
vicorpower.com
800 927.9474