SQM48 Series - 20A
The new
20A SemiQ™ Family
of DC/DC converters from
di/dt provides a high efficiency single output in a size that is
only 60% of industry-standard quarter bricks, while preserv-
ing the same pinout and functionality.
The
20A SQM48 Series
converters of the
SemiQ™ Family
provide thermal performance in high temperature environ-
ments that exceeds most competitors' 20-25 A quarter
bricks. This is accomplished through the use of patent pend-
ing 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 heatsinks minimize
airflow shadowing, thus enhancing cooling for downstream
devices. The use of 100% automation for assembly, coupled
with di/dt’s advanced electrical 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 Se-
ries
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 sav-
ings. The device is also available in a surface mount pack-
age.
In both cases the designer can expect reliability improve-
ment over other available converters because of the
SQM48
Series’
optimized thermal efficiency.
Data Sheet
SQM48T and SQM48S Converters
Features
•
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•
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•
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Delivers up to 20 A (66 W)
Industry-standard quarter brick pinout
Extremely small footprint: 0.896” x 2.30” (2.06 in
2
),
40% smaller than conventional quarter bricks
Higher current capability at elevated temperatures
than most competitors' 20-25 A quarter bricks
On-board input differential LC-filter for the lowest
input ripple current in industry
Outputs available in 3.3, 2.5, 2.0, 1.8, 1.5, and 1.2 V
High efficiency – no heatsink required
Start up into pre-biased output
No minimum load required
Available in through-hole and SM packages
Lowest profile in industry: 0.28” (7.1 mm)
Lowest weight in industry: 0.66 oz (18.5 g)
Meets Basic Insulation requirements of EN60950
Withstands 100 V input transient for 100 ms
Fixed frequency operation
Fully protected
Remote output sense
Output voltage trim range: +10%/−20% with Industry-
standard trim equations (except 1.2 V output)
High reliability: MTBF of 3.4 million hours, calculated
per Telcordia TR-332, Method I Case 1
Positive or negative logic ON/OFF option
UL 60950 recognized in US and Canada and DEMKO
certified per IEC/EN 60950 (pending)
Meets conducted emissions requirements of FCC
Class B and EN 55022 Class B with external filter
All materials meet UL94, V-0 flammability rating
Applications
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Telecommunications
Datacommunications
Wireless
Servers
SQM48x20 Family DS Ver 3 03-18-03
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Page 1 of 33
SQM48 Series - 20A
Electrical Specifications
(common to all versions)
Conditions: T
A
=25ºC, Airflow=300 LFM (1.5 m/s), Vin=48 Vdc, All output voltages, unless otherwise specified.
Data Sheet
PARAMETER
ABSOLUTE MAXIMUM RATINGS
Input Voltage
Operating Ambient Temperature
Storage Temperature
Continuous
NOTES
MIN
0
-40
-55
36
TYP
MAX
80
85
125
UNITS
Vdc
°C
°C
Vdc
Vdc
Vdc
Vdc
Vdc
pF
MΩ
kHz
%
%
%
%
%
ms
ms
Vdc
Vdc
Vdc
Vdc
INPUT CHARACTERISTICS
Operating Input Voltage Range
Input Under Voltage Lockout
Turn-on Threshold
Turn-off Threshold
Input Voltage Transient
48
34
32
75
35
33
100
Non-latching
33
31
100 ms
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
-20
-10
117
124
122
132
100
3
+10
+10
+10
127
140
ISOLATION CHARACTERISTICS
I/O Isolation
Isolation Capacitance
Isolation Resistance
FEATURE CHARACTERISTICS
Switching Frequency
1
Output Voltage Trim Range
Remote Sense Compensation
Output Over-Voltage Protection
Auto-Restart Period
Turn-On Time
ON/OFF Control (Positive Logic)
Converter Off
Converter On
ON/OFF Control (Negative Logic)
Converter Off
Converter On
1
-20
2.4
2.4
-20
0.8
20
20
0.8
Additional Notes:
1. Vout can be increased up to 10% via the sense leads or up to 10% via the trim function, however total output voltage trim from all sources
should not exceed 10% of V
OUT
(
NOM
), in order to insure specified operation of over-voltage protection circuitry.
SQM48x20 Family DS Ver 3 03-18-03
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Page 2 of 33
SQM48 Series - 20A
Operation
Input and Output Impedance
These power converters have been designed to be stable
with no external capacitors when used in low inductance in-
put and output circuits.
However, 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 addi-
tion of a 33 µF electrolytic capacitor with an ESR < 1
Ω
across the input helps ensure stability of the converter. In
many applications, the user has to use decoupling capaci-
tance at the load. The power converter will exhibit stable op-
eration with external load capacitance up to 20,000 µF on
3.3 – 1.2 V outputs.
Data Sheet
age of
≤
0.8 V. An external voltage source, of
±20
V max.,
may be connected directly to the ON/OFF input, in which
case it should be capable of sourcing or sinking up to 1 mA
depending on the signal polarity. See the Start-up Informa-
tion 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 con-
verter 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).
Vin (+)
Semi
Q
Family
TM
Rw
Converter
Vout (+)
100
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 con-
trol options available, positive logic and negative logic and
both are referenced to Vin(-). Typical connections are shown
in Fig. A.
Vin (+)
(Top View)
Vin
ON/OFF
SENSE (+)
TRIM
SENSE (-)
10
Rload
Vin (-)
Vout (-)
Rw
Fig. B:
Remote sense circuit configuration.
Semi
Q
Family
TM
Converter
(Top View)
Vout (+)
SENSE (+)
TRIM
SENSE (-)
Rload
Vin
ON/OFF
Vin (-)
CONTROL
INPUT
Vout (-)
If remote sensing is not required, 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 value.
Because the sense leads carry minimal current, large traces
on the end-user board are not required. However, sense
traces should be located close to a ground plane to minimize
system noise and insure optimum performance. When wiring
discretely, twisted pair wires should be used to connect the
sense lines to the load to reduce susceptibility to noise.
The converter’s output over-voltage 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 capabil-
ity of the converter, equal to the product of the nominal out-
put voltage and the allowable output current for the given
Fig. A:
Circuit configuration for ON/OFF function.
The positive logic version turns on when the ON/OFF pin is
at logic high and turns off when at logic low. The converter is
on when the ON/OFF pin is left open
.
The negative logic version turns on when the pin is at logic
low and turns off when the pin is at 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.
ON/OFF pin is internally pulled-up to 5 V through a resistor.
A 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 volt-
SQM48x20 Family DS Ver 3 03-18-03
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Page 3 of 33
SQM48 Series - 20A
conditions.
When using remote sense, the output voltage at the con-
verter 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 con-
verter’s actual output power remains at or below the maxi-
mum allowable output power.
Vin (+)
Data Sheet
Semi
Q
Family
TM
Converter
Vout (+)
SENSE (+)
R
T-INCR
(Top View)
Vin
ON/OFF
TRIM
SENSE (-)
Rload
Vin (-)
Vout (-)
Fig. C:
Configuration for increasing output voltage.
Output Voltage Adjust /TRIM (Pin 6)
The output voltage can be adjusted up 10% or down 20% for
Vout
≥
1.5 V, and
±10%
for Vout = 1.2 V relative to the rated
output voltage by the addition of an externally connected
resistor. For output voltage 3.3 V, trim up to 10% is guaran-
teed only at Vin
≥
40 V, and it is marginal (8% to 10%) at
Vin = 36 V.
The TRIM pin should be left open if trimming is not being
used. To minimize noise pickup, a 0.1 µF capacitor is con-
nected internally between the TRIM and SENSE(-) pins.
To increase the output voltage, refer to Fig. C. A trim resis-
tor, R
T-INCR
, should be connected between the TRIM (Pin 6)
and SENSE(+) (Pin 7), with a value of:
R
T
−
INCR
=
R
T
−
INCR
=
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
=
R
T
−
DECR
=
511
−
10.22
[kΩ] (3.3 – 1.5 V)
|
∆
|
700
−
15
[kΩ] (1.2 V)
|
∆
|
where,
R
T
−DECR
=
Required value of trim-down resistor [kΩ]
and
∆
is as defined above.
5.11(100
+
∆)V
O
−
NOM
−
626
−
10.22
[kΩ] (3.3 –1.5V)
1.225∆
84.6
−
7.2
[kΩ]
∆
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
1.2 V output).
Converters with output voltage 1.2 V are available with alter-
native trim feature to provide the customers with the flexibil-
ity of second sourcing. For these converters, the last charac-
ter in the part number is “T”. The trim equations of “T” ver-
sion of converters and more information can be found in Ap-
plication Note 103.
(1.2 V)
where,
R
T
−INCR
=
Required value of trim-up resistor kΩ]
V
O
−NOM
=
Nominal value of output voltage [V]
∆
=
(V
O-REQ
−
V
O -NOM
)
X 100
[%]
V
O -NOM
Vin (+)
Semi
Q
Family
TM
Converter
(Top View)
Vout (+)
SENSE (+)
TRIM
R
T-DECR
Rload
V
O
−REQ
=
Desired (trimmed) output voltage [V].
Vin
ON/OFF
SENSE (-)
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.
Vin (-)
Vout (-)
Fig. D:
Configuration for decreasing output voltage.
SQM48x20 Family DS Ver 3 03-18-03
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Page 4 of 33
SQM48 Series - 20A
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 protec-
tion (OVP) circuit. The designer should ensure that the dif-
ference 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]
Data Sheet
Over-Temperature Protection (OTP)
The converter will shut down under an over-temperature
condition to protect itself from overheating caused by opera-
tion outside the thermal derating curves, or operation in ab-
normal conditions such as system fan failure. After the con-
verter has cooled to a safe operating temperature, it will
automatically restart.
This equation is applicable for any condition of output sens-
ing and/or output trim.
Safety Requirements
The converters meet North American and International
safety regulatory requirements per UL60950 and EN60950
(pending). 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 be-
low provides the recommended fuse rating for use with this
family of products.
Output Voltage
Fuse Rating
Protection Features
Input Under-Voltage Lockout
Input under-voltage 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 at least 35 V for the converter to
turn on. Once the converter has been turned on, it will shut
off when the input voltage drops below 31 V. This feature is
beneficial in preventing deep discharging of batteries used in
telecom applications.
3.3 V
2.5 -1.8 V
1.5 - 1.2 V
4-A
3-A
2-A
Output Over-Current Protection (OCP)
The converter is protected against over-current or short cir-
cuit conditions. Upon sensing an over-current 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.
Modules are UL approved for maximum fuse rating of 15-A.
To protect a group of modules 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 character-
istics of board mounted component dc-dc converters exist.
However, di/dt tests its converters to several system level
standards, primary of which is the more stringent EN55022,
Information technology equipment - Radio disturbance char-
acteristics - 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
of converters pass the requirements of Class
B conducted emissions per EN55022 and FCC, and meet at
a minimum, Class A radiated emissions per EN 55022 and
Class B per FCC Title 47CFR, Part 15-J. Please contact
di/dt Applications Engineering for details of this testing.
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 refer-
ence, 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.
SQM48x20 Family DS Ver 3 03-18-03
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