For technical support and more information, see inside back cover or visit www.ti.com
Standard Application
Features
Input Voltage Range:
36V to 75V
20W Rated
82% Efficiency
1500 VDC Isolation
Low Profile (8.5 mm)
Small Footprint: 1.52in x 1.73in
Remote On/Off
PT4120 Series
20-W 48-V Input Isolated
DC/DC Converter
PT4120
LOAD
3
2
1
5
4
6
+V
OUT
V
OUT
V
O
Adj
+V
IN
V
IN
Remote
On/Off
Q
1
BSS138
SLTS092B
(Revised 2/26/2002)
Ordering Information
PT4121
H =
3.3V/5A
(16.5W)
PT4122
H =
5.0V/4A
PT4123
H = 12.0V/1
6A
PT4124
H = 15.0V/1
3A
PT4125
H =
5.2V/38A
PT4126
H =
1.5V/5A
(7.5W)
PT4127
H =
1.8V/5A
(9W)
PT4128
H =
2.5V/5A
(12.5W)
PT4129
H =
1.65V/5A (825W)
Pin-Out Information
Pin
Function
1
Remote On/Off
2
Vin
3
+Vin
4
Vout
5
+Vout
6
Vout Adjust
For further information, see
application notes.
Description
The PT4120 power modules are a series
of isolated DC/DC converters housed a low-
profile package. Rated for 20 watts or 5A, the
series includes standard output voltages rang-
ing from as low as 1.5VDC to 15VDC. The
output may be adjusted 10% of nominal.
These converters are ideal for Telecom,
Industrial, Computer, and other distributed
power applications that require input-to-
output isolation.
Using multiple PT4120 modules, system
designers can implement a complete custom
power supply solution. The flexibility of full
isolation also allows the input or output to be
configured for negative voltage operation.
The PT4120 series requires no additional
components for proper operation.
Short Circuit Protection
Over Temperature Shutdown
Under-Voltage Lockout
UL1950 Recognized
CSA 22.2 950 Certified
EN60950 Approved
410
6
Hrs MTBF
PT Series Suffix
(PT1234
x
)
Case/Pin
Order
Package
Configuration
Suffix
Code *
Horizontal
A
(EGD)
SMD
C
(EGE)
* Previously known as package style 710.
(Reference the applicable package code draw-
ing for the dimensions and PC board layout)
For technical support and more information, see inside back cover or visit www.ti.com
PT4120 Series
20-W 48-V Input Isolated
DC/DC Converter
Specifications
(Unless otherwise stated, T
a
=25C, V
in
=48V, C
out
=0F, and I
o
=I
o
max)
PT4120 SERIES
Characteristic
Symbol
Conditions
Min
Typ
Max
Units
Output Current
I
o
Over V
in
range
V
o
= 15V
0.1
(1)
--
1.3
V
o
= 12V
0.1
(1)
--
1.6
A
V
o
=5.0V
0.1
(1)
--
4.0
V
o
3.3V
0.1
(1)
--
5.0
Input Voltage Range
V
in
Over I
o
Range
36.0
48.0
75.0
VDC
Set Point Voltage Tolerance
V
o
tol
V
o
5.0V
--
1
1.5
%V
o
V
o
3.3V
--
--
50
mV
Temperature Variation
Reg
temp
40
T
a
+85C
--
0.5
--
%V
o
Line Regulation
Reg
line
Over V
in
range
V
o
5.0V
--
0.2
1.0
%V
o
V
o
3.3V
--
7
33
mV
Load Regulation
Reg
load
Over I
o
range
Vo
5.0V
--
0.4
1.0
%V
o
V
o
3.3V
--
13
33
mV
Total Output Voltage Variation
V
o
tot
Includes set-point, line load,
V
o
5.0V
--
2
--
%V
o
40
T
a
+85C
V
o
3.3V
--
67
--
mV
Efficiency
V
o
= 15V
--
86
--
V
o
= 12V
--
83
--
V
o
=5.0V
--
82
--
%
V
o
=3.3V
--
78
--
V
o
=1.8V
--
67
--
V
o
Ripple (pk-pk)
V
r
20MHz bandwidth
V
o
5.0V
--
0.5
--
%V
o
V
o
3.3V
--
15
--
mV
pp
Transient Response
t
tr
0.1A/s, load step 50% to 100% I
o
max
--
100
--
s
V
tr
V
o
over/undershoot
V
o
5.0V
--
3.0
--
%V
o
V
o
3.3V
--
150
--
mV
Short Circuit Current
I
sc
--
2xI
o
max
--
A
Switching Frequency
s
Over V
in
range
V
o
12.0V
600
650
700
kHz
V
o
5.2V
800
850
900
Under-Voltage Lockout
UVLO
--
31
--
V
Remote On/Off (Pin 1)
Referenced to Vin (pin 2)
Input High Voltage
V
IH
2.5
--
7.0
(2)
V
Input Low Voltage
V
IL
0.2
--
+0.8
Input Low Current
I
IL
--
10
A
Standby Input Current
I
in
standby
pins 1 & 2 connected
--
7
50
mA
Internal Input Capacitance
C
in
--
0.5
--
F
External Output Capacitance
C
out
Between +V
o
and V
o
0
--
200
F
Isolation Voltage
Input to output
1500
--
--
V
Capacitance
--
1100
--
pF
Resistance
10
--
--
M
Operating Temperature Range
T
a
Over V
in
range
-40
--
+85
(3)
C
Storage Temperature
T
s
--
-40
--
+125
C
Reliability
MTBF
Per Bellcore TR-332
4.0
--
--
10
6
Hrs
50% stress, T
a
=40C, ground benign
Mechanical Shock
--
Per Mil-Std-883D, method 2002.3,
--
500
--
G's
1mS, half-sine, mounted to a fixture
Mechanical Vibration
--
Per Mil-Std-883D, method 2007.2,
--
15
--
G's
20-2000Hz, soldered in a PC board
Weight
--
--
--
23
--
grams
Flammability
--
Materials meet UL 94V-0
Notes:
(1) The DC/DC converter will operate at no load with reduced specifications.
(2) The Remote On/Off (pin 1) has an internal pull-up, and if it is left open circuit the PT4120 will operate when input power is applied. Refer to the
application notes for interface considerations.
(3) See Safe Operating Area curves or contact the factory for the appropriate derating.
For technical support and more information, see inside back cover or visit www.ti.com
Note A:
Characteristic data has been developed from actual products tested at 25C. This data is considered typical data for the Converter.
Note B:
SOA curves represent the conditions at which internal components are at or below the manufacturer's maximum operating temperatures
Typical Characteristics
PT4120 Series
20-W 48-V Input Isolated
DC/DC Converter
PT4122, 5.0 VDC
(See Note A)
Efficiency vs Output Current
Efficiency vs Output Current
Ripple vs Output Current
Ripple vs Output Current
Safe Operating Area, V
in
=48V
(See Note B)
Power Dissipation vs Output Current
Power Dissipation vs Output Current
PT4121, 3.3 VDC
(See Note A)
PT4123, 12.0 VDC
(See Note A)
Efficiency vs Output Current
Ripple vs Output Current
Power Dissipation vs Output Current
50
60
70
80
90
0
1
2
3
4
5
Iout (A)
Efficiency - %
36.0V
48.0V
75.0V
V
in
0
2
4
6
8
10
12
0
1
2
3
4
5
Iout (A)
Ripple - mV
75.0V
48.0V
36.0V
V
in
0
1
2
3
4
5
6
0
1
2
3
4
5
Iout (A)
Pd - Watts
75.0V
48.0V
36.0V
V
in
50
55
60
65
70
75
80
85
90
0
0.5
1
1.5
2
2.5
3
3.5
4
Iout (A)
Efficiency - %
36.0V
48.0V
75.0V
V
in
0
2
4
6
8
10
12
14
16
0
0.5
1
1.5
2
2.5
3
3.5
4
Iout (A)
Ripple - mV
75.0V
48.0V
36.0V
V
in
0
1
2
3
4
5
6
0
0.5
1
1.5
2
2.5
3
3.5
4
Iout (A)
Pd - Watts
75.0V
48.0V
36.0V
V
in
50
55
60
65
70
75
80
85
90
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Iout (A)
Efficiency - %
36.0V
48.0V
75.0V
V
in
0
10
20
30
40
50
60
70
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Iout (A)
Ripple - mV
75.0V
48.0V
36.0V
V
in
0
1
2
3
4
5
6
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Iout (A)
Pd - Watts
75.0V
48.0V
36.0V
V
in
Safe Operating Area, V
in
=48V
(See Note B)
Safe Operating Area, V
in
=48V
(See Note B)
20
30
40
50
60
70
80
90
0
1
2
3
4
5
Iout (A)
Ambient Temperature (C)
200LFM
120LFM
60LFM
Nat conv
Airflow
20
30
40
50
60
70
80
90
0
1
2
3
4
Iout (A)
Ambient Temperature (
C)
200LFM
120LFM
60LFM
Nat conv
Airflow
20
30
40
50
60
70
80
90
0
0.25
0.5
0.75
1
1.25
1.5
1.75
Iout (A)
Ambient Temperature (
C)
200LFM
120LFM
60LFM
Nat conv
Airflow
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
Using the Remote On/Off Function on the PT4120/
PT4140 Series of Isolated DC/DC Converters
For applications requiring output voltage on/off control,
the PT4120/4140 series of DC/DC converters incorporate
a remote on/off function. This function may be used in
applications that require battery conservation, power-up/
shutdown sequencing, and/or to co-ordinate the power-
up of the regulator for active in-rush current control. (See
the related application note, AN21).
This function is provided by the Remote On/Off control,
pin1. If pin 1 is left open-circuit, the converter provides a
regulated output whenever a valid source voltage
3
is ap-
plied between +V
in
(pin 3), and V
in
(pin 2). Applying a
low-level ground signal
1
to pin 1 will disable the regula-
tor output
5
.
Table 1 provides details of the threshold requirements for
the Remote On/Off pin. Figure 1 shows how a discrete
MOSFET (Q
1
)
4
, may be referenced to the negative input
voltage rail and used with this control input.
Table 1 Inhibit Control Thresholds
Parameter
min
max
Enable (V
IH
)
2.5V
(Open Circuit)
2, 4
Disable (V
IL
)
0.3V
0.8V
Notes:
1. The on/off control uses -V
in
(pin 2), the primary side of
the converter as its ground reference. All voltages specified
are with respect to -V
in
.
2. The on/off control internal circuitry is a high impedance
10
A current source. The open-circuit voltage may be as
high as 8.3Vdc.
3. The PT4120/40 series incorporates an "Under Voltage
Lockout" (UVLO) function. This function automatically
inhibits the converter output until there is sufficient input
voltage for the converter to produce a regulated output.
Table 2 gives the applicable UVLO thresholds.
Table 2 UVLO Thresholds
Series
UVLO Threshold
V
in
Range
PT4120
31V Typical
36 75V
PT4140
15V Typical
18 40V
4. The Remote On/Off input of the PT4120/40 series regulators
must be controlled with an open-collector (or open-drain)
discrete transistor or MOSFET.
Do not
use a pull-up resistor.
5. When the converter output is disabled, the current drawn
from the input supply is typically reduced to 8mA (16mA
maximum).
Figure 1
Turn-On Time:
The converter typically produces a fully
regulated output voltage within 50ms after the applica-
tion of power, or the removal of the low voltage signal
6
from the Remote On/Off pin. The actual turn-on time
will vary with the input voltage, output load, and the
total amount of capacitance connected to the output.
Using the circuit of Figure 1, Figure 2 shows the output
voltage and input current waveforms of a PT4121 after
Q
1
is turned off. The turn off of Q
1
corresponds to the
drop in Q
1
V
gs
voltage. The waveforms were measured
with a 48Vdc input voltage, and 2.75-A resistive load.
Figure 2
+V
in
V
in
+V
o
V
o
PT4121
+Vout
V out
+V in
V in
Remote
On/Off
V
o
(adj)
1
2
3
5
4
6
Q 1
B S S 1 3 8
Inh
Note 2
PT4120/4140 Series
Vout (2V/Div)
Iin (0.2A/Div)
Q1 Vgs (10V/Div)
HORIZ. SCALE: 5ms/Div
6. Keep the on/off transition to less than 1ms. This prevents
erratic operation of the ISR, whereby the output voltage
may drift un-regulated between 0V and the rated output
during power-up.
Application Notes
For technical support and more information, see inside back cover or visit www.ti.com
Adjusting the Output Voltage of the PT4120/
PT4140 Series of Isolated DC/DC Converters
The factory pre-set output voltage of Power Trends'
PT4120 and PT4140 series of isolated DC/DC converters
may be adjusted within 10% of nominal. Adjustment is
made from the secondary side of the regulator
1
with a
single external resistor. For the input voltage range
specified in the data sheet Table 1 gives the allowable
adjustment range for each model, as V
o
(min) and V
o
(max).
Adjust Up:
An increase in the output voltage is obtained
by adding a resistor, R
2
between pin 6 (V
o
adjust), and pin
4 (-V
out
).
Adjust Down:
Add a resistor
(R
1
)
, between pin 6 (V
o
ad-
just) and pin 5 (+V
out
).
Refer to Figure 1 and Table 2 for both the placement
and value of the required resistor,
(R
1
)
or R
2
.
Notes:
1. The PT4120 and PT4140 series of DC/DC converters
incorporate isolation between the V
in
and V
o
terminals.
Adjustment of the output voltage is made to the
regulation circuit on the secondary or output side of
the converter.
2. The maximum rated output power for this series is
20W. An increase in the output voltage may therefore
require a corresponding reduction in the maximum
output current (
see Table 1
). The revised maximum
output current must be determined as follows:-
I
o
(max)
=
20
A,
or 5A, whichever is less.
V
a
Where V
a
is the adjusted ouput voltage.
3. Use only a single 1% resistor in either the
(R
1
)
or R
2
location. Place the resistor as close to the ISR as possible.
Table 1
DC/DC CONVERTER ADJUSTMENT RANGE AND FORMULA PARAMETERS
Series Pt #
48V Bus
PT4126
PT4129
PT4127
PT4128
PT4121
PT4122
PT4125
PT4123
PT4124
24V Bus
PT4146
PT4147
PT4148
PT4141
PT4142
PT4143
PT4144
Max Current
2
5A
5A
5A
5A
5A
4A
3.8A
1.6A
1.3A
V
o
(nom)
1.5
1.65
1.8
2.5
3.3
5.0
5.2V
12.0
15.0
Va(min)
1.35
1.49
1.62
2.25
2.95
4.5
4.75
10.8
13.5
Va(max)
1.65
1.81
1.98
2.75
3.65
5.5
5.75
13.2
16.5
V
r
1.225
1.225
1.225
1.225
1.225
2.5
2.5
2.5
2.5
K
o
(Vk
)
67.07
63.9
69.7
64.2
69.3
125.2
134.7
139.8
137.6
R
s
(k
)
43.2
66.5
110.0
187.0
187.0
187.0
243.0
110.0
90.9
Figure 1
( R 1 )
Adj Down
R 2
Adj
U p
+ V
in
V
in
+ V
o
V
o
P T 4 1 2 0 / 4 0
+V out
V out
+V in
V in
Remote
On/Off
V
o
(adj)
1
2
3
5
4
6
4. Never connect capacitors to V
o
adjust. Any capacitance
added to the V
o
adjust control pin will affect the stability of
the ISR.
The values of
(R
1
)
[adjust down], and R
2
[adjust up], can also
be calculated using the following formulas.
(R
1
)
=
K
o
(V
a
V
r
)
R
s
k
V
r
(V
o
V
a
)
R
2
=
K
o
R
s
k
(V
a
V
o
)
Where V
o
= Original output voltage
V
a
= Adjusted output voltage
V
r
= Reference voltage (Table 1)
K
o
= Multiplier constant (Table 1)
R
s
= Internal series resistance (Table 1)
PT4120/4140 Series
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