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PRELIMINARY

Vicor Corp. Tel: 800-735-6200, 978-470-2900 Fax: 978-475-6715

QPO-1 Data Sheet

Page 5 of 8

The slope adjust feature can be set to zero providing relative

can optimize performance based on the expected variation in load

current and the desired power dissipation range. The formula

headroom versus current slope. If the peak detector is enabled,

the peak of the ripple will be added back to the headroom at a

given load condition.

Example: For a 5A maximum load and a 150mV

reduction in headroom.

Peak Detector Function

This feature dynamically adds to the headroom voltage to

accommodate converter ripple variation. This feature can be

in Figure 8.

The active loop performance has been optimized for 45 degrees

1 and 2 must be a low ESR ceramic capacitor. Loading the

QPO-1 directly with low ESR ceramic capacitance will affect the

phase margin and is not recommended. The distributed load

capacitance and inductance of the load path will vary depending

on the application. The effects of a distributed load impedance

on phase margin when very low ESR load capacitance is present

will typically be mitigated by the distributed inductance of the

load path. The transient load response in Figure 4 was measured

with approximately 10nH of distributed inductance between

QPO-1 output and the load board which had a 15µF low ESR

ceramic capacitor across the static load resistance.

The following is a summary of the optional configurations that a

user can select for the QPO-1.

• No slope adjust, no peak detect:

fixed headroom over ripple amplitude and current.

• Same as above, but with peak detect enabled:

peak of ripple amplitude is added to the headroom voltage

optimizing headroom with varying ripple amplitude.

• No peak detection with slope adjust:

to improve transient load range and efficiency trading off

attenuation at high current.

• Using both peak detection and slope adjust:

to accommodate ripple amplitude variation with increased

transient capability and efficiency.

Module

+ OUT

1k

0.1

µF

Figure 8 – Peak detector Disable Circuit

QPO-1 Attenuation vs. Power

Iload=10A

1% Rhr std. values for VOUT=3.3V 15V 28V

Rss=100k (delta Vhr = 0mV from 0.1 to 10A)

3.3V

15V

28V

69.8k 324k 602k

47.5k 215k 402k

39.2k 178k 332k

30.1k 137k 255k

24.9k 113k 210k

21k 95.3k 178k

-60

-50

-40

-30

-20

-10

0

1234

Watts

dB

500kHz

50Hz

Figure 9 – Power vs Attenuation without slope

QPO-1 Attenuation vs. Power

Iload=10A

1% Rhr std. values for VOUT=3.3V 15V 28V

Rss=7.1k (delta Vhr =150mV from 0.1 to 10A)

14.3k 64.9k 121k

16.5k 75k 140k

18.2k 82.5k 154k

21k 95.3k 178k

22.6k 102k 191k

24.9k 113k 210k

3.3V 15V 28V

27.4k 124k 232k

-60

-50

-40

-30

-20

-10

0

12

34

Watt

dB

500kHz

50Hz

Figure 10 – Power vs Attenuation with slope adjust