QPO-2
®
QUIETPOWER ®
QPO-2 Low Voltage Output Ripple Attenuator
Description
Features of the QPO-2
The QPO-2 output ripple attenuator SiP uses active
filtering to reduce supply output ripple and noise (PARD)
by over 30 dB from 1 kHz to 500 kHz. The QPO-2 is biased
through the VAUX input and filters an input voltage
range of 0.3 Vdc to 5.5 Vdc while supporting load currents
as high as 20 A. The VAUX input range is 7 V to 12 V with
a minimum required difference between VAUX and QPO
OUT of 7 V. Output regulation is maintained by using
either the remote sense or the trim adjustment of the
power supply. The product can be used in an open loop
configuration when ripple and noise reduction are the
main objective and load regulation is not as critical. The
QPO-2 architecture improves transient response and
ensures quiet point-of-load regulation when used with
most switching power supplies. The performance
waveform in figure 2 is an example of the ripple
reduction and transient load improvement the QPO-2 can
provide using a 3.3V brick style converter.
• >30 dB PARD attenuation, 1 kHz to 500 kHz
• >20 dB PARD attenuation, 50 Hz to 500 Hz (1)
• 20 A rating over a 0.3-5.5 Vdc operating range
• Supports precise point-of load regulation
• 90-95% efficiency with load vs. headroom trim
• User selectable performance optimization of the
attenuation, power dissipation & transient load
response
• Peak detector function optimizes headroom for
ripple amplitude variation automatically
• 25 x 25 x 4.5 mm SiP (System-in-a-Package)
• Low profile LGA package
• Closed loop control improves transient response
of most DC-DC converters and power supplies
Applications
• Reduces required number of output capacitors to
support dynamic loads.
•
Distributed Point of Load Power Systems
• Patents Pending
•
Sensors Requiring Low Noise Power
•
Medical Instrumentation
Note 1: For off-line supplies 20 dB attenuation can be achieved
down to 50 Hz with additional capacitance added from the VREF
pin to REFGND.
VAUX
LOAD+
VAUX
VOUT+
QPO IN
PEAK IN
CIN*
SENSE+
RCP
RSL
RCLAMP
Rsc
QPO-2L
ADJUST
SC SET
REFGND
VREF
GND
SLOPE ADJ
+TRIM
QPO IN (AC)
QPO OUT
QPO OUT (AC)
CSC
RSA
LOAD CURRENT
SENSE-
RHR
VOUT*Optional
Figure 1 – ADJUST/Trim supports applications that don’t
require remote sense.
Picor Corporation • www.picorpower.com
LOAD-
Figure 2 – Typical performance with a 3.3 Volt converter, showing
1 to 10 A load step.
QPO-2 Data Sheet Rev. 1.6 Page 1 of 11
Absolute Maximum Ratings – Exceeding these parameters may result in permanent damage to the product.
Pins
VAUX to Gnd
All others to Gnd REFGND
VAUX to Gnd
QPOin to QPOout
Package
Package
Package
Package
Package
Package
Parameter
Input voltage
Input voltage
Input bias current
Input to output current
Power dissipation
Operating temperature
Thermal resistance
Thermal resistance
Storage temperature
Re-flow temperature
Notes
Continuous
Continuous
Min
-0.5
-.05
10 seconds @ 25°C
Pd= ILoad x Vhr
PCB to QPO Interface
Free Air
PCB Layout Fig. 12
Max
13.2
6
50
25
4
100
-40
50
12
-40
125
212
20 second exposure @ (4)
Units
Vdc
Vdc
mAdc
Adc
W
°C
°C/W
°C/W
°C
°C
Electrical Characteristics – Parameter limits apply over the operating temp. range unless otherwise noted.
Symbol
ILoad
VQPOOUT
VHR
IAUX
Vtout
Notes
No Internal Current Limit (2)
Continuous
See Applications Detail For Setting
Vnout
Parameter
Operating load current range
Output voltage range
Headroom voltage range
VAUX input current
Transient response-step load
change of 10A@<1A/usec
Output noise
Iscout
Iscout
SC output current accuracy
SC output source current
See applications detail for setting
Input current from QPOIN to Gnd
Min
0.01 (3)
0.3
75
10
Vhr=375mV Cin=200uF
Iload=1A @ t=0 See Figure 2 example
Input PARD=100mVpp 50-500kHz Cvref=25uF
Max
20
5.5
425
20
Units
Adc
Vdc
mVdc
mA
10
5
+2
10
mVdc
mVpp
mVrms
%
mA
50
-2
Note 2: User must protect the load path and limit the steady state load current to be less than the absolute maximum of 20 Amps.
Note 3: User must provide a minimum load current of greater than 10mA at the output of the QPO-2.
Note 4: RoHS compliant product maximum peak temperature is 245°C for 20 seconds.
Pad Descriptions
Description
1, 19, 20
GND
Input ground
2
the
SLOPE ADJ RSA resistor connection allows setting of
slope of headroom voltage vs. load (mV/A)
3
VREF
Input to the active filter, setting the
output voltage at the QPOOUT pins
4
REFGND
Ground reference for the VREF pin
(critical low noise connection)
5
SC SET
Rsc resistor connection allows setting of
the SC/trim current applied to the
converter trim input.
VAUX
Input bias voltage
10
RCLAMP
External resistor to program VREF
quick-charge level at start-up
11, 12, 13, QPOIN
14, 18
Input pins (critical thermal path to remove
heat from the package, see PCB suggested
layout Fig.13)
15
PEAK IN
Ripple Peak Detector Input
16
ADJUST
A current source that mirrors the current
through RSC and drives a converter’s
SC/TRIM pin.
Picor Corporation • www.picorpower.com
12
8
QPO OUT
13
QPO IN
7
6
SC SET
17
18
20
19
14
5
4
3
2
15
PEAK IN
16
ADJUST
1
GND
9
11
SLOPE ADJ
Output pins
10
VREF
QPOOUT
9
REFGND
6, 7, 8, 17
RCLAMP
Name
VAUX
Pad
Number
LGA Pattern
QPO-2 Data Sheet Rev. 1.6 Page 2 of 11
Product Highlights
Functional Description
Picor’s QPO-2, System-in-a-Package (SiP) output ripple
attenuator, is easy to apply and provides the user with
features that can be tailored to optimize the product’s
performance to meet their system needs. It uses active
filtering to achieve greater than 30 dB of attenuation of
Periodic And Random Deviation (PARD) over the frequency
range of 1 kHz to 500 kHz. For converters running off-line
with greater low frequency output ripple, the attenuation
can be extended to be greater than 20 dB down at 50 Hz
by connecting a 25 uF capacitor between the VREF and
REFGRD pins.
The QPO-2 is an active power filter that provides
conducted differential attenuation of power supply output
PARD. It is design to be inserted between the output of the
supply and the load, providing closed loop regulation
through remote sensing or by means of the SC/Trim
feature of supplies having a positive referenced based trim
capability and is set by RSC. The core of the design is a high
bandwidth closed loop function that forces the QPOOUT
pins to be equal to the VREF pin. The VREF pin is a filtered
ratio metric representation of the input voltage that is
determined by the RHR value selection. The voltage
difference between the input to the QPO-2 and VREF pin is
defined as the headroom voltage VHR. The filter time
constant of the VREF pin determines the low frequency
attenuation response of the QPO-2. The high frequency
attenuation response is determined by the roll-off
characteristics of the active loop. To speed up the charging
of the Vref pin the RCP resistor can be used to clamp the
pin just below the steady state regulation point avoiding
excessive delay and headroom during start-up.
The QPO-2 operates over an output voltage range of 0.3 to
5.5 Vdc and requires an external input bias voltage of 7
volts above the QPO output for proper operation. It is
compatible with most switching power supplies and
converters and regulates the output load by using either a
converter’s remote sensing feature or the SC/trim function
of the QPO-2 with the converter. The SC/Trim feature will
correct the converter’s output voltage to compensate for
the headroom voltage drop of the filter if remote sensing
is not available or not preferred. The QPO-2 SC function
works with converters that feature a positive reference
trim adjustment by sourcing correction current into the
trim reference pins commonly found on many power
supplies. The QPO-2 can also be used when remote sense
or SC/trim is not possible. In this mode of operation the
QPO-2 will still provide greater than 30 dB of ripple and
noise attenuation but DC errors will not be corrected for
once the converter and headroom voltages are set,
resulting in reduced load and transient performance.
The QPO-2’s closed loop architecture greatly improves load
transient response of the converter while ensuring steadystate precise point of load voltage regulation. The
headroom setting of the filter dramatically reduces the
capacitance needed at the converter output to provide the
equivalent transient performance and ripple reduction.
Figure 2 demonstrates how the product can be an ideal
solution for noise sensitive applications providing ripple
and noise reduction and improved output regulation with
high current transient load demands.
Picor Corporation • www.picorpower.com
The QPO-2 has a current sensing function that creates a
voltage at the Slope Adjust pin that is proportional with
the load current. This feature can be used to improve the
efficiency of the filter when supply ripple amplitude
reduces with increasing load as with Vicor products. By
selecting the appropriate RSA resistor value the slope of the
headroom reduction versus load can be set. The effect of
this function is to reduce the headroom voltage by the
amount determined by the RSA value resulting in reduced
power dissipation and increased efficiency as compared to
a fixed headroom setting.
There is also a Peak Detection function that adds the input
peak of the ripple voltage to the headroom voltage. The
QPO-2 will track the input ripple adjusting the headroom
within the dynamic range of the filter as the peak of the
ripple changes. The peak of the ripple will automatically be
summed with the DC setting of the headroom voltage.
This feature in combination with the slope adjust feature
allows the user to optimize the initial headroom voltage
and overall efficiency required for their specific
application.
QPO-2 Data Sheet Rev. 1.6 Page 3 of 11
Remote Sense Application Circuit Schematic
RCP
VOUT+
VAUX
9
10
RRS
5.1
RCLAMP VAUX
11
12
QPO OUT
13 QPO IN
14
18
PEAK IN
15
QPO-2L SC SET
16 ADJUST
}
SENSE+
CRS
22μF
SC/TRIM
19
GND
GND
20
1
2
REFGND
GND
Csc*
VREF
SLOPE ADJ
CIN*
{
3
4
LOAD+
17
8
7
6
5
SENSERHR
RSA
LOAD-
VOUT* Optional
Bold lines indicate high-current path.
Figure 3 – Use this circuit for applications requiring remote sensing. Components marked * are optional, see text.
SC/Trim Application Circuit Schematic
VAUX
LOAD+
RCP
VOUT+
10
SENSE+
Cin*
ADJUST+
GND
SENSE-
GND
GND
20
Rsc
17
8
7
6
QPO-2L
1
Rsa
2
SC SET
REFGND
19
RCLAMP VAUX
QPO OUT
QPO OUT
QPO OUT
QPO OUT
VREF
Csc
16
QPO IN
QPO IN
QPO IN
QPO IN
QPO IN
PEAK IN
SLOPE ADJ
+TRIM
Rsl
18
11
12
13
14
15
9
3
4
5
Rhr
LOADVOUT* Optional
Bold lines indicate high-current path.
Figure 4 – Simplest application of QPO-2 when the SC/Trim pin is available, see text.
Picor Corporation • www.picorpower.com
QPO-2 Data Sheet Rev. 1.6 Page 4 of 11
Application of the QPO-2
This product can be used over a 0.3 Vdc to 5.5 Vdc output
voltage range using either the remote sense or the
voltage trim feature of the selected converter. These
circuit configurations are shown in Figures 3 and 4.
In either configuration, the source output voltage will
increase to accommodate the headroom voltage of the
QPO-2 filter in order to maintain the load voltage at the
required level. In the case where remote sense or SC/Trim
use is not possible the QPO-2 can still be used to provide
PARD attenuation with the DC loss of the headroom
voltage at the load. If the supply output can be trimmed
up, the headroom voltage drop of the QPO-2 can be
compensated for at a given load. Further DC correction
for load variation at the QPO-2 output will occur only
within the supply’s control loop. The QPO-2’s output will
be controlled to the voltage present at the VREF pin in
this open loop filter configuration.
Maximum Headroom
Voltage (mVolts)
The user must decide on the control mode to be used and
to select the appropriate circuit configuration for that
mode. They must take into consideration the effects of
the headroom setting and power dissipation versus PARD
attenuation. The majority of the power dissipation of the
QPO-2 is the product of the headroom voltage times the
load current and must always be less than 4 watts. The
dynamic headroom range of the QPO-2 is 75 mv to 425 mv
as long as the maximum power is not exceeded. It is
important that the user understands the range of
expected ripple and transient performance of their power
source to properly bias and utilize the QPO features. The
objective is to maximize attenuation and minimize
dissipation while staying within the QPO-2 dynamic
operating range. Knowing the worse case maximum
steady state ripple, output impedance and transient
response time of the power source will determine the
minimum required headroom of the QPO-2, which is set
by the value of RHR. See figure 5 below for the safe
operating power curve.
450
400
350
300
250
200
150
100
50
0
0
2
4
6
8
10
12
14
Output Current (Amps)
Figure 5 – Safe operating power curve.
Picor Corporation • www.picorpower.com
16
18
20
If the peak detector option is enabled the headroom will
automatically increase by the peak of the ripple amplitude
from the setting determined by RHR. This makes the initial
headroom setting less critical because the headroom
and dynamic range will track the peak of the ripple,
maintaining the required QPO-2 biasing to actively
attenuate. Caution must be taken such that the added
peak detection headroom does not cause power
dissipation in excess of 4 watts. The time constant of this
feature is roughly 30 ms in response to ripple amplitude
changes. This feature can be enabled by connecting the
PEAKIN pin to the QPOIN pins and disabled by putting a
resistor between QPOIN and the PEAKIN pin as shown in
Figure 6.
VOUT
QPO-1 IN
PEAK IN
0.1 uF
Figure 6 – Peak detect disable circuit.
Conversely the optional slope adjust feature will reduce
the headroom proportional to load current depending on
the RSA value selected. This will reduce the maximum
ripple range so this feature is most useful when the
converter ripple amplitude decreases with increased load
current. The feature can be enabled by selecting the
proper RSA value as described in the headroom slope
adjust section of the datasheet and effectively disabled by
using RSA = 100 Kohms.
Figure 7 shows the relationship of the headroom voltage
versus attenuation of the QPO-2 for a 3.3 volt output with
a 15 amp load. This relationship is relatively constant over
the full output voltage rating of the product so this graph
can be used for the 0.3 V to 5.5 V range when selecting
the headroom voltage. The value of headroom resistor
will be dependent on desired output and headroom
voltages. The selection of the final headroom voltage
should be based on the maximum expected ripple, desired
attenuation, based on the curves in Figure 7, and the
transient response time of the converter. Formulas for SC
current setting resistor, RSC and the RCP clamp setting
resistor, are provided in their respective sections. The
headroom range indicated in Figure 7 shows that
increasing the headroom voltage will increase the
attenuation, up to a point of diminishing returns, over the
range of 10 kHz to over 1 Mhz. With an external 25 uF
QPO-2 Data Sheet Rev. 1.6 Page 5 of 11
capacitor connected between the VREF and REFGND pins
the low frequency attenuation from 10 Hz to 10 kHz will
reduce by roughly 10 dB. Review the following transient
considerations below before selecting the operating
headroom. The RHR resistor value is determined by using
the following formula.
RHR =
QPOOUT
* 2.5 k
VHR +15 mV
In Figure 2, a maximum load of 10 Amps allowed for the
RHR value to be calculated to provide 375 mV of headroom
to avoid exceeding 4 Watts. In this example, based on the
attenuation graph in Figure 7, 300 mV of headroom is the
point of diminishing returns so the maximum attenuation
would be achieved at the fundamental ripple frequency.
To stay within the dynamic range required by the active
loop during a transient, a total of 375 mV was used in the
formula to determine the RHR resistor value. The peak
detector will dynamically add 30 mV (derived from the 60
mV peak to peak input ripple) to the static headroom
setting providing the total dynamic headroom of typically
405 mV with the detector enabled.
where; RHR is headroom setting resistor value,
QPOOUT is the expected voltage on the
QPO’s output,
VHR is the target headroom voltage for the
desired range of attenuation.
0
Rhr=43.2k Ω (Vheadroom=159mV)
37.4k Ω (189mV)
-20
33.2k Ω (216mV)
dB
-40
-60
31.6k Ω (229mV)
Vout=3.3V
Iload=15A Ω
Rslope=100K
-80
27.4k Ω (269mV)
-100
10
100
1K
10K
100K
1M
3M
Frequency [Hz]
Figure 7 – Attenuation curves without slope adjust.
0
Rhr=29.4k Ω (Vheadroom=103mV)
The input capacitance to the QPO-2 will provide the
transient load current keeping the QPOOUT at the VREF
voltage until the converter loop responds to regulate the
load. During this time the transient load current capability
can be approximated by the formula below. The
capacitance CIN may be within the power supply that is
used or supplemented by external capacitance.
Consideration of the power supply’s sensitivity to
additional output capacitance and stability must be
understood before additional capacitance is added for
transient performance enhancement.
∅I
27.4k Ω (126mV)
-20
To ensure sufficient headroom during transient load
changes, a greater headroom voltage than what would
normally be set based on maximum ripple should be
considered. To provide margin to cover the instantaneous
drop in the converter output and the line drops,
additional headroom will be needed. In the example
shown in Figure 2 an additional 75 mV was included with
the headroom voltage value selected from the graph in
Figure 7 to cover the instantaneous drop in the supply
output during the 10 Amp step as explained below.
=
VHR
* CIN
2Tr
26.1k Ω (146mV)
dB
-40
where; CIN = Input capacitance (assuming low
ESR/ceramic type) at the QPO-2 input,
Vout=3.3V
Iload=10A
Rslope=8.2K W
-60
23.7k Ω (173mV)
-80
22.1k Ω (198mV)
Tr = Converter response time,
-100
10
100
1K
10K
100K
Figure 8 – Attenuation Curves Using Slope Adjust Feature
Picor Corporation • www.picorpower.com
1M
I = Step load current change,
3M
VHR = headroom voltage.
The output voltage drop for a given supply during a
transient load step will be reduced at the output of the
QPO-2, effectively multiplying the CIN capacitance by the
ratio of VIN/VOUT which is typically greater than a
factor of 10.
QPO-2 Data Sheet Rev. 1.6 Page 6 of 11
The line inductance from the output of the QPO-2 to the
load should be minimized. This inductance will cause
voltage spikes and ringing proportional to the inductance
and the rate of change in the transient load current. This
effect is outside the control of the QPO-2 and may require
low ESR capacitance placed at the switching load when
long lines exists between the QPO-2 output and reference
ground and load. The rate of load change should be less
than 1 Amp per microsecond to minimize excessive
voltage ringing during the di/dt. The line inductance
between the power supply output and QPO input should
also follow low inductance layout practices.
The user must be aware of the converter’s over-voltage set
point and not create a headroom voltage that will cause a
shutdown condition. For this reason it is recommended
that the QPO-2 be used with power supplies running at
the factory pre-set voltages or in a trimmed down
configuration.
SC/Trim Adjustment
The RSC resistor is tied between QPOOUT and SC SET pin
and controls the correction current used to trim the
converter to compensate for the headroom voltage.
The value for the SC SET resistor is calculated by the
following equation:
RSC =
R I N * VOUT
∅VRPT
where; RSC is SC SET resistor value,
RIN is the input resistance of the SC or TRIM
input of the converter (4)
The active loop performance of the QPO-2 has been
optimized to provide adequate phase margin over a worse
case load impedance range. Loading the QPO-2 directly
with low ESR ceramic capacitance however will
significantly reduce the phase margin and is not
recommended. The effects of the typical distributed
inductance of the load path will mitigate the reduction in
phase margin when low ESR ceramic capacitors are
dispersed about the load path. Tantalum and Electrolytic
capacitors are higher ESR components and are not a
concern for phase margin.
When using the QPO as shown in Figure 4 the CSC
capacitor creates a soft starting of the headroom
correction current being sourced into the SC/Trim input of
the converter, preventing the output from tripping the
over voltage function while the QPO-2 output reaches
regulation. The QPO-2 ramp up time is typically 5 to 10
milliseconds. The CSC value will be supply dependent but
is typically around 1 to 10 µF.
The RSL resistor provides a means to isolate the SC/Trim pin
of the converter from CSC as well as limit the correction
current to a level below what will cause an OVP trip
condition during start up. The compliance of the SC
output current source is QPOIN plus 10 volts so the RSL
formula below can be used to limit the worst-case
correction current below the maximum trim up
specification of the converter being used. Note the
correction current set by RSC must always be lower than
the ISCMAX current after the start-up settling time interval
for proper headroom correction.
RSL =
QPOIN + 10 V
ISCMAX
VOUT is the desired QPO output voltage,
VRPT is the pre-trimmed reference of the
SC or TRIM.
This feature can be used in conjunction with an initially
trimmed down supply.
Note 4: When applicable consider the equivalent impedance of
the SC/Trim pin after a trimmed down adjustment has been made
to the supply. Use the power supply manufacturer’s trim down
procedure by connecting a resistor from the SC/Trim pin to
ground.
Picor Corporation • www.picorpower.com
Headroom Slope Adjustment
This feature can be used to allow more headroom at
lighter loads inceasing the delta voltage available to
improve transient load capability, while approximating
constant power dissipation of the QPO-2 over the full load
range. The slope of this curve is set by the slope adjust
resistor RSA. Figure 9 shows the relationship of headroom
resistance versus power dissipation for a load current of 10
Amps. The same data is plotted in Figure 10 with the slope
adjust feature reducing the headroom by 150 mV over the
load range of 1 to 10 A, for a typical range of RHR values
with a 3.3 volt output. The headroom setting RHR value
was selected at the minimum load condition while
enabling the slope function using an RSA value of 8.2 k.
This feature is useful in improving the QPO-2 efficiency
QPO-2 Data Sheet Rev. 1.6 Page 7 of 11
when using switching power supplies that have decreasing
ripple with increasing load current, like Vicor converters.
Figure 8 shows the headroom voltage vs. load with
different headroom resistors with RSA =8.2 k.
Rhr=64.9 k
400mV
V Headroom
The slope adjust feature can be effectively disabled,
providing relatively constant headroom versus load, by
using an RSA of 100k. The user can optimize performance
based on the expected variation in load current and the
desired power dissipation range. The formula below
should be used to calculate the RSA value for the desired
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.
600mV
75 k
82.5 k
93.1 k
102 k
113 k
124 k
200mV
0V
1A
2A
3A
4A
5A
6A
7A
8A
9A
10A
Load Current (A)
Figure 8 – Effect of slope adjust on headroom value with
increasing current and RSA = 8.2 k.
0
RSA = 0.05(V/A) *
∅I OUT
∅VHR
-10
* 2.5 k
3.3 V QPO-2 output voltage
69.8 k Headroom resistor
-20
dB
500 khz
where: IOUT = Maximum load current change,
VHR = Change in headroom desired over
the load range,
RSA = Slope adjust resistor value,
-30
50 hz
47.5 k
-40
39.2 k
30.1 k
-50
24.9 k
21 k
-60
1
2
3
4
Watts
Example: For a 5 A maximum load and a 150mV reduction
in headroom.
RSA = 0.05(V/I) *
5A
0.15 V
Iload=10A (Vref Cap=25uF) 1% Rhr std. values for VOUT=3.3V
Rsa=100k (delta Vhr=0mV from 0.1 to 10A)
Figure 9 – Power dissipation vs. RHR (Headroom voltage)
* 2.5 k = 4.167 k
0
-10
3.3 V QPO-2 output voltage
27.4 k Headroom resistor
-20
dB
Figures 9 and 10 demonstrate the attenuation versus
power dissipation relationship with different headroom
resistor values with corresponding increasing power
dissipation at a fixed 10 A load. The low frequency
attenuation is flat with changing headroom as indicated
by the 50 Hz line. The active attenuation is dependent on
the headroom voltage and correlates to the attenuation
curves presented previously.
500 kHz
50 Hz
24.9 k
-30
22.6k
-40
21 k
18.2 k
-50
16.5 k
14.3 k
-60
Figure 10 shows the increase in attenuation that can be
gained by using the slope adjust feature setting higher
headroom at lower loads while limiting the power
dissipation with reduced headroom at higher loads staying
within the 4 Watt limitation of the package. As stated
previously this will also increase the transient capability
with a load step providing more delta voltage across the
filter at lower loads.
Picor Corporation • www.picorpower.com
1
2
Watts
3
4
Iload=10A (VREF Cap=25μF) 1% Rhr std. values for VOUT=3.3V
Rsa=8.4K (delta Vhr=150mV from 0.1 to 10A)
Figure 10 – Power dissipation vs. RHR (Headroom voltage) with
150 mV of slope adjust.
QPO-2 Data Sheet Rev. 1.6 Page 8 of 11
Headroom Start-up Clamp Feature
This feature allows for pre-charging the Vref capacitance
to the level just below the steady state headroom voltage.
It reduces the time for the QPOout to reach the desired
regulation voltage and converter output overshoot that
results in the delay through the QPO filter during start-up.
The following formula can be used to calculate the RCP
resistor value to set the clamp at 90% of the final output
value. To set the clamp voltage to different percentages of
the output substitute the 0.90 with the desired factor.
QPO Package Outline
0.4850
0.4410
0.3970
4 places
QPO PCB Pad Pattern
(Top View)
0.3000
0.2560
0.1500
0.1000
0.492
0.0000
15 places
0.1000
0.1500
0.0880
0.0655
0.3000
100k* (VQPOIN - 0.90 * VQPOOUT)
0.3970
0.4850
0.0880
0.3970
0.4410
0.4850
0.3000
0.2000
0.1000
0.0000
0.1000
0.2000
0.3000
0.90 * VQPOOUT
0.4850
0.4410
0.3970
RCP =
0.2060
0.1310
The following is a summary of typical configurations that a
user can select for the QPO-2.
• No slope adjust, no peak detect, fixed headroom,
attenuation vs headroom graph in Figure 7 apply
Figure 11 - Recommended PCB receptor patterns. (dimensions in
inches)
• No slope adjust, peak detector enabled, headroom will
increase by the peak of the ripple amplitude
• Slope adjust enabled, no peak detect, headroom will
decrease with the increase in load current
• Slope adjust enabled, peak detector enabled,
headroom will vary with ripple amplitude and load
variations
The attributes of these features have been explained in
this datasheet. The optimum use of them requires an
understanding of the characteristics of the power supply
to be filtered.
QPO IN
0.4410
QPO OUT
0.4410
Vias to ground plane
Figure 12 - Recommended PCB copper lands for low thermal resistance.
Picor Corporation • www.picorpower.com
QPO-2 Data Sheet Rev. 1.6 Page 9 of 11
0.325
0.2500
4 places
0.075
0.000
0.075
0.325
0.1773
0.492
0.441
0.400
0.2000
QPO SIP Package
0.300
0.250
45.000°
0.100
0.0625
0.050
0.000
0.050
0.000
0.100
0.0820
0.250
0.300
0.400
0.441
0.492
0.300
0.100
0.000
0.100
0.0200
0.300
0.0820
0.492
0.441
15 places
0.1250
(Bottom View)
0.400
0.441
0.492
Figure 13 - Package dimensions (dimensions in inches)
Post Solder Cleaning
Picor lidded QP SIPs are not hermetically sealed and must
not be exposed to liquid, including but not limited to
cleaning solvents, aqueous washing solutions or
pressurized sprays.
When soldering, it is recommended that no-clean flux
solder be used, as this will insure that potentially
corrosive mobile ions will not remain on, around, or
under the module following the soldering process.
Ordering Information
Part
Number
QPO-2LZ
Description
QPO-2 LGA Package, RoHS Compliant
QPO-2LZ-01 QPO-2 LGA, RoHS Compliant
Open Frame Package
For applications requiring water wash compatibility the
“–01” open frame version should be used.
Picor Corporation • www.picorpower.com
QPO-2 Data Sheet Rev. 1.6 Page 10 of 11
Vicor’s comprehensive line of power solutions includes high-density
AC-DC & DC-DC modules and accessory components, fully
configurable AC-DC & DC-DC power supplies, and complete
custom power systems.
Information furnished by Vicor is believed to be accurate and reliable. However, no
responsibility is assumed by Vicor for its use. No license is granted by implication or otherwise
under any patent or patent rights of Vicor. Vicor components are not designed to be used in
applications, such as life support systems, wherein a failure or malfunction could result in
injury or death. All sales are subject to Vicor’s Terms and Conditions of Sale, which are
available upon request.
Specifications are subject to change without notice.
Vicor Corporation
25 Frontage Road
Andover, MA, USA 01810
Tel: 800-735-6200
Fax: 978-475-6715
Email
Vicor Express: [email protected]
Technical Support: [email protected]
Picor Corporation • www.picorpower.com • QPO-2 Data Sheet
P/N 29738
Rev. 1.6
10/08