TI PT4474A

PT4474—24V
100-W 20-A Programmable
Isolated DC/DC Converter
SLTS106C
(Revised 6/21/2002)
Features
• 18V to 36V Input Voltage Range
• Programmable Output Voltage
Range: 4.6V to 5.7V
• -40° to +85°C Ambient
• 1500 VDC Isolation
• 90% Efficiency
• On/Off Inhibit
• Differential Remote Sense
• 40A Output with PT4494
•
•
•
•
•
•
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
Description
Ordering Information
Pin-Out Information
The PT4474 Excalibur™ DC/DC
converter module combines state-of-theart power conversion technology with
un-paralleled flexibility. Incorporating
high efficiency and ultra-fast transient
response, these modules provide up to
20A of output current over the programmable voltage range of 4.6V to 5.7V.
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 additional output current, one
PT4474 may be operated with up to two
PT4494 compatible booster modules.
Each PT4494 adds an additional 20A of
output current capability.
PT4474o = 4.6 to 5.7 Volts
PT4494o = 20-A Booster
Pin
PT Series Suffix (PT1234 x )
Case/Pin
Configuration
Order
Suffix
Package
Code *
N
A
C
Vertical
Horizontal
SMD
(EKD)
(EKA)
(EKC)
* Previously known as package styles 1200,
1210, and 1215.
(Reference the applicable package code drawing for the dimensions and PC board layout)
Function
Pin
Function
1
+Vin
14
–Vout
2
–Vin
15
–Vout
3
Inhibit
16
–Vout
4
Vr †
17
–Vout
5
Va †
18
–Vout
6
Do not connect
19
–Vout
7
(+)Remote Sense
20
(–)Remote Sense
8
+Vout
21
Do not connect
9
+Vout
22
VID1
10 +Vout
23
VID2
11 +Vout
24
VID3
12 +Vout
25
VID4
13 +Vout
26
DRV †
† Pins 4, 5, & 26 are used for booster applications. For
stand-alone operation, leave open circuit.
• Shaded functions indicate those pins that are
referenced to primary-side potential.
Standard Application
+ V IN
1
2
+
C1
C2
+ V in
– V in
Inhibit
3
+ V OUT
7
+ V sns
+ V out 8-13
PT4474
-V out
VID1 - VID4
22 23 24 25
-V sns
• Co = Optional 150µF electrolytic capacitor
14-19
L
O
A
D
+
Co
20
– V IN
– V OUT
PROGRAMMING PINS
For technical support and more information, see inside back cover or visit www.ti.com
• C1 = Optional 33µF, 50V electrolytic capacitor
• C2 = Optional 1µF, 50V ceramic capacitor
• Programming pins, VID1–VID4, are shown
configured for Vo =5.0V
• For normal operation, pin 3 (Inhibit) must be
connected to –Vin.
PT4474—24V
100-W 20-A Programmable
Isolated DC/DC Converter
PT4470 Series Comparison
Programming Information
VID3 VID2 VID1
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
VID4=1
Vout
VID4=0
Vout
5.00V
5.10V
5.20V
5.30V
5.40V
5.50V
5.60V
5.70V
4.60V
4.65V
4.70V
4.75V
4.80V
4.85V
4.90V
4.95V
Logic 0 = Connect to (–)Remote Sense, pin 20
Logic 1 = Open circuit (no pull-up resistors)
VID4 must not be changed while the unit is operating.
Functionality
Output Voltage
Program Range
Configuration for
Current Sharing
PT4471
Regulator
1.3V– 3.5V
N+1 with other PT4471s
PT4472
Regulator
1.3V– 3.5V
With PT4495 boosters
PT4495
PT4472 Booster
N/A
Used only with PT4472
PT4473
Regulator
4.6V–5.7V
N+1 with other PT4473s
# PT4474
Regulator
4.6V–5.7V
With PT4494 boosters
# PT4494
PT4474 Booster
N/A
Used only with PT4474
PT4475
Regulator
6.5V– 17.5V
N+1 with other PT4475s
PT4476
Regulator
6.5V–17.5V
With PT4493 boosters
PT4493
PT4476 Booster
N/A
Used only with PT4476
# This specification covers only the PT4474 regulator and PT4494 current booster.
Specifications
(Unless otherwise stated, Ta =25°C, V in =24V, Vo =5V, C o =0µF, and Io =Iomax)
Characteristic
Symbol
Conditions
Min
PT4474
Typ
Max
Units
Output Current
Input Voltage Range
Set Point Voltage Tolerance
Temperature Variation
Line Regulation
Load Regulation
Total Output Voltage Variation
Io
Vin
Vo tol
Regtemp
Regline
Regload
∆Votot
Over Vin range
Over Io Range
0
18
—
—
—
—
—
24
±1
±0.5
±0.1
±0.5
20
36
±1.5
—
±1
±1
A
VDC
%Vo
%Vo
%Vo
%Vo
—
±2
±3
%Vo
Efficiency
Vo Ripple (pk-pk)
Transient Response
η
Vr
ttr
∆Vtr
—
—
—
—
—
—
90
60
N/A
1
75
±6
—
75
—
—
—
—
%
mVpp
µs
%Vo
µs
%Vo
Current Limit
Ilim
—
25
—
A
Current Share Tolerance
Over-Voltage Protection
Switching Frequency
Under-Voltage Lockout
Inhibit (Pin 3)
Input High Voltage
Input Low Voltage
Input Low Current
Ishr tol
OVP
ƒs
UVLO
—
—
270
—
±10
125
300
17
—
—
350
—
%
%Vo
kHz
V
2.5
–0.5
—
—
—
0
1500
—
10
-40
—
-40
—
—
–0.2
4
3
—
—
1100
—
—
120
—
Open (1)
+0.8
—
10
—
10,000
—
—
—
+115 (2)
—
+125
V
mA
mA
µF
µF
V
pF
MΩ
°C
°C
°C
1.4
—
—
106 Hrs
—
500
—
G’s
—
20 (3)
—
G’s
—
90
—
grams
Standby Input Current
Internal Input Capacitance
External Output Capacitance
Isolation Voltage
Capacitance
Resistance
Operating Temperature Range
Over-Temperature Shutdown
Storage Temperature
Reliability
VIH
VIL
IIL
Iin standby
Cin
Cout
Tc
OTP
Ts
MTBF
Mechanical Shock
—
Mechanical Vibration
—
Weight
Flammability
—
—
–40° ≤Tcase ≤ +100°C, Io =0
Over Vin range
Over Io range
Includes set-point, line, load,
–40° ≤Tcase ≤ +100°C
Io =15A
20MHz bandwidth
0.1A/µs load step, 50% to 75% Iomax
Vo over/undershoot
1A/µs load step, 50% to 100% Iomax
Vo over/undershoot
Vin =18V, ∆Vo = –1%
foldback continuous limit
with PT4494 booster
Shutdown and latch off
Over Vin range
Referenced to –Vin (pin 2)
pins 3 & 2 connected
Between +Vo and –Vo
Input–output/input–case
Input to output
Input to output
Case temperature, over Vin range
Case temperature, auto reset
—
Per Bellcore TR-332
50% stress, Ta =40°C, ground benign
Per Mil-Std-883D, method 2002.3,
1mS, half-sine, mounted to a fixture
Mil-Std-883D, Method 2007.2
Horizontal
20-2000Hz, pcb mounted
—
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
Typical Characteristics
PT4474—24V
100-W 20-A Programmable
Isolated DC/DC Converter
Performance Characteristics, Vo =5V (See Note A)
Safe Operating Area, Vin =24V
Efficiency vs Output Current
(See Note B)
Stand Alone, No Heatsink
100
90
Efficiency - %
VIN
80
18.0V
24.0V
36.0V
70
60
Ambient Temperature (°C)
80
90
Airflow
70
300LFM
200LFM
100LFM
Nat conv
60
50
40
30
50
20
0
4
8
12
16
20
0
Iout (A)
4
8
12
16
Iout (A)
Ripple vs Output Current
100
80
Ripple - mV
VIN
60
18.0V
24.0V
36.0V
40
20
0
0
4
8
12
16
20
Iout (A)
Power Dissipation vs Output Current
14
12
Pd - Watts
10
VIN
8
18.0V
24.0V
36.0V
6
4
2
0
0
4
8
12
16
20
Iout (A)
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
For technical support and more information, see inside back cover or visit www.ti.com
20
Application Notes
PT4474, PT4494
Increasing the Output Current of the PT4474
with the PT4494 Compatible Current Booster
Notes:
1. Refer to the PT4474 specification table for the
performance of the regulator/booster combination.
The PT4494 is a 20-A “Current Booster” module
designed specifically for the PT4474 programmable
DC/DC converter. The booster is controlled directly
by the regulator, and effectively adds an additional
output stage that operates in parallel. This allows
the system to run sychronously, providing a low
noise solution. Up to two booster modules can be
connected to a PT4474 converter. Each booster
module increases the available output current by
20A. A combination of one PT4474 converter and
two PT4494 booster modules can supply up to 60A
of output current; enough to supply a large multiprocessor system. Figure 1-1 shows the connection
schematic for the regulator and current booster
combination.
2. The pin-out of the current booster modules include a
number pins identified, “Do not connect” (see Table 1-1).
These pins are not connected internally to the module
but must be soldered to a pad to preserve the unit’s
mechanical integrity.
3. A minimum of 150µF of output capacitance is required
across the output of each PT4494 booster for proper
operation. A value greater than 150µF will further
reduce transients due to large and/or fast load steps.
4. The converter and all boosters must be located on
the same printed circuit board. A similar footprint
and trace layout for each module will also facilitate
current sharing.
Table 1-1; Booster Pin-Out Information
A current booster is not a stand-alone product, and
can only operate with a regulator. It is housed in
the same package as its compatible regulator, and
shares the same mechanical outline. Except for an
increase in output current, the overall performance
of a converter/booster combination is identical to
that of a stand-alone converter.
Pin Function
Pin Function
Pin Function
1
+Vin
10 +Vout
19 –Vout
2
–V in
11 +Vout
20 (–)Vsense
3
4
Do not connect
Vr
12 +Vout
13 +Vout
21 Do not connect
22 Do not connect
5
Va
14 –Vout
23 Do not connect
6
Do not connect
15 –Vout
24 Do not connect
7
8
Do not connect
+V out
16 –Vout
17 –Vout
25 Do not connect
26 DRV
9
+V out
18 –Vout
Figure 1-1; Current Booster Application Schematic
PROGRAMMING PINS
VID1
VID2
VID3
VID4
REMOTE SENSE (+)
25
+VIN
Inhibit
1
CIN
33µF
Optional
+
24
23
7
22
PT4474
2
3
4 5 26
20
+VOUT
8 - 13
14-19
COUT
150µF
Optional
+
LOAD
-VOUT
–VIN
REMOTE SENSE (-)
4 5 26
1
CIN
33µF
Optional
+
20
PT4494
2
8 - 13
COUT
150µF
Required 3
14 - 19
+
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
PT4470, PT4480 Series
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 overvoltage (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.
For technical support and more information, see inside back cover or visit www.ti.com
Over-Temperature Protection
Over-temperature protection is provided by an internal
temperature sensor, which closely monitors the temperature 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 converters are production tested to a primary-secondary
withstand voltage of 1500VDC. This specification complies 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 specifications). The recommended direction for airflow is into
the longest side of the module’s metal case. See Figure 1.
Figure 1
Recommended direction for airflow is
into (perpendicular to) the longest side.
Application Notes
PT4470, PT4480 Series
Using the Inhibit Function on the PT4470 &
PT4480 Series of Isolated DC/DC Converters
The PT4470/44480 series of DC/DC converters incorporate 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 application 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)
Disable (VIL)
–0.5V
2.5V
0.8V
(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.
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.
Figure 2-1
+V IN
1
+
2
+V in
– V in
C1
1 =Enable
7
+V sns
+V out 8 - 1 3
Inhibit
3
PT4472
VID0 - VID4
21 22 23 24 25
+2.5V
-Vout 1 4 - 1 9
-Vsns
20
0V
Q1
BSS138
PROGRAMMING PINS
–V IN
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 Q 1 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
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
PT4470
PT4480
17.0V Typical
34.5V Typical
Vout (1V/Div)
Iin (2A/Div)
Vin Range
18 – 36V
36 – 75V
4. The Inhibit input must be controlled with an opencollector (or open-drain) discrete transistor or
MOSFET. Do not use a pull-up resistor.
Vinh (5V/Div)
HORIZ SCALE: 5ms/Div
5. When the converter output is disabled, the current
drawn from the input supply is typically reduced to
4mA (10mA maximum).
For technical support and more information, see inside back cover or visit www.ti.com
PACKAGE OPTION ADDENDUM
www.ti.com
18-Oct-2005
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
PT4474A
ACTIVE
SIP MOD
ULE
EKA
26
6
TBD
Call TI
Level-1-215C-UNLIM
PT4474C
ACTIVE
SIP MOD
ULE
EKC
26
6
TBD
Call TI
Level-3-215C-168HRS
Lead/Ball Finish
MSL Peak Temp (3)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS) or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
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Addendum-Page 1
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