SRS20A-12W
Series
Miniature, Non-isolated
20A Output, Switching
POL Regulators
Electrical Specifications
Specifications typical @ +25°C, nominal input voltage & rated output current, unless otherwise noted. Specifications subject to change without notice.
Key Features:
•
20A Output Current
•
Wide 6V - 14V Input Range
•
Efficiency to 94%
•
EN 60950 Approved (UL)
•
Sequencing Capability
•
Compact SIP Case
•
Short Circuit Protected
•
Thermal Shutdown
•
Remote On/Off Control
•
Industry Standard Footprint
Input
Parameter
Input Voltage Range
Under Voltage Lockout, Power Up
Maximum Input Current
Off Input Current
Input Filter
Input Reflected Ripple Current
Conditions
Min.
6.0
Typ.
12.0
5.0
4.0
1.0
Max.
14.0
Units
VDC
VDC
19.0
10
220
Max.
A
mA
mA P-P
Units
%
%
%
mV P-P
mV RMS
µSec
%/°C
Turn On Voltage Threshold
Turn Off Voltage Threshold
Lockout Hysteresis Voltage
I
OUT
= 100%, V
In =
0 to 14 VDC
Input Idle Current
Capacitive
See Note 1
Output
Parameter
Output Voltage/Current
Output Voltage Tolerance
Line Regulation
Load Regulation
Ripple & Noise (20 MHz)
Transient Recovery Time, See Note 3
Temperature Coefficient
Power Good Signal, See Note 4
Short Circuit Protection
Over Temperature Protection
Overload Protection
Conditions
Min.
Typ.
See Model Selection Guide
±1.5
V
IN
= Min to Max
±0.2
±0.5
I
OUT
= 0% to 100%
75
See Note 2
30
50% Load Change
200
±0.03
TTL High Signal When V
OUT
= 90% to 110%
Continuous (Hiccup Mode)
See Note 5
130
See Note 6
150
Conditions
Min.
Not Isolated
Fixed
Min.
0.0
Typ.
300
Typ.
Max.
Open or V
IN
0.4
1
Max.
°C
%
Units
kHz
Units
VDC
mA
Units
°C
°C
%
General
Parameter
Isolation Voltage
Switching Frequency
Remote On/Off,
See Note 7
Parameter
Unit On
Unit Off
On/Off Current
Conditions
Logic High
Logic Low
V
ON
/V
OFF
= 0.0V
Conditions
Environmental
MicroPower Direct
292 Page Street
Suite D
Stoughton, MA 02072
USA
T:
(781) 344-8226
F:
(781) 344-8481
E:
sales@micropowerdirect.com
W:
www.micropowerdirect.com
Parameter
Operating Temperature Range
Storage Temperature Range
Cooling
Humidity
Physical
Size
Weight
Min.
Typ.
Max.
Ambient
-40
+25
+85
-55
+125
Free Air Convection (See Derating Curves)
RH, Non-condensing
93
2.4 x 0.51 x 0.32 Inches (61.0 x 12.95 x 8.3 mm)
0.357 Oz (11.0g)
Conditions
Min.
Typ.
MIL HDBK 217F, 25°C, Gnd Benign
900
UL 60950, EN 60950
Max.
Units
kHours
Reliability Specifications
Parameter
MTBF
Safety Standards
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Model Selection Guide
Input
Voltage
(VDC)
Current
(mA)
Voltage
Range
Full-Load No-Load
(VDC)
1,603
40
0.75
2,381
50
1.20
2,874
50
1.50
6.0 - 14.0
3,409
50
1.80
SRS20A-12W-5.0
3,745
60
2.00
4,630
65
2.50
5,978
75
3.30
6.5 - 14.0
8,865
95
5.00
Model
Number
Notes:
1. Measured over a bandwidth of 5 Hz to 20 MHz using a 1 µH inductor.
2. Output ripple is measured at 20 MHz bandwidth using a 1.0 µF ceramic
capacitor and a 10 µF tantalum capacitor connected in parallel as close
to the output terminals as possible.
3. Transient recovery is measured to within a 200 mV error band for a 50%
load change.
4. The “Power Good” signal is optional. To include this, add a “P” to the
product number (SRS20A-12W-5.0P). If it is not included, then pin 6 is
not installed.
5. These units include a non-latching over temperature protection circuit.
If the temperature exceeds approximately 130°C at the monitored “hot
spot”, the unit will be shut down. When the temperature decreases, the
unit will automatically restart. See page 3 for temperature measurement
information.
6. These units will provide up to 150% of rated current. In the event of
an over current fault, the unit will go into hiccup mode until the fault is
removed.
7. Standard units feature an active high remote control input. See the note
and diagram at right.
8. These units do not include an internal fuse. It is recommended that an
external slow-blow fuse be used with a rating as shown in the table above.
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Output
Current
(A, Max)
Current
(A, Min)
Efficiency Capacitive Fuse Rating
Load
Slow-Blow
(%, Typ)
(µF Max)
(A)
20.0
0.0
78
84
87
88
89
90
92
94
8,000
25
Remote On/Off
These units include an active high
On/OFF control input. The unit is
“ON” if the input to the control pin
(pin 11) is high; or if the pin is left
open (or floating). The signal level
of the control input is referenced
to ground. A recommended drive
circuit for the control pin is shown
at left. The resistors R
1
& R
2
have
been added to help reduce pos-
sible false triggering of the control
input due to leakage currents.
Units are available with an active
low control input. With this input,
the unit will remain off if the con-
trol input remains above 2.8 VDC.
For more information on the active
low option, contact the factory.
Typical Connection
Notes:
Fuse:
SRS20A-12W
regulators do not include an internal fuse. For
safety and protection, a external slow-blow fuse should be
placed in the input (+V
IN
) line. A 25A fuse is recommended.
The unit must be connected to a low AC impedance source,
and to avoid loop stability issues, the source inductance
should also be low. To significantly reduce ripple caused by
the switching action of the POL, the
SRS20A-12W
includes
onboard filtering. However, adding input capacitors C
1
and
C
2
will further reduce ripple currents (C
1
) and high frequency
noise spikes (C
2
). These capacitors should be placed as
close to the input pins as possible (see board layout at right).
It is recommended that low ESR (<100 m ) and low ESL
ceramic capacitors be used. Recommended values are:
C
1
33
µF
to 250
µF
C
2
0.01
µF
Output Trim:
Remote Sense:
See note on page 4
The remote sense helps regulate the output voltage at
the point of load by minimizing the effects of distribution
losses. The voltage between the sense pin (Pin 3) and
the point of load should not exceed 500 mV. When using
the remote sense function, the output voltage level may
rise. Care must be taken not to exceed the maximum
rated output power of the regulator. When not in use, the
remote sense pin should be tied to the output pin of the
regulator.
Output filtering is not required, but may be used to further
reduce output ripple & noise; or to adjust the transient
response time of the unit. Care must be taken not to exceed
8,000
µF,
the maximum value of output capacitance the
unit is rated for. The values given in the connection dia-
gram are typical for light filtering.
Input Filter:
Output Filter:
Remote ON/OFF:
See note above
292 Page Street Ste D Stoughton, MA 02072
•
TEL: (781) 344-8226
•
FAX: (781) 344-8481
•
E-Mail: sales@micropowerdirect.com
Derating Curves
SRS20A-12W-5.0 - V
IN
= 12 VDC, V
OUT
= 5.0 VDC
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SRS20A-12W-5.0 - V
IN
= 12 VDC, V
OUT
= 3.3 VDC
SRS20A-12W-5.0 - V
IN
= 12 VDC, V
OUT
= 2.5 VDC
SRS20A-12W-5.0 - V
IN
= 12 VDC, V
OUT
= 2.0 VDC
SRS20A-12W-5.0 - V
IN
= 12 VDC, V
OUT
= 1.8 VDC
SRS20A-12W-5.0 - V
IN
= 12 VDC, V
OUT
= 1.5 VDC
SRS20A-12W-5.0 - V
IN
= 12 VDC, V
OUT
= 1.2 VDC
SRS20A-12W-5.0 - V
IN
= 12 VDC, V
OUT
= 0.75 VDC
Temperature Measurement
These switching regulators may be used in a wide variety of thermal environments, but must be properly cooled to ensure
long reliable operation. The derating curves shown above are approximations of the ambient temperature and airflow
required to maintain the switching regulator temperature below its maximum rating.
Airflow should move parallel to the long axis of the unit, as shown at left. Proper cooling can be verified by measuring the
temperature at pin six of Q
1
(as shown at left). The thermocouple should be mounted approximately 0.5 in. off the unit board.
The temperature at this location should not exceed 120°C.
MicroPower Direct
•
292 Page Street Ste D Stoughton, MA 02072
•
TEL: (781) 344-8226
•
FAX: (781) 344-8481
•
E-Mail: sales@micropowerdirect.com
Output Voltage Trim
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The output voltage level of the
SRS20-12W
series is adjust-
able over a wide range by the simple addition of an external
resistor. This trim resistor is connected between the circuit
common and the trim input, as shown in the diagram at left.
SRS20A-12W-5.0
SRS20A-12W-5.0
V
OUT
(VDC)
R
TRIM
(k )
V
OUT
(VDC)
R
TRIM
(k )
0.75
Open
2.00
7.417
1.20
22.46
2.50
5.009
1.50
13.05
3.30
3.122
1.80
9.024
5.00
1.472
The required resistor value for various output levels is
given in the table above. To calculate the correct value
for a different output level, the formula is:
Sequencing
R
TRIM
=
10, 500
- 1, 000
V
OUT
- 0.7525
Where: R
TRIM
= The external trim resistor
V
OUT
= The desired output voltage
If a trim resistor is not connected, the output is 0.75 VDC.
Suggested Board Layout
This diagram illustrates a simple
board layout for use with the
SRS20A-12W
series. A recom-
As
mended, external components
com
are placed as close to the unit
as possible. To help shi
shield exter-
nal circuitry, the ground plane
grou
has been extended under the
u
unit. Any signal trace should
traces
not be routed undern
underneath the
unit (unless they are o a layer
on
under the ground plane to avoid
plane)
unwanted noise interference.
interfe
The outputs of multiple
SRS20A-12W
modules may be
controled via the sequencing feature. When not using
this feature, the S
EQ
input should be left open or tied to
V
IN
. Connecting modules (as shown above), allows users
to control the timing of the outputs of multiple modules.
For proper sequencing, the input voltage is applied to
the module. The On/Off input of each module is left
open so that the module is on by default. A minimum 10
mS delay (after the input voltage is applied) is required
before applying a voltage on the S
EQ
input. As a voltage
is applied to the S
EQ
input, the module output voltage
will track this control voltage (on a one-to-one volt basis)
until the set-point voltage level is reached.
To achieve a simultaneous shutdown of the modules,
the S
EQ
input voltage is lowered in a controlled manner.
The module output voltages will track this input below
their set-point voltages on a one-to-one basis. The input
voltage must be maintained within specified limits until
the tracking and output voltages reach ground potential.
Pin Connections
Mechanical Dimensions
Pin
1
2
3
4
5
6
7
8
9
10
11
12
Description
+V Output
+V Output
Sense
+V Output
Common
Power Good (Opt)
Common
+V Input
+V Input
Sequence
Trim
Remote On/Off
MicroPower Direct
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292 Page Street Ste D Stoughton, MA 02072
•
Notes:
•
All dimensions are typical in inches (mm)
•
Tolerance x.xx =
±
0.02 (
±
0.50)
FAX: (781) 344-8481
•
TEL: (781) 344-8226
•
E-Mail: sales@micropowerdirect.com
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