QPO-2L
®
QuietPower ™
QPO-2L 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 30dB from 1kHz to 500kHz. The
QPO-2 is biased through the VAUX input and filters
an input voltage range of 0.3VDC to 5.5VDC while
supporting load currents as high as 20A. The VAUX
input range is 7V to 12V with a minimum required
difference between VAUX and QPO OUT of 7V.
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, 1kHz to 500kHz
• >20 dB PARD attenuation, 50Hz to 500Hz (1)
• 20A rating over a 0.3-5.5Vdc 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 with LGA mounting
• Closed loop control improves transient response
of most DC/DC converters and power supplies
• Reduces required number of output capacitors to
support dynamic loads.
• Patents Pending
Applications
•
Distributed Point of Load Power Systems
•
Sensors Requiring Low Noise Power
•
Medical Instrumentation
Note 1: For off-line supplies 20dB attenuation can be achieved
down to 50Hz with additional capacitance added from the VREF
pin to REFGND.
Typical Application
QPO-2 Performance
VAUX
LOAD+
VAUX
VOUT+
QPO IN
PEAK IN
CIN*
SENSE+
RCLAMP
Rsc
QPO-2L
ADJUST
SC SET
QPO OUT (AC)
REFGND
VREF
GND
SLOPE ADJ
+TRIM
RCP
RSL
QPO IN (AC)
QPO OUT
CSC
LOAD CURRENT
RSA
SENSE-
RHR
VOUT*Optional
LOAD-
Figure 1 – ADJUST/Trim supports applications that don’t
require remote sense.
Picor Corporation • www.picorpower.com
Figure 2 – Typical performance with a 3.3 Volt converter,
showing 1 to 10 A load step.
QPO-2L Data Sheet Rev. 1.1 Page 1 of 12
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
-40
50
12
-40
20 second exposure @
Max
13.2
6
50
25
4
100
125
212
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.
VAUX
RCLAMP
LGA Pattern
9
10
QPO-2: (bottom view)
11
12
8
QPO OUT
QPO IN
7
6
SC SET
GND
SLOPE ADJ
VREF
REFGND
SC SET
QPO OUT
VAUX
RCLAMP
QPO IN
PEAK IN
ADJUST
13
17
18
20
19
14
5
3
2
PEAK IN
16
ADJUST
REFGND
VREF
SLOPE ADJ
1
GND
4
15
1,19,20
2
3
4
5
6,7,8,17
9
10
11,12,13,14,18
15
16
Pad Designations
Pad Description
GND
Input ground
SLOPE ADJ RSA resistor connection allows setting of
the slope of headroom voltage vs. load (mV/A)
VREF
Input to the active filter, setting the
output voltage at the QPOOUT pins
REFGND
Ground reference for the VREF pin
(critical low noise connection)
SC SET
Rsc resistor connection allows setting of
the SC/trim current applied to the converter
trim input.
Picor Corporation • www.picorpower.com
QPOOUT
Output pins
VAUX
Input bias voltage
RCLAMP
External resistor to program VREF quick-charge
level at start-up
QPOIN
Input pins (critical thermal path to remove
heat from the package, see PCB suggested
layout Fig.13)
PEAK IN
Ripple Peak Detector Input
ADJUST
A current source that mirrors the current
through RSC and drives a converter’s SC/TRIM pin.
QPO-2L Data Sheet Rev. 1.1 Page 2 of 12
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 1kHz
to 500kHz. For converters running off-line with
greater low frequency output ripple, the attenuation
can be extended to be greater than 20dB down at
50Hz by connecting a 25uF 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 5.5Vdc 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 QPO2 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 30dB 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 steady-state 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-2L Data Sheet Rev. 1.1 Page 3 of 12
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
LOAD+
VOUT+
18
SENSE+
Cin*
Rsl
+TRIM
18
QPO IN QPO OUT
11
12
QPO OUT
QPO IN
13
14
15 PEAK IN
QPO-2L
16
ADJUST
SC SET
19
GND
}
{
REFGND
2
VREF
SENSE-
1
SLOPE ADJ
20
GND
GND
Csc
17
3
4
Rsa
Rsc
17
8
7
6
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-2L Data Sheet Rev. 1.1 Page 4 of 12
Application of the QPO-2
This product can be used over a 0.3VDC to 5.5VDC
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 QPO2 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.
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 30ms 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
1K
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 75mv
to 425mv 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
PEAK IN
0.1uF
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
= 100KΩ.
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 0.3V to 5.5V 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
QPO-2L Data Sheet Rev. 1.1 Page 5 of 12
headroom voltage will increase the attenuation, up
to a point of diminishing returns, over the range of
10kHz to over 1Mhz. With an external 25uF
capacitor connected between the VREF and REFGND
pins the low frequency attenuation from 10Hz to
10kHz will reduce by roughly 10dB. 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 kΩ
Vhr +15mV
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)
27.4k Ω (126mV)
-20
26.1k Ω (146mV)
dB
-40
Vout=3.3V
Iload=10A
Rslope=8.2K W
-60
23.7k Ω (173mV)
-80
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
75mV 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.
In Figure 2, a maximum load of 10 Amps allowed for
the RHR value to be calculated to provide 375mV of
headroom to avoid exceeding 4 Watts. In this
example, based on the attenuation graph in Figure
7, 300mV 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 375mV was used
in the formula to determine the RHR resistor value.
The peak detector will dynamically add 30mV
(derived from the 60mV peak to peak input ripple)
to the static headroom setting providing the total
dynamic headroom of typically 405mV with the
detector enabled.
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 =
Vhr
* Cin
2Tr
22.1k Ω (198mV)
-100
10
100
1K
10K
100K
1M
3M
Figure 8 – . Attenuation Curves Using Slope Adjust Feature
Picor Corporation • www.picorpower.com
where; CIN = Input capacitance (assuming low
ESR/ceramic type) at the QPO-2 input,
∆I = Step load current change,
Tr = Converter response time,
VHR = headroom voltage.
QPO-2L Data Sheet Rev. 1.1 Page 6 of 12
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.
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 overvoltage 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.
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.
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 QPO2 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 10µF.
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 IN * VOUT
∆VRPT
where; RSC is SC SET resistor value,
RIN is the input resistance of the SC or TRIM
input of the converter (4)
VOUT is the desired QPO output voltage,
VRPT is the pre-trimmed reference of the SC
or TRIM.
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 + 10V
ISCMAX
This feature can be used in conjunction with an
initially trimmed down supply.
Picor Corporation • www.picorpower.com
QPO-2L Data Sheet Rev. 1.1 Page 7 of 12
Headroom Slope Adjustment
The slope adjust feature can be effectively disabled,
providing relatively constant headroom versus load,
by using an RSA of 100kΩ. 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
Rhr=64.9 k
V Headroom
400mV
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 kΩ.
Figures 9 and 10 demonstrate the attenuation versus
power dissipation relationship with different
headroom resistor values with corresponding
increasing power dissipation at a fixed 10A load. The
low frequency attenuation is flat with changing
headroom as indicated by the 50Hz line. The active
attenuation is dependent on the headroom voltage
and correlates to the attenuation curves presented
previously.
0
-10
3.3 V QPO-2 output voltage
69.8 k Headroom resistor
-20
500 khz
dB
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
150mV over the load range of 1 to 10A, 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 8.2kΩ. This feature is
useful in improving the QPO-2 efficiency 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 =8.2kΩ.
-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
Iload=10A (Vref Cap=25uF) 1% Rhr std. values for VOUT=3.3V
Rsa=100k (delta Vhr=0mV from 0.1 to 10A)
RSA = 0.05(V/A) *
∆ Iout
* 2.5 kΩ
∆Vhr
where: ∆IOUT = Maximum load current change,
∆VHR = Change in headroom desired over
the load range,
RSA = Slope adjust resistor value,
Example: For a 5A maximum load and a 150mV
reduction in headroom.
RSA = 0.05(V/I) *
Figure 9 - Power dissipation vs. RHR (Headroom voltage)
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.
5A
* 2.5 kΩ = 4.167 kΩ
0.15 V
Picor Corporation • www.picorpower.com
QPO-2L Data Sheet Rev. 1.1 Page 8 of 12
The following is a summary of typical configurations
that a user can select for the QPO-2.
0
-10
3.3 V QPO-2 output voltage
27.4 k Headroom resistor
dB
-20
500 kHz
50 Hz
24.9 k
-30
22.6k
-40
21 k
18.2 k
-50
16.5 k
14.3 k
-60
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
150mV of slope adjust.
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.
o No slope adjust, no peak detect, fixed headroom,
attenuation vs headroom graph in figure 7 apply
o No slope adjust, peak detector enabled, headroom
will increase by the peak of the ripple amplitude
o Slope adjust enabled, no peak detect, headroom
will decrease with the increase in load current
o 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.
RCP = 100k* (VQPOIN - 0.90*VQPOOUT)
Ω
0.90*VQPOOUT
Picor Corporation • www.picorpower.com
QPO-2L Data Sheet Rev. 1.1 Page 9 of 12
QPO Package Outline
0.4850
0.4410
0.3970
4 places
QPO PCB Pad Pattern
(Top View)
0.3000
0.2060
0.2560
0.1500
0.1000
0.492
0.0000
15 places
0.1000
0.1500
0.0880
0.0655
0.3000
0.3970
0.4850
0.3970
0.4410
0.4850
0.3000
0.2000
0.1000
0.0000
0.1000
0.2000
0.3000
0.4850
0.4410
0.3970
0.0880
0.1310
Figure 11 - Recommended PCB receptor patterns. (dimensions in inches)
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-2L Data Sheet Rev. 1.1 Page 10 of 12
4 places
0.325
0.2500
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)
Ordering Information
Part Number
Description
QPO-2L
QPO-2 Land Grid Array
Picor Corporation • www.picorpower.com
QPO-2L Data Sheet Rev. 1.1 Page 11 of 12
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 L Data Sheet
P/N 29738
Rev. 1.1
4/05