QME48T20120 DC-DC Converter Data Sheet
36-75 VDC Input; 12 VDC @ 20 A Output
Data Sheet
Features
RoHS lead free solder and lead-solder-exempted
products are available
Delivers up to 20 A
Industry-standard quarter-brick pinout
On-board input differential LC-filter
Startup into pre-biased load
No minimum load required
Dimensions: 1.45” x 2.30” x 0.482”
(36.83 x 58.42 x 12.24 mm)
Weight: 1.25 oz [35.85 g]
Meets Basic Insulation requirements of EN60950
Withstands 100 V input transient for 100 ms
Fixed-frequency operation
Fully protected
Remote output sense
Fully protected with automatic recovery
Positive or negative logic ON/OFF option
Output voltage trim range: +10%/−20% with
industry-standard trim equations
High reliability: MTBF approx. 8.7 million hours,
calculated per Telcordia TR-332, Method
I
Case 1
UL/CSA60950-1, EN60950-1, and IEC60950-1
safety approved
Designed to meet Class B conducted emissions per
FCC and EN55022 when used with external filter
All materials meet UL94, V-0 flammability rating
Applications
Telecommunications
Data communications
Wireless communications
Servers, workstations
Benefits
High efficiency – no heat sink required
Description
The QME48T20120 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.
ZD-01742 Rev 3.4, 21-Jan-10
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Page 1 of 14
QME48T20120 DC-DC Converter Data Sheet
36-75 VDC Input; 12 VDC @ 20 A Output
Data Sheet
Electrical Specifications
Conditions: T
A
= 25 ºC, Airflow = 300 LFM (1.5 m/s), Vi n = 48 VDC, unless otherwise specified.
Parameter
Absolute Maximum Ratings
Input Voltage
Operating Ambient Temperature
Storage Temperature
Isolation Characteristics
I/O Isolation
Isolation Capacitance
Isolation Resistance
Feature Characteristics
Switching Frequency
Output Voltage Trim Range
1
Remote Sense Compensation
1
Output Overvoltage Protection
Overtemperature Shutdown (PCB)
Auto-Restart Period
Turn-On Time
ON/OFF Control (Positive Logic)
Converter Off (logic low)
Converter On (logic high)
ON/OFF Control (Negative Logic)
Converter Off (logic high)
Converter On (logic low)
Additional Notes:
1
Notes
Continuous
Min
0
-40
-55
2000
Typ
Max
80
85
125
Units
VDC
°C
°C
VDC
3
10
380
Industry-std. equations
Percent of V
OUT
(
NOM
)
Non-latching
Non-latching
Applies to all protection features
117
122
125
200
4
-20
2.4
2.4
-20
0.8
20
20
0.8
-20
+10
+10
127
ηF
MΩ
kHz
%
%
%
°C
ms
ms
VDC
VDC
VDC
VDC
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 V
OUT
(
NOM
), in order to ensure specified operation of overvoltage protection circuitry.
Operating ambient temperature range of -40 ºC to 85 ºC for converter.
2
ZD-01742 Rev 3.4, 21-Jan-10
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Page 2 of 14
QME48T20120 DC-DC Converter Data Sheet
36-75 VDC Input; 12 VDC @ 20 A Output
Data Sheet
Electrical Specifications (continued)
Conditions: T
A
= 25 ºC, Airflow = 300 LFM (1.5 m/s), Vin = 48 VDC, unless otherwise specified.
Parameter
Input Characteristics
Operating Input Voltage Range
Input Under Voltage Lockout
Turn-on Threshold
Turn-off Threshold
Input Voltage Transient
Maximum Input Current
Input Stand-by Current
Input No Load Current (0 load on the output)
Input Reflected-Ripple Current
Input Voltage Ripple Rejection
Output Characteristics
Output Voltage Set Point (no load)
Output Regulation
Over Line
Over Load
Output Voltage Range
External Load Capacitance
Output Current Range
Current Limit Inception
Peak Short-Circuit Current
RMS Short-Circuit Current
Dynamic Response
Load Change 50%-75%-50%, di/dt = 0.1 A/µs
di/dt = 5 A/µs
Settling Time to 1%
Efficiency
100% Load
50% Load
93
94
%
%
Co = 1 µF ceramic
Co = 470 µF POS + 1 µF ceramic
50
120
30
mV
mV
µs
Non-latching
Non-latching, Short = 10 mΩ
Non-latching
Over line, load and temperature
2
Plus full load (resistive)
0
22
24
50
5
11.76
60
Output Ripple and Noise – 25 MHz bandwidth Full load + 10 µF tantalum + 1 µF ceramic
±4
±4
±10
±10
12.24
120
2,200
20
26.6
mV
mV
VDC
mV
PK-PK
µF
ADC
ADC
A
Arms
11.88
12.00
12.12
VDC
100 ms
20 ADC, 12 VDC Out @ 36 VDC In
Vin = 48 V, converter disabled
Vin = 48 V, converter enabled
25 MHz bandwidth
120 Hz
3
69
20
65
Non-latching
33
31
34
32
35
33
100
7.5
VDC
VDC
VDC
ADC
mADC
mADC
mA
PK-PK
dB
36
48
75
VDC
Notes
Min
Typ
Max
Units
ZD-01742 Rev 3.4, 21-Jan-10
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Page 3 of 14
QME48T20120 DC-DC Converter Data Sheet
36-75 VDC Input; 12 VDC @ 20 A Output
Data Sheet
Operations
Input and Output Impedance
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.
ON/OFF (Pin 2)
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
Converter
(Top View)
Vin
ON/OFF
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.
Remote Sense (Pins 5 and 7)
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
(Top View)
Vin
ON/OFF
Vout (+)
100
Rw
SENSE (+)
TRIM
SENSE (-)
10
Rload
Vin (-)
Vout (+)
Rw
Fig. 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.
Vin (+)
Vout (+)
SENSE (+)
TRIM
SENSE (-)
Rload
Vin (-)
CONTROL
INPUT
Vout (-)
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)
Page 4 of 14
Fig. 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
ZD-01742 Rev 3.4, 21-Jan-10
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QME48T20120 DC-DC Converter Data Sheet
36-75 VDC Input; 12 VDC @ 20 A Output
Data Sheet
by the same percentage to ensure the converter’s
actual output power remains at or below the
maximum allowable output power.
Output Voltage Adjust /TRIM (Pin 6)
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, R
T-INCR
, should be connected between the
TRIM (Pin 6) and SENSE(+) (Pin 7), with a value of:
where,
R
T
DECR
½
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)
Vout (+)
SENSE (+)
TRIM
SENSE (-)
R
T-DECR
Rload
Vin
ON/OFF
Vin (-)
Vout (-)
R
T
INCR
½
where,
5.11(100
Δ)V
O
NOM
626
10.22
1.225Δ
[kΩ]
Fig. D: Configuration for decreasing output voltage
.
R
T
INCR
½
Required value of trim-up resistor [kΩ]
V
O
NOM
½
Nominal value of output voltage [V]
Δ
½
(V
O-REQ
V
O-NOM
)
X 100
V
O -NOM
[%]
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 V
OUT
(
NOM
),
or:
[V
OUT
(
)
V
OUT
(
)]
[V
SENSE
)
V
SENSE
)]
V
O - NOM X
10%
[V]
(
(
V
O
REQ
½
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.
QME Series
Converter
(Top View)
Vin
ON/OFF
This equation is applicable for any condition of
output sensing and/or output trim.
Vin (+)
Vout (+)
SENSE (+)
R
T-INCR
TRIM
SENSE (-)
Rload
Vin (-)
Vout (-)
Fig. C: Configuration for increasing output voltage.
To decrease the output voltage (Fig. D), a trim
resistor, R
T-DECR
, should be connected between the
TRIM (Pin 6) and SENSE(-) (Pin 5), with a value of:
R
T
DECR
½
511
10.22
|
Δ
|
[kΩ]
ZD-01742 Rev 3.4, 21-Jan-10
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