The QME48T40050 converter of the QME-Series provides outstanding
thermal performance in high temperature environments. This performance is
accomplished through the use of patented/patent-pending circuits,
packaging, and processing techniques to achieve ultra-high efficiency,
excellent thermal management, and a low-body profile.
The low-body profile and the preclusion of heat sinks minimize impedance to
system airflow, thus enhancing cooling for both upstream and downstream
devices. The use of 100% automation for assembly, coupled with advanced
electronic circuits and thermal design, results in a product with extremely
high reliability.
Operating from a 36-75 V input, the QME-Series converters provide outputs
that can be trimmed from –20% to +10% of the nominal output voltage, thus
providing outstanding design flexibility.
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•
•
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•
•
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36-75 VDC Input
5 VDC @ 40 A Output
Industry-standard quarter-brick pinout
On-board input differential LC-filter
Start-up into pre-biased load
No minimum load required
Dimensions: 1.45” x 2.30” x 0.425” (36.83 x 58.42 x 10.8 mm)
Weight: 1.22 oz [34.98 g]
Withstands 100 V input transient for 100 ms
Fixed-frequency operation
Fully protected
Latching and non-latching protection available
Remote output sense
Positive or negative logic ON/OFF option
Output voltage trim range: +10%/−20% with industry-standard trim
equations
High reliability: MTBF = 9.7 million hours, calculated per Telcordia
TR-332, Method I Case
Approved to the latest edition of the following safety standards:
UL/CSA 62368-1, EN/IEC 62368-1
Designed to meet Class B conducted emissions per FCC and EN 55032
when used with external filter
All materials meet UL94, V-0 flammability rating
QME48T40050
2
Conditions: TA = 25 ºC, Airflow = 300 LFM (1.5 m/s), unless otherwise specified.
PARAMETER
DESCRIPTION / CONDITION
MIN
TYP
MAX
UNITS
Absolute Maximum Ratings
Input Voltage
0
80
VDC
Operating Ambient Temperature
Continuous
-40
85
°C
Storage Temperature
-55
125
°C
Isolation Characteristics
I/O Isolation
2000
Isolation Capacitance
VDC
ηF
3
Isolation Resistance
10
MΩ
Feature Characteristics
Switching Frequency
440
kHz
Output Voltage Trim Range1
Industry-std. equations
Remote Sense Compensation1
Percent of VOUT(NOM)
Output Overvoltage Protection
Latching or Non-latching
Overtemperature Shutdown (PCB)
Non-latching
125
°C
Auto-Restart Period (For non-latching option)
Applies to all protection features
200
ms
4
ms
-20
117
Turn-On Time
ON/OFF Control (Positive Logic)
ON/OFF Control (Negative Logic)
122
+10
%
+10
%
127
%
Converter Off (logic low)
-20
0.8
VDC
Converter On (logic high)
2.4
20
VDC
Converter Off (logic high)
2.4
20
VDC
Converter On (logic low)
-20
0.8
VDC
Input Characteristics
Operating Input Voltage Range
Input Under Voltage Lockout
36
48
75
VDC
33
34
35
VDC
31
32
Non-latching
Turn-on Threshold
Turn-off Threshold
33
VDC
Input Voltage Transient
100 mS
100
VDC
Maximum Input Current
40 ADC, 5.0 VDC Out @ 36 VDC In
6.1
ADC
Input Stand-by Current
Vin = 48 V, converter disabled
3
Input No Load Current (0 load on the output)
Vin = 48 V, converter enabled
90
mADC
Input Reflected-Ripple Current
25 MHz bandwidth
14
mAPK-PK
Input Voltage Ripple Rejection
120 Hz
75
dB
mADC
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QME48T40050
3
Output Characteristics
Output Voltage Set Point (no load)
Output Regulation
4.950
Over Line
Over Load
temperature2
Output Voltage Range
Over line, load and
Output Ripple and Noise – 25 MHz bandwidth
Full load + 10 µF tantalum + 1 µF ceramic
External Load Capacitance
Plus full load (resistive)
Output Current Range
5.000
5.050
VDC
±2
±5
mV
±2
±5
mV
4.925
60
0
42
47
5.075
VDC
120
mVPK-PK
10,000
µF
40
ADC
52
ADC
Current Limit Inception
Non-latching
Peak Short-Circuit Current
For non-latching option, Short = 10 mΩ
50
A
RMS Short-Circuit Current
For non-latching option
9
Arms
Load Change 50%-75%-50%, di/dt = 0.1 A/µs
Co = 1 µF ceramic
40
mV
di/dt = 5 A/µs
Co = 470 µF POS + 1 µF ceramic
140
mV
15
µs
100% Load
92
%
50% Load
93
%
Dynamic Response
Settling Time to 1%
Efficiency
1
Vout can be increased up to 10% via the sense leads or up to 10% via the trim function. However, the total output voltage trim from all sources
should not exceed 10% of VOUT (NOM), in order to ensure specified operation of overvoltage protection circuitry.
2 Operating
ambient temperature range of -40 ºC to 85 ºC for converter.
These power converters have been designed to be stable with no external capacitors when used in low inductance input
and output circuits.
In many applications, the inductance associated with the distribution from the power source to the input of the converter
can affect the stability of the converter. The addition of a 33 µF electrolytic capacitor with an ESR < 1 across the input
helps to ensure stability of the converter. In many applications, the user has to use decoupling capacitance at the load. The
power converter will exhibit stable operation with external load capacitance up to 10,000 µF on 5 V output.
Additionally, see the EMC section of this data sheet for discussion of other external components which may be required for
control of conducted emissions.
The ON/OFF pin is used to turn the power converter on or off remotely via a system signal. There are two remote control
options available, positive and negative logic with both referenced to Vin (-). A typical connection is shown in Fig. A.
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QME48T40050
4
QME Series
Vin (+)
Converter
(Top View)
Vout (+)
SENSE (+)
ON/OFF
Vin
TRIM
Rload
SENSE (-)
Vin (-)
Vout (-)
CONTROL
INPUT
Figure A. Circuit configuration for ON/OFF function.
The positive logic version turns on when the ON/OFF pin is at a logic high and turns off when at a logic low. The converter is
on when the ON/OFF pin is left open. See the Electrical Specifications for logic high/low definitions.
The negative logic version turns on when the pin is at a logic low and turns off when the pin is at a logic high. The ON/OFF pin
can be hardwired directly to Vin (-) to enable automatic power up of the converter without the need of an external control
signal.
The ON/OFF pin is internally pulled up to 5 V through a resistor. A properly debounced mechanical switch, open collector
transistor, or FET can be used to drive the input of the ON/OFF pin. The device must be capable of sinking up to 0.2 mA at a
low level voltage of 0.8 V. An external voltage source (±20 V maximum) may be connected directly to the ON/OFF input, in
which case it must be capable of sourcing or sinking up to 1 mA depending on the signal polarity. See the Startup Information
section for system timing waveforms associated with use of the ON/OFF pin.
The remote sense feature of the converter compensates for voltage drops occurring between the output pins of the converter
and the load. The SENSE (-) (Pin 5) and SENSE (+) (Pin 7) pins should be connected at the load or at the point where regulation
is required (see Fig. B).
QME Series
Vin (+)
Converter
Rw
Vout (+)
100
(Top View)
Vin
ON/OFF
SENSE (+)
TRIM
Rload
SENSE (-)
10
Vin (-)
Vout (+)
Rw
Figure B. Remote sense circuit configuration.
CAUTION
If remote sensing is not utilized, the SENSE(-) pin must be connected to the Vout(-) pin (Pin 4), and the SENSE(+) pin
must be connected to the Vout(+) pin (Pin 8) to ensure the converter will regulate at the specified output voltage. If
these connections are not made, the converter will deliver an output voltage that is slightly higher than the specified
data sheet value.
Because the sense leads carry minimal current, large traces on the end-user board are not required. However, sense traces
should be run side by side and located close to a ground plane to minimize system noise and ensure optimum performance.
The converter’s output overvoltage protection (OVP) senses the voltage across Vout(+) and Vout(-), and not across the sense
lines, so the resistance (and resulting voltage drop) between the output pins of the converter and the load should be minimized
to prevent unwanted triggering of the OVP.
When utilizing the remote sense feature, care must be taken not to exceed the maximum allowable output power capability
of the converter, which is equal to the product of the nominal output voltage and the allowable output current for the given
conditions.
When using remote sense, the output voltage at the converter can be increased by as much as 10% above the nominal rating
in order to maintain the required voltage across the load. Therefore, the designer must, if necessary, decrease the maximum
current (originally obtained from the derating curves) by the same percentage to ensure the converter’s actual output power
remains at or below the maximum allowable output power.
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QME48T40050
5
The output voltage can be adjusted up 10% or down 20% relative to the rated output voltage by the addition of an externally
connected resistor.
The TRIM pin should be left open if trimming is not being used. To minimize noise pickup, a 0.1 µF capacitor is connected
internally between the TRIM and SENSE(-) pins.
To increase the output voltage, refer to Fig. C. A trim resistor, RT-INCR, should be connected between the TRIM (Pin 6) and
SENSE(+) (Pin 7), with a value of:
RT−INCR =
5.11(100 + Δ)VO−NOM − 626
− 10.22
1.225Δ
[k],
where,
RT−INCR = Required value of trim-up resistor [k]
VO−NOM = Nominal value of output voltage [V]
Δ=
(VO -REQ − VO -NOM )
X 100
VO -NOM
[%]
VO−REQ = Desired (trimmed) output voltage [V].
When trimming up, care must be taken not to exceed the converter‘s maximum allowable output power. See the previous
section for a complete discussion of this requirement.
Vin (+)
QME Series
(Top View)
Vin
Vout (+)
Converter
SENSE (+)
R T-INCR
ON/OFF
TRIM
Rload
SENSE (-)
Vin (-)
Vout (-)
Figure C. Configuration for increasing output voltage.
To decrease the output voltage (Fig. D), a trim resistor, RT-DECR, should be connected between the TRIM (Pin 6) and SENSE(-)
(Pin 5), with a value of:
RT−DECR =
511
− 10.22
|Δ|
[kΩ]
where,
RT−DECR = Required value of trim-down resistor [kΩ] and Δ is defined above.
NOTE:
The above equations for calculation of trim resistor values match those typically used in conventional industry-standard quarterbricks.
Vin (+)
QME Series
Converter
(Top View)
Vin
ON/OFF
Vout (+)
SENSE (+)
TRIM
Rload
R T-DECR
SENSE (-)
Vin (-)
Vout (-)
Figure D. Configuration for decreasing output voltage.
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QME48T40050
6
Trimming/sensing beyond 110% of the rated output voltage is not an acceptable design practice, as this condition could
cause unwanted triggering of the output overvoltage protection (OVP) circuit. The designer should ensure that the difference
between the voltages across the converter’s output pins and its sense pins does not exceed 10% of VOUT(nom), or:
[VOUT(+) − VOUT(−)] − [VSENSE(+) − VSENSE(−)] VO - NOM X 10% [V]
This equation is applicable for any condition of output sensing and/or output trim.
Input undervoltage lockout is standard with this converter. The converter will shut down when the input voltage drops below
a pre-determined voltage.
The input voltage must be typically 34 V for the converter to turn on. Once the converter has been turned on, it will shut off
when the input voltage drops typically below 32 V. This feature is beneficial in preventing deep discharging of batteries used
in telecom applications.
The converter is protected against overcurrent or short circuit conditions. Upon sensing an overcurrent condition, the
converter will switch to constant current operation and thereby begin to reduce output voltage. When the output voltage
drops below 60% of the nominal value of output voltage, the converter will shut down.
Once the converter has shut down, it will attempt to restart nominally every 200 ms with a typical 3-5% duty cycle. The
attempted restart will continue indefinitely until the overload or short circuit conditions are removed or the output voltage
rises above 60% of its nominal value.
Once the output current is brought back into its specified range, the converter automatically exits the hiccup mode and
continues normal operation.
For implementations where latching is required, a “Latching” option (L) is available for short circuit and OVP protections.
Converters with the latching feature will latch off if either event occurs. The converter will attempt to restart after either the
input voltage is removed and reapplied OR the ON/OFF pin is cycled.
The converter will shut down if the output voltage across Vout(+) (Pin 8) and Vout(-) (Pin 4) exceeds the threshold of the OVP
circuitry. The OVP circuitry contains its own reference, independent of the output voltage regulation loop. Once the converter
has shut down, it will attempt to restart every 200 mS until the OVP condition is removed.
For implementations where latching is required, a “Latching” option (L) is available for short circuit and OVP protections.
Converters with the latching feature will latch off if either event occurs. The converter will attempt to restart after either the
input voltage is removed and reapplied OR the ON/OFF pin is cycled.
The converter will shut down under an overtemperature condition to protect itself from overheating caused by operation
outside the thermal derating curves, or operation in abnormal conditions such as system fan failure. After the converter has
cooled to a safe operating temperature, it will automatically restart for non-latching option.
Approved to the latest edition of the following safety standards: UL/CSA 62368-1, EN 62368-1 and IEC 62368-1. Basic
Insulation is provided between input and output.
To comply with safety agencies’ requirements, an input line fuse must be used external to the converter. A 10 A fuse is
recommended for use with this product.
All QME converters are UL approved for a maximum fuse rating of 15 Amps. To protect a group of converters with a single
fuse, the rating can be increased from the recommended value above.
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QME48T40050
7
EMC requirements must be met at the end-product system level, as no specific standards dedicated to EMC characteristics
of board mounted component dc-dc converters exist. However, Bel Power Solutions tests its converters to several system
level standards, primary of which is the more stringent EN 55032, Information technology equipment - Radio disturbance
characteristics-Limits and methods of measurement.
An effective internal LC differential filter significantly reduces input reflected ripple current, and improves EMC.
With the addition of a simple external filter, all versions of the QME-Series of converters pass the requirements of Class B
conducted emissions per EN 55032 and FCC requirements. Please contact Bel Power Solutions Applications Engineering
for details of this testing.
The converter has been characterized for many operational aspects, to include thermal derating (maximum load current as
a function of ambient temperature and airflow) for vertical and horizontal mountings, efficiency, startup and shutdown
parameters, output ripple and noise, transient response to load step-change, overload, and short circuit.
The following pages contain specific plots or waveforms associated with the converter. Additional comments for specific
data are provided below.
All data presented were taken with the converter soldered to a test board, specifically a 0.060” thick printed wiring board
(PWB) with four layers. The top and bottom layers were not metalized. The two inner layers, comprised of two-ounce copper,
were used to provide traces for connectivity to the converter.
The lack of metalization on the outer layers as well as the limited thermal connection ensured that heat transfer from the
converter to the PWB was minimized. This provides a worst-case but consistent scenario for thermal derating purposes.
All measurements requiring airflow were made in the vertical and horizontal wind tunnel using Infrared (IR) thermography
and thermocouples for thermometry.
Ensuring components on the converter do not exceed their ratings is important to maintaining high reliability. If one
anticipates operating the converter at or close to the maximum loads specified in the derating curves, it is prudent to check
actual operating temperatures in the application. Thermographic imaging is preferable; if this capability is not available, then
thermocouples may be used. The use of AWG #40 gauge thermocouples is recommended to ensure measurement accuracy.
Careful routing of the thermocouple leads will further minimize measurement error. Refer to Fig. H for the optimum measuring
thermocouple location.
Fig. E: Location of the thermocouple for thermal testing.
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8
Load current vs. ambient temperature and airflow rates are given in Fig. 1 and Fig. 2 for vertical and horizontal converter
mountings. Ambient temperature was varied between 25°C and 85°C, with airflow rates from 30 to 500 LFM
(0.15 to 2.5 m/s). For each set of conditions, the maximum load current was defined as the lowest of:
(i)
The output current at which any FET junction temperature does not exceed a maximum specified temperature of
120 °C as indicated by the thermographic image, or
(ii)
The temperature of the inductor does not exceed 120 °C, or
(iii)
The nominal rating of the converter (40 A).
During normal operation, derating curves with maximum FET temperature less or equal to 120 °C should not be exceeded.
Temperature at the thermocouple location shown in Fig. H should not exceed 120 °C in order to operate inside the
derating curves.
Fig. 3 shows the efficiency vs. load current plot for ambient temperature of 25 ºC, airflow rate of 300 LFM (1.5 m/s) with
vertical mounting and input voltages of 36 V, 48 V, and 72 V. Also, a plot of efficiency vs. load current, as a function of
ambient temperature with Vin = 48 V, airflow rate of 200 LFM (1 m/s) with vertical mounting is shown in Fig. 4.
Fig. 5 shows the power dissipation vs. load current plot for Ta = 25 ºC, airflow rate of 300 LFM (1.5 m/s) with vertical mounting
and input voltages of 36 V, 48 V, and 72 V. Also, a plot of power dissipation vs. load current, as a function of ambient
temperature with Vin = 48 V, airflow rate of 200 LFM (1 m/s) with vertical mounting is shown in Fig. 6.
Output voltage waveforms, during the turn-on transient using the ON/OFF pin for full rated load currents (resistive load) are
shown without and with external load capacitance in Error! Reference source not found. and Figure 7, respectively.
Fig. 10 show the output voltage ripple waveform, measured at full rated load current with a 10 µF tantalum and 1 µF ceramic
capacitor across the output. Note that all output voltage waveforms are measured across a 1 µF ceramic capacitor.
The input reflected ripple current waveforms are obtained using the test setup shown in Fig 11. The corresponding
waveforms are shown in Figs. 12-13.
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QME48T40050
9
Scenario #1: Initial Start-up From Bulk Supply
ON/OFF function enabled, converter started via application of VIN.
See Figure F.
Time
Comments
t0
ON/OFF pin is ON; system front end power is toggled
on, VIN to converter begins to rise.
t1
VIN crosses Under-Voltage Lockout protection circuit
threshold; converter enabled.
t2
Converter begins to respond to turn-on command
(converter turn-on delay).
t3
Converter VOUT reaches 100% of nominal value.
For this example, the total converter start-up time (t3- t1) is
typically 4 ms.
VIN
ON/OFF
STATE
OFF
ON
VOUT
t0
t1 t2
t
t3
Figure F. Startup scenario #1.
Scenario #2: Initial Start-up Using ON/OFF Pin
With VIN previously powered, converter started via ON/OFF pin.
See Figure G.
Time
Comments
t0
VINPUT at nominal value.
t1
Arbitrary time when ON/OFF pin is enabled
(converter enabled).
t2
End of converter turn-on delay.
t3
Converter VOUT reaches 100% of nominal value.
For this example, the total converter start-up time (t3- t1) is
typically 4 ms.
VIN
ON/OFF
STATE OFF
ON
VOUT
t0
t1 t2
t
t3
Figure G. Startup scenario #2.
Scenario #3: Turn-off and Restart Using ON/OFF Pin
With VIN previously powered, converter is disabled and then
enabled via ON/OFF pin. See Figure H.
Time
Comments
t0
VIN and VOUT are at nominal values; ON/OFF pin ON.
t1
ON/OFF pin arbitrarily disabled; converter output falls
to zero; turn-on inhibit delay period (200 ms typical) is
initiated, and ON/OFF pin action is internally inhibited.
t2
ON/OFF pin is externally re-enabled.
If (t2- t1) ≤ 200 ms, external action of ON/OFF pin
is locked out by start-up inhibit timer.
If (t2- t1) > 200 ms, ON/OFF pin action is internally
enabled.
t3
Turn-on inhibit delay period ends. If ON/OFF pin is ON,
converter begins turn-on; if off, converter awaits
ON/OFF pin ON signal; see Figure F.
t4
End of converter turn-on delay.
t5
Converter VOUT reaches 100% of nominal value.
For the condition, (t2- t1) ≤ 200 ms, the total converter start-up
time (t5- t2) is typically 203 ms. For (t2- t1) > 200 ms, start-up will
be typically 4 ms after release of ON/OFF pin.
VIN
100 ms
ON/OFF
STATE OFF
ON
VOUT
t0
t1
t2
t3 t4
t5
t
Figure H. Startup scenario #3.
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QME48T40050
50
50
40
40
Load Current [Adc]
Load Current [Adc]
10
30
500 LFM (2.5 m/s)
400 LFM (2.0 m/s)
300 LFM (1.5 m/s)
200 LFM (1.0 m/s)
100 LFM (0.5 m/s)
NC - 30 LFM (0.15 m/s)
20
10
30
500 LFM (2.5 m/s)
400 LFM (2.0 m/s)
300 LFM (1.5 m/s)
200 LFM (1.0 m/s)
100 LFM (0.5 m/s)
NC - 30 LFM (0.15 m/s)
20
10
0
0
20
30
40
50
60
70
80
20
90
30
40
60
70
80
90
Fig. 2: Available load current vs. ambient air temperature and
airflow rates for converter with G height pins mounted horizontally
with air flowing from pin 1 to pin 3, MOSFET temperature 120 C,
Vin = 48 V
1.00
1.00
0.95
0.95
0.90
0.90
Efficiency
Efficiency
Fig. 1: Available load current vs. ambient air temperature and
airflow rates for converter with G height pins mounted vertically
with air flowing from pin 1 to pin 3, MOSFET temperature 120 C,
Vin = 48 V
Note: NC – Natural convection
0.85
72 V
48 V
36 V
0.80
0.85
70 C
55 C
40 C
0.80
0.75
0.75
0
8
16
24
32
40
0
48
8
16
24
32
40
48
Load Current [Adc]
Load Current [Adc]
Fig. 3: Efficiency vs. load current and input voltage for converter
mounted vertically with air flowing from pin 1 to pin 3 at a rate of
300 LFM (1.5 m/s) and Ta = 25 C.
Fig. 4: Efficiency vs. load current and ambient temperature for
converter mounted vertically with Vin = 48 V and air flowing from
pin 1 to pin 3 at a rate of 200 LFM (1.0 m/s)
25.00
25.00
20.00
20.00
Power Dissipation [W]
Power Dissipation [W]
50
Ambient Temperature [°C]
Ambient Temperature [°C]
15.00
10.00
72 V
48 V
36 V
5.00
15.00
10.00
70 C
55 C
40 C
5.00
0.00
0.00
0
8
16
24
32
40
48
Load Current [Adc]
Fig. 5: Power dissipation vs. load current and input voltage for
converter mounted vertically with air flowing from pin 1 to pin 3 at a
rate of 300 LFM (1.5 m/s) and Ta = 25 C
0
8
16
24
32
40
48
Load Current [Adc]
Fig. 6: Power dissipation vs. load current and ambient temperature
for converter mounted vertically with Vin = 48 V and air flowing
from pin 1 to pin 3 at a rate of 200 LFM (1.0 m/s)
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11
Fig. 7: Turn-on transient at full rated load current (resistive) with no
output capacitor at Vin = 48 V, triggered via ON/OFF pin. Top trace
ON/OFF signal (5 V/div.). Bottom trace: output voltage (2 V/div.)
Time scale: 2 ms/div.
Fig. 8: Turn-on transient at full rated load current (resistive) plus
10,000 µF at Vin = 48 V, triggered via ON/OFF pin. Top trace:
ON/OFF signal (5 V/div.). Bottom trace: output voltage (5
V/div.)Time scale: 2 ms/div
Fig. 9: Output voltage response to load current step-change (20 A
30 A – 20 A) at Vin = 48 V. Top trace: output voltage (100 mV/div.).
Bottom trace: load current (10 A/div.). Current slew rate: 0.1 A/µs
Co = 1 µF ceramic. Time scale: 0.2 ms/div
Fig. 10: Output voltage response to load current step-change (20 A
–30 A – 20 A) at Vin = 48 V. Top trace: output voltage (100
mV/div.).Bottom trace: load current (10 A/div.). Current slew rate: 5
A/µs. Co =470 µF POS + 1 µF ceramic. Time scale: 0.2 ms/div.
iS
10 H
source
inductance
Vsource
Fig. 11: Output voltage ripple (20 mV/div.) at full rated load current
into a resistive load with Co = 10 µF tantalum + 1 µF ceramic and
Vin = 48 V. Time scale: 1 µs/div.
iC
33 F
ESR