The SemiQ™
Family 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 -30 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 electric and thermal design, results in a product
with extremely high reliability.
Operating from an 18-36
V input, the SQ24 Series converters of the SemiQ™ Family
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 SQ24 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. 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 SQ24 Series’ optimized thermal efficiency.
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18-36 VDC Input; Outputs from 1-12 VDC
Available in through-hole and SM packages
Outputs available in 12.0, 8.0, 6.0, 5.0, 3.3, 2.5, 2.0, 1.8, 1.5, 1.2 & 1.0 V
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
Fixed-frequency operation
Fully protected
Remote output sense
Output voltage trim range: +10%/−20% (except 1.2 V and 1.0 V 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
All materials meet UL94, V-0 flammability rating
Approved to the latest edition and amendment of ITE Safety standards,
UL/CSA 60950-1 and IEC60950-1
RoHS lead-free solder and lead-solder-exempted products are available
2
SQ24 Series
ELECTRICAL SPECIFICATIONS
Conditions: T
A
= 25 ºC, Airflow = 300 LFM (1.5 m/s), Vin = 24 VDC, All output voltages, unless otherwise specified.
1
PARAMETER
NOTES
MIN
TYP
MAX
UNITS
Absolute Maximum Ratings
Input Voltage
Operating Ambient Temperature
Storage Temperature
Continuous
0
-40
-55
40
85
125
VDC
°C
°C
Input Characteristics
Operating Input Voltage Range
Turn-on Threshold
Input Under Voltage Lockout (Non-latching)
Turn-off Threshold
15
16
16.5
VDC
18
16
24
17
36
17.5
VDC
VDC
Isolation Characteristics
I/O Isolation
1.0 - 3.3 V
Isolation Capacitance
5.0 - 6.0 V
8.0 V, 12 V
Isolation Resistance
10
2000
160
260
230
VDC
pF
pF
pF
MΩ
Feature Characteristics
Switching Frequency
Industry-std. equations (1.5 - 12 V)
Output Voltage Trim Range
1
Industry-std. equations (1.0 - 1.2 V)
Remote Sense Compensation
1
Output Over-Voltage Protection
Non-latching (1.0 - 1.2 V)
Auto-Restart Period
Turn-On Time
Converter Off
ON/OFF Control (Positive Logic)
Converter On
Converter Off
ON/OFF Control (Negative Logic)
Converter On
-20
0.8
VDC
2.4
2.4
20
20
VDC
VDC
-20
Applies to all protection features
124
132
100
4
0.8
140
%
ms
ms
VDC
Percent of V
OUT
(NOM)
Non-latching (1.5 - 12 V)
117
125
-10
+10
+10
140
%
%
%
-20
415
+10
kHz
%
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.
tech.support@psbel.com
SQ24 Series
2
2.1
3
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.
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 addition of a 100 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 1000 µF on 12 V, 2,200 µF on 8.0 V, 10,000 µF on 5.0 V
–
6.0 V, and 15,000 µF on 3.3 V
–
1.0 V outputs.
2.2
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(-). Typical connections are shown in Fig. A.
Vin (+)
Semi
Q
Family
Converter
(Top View )
TM
Vout (+)
SENSE (+)
TRIM
SENSE (-)
Rload
Vin
ON/OFF
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 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 0.2mA at a low level voltage 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 Information section for system timing waveforms associated with use of the
ON/OFF pin.
2.3
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).
Vin (+)
Semi
Q
Family
Converter
(Top View )
TM
Rw
Vout (+)
100
SENSE (+)
TRIM
SENSE (-)
10
Rload
Vin
ON/OFF
Vin (-)
Vout (-)
Rw
Fig. B: Remote sense circuit configuration.
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© 2018 Bel Power Solutions & Protection
4
SQ24 Series
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 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 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.
2.4
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 current.
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
TINCR
½
5.11(100
Δ)V
ONOM
626
10.22
1.225Δ
[k] (1.5-12 V)
R
T
INCR
½
485
Δ
[k] (1.2 V)
R
T
INCR
½
where,
323
2
[k] (1.0 V)
Δ
R
TINCR
½
Required value of trim-up resistor [k]
V
ONOM
½
Nominal value of output voltage [V]
Δ
½
(V
O -REQ
V
O -NOM
)
X 100
V
O -NOM
[%]
V
OREQ
½
Desired (trimmed) output voltage [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.
TM
Vin (+)
Semi
Q
Family
Converter
(Top View )
Vout (+)
SENSE (+)
R
T-INCR
Vin
ON/OFF
TRIM
SENSE (-)
Rload
Vin (-)
Vout (-)
Fig. C: Configuration for increasing output voltage.
tech.support@psbel.com
SQ24 Series
R
T
DECR
½
where,
5
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:
511
10.22
|Δ|
[kΩ] (1.0
–
12 V)
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.
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.
Semi
Q
Family
Converter
(Top View )
Vin
ON/OFF
TM
Vin (+)
Vout (+)
SENSE (+)
TRIM
R
T-DECR
Rload
SENSE (-)
Vin (-)
Vout (-)
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 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]
This equation is applicable for any condition of output sensing and/or output trim.
3
3.1
PROTECTION FEATURES
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 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.
3.2 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 50% of the
nominal value of output voltage, 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.
3.3 OUTPUT OVERVOLTAGE 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.
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+86 755 298 85888
Europe, Middle East
+353 61 225 977
North America
+1 408 785 5200
BCD.00706_AB
© 2018 Bel Power Solutions & Protection
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