SQM48T/S20 DC-DC Converter Data Sheet
36-75 VDC Input; 1.2-3.3 VDC @ 20A Outputs
Features
RoHS lead-free solder and lead-solder-exempted
products are available
Delivers up to 20 A
Industry-standard, quarter-brick pinout
Outputs available in 3.3, 2.5, 2.0,1.8, 1.5, and 1.2 V
Available in through-hole and SM packages
Low profile: 0.28” (7.1 mm)
Low weight: 0.66 oz (18.5 g)
Onboard input differential LC-filter for the low input
ripple current
Start-up into pre-biased output
No minimum load required
Meets Basic insulation requirements of EN60950
Withstands 100 V input transient for 100 ms
Fixed-frequency operation
Fully protected
Remote output sense
Positive or negative logic ON/OFF option
Output voltage trim range: +10%/−20% with
industry-standard trim equations
(except 1.2 V output)
High reliability: MTBF = 3.4 million hours,
calculated per Telcordia TR-332, Method
I
Case 1
UL60950 recognized in US and Canada and
DEMKO certified per IEC/EN60950
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
Benefits
High efficiency – no heat sink required
Higher current capability at elevated temperatures
than most competitors' 20-25 A quarter-bricks
Extremely small footprint: 0.896” x 2.30” (2.06 in
2
),
38% smaller than conventional quarter-bricks
Description
The
20A SemiQ™ Family
of DC-DC converters provide a high efficiency single output in a size that is only 60% of
industry-standard quarter bricks, while preserving the same pinout and functionality.
The
20A SQM48 Series
converters of the
SemiQ™ Family
provide thermal performance in high temperature
environments that exceeds most competitors' 20-25 A quarter-bricks. This is accomplished through the use of
patent pending circuit, packaging and processing techniques to achieve ultra-high efficiency, excellent thermal
management, and a very low body profile.
Low body profile and the preclusion of heat sinks minimize airflow shadowing, thus enhancing cooling for
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
20A SQM48 Series
converters provide any standard output voltage from
3.3 V down to 1.2 V. Outputs can be trimmed from –20% to +10% of the nominal output voltage (±10% for output
voltage 1.2 V), thus providing outstanding design flexibility.
With a standard pinout and trim equations, the
SQM48 Series
converters are perfect drop-in replacements for
existing 20 A quarter brick designs. Inclusion of this converter in new designs can result in significant board space
and cost savings. The device is also available in a surface mount package.
In both cases the designer can expect reliability improvement over other available converters because of the
SQM48 Series’
optimized thermal efficiency.
MCD10208 Rev. 1.0, 08-Jul-10
Page 1 of 33
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SQM48T/S20 DC-DC Converter Data Sheet
36-75 VDC Input; 1.2-3.3 VDC @ 20A Outputs
Electrical Specifications (common for all versions)
Conditions: T
A
=25 ºC, Airflow=300 LFM (1.5 m/s), Vin=48 VDC, All output voltages, unless otherwise specified.
Parameter
Absolute Maximum Ratings
Input Voltage
Operating Ambient Temperature
Storage Temperature
Input Characteristics
Operating Input Voltage Range
Input Under Voltage Lockout
Turn-on Threshold
Turn-off Threshold
Input Voltage Transient
Isolation Characteristics
I/O Isolation
Isolation Capacitance
Isolation Resistance
Feature Characteristics
Switching Frequency
Output Voltage Trim Range
1
Remote Sense Compensation
1
Output Over-Voltage Protection
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)
100 ms
Non-latching
Continuous
Notes
Min
0
-40
-55
36
33
31
Typ
Max
80
85
125
Units
VDC
°C
°C
VDC
VDC
VDC
VDC
VDC
48
34
32
75
35
33
100
2000
160
10
415
Industry-std. equations (3.3 - 1.5 V)
Use trim equation on Page 4 (1.2 V)
Percent of V
OUT
(
NOM
)
Non-latching (3.3 – 1.5 V)
Non-latching (1.2 V)
Applies to all protection features
See Figs. F, G and H
-20
2.4
2.4
-20
117
124
122
132
100
3
0.8
20
20
0.8
-20
-10
+10
+10
+10
127
140
pF
MΩ
kHz
%
%
%
%
%
ms
ms
VDC
VDC
VDC
VDC
Additional Notes:
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 V
OUT
(
NOM
), in order to insure specified operation of overvoltage protection circuitry.
MCD10208 Rev. 1.0, 08-Jul-10
Page 2 of 33
www.power-one.com
SQM48T/S20 DC-DC Converter Data Sheet
36-75 VDC Input; 1.2-3.3 VDC @ 20A Outputs
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 33 µF electrolytic capacitor with an
ESR < 1 across the input helps 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 20,000 µF on 3.3 – 1.2 V
outputs.
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 logic and
negative logic and both are referenced to Vin(-). A
typical connection is shown in Fig. A.
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 Start-up 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).
Semi
Q
Family
TM
Rw
Vin (+)
Converter
Vout (+)
100
(Top View)
Vin
ON/OFF
SENSE (+)
TRIM
SENSE (-)
10
Rload
Vin (-)
Vout (+)
Rw
Fig. B:
Remote sense circuit configuration.
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 (+)
Semi
Q
Family
TM
Converter
Vout (+)
SENSE (+)
TRIM
SENSE (-)
Rload
(Top View)
Vin
ON/OFF
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 insure optimum performance.
When using the remote sense function, 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, 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
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Vin (-)
CONTROL
INPUT
Vout (-)
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 table, page 2 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 hard wired 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 5V 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 0.2mA at a low level voltage
MCD10208 Rev. 1.0, 08-Jul-10
Page 3 of 33
SQM48T/S20 DC-DC Converter Data Sheet
36-75 VDC Input; 1.2-3.3 VDC @ 20A Outputs
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.
Output Voltage Adjust /TRIM (Pin 6)
The output voltage can be adjusted up 10% or down
20% for Vout
≥
1.5V, and
±10%
for Vout = 1.2V
relative to the rated output voltage by the addition of
an externally connected resistor. For output voltage
3.3V, trim up to 10% is guaranteed only at Vin
≥
40V,
and it is marginal (8% to 10%) at Vin = 36V
The TRIM pin should be left open if trimming is not
being used. To minimize noise pickup, a 0.1µF
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:
5.11(100
Δ)V
O
NOM
626
10.22
1.225Δ
for 3.3 – 1.5V.
R
T
INCR
½
84.6
R
T
INCR
½
7.2
[k] (1.2V)
Δ
where,
R
T
INCR
½
Required value of trim-up resistor k]
V
O
NOM
½
Nominal value of output voltage [V]
(V
O-REQ
V
O-NOM
)
Δ
½
X 100
[%]
V
O -NOM
V
O
REQ
½
Desired (trimmed) output voltage [V].
R
T
DECR
½
R
T
DECR
½
511
10.22
Δ
700
15
Δ
[k] (3.3 – 1.5V)
[k] (1.2V)
where,
R
T
DECR
½
Required value of trim-down resistor [k]
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 and
one-eighth bricks (except for 1.2V output).
Converters with output voltages 1.2V is available with
alternative trim feature to provide the customers with
the flexibility of second sourcing. For these
converters, the last character in the part number is
“T”. The trim equations of “T” version of converters
and more information can be found in Application
Note 103.
Vin (+)
[k],
Semi
Q
Family
TM
Converter
Vout (+)
SENSE (+)
TRIM
SENSE (-)
R
T-DECR
Rload
(Top View)
Vin
ON/OFF
Vin (-)
Vout (-)
Fig. D:
Configuration for decreasing output voltage.
Vin (+)
Semi
Q
Family
TM
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 over-voltage 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]
(
(
R
T-INCR
Rload
Converter
Vout (+)
SENSE (+)
TRIM
SENSE (-)
(Top View)
Vin
ON/OFF
This equation is applicable for any condition of output
sensing and/or output trim.
Vin (-)
Vout (-)
Protection Features
Fig. C:
Configuration for increasing output voltage.
Input Undervoltage Lockout
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.
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When trimming up, care must be taken not to exceed
the converter‘s maximum allowable output power.
See previous section for a complete discussion of
this requirement.
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:
MCD10208 Rev. 1.0, 08-Jul-10
Page 4 of 33
SQM48T/S20 DC-DC Converter Data Sheet
36-75 VDC Input; 1.2-3.3 VDC @ 20A Outputs
Output Protections
All output circuit protection features are non-latching
and operate in a “hiccup” mode. After an output
protection event occurs, the converter will be turned
off, and held off for approximately 100 ms after
which, the protection circuit will reset and the
converter will attempt to restart. If the fault is still
present, the converter will repeat the above action.
Once the fault is removed, the converter will start
normally.
Output Overcurrent Protection (OCP)
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
40-50% of the nominal value of output voltage, the
converter will shut down (Fig. x.11).
Once the converter has shut down, it will attempt to
restart nominally every 100 ms with a typical 1-2%
duty cycle (Fig. x.12). The attempted restart will
continue indefinitely until the overload or short circuit
conditions are removed or the output voltage rises
above 40-50% 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.
Output Over-Voltage Protection (OVP)
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 100 ms until the
OVP condition is removed.
Over-Temperature Protection (OTP)
The converter will shut down under an over-
temperature 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.
Safety Requirements
The converters meet North American and
International safety regulatory requirements per
UL60950 and EN60950. 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.
The Table below provides the recommended fuse
rating for use with this family of products.
Output Voltage
3.3V
2.5 -1.8V
1.5 - 1.2V
Fuse Rating
4A
3A
2A
All SQM converters are UL approved for maximum
fuse rating of 15 A. To protect a group of converters
with a single fuse, the rating can be increased from
the recommended values above.
Electromagnetic Compatibility (EMC)
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, Power-One 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.
Effective internal LC differential filter significantly
reduces input reflected ripple current (Fig. x.9), and
improves EMC.
With the addition of a simple external filter, all
versions of the
SQM48 Series
converters pass the
requirements of Class B conducted emissions per
EN55022 and FCC requirements. Please contact
Power-One Applications Engineering for details of this
testing.
Characterization
General Information
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
mounting, efficiency, start-up and shutdown
parameters, output ripple and noise, transient
response to load step-change, overload and short
circuit.
The figures are numbered as Fig. x.y, where x
indicates the different output voltages, and y
associates with specific plots (y = 1 for the vertical
thermal derating, …). For example, Fig. x.1 will refer
to the vertical thermal derating for all the output
voltages in general.
MCD10208 Rev. 1.0, 08-Jul-10
Page 5 of 33
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