For technical support and more information, see inside back cover or visit www.ti.com
Standard Application
Features
•36V to 75V Input Voltage Range
•Programmable Output Voltage
Range: 1.3V to 3.5V
•-40° to +85°C Ambient
•1500 VDC Isolation
•89% Efficiency
•On/Off Inhibit
•Differential Remote Sense
•N+1 Current Sharing
SLTS024C
(Revised 6/20/2002)
Description
The PT4481 Excalibur™ DC/DC
converter module combines state-of-the-
art power conversion technology with
un-paralleled flexibility. Incorporating
high efficiency and ultra-fast transient
response, these modules provide up to
30A of output current over the program-
mable voltage range of 1.3V to 3.5V.
This represents a full 100W output at
3.3V.
The modules include a number of
inbuilt features to facilitate system
integration. These include a foldback
output current limit, over-temperature
protection, and an inhibit on/off control.
A differential remote sense is also provided
to compensate for voltage drop between
the converter and load.
For applications requiring power
supply redundancy, multiple PT4481
modules may connected for operation in
an ‘N+1’ configuration. Each PT4481
connected will share the load current with
other active PT4481 modules.
•Over-Current Protection
•Over-Temperature Protection
•Over-Voltage Protection
•Space-Saving Package
•Solderable Copper Case
•Safety Approvals:
UL 60950
CSA 22.2 950
VDE EN60950 Pending
L
O
A
D
PT4481
+V
sns
+V
out
-V
out
-V
sns
7
8-13
14-19
202522 2423
VID0 - VID4
+V
in
–V
in
1
2
3
Inhibit
C
1
+
PROGRAMMING PINS
+V
OUT
+V
IN
–V
IN
–V
OUT
C
o
+
21
C
2
•C
o = Optional 330µF electrolytic capacitor
•C
1 = Optional 33µF, 100V electrolytic capacitor
•C
2 = Optional 1µF, 100V ceramic capacitor
• Programming pins, VID0–VID4, are shown
configured for Vo =3.3V
• For normal operation, pin 3 (Inhibit) must be
connected to –Vin.
• For details on additional N+1 components
consult the related application note.
Ordering Information
PT4481o = 1.3 to 3.5 Volts
PT Series Suffix (PT1234x)
Case/Pin Order Package
Configuration Suffix Code *
Vertical N(EKD)
Horizontal A(EKA)
SMD C(EKC)
* Previously known as package styles 1200,
1210, and 1215.
(Reference the applicable package code draw-
ing for the dimensions and PC board layout)
Pin-Out Information
Pin Function
1+V
in
2–V
in
3 Inhibit
4 Do not connect
5 Do not connect
6 Sync †
7 (+)Remote Sense
8 +Vout
9+V
out
10 +Vout
11 +Vout
12 +Vout
13 +Vout
Pin Function
14 –Vout
15 –Vout
16 –Vout
17 –Vout
18 –Vout
19 –Vout
20 (–)Remote Sense
21 VID0
22 VID1
23 VID2
24 VID3
25 VID4
26 Share †
PT4481—48V
100-W 30-A Programmable
Isolated DC/ DC Converter
† Pins 6 & 26 are used for N+1 configuration (see
related application note). For stand-alone
operation, leave open circuit.
• Shaded functions indicate those pins that are
referenced to primary-side potential.
For technical support and more information, see inside back cover or visit www.ti.com
PT4480 Series Comparison
Output Voltage Configuration for
Functionality Program Range Current Sharing
PT4481 Regulator 1.3V– 3.5V N+1 with other PT4481s
PT4482 Regulator 1.3V– 3.5V With PT4499 boosters
PT4499 PT4482 Booster N/A Used only with PT4482
PT4483 Regulator 4.6V–5.7V N+1 with other PT4483s
PT4484 Regulator 4.6V–5.7V With PT4498 boosters
PT4498 PT4484 Booster N/A Used only with PT4484
PT4485 Regulator 6.5V– 17.5V N+1 with other PT4485s
PT4486 Regulator 6.5V–17.5V With PT4497 boosters
PT4497 PT4486 Booster N/A Used only with PT4486
PT4481—48V
100-W 30-A Programmable
Isolated DC/ DC Converter
Programming Information
VID4=1 VID4=0
VID3 VID2 VID1 VID0 Vout Vout
1 1 1 1 2.0V 1.30V
1 1 1 0 2.1V 1.35V
1 1 0 1 2.2V 1.40V
1 1 0 0 2.3V 1.45V
1 0 1 1 2.4V 1.50V
1 0 1 0 2.5V 1.55V
1 0 0 1 2.6V 1.60V
1 0 0 0 2.7V 1.65V
0 1 1 1 2.8V 1.70V
0 1 1 0 2.9V 1.75V
0 1 0 1 3.0V 1.80V
0 1 0 0 3.1V 1.85V
0 0 1 1 3.2V 1.90V
0 0 1 0 3.3V 1.95V
0 0 0 1 3.4V 2.00V
0 0 0 0 3.5V 2.05V
Logic 0 = Connect to (–)Remote Sense, pin 20
Logic 1 = Open circuit (no pull-up resistors)
VID3 & VID4 must not be changed while unit is operating
# This specification covers only the PT4481 regulator.
Specifications (Unless otherwise stated, Ta =25°C, Vin =48V, Vo =3.3V, Co =0µF, and Io =Iomax)
PT4481
Characteristic Symbol Conditions Min Typ Max Units
Output Current IoOver Vin range 0 — 30 A
Input Voltage Range Vin Over Io Range 36 48 75 VDC
Set Point Voltage Tolerance Vo tol — ±1 ±1.5 %Vo
Temperature Variation Regtemp –40° ≤Tcase ≤ +100°C, Io =0 — ±0.5 — %Vo
Line Regulation Regline Over Vin range — ±0.1 ±1 %Vo
Load Regulation Regload Over Io range — ±0.2 ±1 %Vo
Total Output Voltage Variation ∆Votot Includes set-point, line, load, —±2±3%V
o
–40° ≤Tcase ≤ +100°C
Efficiency ηIo =15A Vo =3.3V — 89 —
Vo =2.5V — 87 — %
Vo =1.5V — 81 —
Vo Ripple (pk-pk) Vr20MHz bandwidth Vo >2V — 60 75 mVpp
Vo ≤2V — 45 55
Transient Response ttr 0.1A/µs load step, 50% to 75% Iomax — N/A — µs
∆Vtr Vo over/undershoot — 1 — %Vo
1A/µs load step, 50% to 100% Iomax — 75 — µs
Vo over/undershoot — ±5 — %Vo
Current Limit Ilim Vin =36V, ∆Vo = –1% —35—A
foldback continuous limit
Current Share Tolerance Ishr tol With other PT4481 modules in N+1 — ±10 — %
Over-Voltage Protection OVP Shutdown and latch off — 125 — %Vo
Switching Frequency ƒsOver Vin range 270 300 350 kHz
Under-Voltage Lockout UVLO — 34.5 — V
Inhibit (Pin 3) Referenced to –Vin (pin 2)
Input High Voltage VIH 2.5 — Open (1) V
Input Low Voltage VIL –0.5 — +0.8
Input Low Current IIL — –0.2 — mA
Standby Input Current Iin standby pins 3 & 2 connected — 4 10 mA
Internal Input Capacitance Cin —3 —µF
External Output Capacitance Cout Between +Vo and –Vo0 — 10,000 µF
Isolation Voltage Input–output/input–case 1500 — — V
Capacitance Input to output — 1100 — pF
Resistance Input to output 10 — — MΩ
Operating Temperature Range T
cCase temperature, over Vin range -40 — +115 (2) °C
Over-Temperature Shutdown OTP Case temperature, auto reset — 120 — °C
Storage Temperature Ts— -40 — +125 °C
Reliability MTBF Per Bellcore TR-332 1.4 — — 106 Hrs
50% stress, Ta =40°C, ground benign
Mechanical Shock — Per Mil-Std-883D, method 2002.3, — 500 — G’s
1mS, half-sine, mounted to a fixture
Mechanical Vibration — Mil-Std-883D, Method 2007.2 Suffixes A, C — 20 (3) —G’s
20-2000Hz, pcb mounted
Weight — — — 90 — grams
Flammability — Materials meet UL 94V-0
Notes: (1) The Inhibit (pin 3) has an internal pull-up, which if left open circuit allows the converter to operate when input power is applied. The open-circuit is
limited to 6.5V. Refer to the application notes for interface considerations.
(2) See Safe Operating Area curves or contact the factory for the appropriate derating.
(3) The case pins on through-hole pin configuration (suffix A) must be soldered. For more information see the applicable package outline drawing.
#
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 25°C. 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
Efficiency vs Output Current
Ripple vs Output Current
Power Dissipation vs Output Current
Typical Characteristics
PT4481—48V
100-W 30-A Programmable
Isolated DC/ DC Converter
Stand Alone, No Heatsink
Safe Operating Area, Vin =48V (See Note B)Performance Characteristics, Vo =3.3V (See Note A)
20
30
40
50
60
70
80
90
0 5 10 15 20 25 30
Iout
(
A
)
Ambient Temperature (°C
)
500LFM
400LFM
300LFM
200LFM
100LFM
Nat conv
Airflow
50
60
70
80
90
100
0 5 10 15 20 25 30
Iout
(
A
)
Efficiency - %
48.0V
75.0V
36.0V
VIN
0
20
40
60
80
100
0 5 10 15 20 25 30
Iout
(
A
)
Ripple - mV
75.0V
48.0V
36.0V
VIN
0
4
8
12
16
20
0 5 10 15 20 25 30
Iout
(
A
)
Pd - Watts
36.0V
75.0V
48.0V
VIN
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
PT4481
Configuring PT4481 DC/DC Converters
for N+1 Operation
‘N+1’ vs OR’ing
The PT4481 DC/DC converter modules may be
operated with other PT4481 modules in ‘N+1’
configurations. A simple OR’ing connection allows
a number of converters to share the load current. An
‘N+1’ configuration adds redundancy by employing
at least one more converter than is necessary to
supply the load. This ensures that upon the loss of
one converter, sufficient capacity remains to supply
the load without interruption. As an example, a 45-A
load configured for ‘N+1’ would require no less than
three PT4481 converters. Two are needed to meet
the load demand, plus one additional converter to
ensure redundancy. Figure 1-1 shows the schematic
for operating two PT4481 converters in an ‘N+1’
configuration for a 25-A load application.
Blocking Diodes
A true ‘N+1’ redundant system must also protect the
output bus against fault current back-feeding a con-
verter. Without a blocking diode, a converter will sink
current as a result of a fault at its output, or due to the
loss of its input source. The blocking diodes 4, (D1
PT4481
PT4481
1
2
8–13
20
7
REMOTE SENSE (+)
REMOTE SENSE (–)
PROGRAMMING PINS
3
C
OUT
, 330µF
(Required)
+
18–13
14–19
25 24 23 22 21
14–19
2
626
20626
7
REMOTE SENSE (+)
2122232425
3
PROGRAMMING PINS
D
2
, OR'ing Diode
(Required)
–V
IN
+V
IN
25-A
LOAD
Inhibit
–V
OUT
+V
OUT
+V
IN
–V
IN
+V
OUT
–V
OUT
VID4 – VID0 +Sns
–SnsShareSyncInhibit
–SnsShareSyncInhibit
+Sns
+V
IN
–V
IN
+V
OUT
–V
OUT
VID4 – VID0
C
IN
+
C
IN
+
D
1
, OR'ing Diode
(Required)
F1
F2
C
OUT
, 330µF
(Required)
+
Figure 1-1; Connection Schematic for Operation in Parallel/N+1 Configuration
& D2 in Figure 1-1), protect against reverse current
flow under such conditions.
Notes
1. For ‘N+1’ redundancy, always use one more
converter than is required to supply the load.
2. The VID pins for all converter modules must be
independently set to the same voltage program code.
3. All converters connected for ‘N+1’ operation
must be located on the same printed circuit
board. A similar footprint and trace layout for
each converter will facilitate current sharing.
4 A number of high-current rectifier diodes are
available with a low forward voltage drop. They
are specifically designed for OR’ing applications
in ‘N+1’ systems. Eg. The 82CNQ030, and
MBRB2515.
5. As a result of excess capacity and the losses in the
blocking diodes, system efficiency is reduced.
6. The interconnection of pin 6 (Sync), and pin 26
(Share) between all modules are required for load
current sharing and operation at a common
frequency.
Application Notes
For technical support and more information, see inside back cover or visit www.ti.com
Operating Features of the PT4470 and PT4480
Series of Isolated DC/DC Converters
Under-Voltage Lockout
An Under-Voltage Lock-Out (UVLO) inhibits the
operation of the converter until the input voltage is
above the UVLO threshold (see the applicable data
sheet specification). Below this voltage, the module’s
output is held off, irrespective of the state of the Inhibit
control (pin 3). If the Inhibit control is connected to –Vin
(pin 2), the module will automatically power up when
the input voltage rises above the UVLO threshold. The
UVLO allows the module to produce a clean transition
during both power-up and power-down, even when the
input voltage is rising or falling slowly. It also reduces
the high start-up current during normal power-up of
the converter, and minimizes the current drain from the
input source during low-input voltage conditions. The
UVLO threshold includes about 2V of hysteresis. Once
operational, the converter will conform to its operating
specifications when the minimum specified input voltage
is reached.
Over-Current Protection
To protect against load faults, the PT4470/80 series of
DC/DC converters incorporate an output current limit.
Once the load current drawn from the module reaches
the current limit threshold, any attempt by the load to
draw additional current will result in a significant drop
in the module’s regulated output voltage. The current
limit circuitry incorporates a limited amount of foldback.
This has the effect of slightly reducing the output current
from the module when supplying an absolute short circuit.
Upon removal of the load fault, the output voltage from
the converter will automatically recover to its programmed
regulation voltage.
Output Over-Voltage Protection
The PT4470/80 series of DC/DC converters incorporate
circuitry that continually senses the output for an over-
voltage (OV) condition. The OV threshold automatically
tracks the VID output voltage program setting to a level
25% higher than that programmed at the control pins,
VID0 through VID4. If the converter output voltage
exceeds the OV threshold, the converter is immediately
shut down and remains in a latched-off state. To resume
normal operation the converter must be actively reset.
This is accomplished by either cycling the status of the
Inhibit control (pin 3) from “On” to “Off” and then back
“On” again, or by momentarily removing the input power
to the converter. For failsafe operation and redundancy,
the OV protection uses circuitry that is independent of
the converter’s internal feedback loop.
Over-Temperature Protection
Over-temperature protection is provided by an internal
temperature sensor, which closely monitors the tempera-
ture of the converter’s metal case. If the case temperature
exceeds the specified limit (see applicable data sheet),
the converter will shut down. The converter will then
automatically restart when the sensed temperature drops
by about 10°C. When operated outside its recommended
thermal derating envelope (see data sheet SOA curves),
the converter will typcially cycle on and off at intervals
from a few seconds to one or two minutes. This is to ensure
that the internal components are not permanently damaged
from excessive thermal stress.
Primary-Secondary Isolation
Electrical isolation is provided between the input terminals
(primary) and the output terminals (secondary). All con-
verters are production tested to a primary-secondary
withstand voltage of 1500VDC. This specification com-
plies with UL60950 and EN60950 and the requirements
for operational isolation. Operational isolation allows
these converters to be configured for either a positive or
negative input voltage source. The data sheet ‘Pin-Out
Information’ uses shading to indicate which pins are
associated with the primary. They include pins 1 through
5, inclusive.
Fuse Recommendations
If desired, an input fuse may be added to protect against
the application of a reverse input voltage.
Thermal Considerations
Airflow may be necessary to ensure that the module can
supply the desired load current in environments with
elevated ambient temperatures. The required airflow
rate may be determined from the Safe Operating Area
(SOA) thermal derating chart (see converter specifica-
tions). The recommended direction for airflow is into
the longest side of the module’s metal case. See Figure 1.
Recommended direction for airflow is
into (perpendicular to) the longest side.
Figure 1
PT4470, PT4480 Series
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
Using the Inhibit Function on the PT4470 &
PT4480 Series of Isolated DC/DC Converters
The PT4470/44480 series of DC/DC converters incor-
porate an On/Off Inhibit function. This function may be
used in applications that demand battery conservation,
power-up/shutdown sequencing, and/or to coordinate
power-up for active in-rush current control.
The On/Off feature is provided by the Inhibit control,
pin 3. The Inhibit pin of the PT4470/4480 series of
converters is an active low enable. The pin must be
either connected, or actively pulled low, to –Vin (pin 2)
to enable the converter output (see standard applica-
tion schematic). When pins 2 & 3 are connected, the
converter provides a regulated output whenever a valid
source voltage3 is applied between +Vin (pin 1), and –Vin
(pin 2). If pin 3 is disconnected, or allowed to become
high impedance, the regulator output will be disabled. 5
Table 2-1 provides details of the interface requirements
for the Inhibit pin. Figure 2-1 shows how a discrete
MOSFET (Q1) 4, may be referenced to –Vin and used to
control the input.
Table 2-1 Inhibit Control Requirements
Parameter Min Max
Enable (VIH) –0.5V 0.8V
Disable (VIL) 2.5V (Open Circuit)
Notes:
1.
The Inhibit control uses –Vin (pin 2), on the primary side
of the converter, as its ground reference. All voltages
specified are with respect to –Vin.
2. The internal circuitry is simple pull-up resistor. The
open-circuit voltage may be as high as 6.5Vdc.
3. These converters incorporate an “Under-Voltage
Lockout” (UVLO) function. This function automatically
disables the converter output until there is sufficient input
voltage to produce a regulated output. Table 2 gives the
applicable UVLO thresholds.
Table 2-2 UVLO Thresholds 1
Series UVLO Threshold Vin Range
PT4470 17.0V Typical 18 – 36V
PT4480 34.5V Typical 36 – 75V
4.
The Inhibit input 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
4mA (10mA maximum).
Figure 2-1
Turn-On Time: With input power applied, the converter
typically produces a fully regulated output voltage within
25ms after applying a low-voltage signal to the Inhibit
control 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 2-1, Figure 2-2 shows the typical output voltage
and input current waveforms of a PT4472 after Q1 is
turned on. The turn on of Q1 correlates to the fall in
Vinh. The output voltage was set to 2.5V. The waveform
was measured with a 48-Vdc input voltage, and 15-A load
current.
Figure 2-2
PT4470, PT4480 Series
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.
Vout (1V/Div)
Iin (2A/Div)
Vinh (5V/Div)
HORIZ SCALE: 5ms/Div
PT4472
+V
sns
+V
out
-V
out
-V
sns
7
8-13
14-19
2021 2522 2423
VID0 - VID4
+V
in
–V
in
1
2
3
Inhibit
C
1
+
PROGRAMMING PINS
+2.5V
+V
IN
–V
IN
0V
1 =Enable
Q
1
BSS138
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