PI352X-00 Datasheet, PDF (23/34 Pages) Vicor Corporation – 30VIN to 60VIN Cool-Power ZVS Buck Regulator

Input Overvoltage Lockout
If V_IN exceeds the input Overvoltage Lockout (OVLO) threshold
(V_OVLO), while the controller is running, the PI352x-00 will
complete the current cycle and stop switching. If V_IN remains
above OVLO for at least t_{FR_DLY}, then the input voltage is
considered reestablished once V_IN goes below V_OVLO-V_{OVLO_HYS}.
If V_IN goes below OVLO before t_{FR_DLY} elapses, then the input
voltage is considered reestablished once V_IN goes below V_OVLO.
The system will soft start once the input voltage is reestablished
and after the Fault Restart Delay.
Output Overvoltage Protection
The PI352x-00 family is equipped with output Overvoltage
Protection (OVP) to prevent damage to input voltage sensitive
devices. If the output voltage exceeds V_OVP-REL or V_OVP-ABS, the
regulator will complete the current cycle and stop switching. The
system will resume operation once the output voltage falls below
the OVP threshold and after Fault Restart Delay.
Overtemperature Protection
The PI352x features an over temperature protection (OTP), which
will not engage until after the product is operated above the
maximum rated temperature. The OTP circuit is only designed to
protect against catastrophic failure due to excessive temperatures
and should not be relied upon to ensure the device stays within
the recommended operating temperature range. Thermal
shutdown terminates switching and discharges the soft-start
capacitor. As the temperature falls the PI352x will restart,
and this will always occur before the product returns to rated
temperature range.
PI352x-00
Pulse Skip Mode (PSM)
PI352x-00 features a Pulse Skip Mode (PSM) to achieve high
efficiency at light loads. The regulators are setup to skip pulses
if EAO falls below a PSM threshold (PSM_SKIP). Depending on
conditions and component values, this may result in single pulses
or several consecutive pulses followed by skipped pulses. Skipping
cycles significantly reduces gate drive power and improves light
load efficiency. The regulator will leave PSM once the EAO rises
above the Pulse Skip Mode threshold.
Variable Frequency Operation
Each PI352x-00 is preprogrammed to a base operating frequency,
with respect to the power stage inductor (see Table 2), to operate
at peak efficiency across line and load variations. At low line
and high load applications, the base frequency will decrease to
accommodate these extreme operating ranges. By stretching
the frequency, the ZVS operation is preserved throughout
the total input line voltage range therefore maintaining
optimum efficiency.
Thermal Characteristics
Figure 55(a) and 61(c) thermal impedance models that can predict
the maximum temperature of the hottest component for a given
operating condition. This model assumes that all customer PCB
connections are at one temperature, which is PCB equivalent
Temperature T_PCB °C.
The SiP model can be simplified as shown in Figure 55(b). which
assumes all PCB nodes are at the same temperature.
Cool-Power^® ZVS Switching Regulators
Page 23 of 34
Rev 1.3
06/2017
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