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QPI-9 Data Sheet Rev. 1.3 Page 4 of 8

Applications Information – Hot-Swap

The QPI-9's high-temperature rating of 6 amps provides

filtering for up to 144 W of power from a 24 V bus with

a 70°C PCB temperature. The 1.0" x1.0" x 0.2" surface

mount LGA package provides ease of manufacturing by

eliminating thru-hole assembly. The current derating

curve, shown in Figure 5, should be used when the PCB

temperature that the QPI-9 is mounted to exceeds 70°C.

The hot-swap feature is created with an internal switch

that controls the current path between BUS- and SW

pins. The state of the switch can be on, off or in a

current control mode depending on the state of the

control function.

The QPI-9 has two signal pins that can be used to

indicate the power-up status of the QPI-9. Both are

active-low when power is not good. PWRGD1 is an

open-drain that is referenced to the BUS- rail of the

QPI-9. PWRGD2 is an open-drain that is referenced to

the QPI- rail, allowing it to directly control the enable

signal translation required. An example circuit of both

options can be seen in Figures 9a and 9b.

The QPI-9 is designed to have an under-voltage range

of 16 V to 18 V set point when the UVEN pin is tied

directly to the BUS+ pin. The QPI-9 becomes enabled

when the input voltage exceeds 18 V and continues to

work down to 16 V before being disabled.

The QPI-9 over-voltage range is designed to be 36 V to

38 V when the OV pin is tied directly to the BUS+ pin.

The QPI-9 remains functioning until the input voltage

surpasses 38 V, where the QPI-9 will shutdown until the

input voltage falls below 36 V.

External resistors can be added to trim the UV and OV

trip points higher. The graph in Figure 6 shows the

trimming effect for a range of external series resistors.

The equations in Figure 7 can be used to calculate the

required series resistor for increasing the

preprogrammed trip points.

Figure 8 shows a 5 ms, zero-volt BUS transient event

with a 40 W load and 4700 µF of capacitance on the

QPI-9's output. The external capacitor CE, shown in

Figures 9a and 9b, will provide the required hold-up

filtering during the transient event. This filtering will

enable the Power-good state of the QPI-9 to remain

unchanged during this transient, provided there is

enough input energy to maintain the power

converter's operation. Without this capacitor, the QPI-9

would detect an under-voltage fault and shut off its

internal pass switch. The fault would also initiate a

re-start of the hot-swap control and would require up

to 45 ms to turn back on its internal switch.

Note: When using CE in this manner, RUVEN should be used

QPI-9 Current Derating Curve

0

2

4

6

8

0

10203040

5060708090

100

PCB to QPI Interface Temperature (°C)

Figure 5 – QPI-9 current derating curve over temperature.

Figure 8 – 5 ms Transient with 40 W Load.

Figure 7 – UVEN and OV resistor equations.

UVEN

18700

UVEN

OV

OV

7150

UV/OV Trim

0.00

10.00

20.00

30.00

40.00

50.00

0

5000

10000

15000

20000

25000

30000

Series Resistor

OV-High

OV-Low

UV-High

UV-Low

Figure 6 – Trimming UV/OV with an external series resistor.