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.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
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 TR332, 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
1
SQ24 Series
ELECTRICAL SPECIFICATIONS
Conditions: TA = 25 ºC, Airflow = 300 LFM (1.5 m/s), Vin = 24 VDC, All output voltages, unless otherwise specified.
PARAMETER
NOTES
MIN
TYP
MAX
UNITS
0
40
VDC
Operating Ambient Temperature
-40
85
°C
Storage Temperature
-55
125
°C
Absolute Maximum Ratings
Input Voltage
Continuous
Input Characteristics
Operating Input Voltage Range
18
24
36
VDC
Turn-on Threshold
16
17
17.5
VDC
Turn-off Threshold
15
16
16.5
VDC
Input Under Voltage Lockout (Non-latching)
Isolation Characteristics
I/O Isolation
2000
Isolation Capacitance
VDC
1.0 - 3.3 V
160
pF
5.0 - 6.0 V
260
pF
8.0 V, 12 V
230
pF
Isolation Resistance
10
MΩ
Feature Characteristics
Switching Frequency
415
kHz
Industry-std. equations (1.5 - 12 V)
-20
+10
%
Industry-std. equations (1.0 - 1.2 V)
-10
+10
%
+10
%
Output Voltage Trim Range1
Remote Sense Compensation
1
Percent of VOUT(NOM)
Non-latching (1.5 - 12 V)
117
125
140
%
Non-latching (1.0 - 1.2 V)
124
132
140
%
Output Over-Voltage Protection
Auto-Restart Period
Applies to all protection features
Turn-On Time
100
ms
4
ms
Converter Off
-20
0.8
VDC
Converter On
2.4
20
VDC
Converter Off
2.4
20
VDC
Converter On
-20
0.8
VDC
ON/OFF Control (Positive Logic)
ON/OFF Control (Negative Logic)
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 VOUT(NOM), in order to insure specified operation of over-voltage protection circuitry. See “Output Voltage Adjust/Trim” for detailed
information.
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SQ24 Series
2
2.1
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.
TM
Vin (+)
SemiQ Family
Converter
(Top View )
ON/OFF
Vin
Vout (+)
SENSE (+)
TRIM
Rload
SENSE (-)
Vin (-)
Vout (-)
CONTROL
INPUT
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).
TM
Vin (+)
SemiQ Family
Converter
Rw
Vout (+)
100
(Top View )
Vin
ON/OFF
SENSE (+)
TRIM
Rload
SENSE (-)
10
Vin (-)
Vout (-)
Rw
Fig. B: Remote sense circuit configuration.
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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, RT-INCR, should be connected between the TRIM (Pin 6) and SENSE(+) (Pin
7), with a value of:
RTINCR
RTINCR
485
Δ
RTINCR
323
2 [k] (1.0 V)
Δ
5.11(100 Δ)VONOM 626
10.22
1.225Δ
[k] (1.5-12 V)
[k] (1.2 V)
where,
RTINCR Required value of trim-up resistor [k]
VONOM Nominal value of output voltage [V]
Δ
VOREQ
(VO -REQ VO -NOM )
X 100
VO -NOM
[%]
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 (+)
SemiQ Family
Converter
(Top View )
Vin
ON/OFF
Vout (+)
SENSE (+)
R
T-INCR
TRIM
Rload
SENSE (-)
Vin (-)
Vout (-)
Fig. C: Configuration for increasing output voltage.
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SQ24 Series
To decrease the output voltage (Fig. D), a trim resistor, RT-DECR, should be connected between the TRIM (Pin 6) and SENSE(-) (Pin 5), with
a value of:
RTDECR
511
10.22
|Δ|
[kΩ] (1.0 – 12 V)
where,
RTDECR 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.
TM
Vin (+)
SemiQ Family
Converter
(Top View )
ON/OFF
Vin
Vout (+)
SENSE (+)
TRIM
Rload
R T-DECR
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
VOUT(NOM), or:
[VOUT() VOUT()] [VSENSE() VSENSE()] VO - 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 predetermined 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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SQ24 Series
3.4 OVERTEMPERATURE PROTECTION (OTP)
The converter will shut down under an overtemperature 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.
3.5 SAFETY REQUIREMENTS
The converters meet the requirements of the latest edition and amendment of ITE Safety standards UL/CSA 60950-1.
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
FUSE RATING
3.3 V
8A
12 V - 5.0 V, 2.5 V
6A
2.0 V - 1.0 V
4A
If one input fuse is used for a group of modules, the maximum fuse rating should not exceed 15-A (SQ modules are UL approved with
up to a 15-A fuse).
3.6 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, Bel Power Solutions 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.
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 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.
4
4.1
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 associated with the converter. Additional comments for specific data are
provided below.
4.2
TEST CONDITIONS
All data presented were taken with the converter soldered to a test board, specifically a 0.060” thick printed wiring board (PWB) with
four layers. The top and bottom layers were not metalized. The two inner layers, comprising two-ounce copper, were used to provide
traces for connectivity to the converter.
The lack of metalization on the outer layers as well as the limited thermal connection ensured that heat transfer from the converter to the
PWB was minimized. This provides a worst-case but consistent scenario for thermal derating purposes.
All measurements requiring airflow were made in vertical and horizontal wind tunnel facilities using Infrared (IR) thermography and
thermocouples for thermometry.
Ensuring components on the converter do not exceed their ratings is important to maintaining high reliability. If one anticipates operating
the converter at or close to the maximum loads specified in the derating curves, it is prudent to check actual operating temperatures in
the application. Thermographic imaging is preferable; if this capability is not available, then thermocouples may be used. Bel Power
Solutions recommends the use of AWG #40 gauge thermocouples to ensure measurement accuracy. Careful routing of the thermocouple
leads will further minimize measurement error. Refer to Figure H for optimum measuring thermocouple location.
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SQ24 Series
4.3
THERMAL DERATING
Load current vs. ambient temperature and airflow rates are given in Fig. x.1 for through-hole version. Ambient temperature was varied
between 25 °C and 85 °C, with airflow rates from 30 to 500 LFM (0.15 to 2.5 m/s), and vertical and horizontal converter mounting.
For each set of conditions, the maximum load current was defined as the lowest of:
(i)
(ii)
The output current at which any FET junction temperature did not exceed a maximum specified temperature (120 °C) as indicated
by the thermographic image, or
The nominal rating of the converter (4 A on 12 V, 5.3 A on 8.0 V, 8 A on 6.0 V, 10 A on 5.0 V, and 15 A on 3.3 – 1.0 V).
During normal operation, derating curves with maximum FET temperature less than or equal to 120 °C should not be exceeded.
Temperature on the PCB at the thermocouple location shown in Fig. H should not exceed 118 °C in order to operate inside the derating
curves.
Fig. H: Location of the thermocouple for thermal testing.
4.4
EFFICIENCY
Fig. x.5 shows the efficiency vs. load current plot for ambient temperature of 25 ºC, airflow rate of 300 LFM (1.5 m/s) with vertical
mounting and input voltages of 18 V, 24 V and 36 V. Also, a plot of efficiency vs. load current, as a function of ambient temperature with
Vin = 24 V, airflow rate of 200 LFM (1 m/s) with vertical mounting is shown in Fig. x.6.
4.5
POWER DISSIPATION
Fig. x.7 shows the power dissipation vs. load current plot for Ta = 25 ºC, airflow rate of 300 LFM (1.5 m/s) with vertical mounting and
input voltages of 18 V, 24 V and 36 V. Also, a plot of power dissipation vs. load current, as a function of ambient temperature with Vin =
24 V, airflow rate of 200 LFM (1 m/s) with vertical mounting is shown in Fig. x.8.
4.6
START-UP
Output voltage waveforms, during the turn-on transient using the ON/OFF pin for full rated load currents (resistive load) are shown
without and with external load capacitance in Fig. x.9 and Fig. x.10, respectively.
4.7
RIPPLE AND NOISE
Fig. x.13 shows the output voltage ripple waveform, measured at full rated load current with a 10 µF tantalum and 1 µF ceramic
capacitor across the output. Note that all output voltage waveforms are measured across a 1 F ceramic capacitor.
The input reflected ripple current waveforms are obtained using the test setup shown in Fig x.14. The corresponding waveforms are
shown in Fig. x.15 and Fig. x.16.
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SQ24 Series
4.8 START-UP INFORMATION (USING NEGATIVE ON/OFF)
Scenario #1: Initial Start-up From Bulk Supply
ON/OFF function enabled, converter started via application of VIN.
See Figure E.
Comments
ON/OFF pin is ON; system front end power is toggled
on, VIN to converter begins to rise.
t1
VIN crosses Under-Voltage Lockout protection circuit
threshold; converter enabled.
t2
Converter begins to respond to turn-on command
(converter turn-on delay).
t3
Converter VOUT reaches 100% of nominal value.
For this example, the total converter start-up time (t3- t1) is typically
4 ms.
VIN
Time
t0
ON/OFF
STATE
OFF
ON
VOUT
t0
t1 t2
t
t3
Fig. E: Start-up scenario #1
Scenario #2: Initial Start-up Using ON/OFF Pin
With VIN previously powered, converter started via ON/OFF pin.
See Figure F.
Comments
VINPUT at nominal value.
Arbitrary time when ON/OFF pin is enabled
(converter enabled).
t2
End of converter turn-on delay.
t3
Converter VOUT reaches 100% of nominal value.
For this example, the total converter start-up time (t3- t1) is
typically 4 ms.
VIN
Time
t0
t1
ON/OFF
STATE OFF
ON
VOUT
t0
t1 t2
t
t3
Fig. F: Start-up scenario #2.
Scenario #3: Turn-off and Restart Using ON/OFF Pin
With VIN previously powered, converter is disabled and then
enabled via ON/OFF pin. See Figure G.
Time
Comments
t0
VIN and VOUT are at nominal values; ON/OFF pin ON.
t1
ON/OFF pin arbitrarily disabled; converter output falls to
zero; turn-on inhibit delay period (100 ms typical) is initiated, and
ON/OFF pin action is internally inhibited. t2
ON/OFF pin is
externally re-enabled.
If (t2- t1) ≤ 100 ms, external action of ON/OFF pin
is locked out by start-up inhibit timer.
If (t2- t1) > 100 ms, ON/OFF pin action is internally
enabled.
t3
Turn-on inhibit delay period ends. If ON/OFF pin is ON,
converter begins turn-on; if off, converter awaits ON/OFF pin
ON signal; see Figure F. t4 End of converter turn-on delay.
t5
Converter VOUT reaches 100% of nominal value. For
the condition, (t2- t1) ≤ 100 ms, the total converter start-up time
(t5- t2) is typically 104 ms. For (t2- t1) > 100 ms, start-up will be
typically 4 ms after release of ON/OFF pin.
V IN
ON/OFF
STATE
100 ms
OFF
ON
V OUT
t1
t2
t3 t4
t5
Fig. G: Start-up scenario #3
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t
SQ24 Series
5
9
SQ24T/S04120 (12.0 VOUT)
ELECTRICAL SPECIFICATIONS: SQ24T/S04120 (12 VOLTS OUT)
Conditions: TA = 25ºC, Airflow = 300 LFM (1.5 m/s), Vin = 24 VDC, Vout = 12 VDC unless otherwise specified.
Input Characteristics
Maximum Input Current
4 ADC, 12 VDC Out @ 18 VDC In
3.1
ADC
Input Stand-by Current
Vin = 24 V, converter disabled
3
mADC
Input No Load Current (0 load on the output)
Vin = 24 V, converter enabled
100
mADC
Input Reflected-Ripple Current
25 MHz bandwidth
6
mAPK-PK
Input Voltage Ripple Rejection
120 Hz
TBD
dB
Output Characteristics
Output Voltage Set Point (no load)
11.88
12.00
12.12
VDC
Over Line
±4
±10
mV
Over Load
±4
±10
mV
12.18
VDC
120
mVPK-PK
1000
μF
4
ADC
5
5.5
ADC
7.5
10
A
1
Arms
Output Regulation
Output Voltage Range
Over line, load and temperature (-40ºC to 85ºC)
Output Ripple and Noise - 25 MHz bandwidth
Full load + 10 μF tantalum + 1 μF ceramic
External Load Capacitance
Plus full load (resistive)
Output Current Range
11.82
90
0
Current Limit Inception
Non-latching
Peak Short-Circuit Current
Non-latching. Short = 10 mΩ.
RMS Short-Circuit Current
Non-latching
Dynamic Response
Co = 1 μF ceramic
150
mV
1 μF ceramic
200
mV
20
µs
100% Load
87
%
50% Load
87
%
Load Change 25% of Iout Max, di/dt = 0.1 A/μs
di/dt = 5 A/μs
Setting Time to 1%
Efficiency
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SQ24 Series
SQ24T/S04120 (12.0 VOUT)
Ambient Temperature [°C]
Fig. 12V.1: Available load current vs. ambient air temperature and
airflow rates for SQ24T04120 converter with B height pins
mounted vertically with Vin = 24V, air flowing from pin 3 to pin 1
and maximum FET temperature ≤ 120°C.
Ambient Temperature [°C]
Fig. 12V.2: Available load current vs. ambient air temperature and
airflow rates for SQ24T04120 converter with B height pins
mounted horizontally with Vin = 24V, air flowing from pin 3 to pin 1
and maximum FET temperature ≤ 120°C.
Ambient Temperature [°C]
Fig. 12V.3: Available load current vs. ambient temperature and
airflow rates for SQ24S04120 converter mounted vertically with
Vin = 24V, air flowing from pin 3 to pin 1 and maximum FET
temperature ≤ 120°C.
Ambient Temperature [°C]
Fig. 12V.4: Available load current vs. ambient temperature and
airflow rates for SQ24S04120 converter mounted horizontally with
Vin = 24V, air flowing from pin 3 to pin 1 and maximum FET
temperature ≤ 120°C.
0.95
0.95
0.90
0.90
0.85
0.85
0.80
0.80
36 V
24 V
18 V
0.75
70 C
55 C
40 C
0.75
0.70
0.70
0.65
0.65
0
1
2
3
4
Load Current [Adc]
Fig. 12V.5: Efficiency vs. load current and input voltage for
SQ24T/S04120 converter mounted vertically with air flowing from
pin 3 to pin 1 at a rate of 300 LFM (1.5 m/s) and Ta = 25°C.
5
0
1
2
3
4
Load Current [Adc]
Fig. 12V.6: Efficiency vs. load current and ambient temperature
for SQ24T/S04120 converter mounted vertically with Vin = 24V
and air flowing from pin 3 to pin 1 at a rate of 200 LFM (1.0 m/s).
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11
SQ24T/S04120 (12.0 VOUT)
10.00
10.00
8.00
8.00
Power Dissipation [W]
Power Dissipation [W]
SQ24 Series
6.00
4.00
36 V
24 V
18 V
2.00
6.00
4.00
70 C
55 C
40 C
2.00
0.00
0.00
0
1
2
3
4
5
0
Load Current [Adc]
1
2
3
4
Load Current [Adc]
Fig. 12V.7: Power dissipation vs. load current and input voltage
for SQ24T/S04120 converter mounted vertically with air flowing
from pin 3 to pin 1 at a rate of 300 LFM (1.5 m/s) and Ta = 25°C.
Fig. 12V.8: Power dissipation vs. load current and ambient
temperature for SQ24T/S04120 converter mounted vertically with
Vin = 24V and air flowing from pin 3 to pin 1 at a rate of 200 LFM
(1.0 m/s).
Fig. 12V.9: Turn-on transient at full rated load current (resistive)
with no output capacitor at Vin = 24V, triggered via ON/OFF pin.
Top trace: ON/OFF signal (5 V/div.). Bottom trace: output voltage
(5 V/div.). Time scale: 1 ms/div.
Fig. 12V.10: Turn-on transient at full rated load current (resistive)
plus 1,000F at Vin = 24V, triggered via ON/OFF pin. Top trace:
ON/OFF signal (5 V/div.). Bottom trace: output voltage (5 V/div.).
Time scale: 2 ms/div.
Fig. 12V.11: Output voltage response to load current step-change
(1A – 2A – 1A) at Vin = 24V. Top trace: output voltage (200
mV/div.). Bottom trace: load current (1 A/div.). Current slew rate:
0.1 A/s. Co = 1 F ceramic. Time scale: 0.5 ms/div.
Fig. 12V.12: Output voltage response to load current step-change
(1A – 2A – 1A) at Vin = 24V. Top trace: output voltage (200
mV/div.). Bottom trace: load current (1 A/div.). Current slew rate: 5
A/s. Co = 1 F ceramic. Time scale: 0.5 ms/div.
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5
12
SQ24 Series
SQ24T/S04120 (12.0 VOUT)
iS
10 H
source
inductance
Vsource
iC
33 F
ESR
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