SQ24 Series
Data Sheet
The new
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 preserving the
same pinout and functionality.
In high temperature environments, for output voltages rang-
ing from 3.3V to 1.0V, the thermal performance of
SemiQ™
converters exceeds that of most competitors' 20-30A 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 heat sinks minimize
airflow shadowing, thus enhancing cooling for downstream
devices. The use of 100% automation for assembly, coupled
with di/dt’s advanced electric and thermal design, results in a
product with extremely high reliability.
Operating from a 18-36V input, the
SQ24 Series
converters
of the
SemiQ™ Family
provides any standard output volt-
age from 12V down to 1.0V. Outputs can be trimmed from –
20% to +10% of the nominal output voltage (±10% for output
voltages 1.2V and 1.0V), thus providing outstanding design
flexibility.
With a standard pinout and trim equations, the
SQ24 Series
converters are perfect drop-in replacements for existing
quarter brick designs. Inclusion of this converter in new de-
signs 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 improve-
ment over other available converters because of the
SQ24
Series’
optimized thermal efficiency.
SQ24T and SQ24S Converters
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Delivers up to 15A (50 W)
Available in through-hole and SM packages
Lowest weight in industry: 0.53 oz (15 g)
Lowest profile in industry: 0.274” (6.96 mm)
Extremely small footprint: 0.896” x 2.30” (2.06 in
2
)
Outputs available in 12.0, 8.0, 6.0, 5.0, 3.3, 2.5, 2.0,
1.8, 1.5, 1.2 and 1.0V
High efficiency – no heat sink required
On-board input differential LC-filter
Extremely low output and input ripple
Start up into pre-biased output
No minimum load required
Meets Basic Insulation requirements of EN60950
Fixed frequency operation
Fully protected
Remote output sense
Output voltage trim range: +10%/−20% (except 1.2V
and 1.0V outputs with trim range
±10%)
with industry-
standard trim equations
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 recognition in US and Canada and DEMKO
certification per IEC/EN 60950
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
SQ24 Family DS Ver 5 05-14-04
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SQ24 Series
Electrical Specifications
(common to all versions)
Conditions: T
A
=25ºC, Airflow=300 LFM (1.5 m/s), Vin=24Vdc, 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
18
TYP
MAX
40
85
125
UNITS
Vdc
°C
°C
Vdc
Vdc
Vdc
Vdc
pF
pF
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
24
17
16
36
17.5
16.5
Non-latching
16
15
2000
1.0 - 3.3V
5.0 - 6.0V
8.0V, 12V
10
415
Industry-std. equations (1.5 - 12V)
Industry-std. equations (1.0 - 1.2V)
Percent of V
OUT
(
NOM
)
Non-latching (1.5 - 12V)
Non-latching (1.0 - 1.2V)
Applies to all protection features
-20
-10
117
124
125
132
100
4
+10
+10
+10
140
140
160
260
230
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. See “Output Voltage Adjust/Trim” for
detailed information.
SQ24 Family DS Ver 5 05-14-04
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Page 2 of 70
SQ24 Series
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 100µF electrolytic capacitor with an ESR < 1Ω
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 1000µF on
12V, 2,200µF on 8.0V, 10,000 µF on 5.0V – 6.0V, and
15,000µF on 3.3V – 1.0V outputs.
Data Sheet
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 volt-
age of
≤
0.8V. An external voltage source (±20V maximum)
may be connected directly to the ON/OFF input, in which
case it must be capable of sourcing or sinking up to 1mA
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).
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 (+)
Vin (+)
Semi
Q
Family
TM
Converter
Vout (+)
100
Rw
(Top View)
Vin
ON/OFF
SENSE (+)
TRIM
SENSE (-)
10
Rload
Vin (-)
Vout (-)
Rw
Semi
Q
Family
TM
Fig. B:
Remote sense circuit configuration.
Vout (+)
SENSE (+)
TRIM
SENSE (-)
Rload
Converter
(Top View)
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-
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
SQ24 Family DS Ver 5 05-14-04
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SQ24 Series
ity of the converter, equal to the product of the nominal out-
put voltage and the allowable output current for the given
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
Vin (+)
Data Sheet
Semi
Q
Family
TM
Converter
Vout (+)
SENSE (+)
R
T-INCR
(Top View)
ON/OFF
TRIM
SENSE (-)
Rload
Vin (-)
Vout (-)
Fig. C:
Configuration for increasing output voltage.
Output Voltage Adjust /TRIM (Pin 6)
The converter’s output voltage can be adjusted up 10% or
down 20% for Vout
≥
1.5V, and
±10%
for Vout = 1.2V and
1.0 V, relative to the rated output voltage by the addition of
an externally connected resistor. For output voltages 3.3V,
trim up to 10% is guaranteed only at Vin
≥
20V, and it is
marginal (8% to 10%) at Vin = 18V depending on load cur-
rent.
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
=
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
=
511
−
10.22
|
∆
|
[kΩ]
(1.0 – 12V)
where,
R
T
−DECR
=
Required value of trim-down resistor [kΩ]
and
∆
is as 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.
Converters with output voltage 1.2V and 1.0V have specific
trim schematic and equations, to provide the customers with
the flexibility of second sourcing. For these converters, the
last character of part number is “T”. More information about
trim feature, including corresponding schematic portions, can
be found in Application Note 103.
Vin (+)
5.11(100
+
∆)V
O
−
NOM
−
626
−
10.22
[kΩ] (1.5 –12V)
1.225∆
485
∆
323
−
2
∆
Semi
Q
Family
TM
Converter
Vout (+)
SENSE (+)
TRIM
SENSE (-)
R
T-DECR
(Top View)
[kΩ] (1.2V)
[kΩ] (1.0V)
Vin
ON/OFF
Rload
Vin (-)
Vout (-)
where,
R
T
−INCR
=
Required value of trim-up resistor kΩ]
V
O
−NOM
=
Nominal value of output voltage [V]
Fig. D:
Configuration for decreasing output voltage.
∆
=
(V
O-REQ
−
V
O -NOM
)
X 100
[%]
V
O -NOM
V
O
−REQ
=
Desired (trimmed) output voltage [V].
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]
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.
SQ24 Family DS Ver 5 05-14-04
This equation is applicable for any condition of output sens-
ing and/or output trim.
Page 4 of 70
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SQ24 Series
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 17.5V for the converter to
turn on. Once the converter has been turned on, it will shut
off when the input voltage drops below 15V. This feature is
beneficial in preventing deep discharging of batteries used in
telecom applications.
Data Sheet
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
3.3V
12V - 5.0V, 2.5V
2.0V - 1.0V
8A
6A
4A
If one input fuse is used for a group of modules, the maxi-
mum fuse rating should not exceed 15-A (SQ modules are
UL approved with up to a 15-A fuse).
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 50% of the nominal value of output volt-
age, the converter will shut down.
Once the converter has shut down, it will attempt to restart
nominally every 100 ms with a typical 1-2% duty cycle. The
attempted restart will continue indefinitely until the overload
or short circuit conditions are removed or the output voltage
rises above 50% of its nominal value.
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.
With the addition of a simple external filter (see application
notes), all versions of the
SQ24 Series
of converters pass
the requirements of Class B conducted emissions per
EN55022 and FCC, and meet at a minimum, Class A radi-
ated emissions per EN 55022 and Class B per FCC Title
47CFR, Part 15-J. Please contact di/dt Applications Engi-
neering 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.
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 is associated with a specific
plot (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.
The following pages contain specific plots or waveforms as-
sociated with the converter. Additional comments for specific
data are provided below.
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.
Safety Requirements
The converters meet North American and International
safety regulatory requirements per UL60950 and EN60950.
Basic Insulation is provided between input and output.
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