QPI-8LZ-01【PDF 6/17 页】IC HOT SWAP EMI FILTER 16LGA

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Sheet目录46

2页 3页 4页 5页 [6页]7页 8页 9页 10页

Picor Corporation ?picorpower.com

QPI-8

Rev 1.5, Page 6 of 17

QPI-8

QUIETPOWER

?/DIV>

Hot-Swap Function

Figure 10 - QPI-8 Block Diagram

The hot-swap of the QPI-8 sits before the active EMI filter and

is designed to align with the AdvancedTCA

PICMG3.0

?/DIV>

guidelines of 48V, 200W boards. Its 6A circuit breaker current

rating allows the QPI-8 to provide 200W of power down to

the minimum bus voltage of 36V. Its 12A maximum current

limit allows for fast charging of a converters input bulk

storage capacitance. Its ability to retry after a circuit

breaker fault time-out enables the QPI-8 to charge large

amounts of bulk capacitance through multiple 12A current

pulses before signaling that power is good via the PWRGD

pin. This signal should be used to enable the QPI-8s load

converter.

Figure 11 - 2 second short applied across QPI-8's outputs.

The waveforms shown in Figure 11 are of a running QPI-8

that has a short applied across its output for a 2 second

duration. The PWRGD signal (blue, CH1) is initially high, the

VSW voltage (light blue, CH2) is low with respect to BUS-, and

the input current (green, CH4) is at a minimum load.

With a short applied, PWRGD drops to a low value and the

voltage on VSW returns to the BUS+ value. The QPI-8 detects

a current fault and begins a cycle of trying to charge the bulk

capacitors, then waiting. Once the short is lifted, the QPI-8

charges the bulk capacitor by the third pulse of current, also

signaling that power is once again good. During the short

circuit the input current is limited to 12A peaks, with an on

duty cycle of about 1%.

The QPI-8 has a default under-voltage limit of 34V to turn on,

and 32V to turn off. The over-voltage limit is 76V to turn off,

72V to turn on. The high-side of each resistor string is

brought out to allow the user to trim up one or both of the

voltage limits, or the pins can be connected directly to BUS+

for the default under and over voltage limits. The equations

in Figure 12 provide the new trip point voltages for a given

added series resistor, R

UVEN

and/or R

, as is shown in Figure

13.

Figure 12 Resulting UVEN and OV voltage equations based

on selected series resistors.

Having access to the high side of the internal resistor divider

string enables the user to filter one or both nodes, allowing

the QPI-8 to pass various transient requirements of

PICMG3.0

?/DIV>

Figure 13 - UVEN filtering for Zero-Volt BUS transients.

The normal response of the QPI-8 to a BUS supply transient

which drops below the UV limit is to assert the PWRGD pin

low and shut off its pass FET. When the UV requirements are

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