The SemiQ™ Series of dc-dc converters 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 ranging
from 3.3 V to 1.0 V, the thermal performance of SemiQ™
converters exceeds that of most competitors' 20-25 A quarter-
bricks. This performance 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.
RoHS lead-free solder and lead-solder-exempted products are
available
Delivers up to 15A (50W)
Industry-standard quarter-brick pinout
Outputs available in 12.0, 8.0, 6.0, 5.0, 3.3, 2.5, 2.0, 1.8, 1.5, 1.2,
and 1.0 V
Available in through-hole and SMT packages
Low profile: 0.258” (6.55 mm)
Low weight: 0.53 oz (15 g)
On-board input differential LC-filter
Startup into pre-biased output
No minimum load required
Meets Basic Insulation requirements
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 and 1.0 V outputs with trim range
± 10%)
Output voltage trim range: +10%/−20% with industry-standard
trim equations (except 1.2 V and 1.0 V outputs with trim range
± 10%)
Safety according to IEC/EN 60950-1 2 Edition and UL/CSA
60950-1 2 Edition
Designed to meet Class B conducted emissions per FCC and
EN55022 when used with external filter
All materials meet UL94, V-0 flammability rating
nd
nd
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 SQ48 Series converters
provide any standard output voltage from 12 V down to 1.0 V.
Outputs can be trimmed from –20% to +10% of the nominal
output voltage (± 10% for output voltages 1.2 V and 1.0 V), thus
providing outstanding design flexibility.
With a standard pinout and trim equations, the SQ48 Series
converters are perfect drop-in replacements for existing quarter-
brick designs. Inclusion of this converter in new designs can
result in significant board space and cost savings. In both cases
the designer can expect reliability improvement over other
available converters because of the SQ48 Series’ optimized
thermal efficiency.
Telecommunications
Data Communications
Wireless Communications
Servers
High efficiency – no heat sink required
For output voltages ranging from 3.3 to 1.0 V, 40% higher
current capability at elevated temperatures than most
competitors' 20-25A quarter-bricks
Extremely small footprint: 0.896” x 2.30” (2.06 in ), 40%
smaller than conventional quarter-bricks
North America
+1-866.513.2839
Asia-Pacific
+86.755.29885888
Europe, Middle East
+353 61 225 977
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2
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BCD.00637_AA
Conditions: T
A
= 25 º C, Airflow = 300 LFM (1.5 m/s), Vin = 48 VDC, Cin=33 µ F, unless otherwise specified.
PARAMETER
Absolute Maximum Ratings
Input Voltage
Operating Ambient Temperature
Storage Temperature
Input Characteristics
Operating Input Voltage Range
Input Undervoltage Lockout
Turn-on Threshold
Turn-off Threshold
Input Voltage Transient
Isolation Characteristics
I/O Isolation
Isolation Capacitance
1.0 - 3.3 V
5.0 - 6.0 V
8.0 - 12 V
Isolation Resistance
Feature Characteristics
Switching Frequency
Industry-std. equations (1.5 - 12V)
Output Voltage Trim Range
1
Remote Sense Compensation
1
Output Overvoltage Protection
Use trim equation on Page 4 (1.0 -1.2 V)
Percent of V
OUT
(
NOM
)
Non-latching ( 1.5 – 12 V)
Non-latching (1.0 -1.2 V)
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)
2.4
-20
20
0.8
VDC
VDC
-20
2.4
0.8
20
VDC
VDC
Applies to all protection features
See Figures F, G and H
117
124
122
132
100
4
-20
-10
415
+10
+10
+10
127
140
kHz
%
%
%
%
%
ms
ms
10
2000
160
260
230
VDC
pF
pF
pF
MΩ
100 ms
Non-latching
33
31
34
32
35
33
100
VDC
VDC
VDC
36
48
75
VDC
Continuous
0
-40
-55
80
85
125
VDC
°C
°C
Notes
MIN
TYP
MAX
UNITS
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
(NOM), in order to ensure specified operation of overvoltage protection circuitry.
OUT
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
Ω
across the input
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BCD.00637_AA
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 1000
μF
on 12 V, 2,200
μF
on 8.0 V,
10,000
μF
on 5.0 – 6.0 V, and 15,000
μF
on 3.3 – 1.0 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.
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, with both referenced to Vin(-). A typical connection is shown in Fig. A.
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 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 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 0.2 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).
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.
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.
When using the remote sense function, the converter’s output overvoltage protection (OVP) senses the voltage across
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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% 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 guaranteed
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 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:
R
T
INCR
½
for 1.5 – 12 V.
[kΩ] (1.2 V)
5.11(100
Δ)V
O
NOM
626
10.22
1.225Δ
[k],
[kΩ] (1.0 V)
where,
R
T
INCR
½
Required value of trim-up resistor k]
V
O
NOM
½
Nominal value of output voltage [V]
Δ
½
(V
O-REQ
V
O-NOM
)
X 100
V
O -NOM
[%]
V
O
REQ
½
Desired (trimmed) output voltage [V].
Fig. C: Configuration for increasing output voltage
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.
To decrease the output voltage (Fig. D), a trim resistor, R
SENSE(-) (Pin 5), with a value of:
T-DECR
, should be connected between the TRIM (Pin 6) and
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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 and one-
eighth bricks (except for 1.2 V and 1.0 V outputs).
Converters with output voltages 1.2 V and 1.0 V are available with alternative trim feature to provide the customers with the
flexibility of second sourcing. These converters have a “T” character in the part number. The trim equations of “T” version
of converters and more information can be found in Application Note 103.
Fig. 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 V
OUT
(
NOM
),
or:
[V
OUT
(
)
V
OUT
(
)]
[V
SENSE
(
)
V
SENSE
(
)]
V
O - 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 50% of the nominal value of output voltage, the converter will shut down (Fig. x.17).
Once the converter has shut down, it will attempt to restart nominally every 100 ms with a typical 1-2% duty cycle (Fig.
x.18). 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.
Once the output current is brought back into its specified range, the converter automatically exits the hiccup mode and
continues normal operation.
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