The QME48T20120 converter of the QME-Series provides outstanding
thermal performance in high temperature environments. This
performance is accomplished through the use of patented/patentpending 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.
•
36-75 VDC Input; 12 VDC @ 20 A Output
•
On-board input differential LC-filter
•
Startup into pre-biased load
•
No minimum load required
•
Withstands 100 V input transient for 100 ms
•
Fixed-frequency operation
•
Remote output sense
•
Fully protected with automatic recovery
•
Positive or negative logic ON/OFF option
•
High reliability: MTBF approx. 8.7 million hours, calculated per
Telcordia TR-332, Method I Case 1
•
Approved to the latest edition and amendment of ITE Safety standards,
UL/CSA 60950-1 and IEC60950-1
•
RoHS lead free solder and lead-solder-exempted products are
available
QME48T20120
2
Stresses in excess of the absolute maximum ratings may cause performance degradation, adversely affect long-term reliability, and
cause permanent damage to the converter.
Input Voltage
Continuous
0
80
VDC
Operating Ambient Temperature
-40
85
C
Storage Temperature
-55
125
C
Conditions: TA = 25ºC, Airflow = 300 LFM (1.5 m/s), Vin = 48 VDC, unless otherwise specified.
2.1 INPUT SPECIFICATIONS
Operating Input Voltage Range
36
48
75
VDC
Input Under Voltage Lockout
(Non-latching)
Turn-on Threshold
33
34
35
VDC
Turn-off Threshold
31
32
33
VDC
Input Voltage Transient
100 ms
100
VDC
Maximum Input Current
20 ADC, 12 VDC Out @ 36 VDC In
7.5
ADC
Input Stand-by Current
Vin = 48 V, converter disabled
3
mADC
Input No Load Current
(0 load on the output)
Vin = 48 V, converter enabled
69
mADC
Input Reflected-Ripple Current
25 MHz bandwidth
20
mAPK-PK
Input Voltage Ripple Rejection
120 Hz
65
dB
2.2 OUTPUT SPECIFICATIONS
Output Voltage Set Point (no load)
11.88
12.00
12.12
VDC
Over Line
±4
±10
mV
Over Load
±4
±10
mV
12.24
VDC
Output Regulation
Output Voltage Range
Over line, load and temperature
(-40ºC to 85ºC)
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
11.76
60
0
24
mVPK-PK
µF
20
ADC
26.6
ADC
Current Limit Inception
Non-latching
Peak Short-Circuit Current
Non-latching, Short = 10 mΩ
50
A
RMS Short-Circuit Current
Non-latching
5
Arms
50
mV
Dynamic Response
Load Change 50%-75%-50%,
di/dt = 0.1 A/µs, Co = 1 µF ceramic
di/dt = 5 A/µs, Co = 470 µF POS + 1 µF
ceramic
120
mV
to 1%
30
µs
100% Load
93
%
50% Load
94
%
Settling Time
22
120
2200
Efficiency
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Switching Frequency
380
Output Voltage Trim Range1
Remote Sense Compensation
Industry-std. equations
1
-20
Percent of VOUT(NOM)
117
%
+10
%
127
%
Output Overvoltage Protection
Non-latching
Overtemperature Shutdown (PCB)
Non-latching
125
°C
Auto-Restart Period
Applies to all protection features
200
ms
Turn-On Time
122
kHz
+10
4
ms
Converter Off (logic low)
-20
0.8
VDC
Converter On (logic high)
2.4
20
VDC
ON/OFF Control (Positive Logic)
Converter Off (logic high)
2.4
20
VDC
Converter On (logic low)
-20
0.8
VDC
ON/OFF Control (Negative Logic)
I/O Isolation
2000
Isolation Capacitance
VDC
3
Isolation Resistance
10
36.83 x 58.42 x 12.24
1.45 x 2.30 x 0.482
1.25
35.85
Dimensions
Weight
MTBF
Calculated per Telcordia TR-332, Method I Case 1
Flammability
All materials meet UL94, V-0 flammability rating
ηF
MΩ
8.7
mm
inch
oz
g
million
hours
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.
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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 100 µF electrolytic capacitor with an ESR < 1 Ω 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 2,200 µF on 12 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.
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.
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QME48T20120
5
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.
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. Trim up to 10% at full load is guaranteed at Vin ≥ 40V.
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:
RTINCR
5.11(100 Δ)VONOM 626
10.22
1.225Δ
[kΩ]
where,
RTINCR Required value of trim-up resistor [kΩ]
VONOM Nominal value of output voltage [V]
Δ
(VO -REQ VO -NOM )
X 100
VO -NOM
[%]
VOREQ 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
Converter
(Top View)
Vin
ON/OFF
Vout (+)
SENSE (+)
R T-INCR
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:
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RTDECR
511
10.22
|Δ|
[kΩ]
where,
RTDECR 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
quarter-bricks.
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.
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 100 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.
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.
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QME48T20120
7
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.
The converters are safety approved to UL/CSA60950-1, EN60950-1, and IEC60950-1. 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 15 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.
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 EN55022, 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 EN55022 and FCC requirements. Please contact Bel Power Solutions Applications Engineering
for details of this testing.
VIN
Scenario #1: Initial Startup From Bulk Supply
ON/OFF function enabled, converter started via application of
VIN. See Figure E.
Time
Comments
t0
ON/OFF pin is ON; system front end power is toggled
on, VIN to converter begins to rise.
t1
VIN crosses undervoltage 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 startup time (t3- t1) is
typically 4 ms.
ON/OFF
STATE
OFF
ON
VOUT
t0
t1 t2
t
t3
Figure E. Startup scenario #1.
VIN
Scenario #2: Initial Startup Using ON/OFF Pin
With VIN previously powered, converter started via ON/OFF pin.
See Figure F.
Time
Comments
VINPUT at nominal value.
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 startup time (t3- t1) is
typically 4 ms.
ON/OFF
STATE OFF
t0
t1
ON
VOUT
t0
t1 t2
t3
t
Figure F. Startup scenario #2.
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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 G.
Comments
Time
VIN and VOUT are at nominal values; ON/OFF pin ON.
t0
ON/OFF pin arbitrarily disabled; converter output falls
t1
to zero; turn-on inhibit delay period (200 ms typical) is
initiated, and ON/OFF pin action is internally inhibited.
ON/OFF pin is externally re-enabled.
t2
If (t2- t1) ≤ 200 ms, external action of ON/OFF pin is
locked out by startup inhibit timer.
If (t2- t1) > 200 ms, ON/OFF pin action is internally
enabled.
Turn-on inhibit delay period ends. If ON/OFF pin is ON,
t3
converter begins turn-on; if off, converter awaits
ON/OFF pin ON signal; see Figure F.
End of converter turn-on delay.
Converter VOUT reaches 100% of nominal value.
For the condition, (t2- t1) ≤ 200 ms, the total converter startup
time (t5- t2) is typically 204 ms. For (t2- t1) > 200 ms, startup will
be typically 4 ms after release of ON/OFF pin.
V IN
200 ms
ON/OFF
STATE
OFF
ON
V OUT
t0
t1
t2
t3 t4
t5
Figure G. Startup scenario #3.
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.
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9
Fig. H: Location of the thermocouple for thermal testing.
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
125 °C as indicated by the thermographic image, or
(ii) The nominal rating of the converter (20 A).
During normal operation, derating curves with maximum FET temperature less or equal to 125 °C should not be exceeded.
Temperature at the thermocouple location shown in Fig. H should not exceed 125 °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 Figs. 7-8, respectively.
Fig. 11 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 12. The corresponding
waveforms are shown in Figs. 13-14.
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25
25
20
20
Load Current [Adc]
Load Current [Adc]
10
15
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)
30 LFM (0.15 m/s)
10
5
15
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)
30 LFM (0.15 m/s)
10
5
0
0
20
30
40
50
60
70
80
90
20
30
40
Ambient Temperature [°C]
50
60
70
80
90
Ambient Temperature [°C]
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 125
C, Vin = 48 V.
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 125
C, Vin = 48 V.
1.00
1.00
0.95
0.95
Efficiency
Efficiency
0.90
0.85
0.80
72 V
48 V
36 V
0.90
0.85
70 C
55 C
40 C
0.80
0.75
0.75
0.70
0
4
8
12
16
20
0
24
4
8
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.
16
20
24
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]
12
Load Current [Adc]
Load Current [Adc]
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
4
8
12
16
20
24
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
4
8
12
16
20
24
Load Current [Adc]
Fig. 6: Power dissipation vs. load current and ambient temp. 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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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
2,200 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 (10 A
– 15 A – 10 A) at Vin = 48 V. Top trace: output voltage (100
mV/div.). Bottom trace: load current (5 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 (10
A – 15 A – 10 A) at Vin = 48 V. Top trace: output voltage (100
mV/div.). Bottom trace: load current (5 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 (50 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
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