PTB48520WAH [TI]
25-A, 48-V INPUT ISOLATED DC/DC CONVERTER WITH AUTO-TRACK⢠SEQUENCING; 25 -A ， 48 V的输入隔离DC / DC ，支持自动TrackA的?? ¢测序转换器
| 型号： | PTB48520WAH |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 25-A, 48-V INPUT ISOLATED DC/DC CONVERTER WITH AUTO-TRACK⢠SEQUENCING |
| 文件： | 总18页 (文件大小：433K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
25-A, 48-V INPUT ISOLATED DC/DC CONVERTER
WITH AUTO-TRACK™ SEQUENCING
FEATURES
APPLICATIONS
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3.3-V Intermediate Bus Architectures
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Input Voltage: 36 V to 75 V
25-A Total Output Current
91% Efficiency
Wide-Adjust Output Voltage: 1.8 V to 3.6 V
Overcurrent Protection
Output Overvoltage Protection
Overtemperature Shutdown
Output Enable Control
Auto-Track Compatible Sequenced Output
Smart-Sense Remote Sensing
Undervoltage Lockout
Industry Standard Size
Surface Mountable
1500-Vdc Isolation
Agency Approvals (Pending):
UL/cUL 60950, EN 60950
Telecom, High-End Computing Platforms
Multi-Rail Power Systems with
Power-Up Sequencing
DESCRIPTION
The PTB48520W is a 25-A rated, 48-V input isolated dc/dc converter that incorporates Auto-Track™ power-up
sequencing. This allows these modules to simultaneously power up with any other downstream non-isolated,
Auto-Track compliant module.
The PTB48520W module provides two outputs, each regulated to the same voltage. During power up, the
voltage at Vo Bus rises first, allowing this output to provide input power to any downstream non-isolated module.
The voltage from Vo Seq is then allowed to rise simultaneously, under the control of Auto-Track, along with the
outputs from the downstream modules.
Whether used to facilitate power-up sequencing, or operated as a stand-alone module, the PTB48520W includes
many features expected of high-performance dc/dc converter modules. The wide output adjust enables the
output voltage to be set to to any voltage over the range, 1.8 V to 3.6 V, using a single external resistor. Precise
output voltage regulation is ensured with a differential remote sense that intelligently regulates the sequenced
output, depending on its sequence status. Other operational features include an input undervoltage lockout
(UVLO) and an output enable control. Overcurrent, overvoltage, and overtemperature protection ensures the
module ability to survive any load fault.
Typical applications include distributed power architectures in both telecom and computing environments,
particularly complex digital systems requiring power sequencing of multiple power supply rails.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Auto-Track is a trademark of Texas Instruments.
PRODUCTION DATA information is current as of publication date.
Copyright © 2004–2005, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
These devices have limited built-in ESD protection. The leads should be shorted together or the device
placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
Typical Circuit
Simultaneous Power Up
V1
V2
4
Track
PTB48520W
8
+Sense
V1 = 3.3 V
10
9
+V
I
V Seq
O
1
2
+V
I
V Bus
O
2
7
Track
V Enable
O
V Adjust
O
V2 = 1.8 V
3
6
PTH03050W
V
I
V
O
5
6
R
887 W
SET
COM
V
O
Inhibit GND Adjust
4
1
5
C1
100 mF
C2
100 mF
−V
I
3
−V
I
−Sense
R1
5.49 kW
ORDERING INFORMATION
PTB48520 (Basic Model)
(1)
Output Voltage
1.8 V to 3.6 V
1.8 V to 3.6 V
Part Number
DESCRIPTION
Package Ref.
PTB48520WAH
PTB48520WAS
Horizontal T/H
ERP
ERQ
(2)
SMD, Standard
(1) See the applicable package reference drawing for the dimensions and PC board layout.
(2) Standard option specifies 63/37, Sn/Pb pin solder material.
ABSOLUTE MAXIMUM RATINGS
UNIT
V(Track)
Track input voltage
0 V to VO Bus + 0.3 V
(1)
I(Track) max Track input current
From external source
10 mA
TA
Operating temperature range
Over VI range
–40°C to 85°C
115°C
Overtemperature protection
Solder reflow temperature
Storage temperature
PCB temperature (near pin 1)
Surface temperature of module or pins
(2)
T(reflow)
Tstg
235°C
–40°C to 125°C
(1) When the Track input is fed from an external voltage source, the input current must be limited. A 2.74-kΩ value series resistor is
recommended.
(2) During solder reflow of SMD package version, do not elevate the module PCB, pins, or internal component temperatures above a peak
of 235°C.
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PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
PACKAGE SPECIFICATIONS
PTB48520W (Suffixes AH and AS)
Weight
28.5 grams
Flammability
Meets UL94V-O
(1)
Horizontal T/H (Suffix AH)
Horizontal SMD (Suffix AS)
Horizontal T/H (Suffix AH)
Horizontal SMD (Suffix AS)
250 Gs
150 Gs
15 Gs
Per Mil-STD-883D, Method 2002.3
1 msec, 1/2 Sine, mounted
Mechanical shock
(1)
(1)
(1)
Mil-STD-883D, Method 2007.2
20-2000 Hz, PCB mounted
Mechanical vibration
5 Gs
(1) Qualification limit.
ELECTRICAL CHARACTERISTICS
(Unless otherwise stated, TA = 25°C, VI = 48 V, VO = 3.3 V, CO = 0 µF, and IO = IOmax)
PARAMETER
TEST CONDITIONS
MIN
0
TYP
MAX
UNIT
(1)
IO Bus
IO Seq
25
Over VI range
A
(1)(2)
IO
VI
Output current
0
10
Sum total IO Bus + IO Seq
Over IO range
0
25
75
A
V
Input voltage range
Set-point voltage tolerance
Temperature variation
Line regulation
36
48
(3)
±0.6
%Vo
%Vo
mV
mV
%Vo
V
-40°C ≤ TA ≤ 85°C
Over VI range
±0.8
±1
VO
Load regulation
Over IO range
±1
(3)
Total output voltage variation Includes set-point, line, load, –40°C ≤ TA≤ 85°C
±1.5
±3
Adjust range
Over VI range
1.8
3.6
RSET = 887 Ω, VO = 3.3 V
RSET = 6.98 kΩ, VO = 2.5 V
RSET = 35.7 kΩ, VO = 2.0 V
RSET = open cct. VO = 1.8 V
91%
90%
89%
88%
20
η
Efficiency
IO = 15 A
VO Ripple (peak-to-peak)
Transient Response
20 MHz bandwidth
mVpp
1 A/µs load step, 50% to 100% IOmax
Recovery time
75
±3
µs
%Vo
mA
V
VO over/undershoot
Input current
Pin connected to VO COM
-0.13
Vo Bus
1
Track input (pin 4)
Open-circuit voltage
Input slew rate limits
0
(4)
0.1
V/ms
Referenced to -VI (pin 3)
(5)
Input high voltage (VIH)
Input low voltage (VIL)
Input low current (IIL)
2
Open
Output enable input (pin 2)
V
-0.2
0.8
–480
2
µA
mA
mA
A
Standby input current
No-load input current
Pin 2 open
Pins 2 and 3 connected, IO Tot = 0
50
Overcurrent threshold, IO (tot) Shutdown, followed by autorecovery
40
(1) See temperature derating curves for safe operating area (SOA), or consult factory for appropriate derating.
(2) When load current is supplied from the VO Seq output, the module exhibits higher power dissipation and slightly lower operating
efficiency.
(3) The set-point voltage tolerance is affected by the tolerance and stability of RSET. The stated limit is unconditionally met if RSET has a
tolerance of 1%, with 100 ppm/°C temperature stability.
(4) When controlling the Track input from an external source, the slew rate of the applied signal must be greater than the minimum limit.
Failure to allow the voltage to completely rise to the voltage at the VO (bus) output, at no less than the minimum specified rate, may
thermally overstress the converter.
(5) The VO Enable input has an internal pull-up, and if left open the converter output isturned off. A discrete MOSFET or bipolar transistor is
recommended to control this input. The open-circuit voltage is approximately 20% of the input voltage. If the output enable feature is not
used, this pin should be permanently connected to –VI. See the application information for other interface considerations.
3
PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
ELECTRICAL CHARACTERISTICS (continued)
(Unless otherwise stated, TA = 25°C, VI = 48 V, VO = 3.3 V, CO = 0 µF, and IO = IOmax)
PARAMETER
TEST CONDITIONS
MIN
TYP
125
34
MAX
UNIT
%Vo
V
OVP
UVLO
ƒS
Output overvoltage protection Output shutdown and latch off
Undervoltage lockout
30
36
Switching frequency
Internal input capacitance
External output capacitance
Isolation voltage
Over VI range
225
275
3
325
kHz
µF
Between both outputs and VO COM
Input-output
0
5000
µF
1500
Vdc
pF
Isolation capacitance
Isolation resistance
Input-output
1000
Input-output
10
MΩ
Telcordia SR-332 50% stress, TA = 40°C,
ground benign
MTBF
Reliability
1.2
106 Hrs
TERMINAL FUNCTIONS
TERMINAL
NAME
DESCRIPTION
NO.
The positive input for the module with respect to –VI. When powering the module from a negative input voltage,
this input is connected to the input source ground.
+VI(1)
–VI(1)
1
The negative input supply for the module, and the 0-V reference for the VO Enable input. When powering the
module from a positive source, this input is connected to the input source return.
3
2
An open-collector (open-drain) negative logic input that is referenced to –VI. This input must be pulled to –VI
potential to enable the output voltage. A high impedance connection disables the module output. If the output
enable feature is not used, pin 2 should be permanently connected to –VI. The module then produces an output
whenever a valid input source is applied.
(1) (2)
VO Enable
VO Bus
Produces a positive power output with respect to VO COM. This is the main output from the converter when
operated in a stand-alone configuration. It is dc isolated from the input power pins and is the first output to rise
when the converter is either powered or enabled. In power-up sequencing applications, this output can provide
a 3.3-V standby source to power the downstream non-isolated modules.
9
This is the sequenced output voltage from the converter. This voltage can be directly controlled from the Track
pin. During power up, VO Seq rises with the Track pin voltage, typically 20 ms after the VO Bus output has
reached regulation.
VO Seq
10
5
This is the output power return for both the VO Bus and VO Seq output voltages. This node should be
connected to the load circuit common.
VO COM
The voltage at this pin directly controls the voltage VO Seq regulated output. It is primarily used to sequence
the voltage VO Seq with the regulated outputs from any downstream non-isolated modules that are powered
from the converter +VO Bus output. In these applications, the Track pin is simply connected to the track control
of each of the non-isolated modules. The Track pin has an internal transistor, which holds it at VO COM
potential for approximately 20 ms after the VO Bus output is in regulation. Following this delay, the Track
voltage and VO Seq rises simultaneously with the output voltage of all the non-isolated modules that are under
the control of Auto-Track.
Track
4
7
A resistor must be connected between this pin and –Sense to set the converter output voltage. A 0.05-W rated
resistor may be used, with tolerance and temperature stability of 1% and 100 ppm/°C, respectively. If this pin is
left open, the converter output voltage defaults to its lowest value. The specification table gives the preferred
resistor values for the popular bus voltages.
VO Adjust
The +Sense pin can be connected to either the VO Bus or VO Seq outputs. When connected to VO Seq, remote
sense compensation will be delayed until the power-up sequence is complete. The voltage at VO Bus is raised
slightly. The pin may be left open circuit, but connecting it to one of the output terminals improves load
regulation of that output.
+Sense
–Sense
8
6
Provides the converter with a remote sense capability when used with +Sense. For optimum output voltage
accuracy, this pin should always be connected to VO COM. This pin is also the reference connection for the
output voltage set-point resistor.
(1) These functions indicate signals electrically common with the input.
(2) Denotes negative logic: Low (–VI) = Normal operation, Open = Output off
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PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
TYPICAL CHARACTERISTICS
(1)
Characteristic Data; VI = 48 V
EFFICIENCY
vs
OUTPUT CURRENT (VO Bus)
OUTPUT VOLTAGE RIPPLE
vs
OUTPUT CURRENT (VO Bus)
50
40
30
20
100
V
= 2.5 V
O
V
= 3 V
O
90
80
70
V
= 2 V
O
V
= 1.8 V
O
V
= 2.5 V
O
V
= 3.3 V
O
10
0
60
50
V
= 2 V
O
V
= 1.8 V
O
0
5
I
10
15
20
25
0
5
10
15
20
25
I
− Output Current − A
− Output Current − A
O
O
Figure 1.
Figure 2.
POWER DISSIPATION
vs
OUTPUT CURRENT (VO Bus)
10
8
V
= 2 V
O
6
4
V
= 2.5 V
O
V
= 3.3 V
O
2
0
V
= 1.8 V
O
0
5
10
15
20
25
I
− Output Current − A
O
Figure 3.
(1) All data listed in Figure 1, Figure 2, and Figure 3 have been developed from actual products tested at 25°C. This data is considered
typical data for the dc-dc converter.
5
PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
TYPICAL CHARACTERISTICS (continued)
(2)
Safe Operating Areas; VI = 48 V
TEMPERATURE DERATING
vs
OUTPUT CURRENT (VO Bus)
TEMPERATURE DERATING
vs
OUTPUT CURRENT (VO Seq)
90
80
70
90
80
70
60
50
40
30
20
100 LFM
Nat Conv
400 LFM
60
200 LFM
50
100 LFM
Nat Conv
40
30
Airflow
Airflow
20
0
5
10
15
20
25
0
2
4
6
8
10
I
− Output Current − A
I
− Output Current − A
O
O
Figure 4.
Figure 5.
(2) The temperature derating curves represent operating conditions at which internal components are at or below manufacturer's maximum
rated operating temperature. See Figure 4 and Figure 5.
APPLICATION INFORMATION
Operating Features and System Considerations for the PTB48520W DC/DC Converter
Overcurrent Protection
To protect against load faults, these converters incorporate output overcurrent protection. Applying a load to the
output that exceeds the converter overcurrent threshold (see applicable specification) causes the output voltage
to momentarily fold back, and then shut down. Following shutdown, the module periodically attempts to
automatically recover by initiating a soft-start power up. This is often described as a hiccup mode of operation,
whereby the module continues in the cycle of successive shutdown and power up until the load fault is removed.
Once the fault is removed, the converter automatically recovers and returns to normal operation.
Output Overvoltage Protection
The converter continually monitors for an output overvoltage (OV) condition, directly across the +VO Bus output.
The OV threshold automatically tracks the output voltage set point to a level that is 25% higher than that set by
the external R(SET) voltage adjust resistor. If the output voltage exceeds this 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 can only be done by momentarily removing the input power to the converter. For fail-safe
operation and redundancy, the OV protection uses circuitry that is independent of the converter internal feedback
loop.
Differential Output Voltage Sense
A differential remote sense allows a converter regulation circuitry to compensate for limited amounts of IR drop,
that may be incurred between the converter and load, in either the positive or return PCB traces. Connecting the
(+)Sense and (–)Sense pins to the respective positive and ground reference of the load terminals improves the
load regulation of the converter output voltage at that connection point. The (–)Sense pin should always be
connected to the VO COM. The (+)Sense pin may be connected to either the +VO Bus or +VO Seq outputs.
When the (+)Sense pin is connected to the VO Seq output, the voltage at VO Bus voltage regulates slightly
6
PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
APPLICATION INFORMATION (continued)
higher. Depending on the load conditions on the VO Seq output, the voltage at VO Bus may be up to 100 mV
higher than the converter set-point voltage. In addition, the Smart-Sense feature (incorporated into the converter)
only engages sense compensation to the VO Seq output when that output voltage is close to the set point. During
other conditions, such as power-up and power-down sequencing events, the sense circuit automatically defaults
to sensing the VO Bus voltage, internal to the converter.
Leaving the (+)Sense and (–)Sense pins open does not damage the converter or load circuitry. The converter
includes default circuitry that keeps the output voltage in regulation. If the remote sense feature is not used, the
(–)Sense pin should always be connected to VO COM.
Note: The remote sense feature is not designed to compensate for the forward drop of nonlinear or frequency
dependent components that may be placed in series with the converter output. Examples include OR-ing diodes,
filter inductors, ferrite beads, and fuses. When these components are enclosed by the sense pin connections,
they are effectively placed inside the regulation control loop, which can adversely affect the stability of the
converter.
Overtemperature Protection
Overtemperature protection is provided by an internal temperature sensor, which monitors the temperature of the
converter PCB (close to pin 1). If the PCB temperature exceeds a nominal 115°C, the converter shuts down. The
converter then automatically restarts when the sensed temperature falls to approximately 105°C. When operated
outside its recommended thermal derating envelope (see data sheet derating curves), the converter typcially
cycles 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.
Undervoltage Lockout
The undervoltage lockout (UVLO) is designed to prevent the operation of the converter until the input voltage is
close to the minimum operating voltage. The converter is held off when the input voltage is below the UVLO
threshold, and turns on when the input voltage rises above the threshold. This prevents 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 converter meets full specifications when the minimum specified input voltage is reached.
The UVLO circuitry also overrides the operation of the VO Enable control. Only when the input voltage is above
the UVLO threshold is the VO Enable control functional.
Primary-Secondary Isolation
These converters incorporate electrical isolation between the input terminals (primary) and the output terminals
(secondary). All converters are tested to a withstand voltage of 1500 VDC. This complies with UL/cUL 60950 and
EN 60950 and the requirements for operational isolation. It allows the converter to be configured for either a
positive or negative input voltage source. The data sheet Terminal Functions table provides guidance as to the
correct reference that must be used for the external control signals.
Output Voltage Adjustment
The VO Adjust control sets the output voltages to a value higher than 1.8 V. For output voltages other than 1.8 V
a single external resistor, R(set), must be connected directly between VO Adjust (pin 7) and (–)Sense (pin 6) pins.
A 0.05-W rated resistor can be used. The tolerance should be 1%, with a temperature stability of 100 ppm/°C (or
better). Place the resistor close to the converter and connect it directly between pins 7 and 6 using dedicated
PCB traces (see typical application). Table 1 gives the preferred value of the external resistor for a number of
standard voltages, along with the actual output voltage that this resistance value provides.
For other output voltages the value of the required adjust resistor may be calculated using Equation 1.
1.225 V
R
+ 6.49 kW
* 4.42 kW
set
V
* 1.805 V
set
(1)
7
PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
Table 1. Standard Values of RSET for Common Output Voltages
VO (Required)
3.6 V
RSET (Standard Value)
VO (Actual)
3.604 V
3.303 V
2.503 V
2.003 V
1.805 V
0 Ω
3.3 V
887 Ω
6.98 kΩ
35.7 kΩ
Open
2.5 V
2.0 V
1.8 V
Input Current Limiting
The converter is not internally fused. For safety and overall system protection, the maximum input current to
the converter must be limited. Active or passive current limiting can be used. Passive current limiting can be a
fast-acting fuse. A 125-V fuse, rated no more than 10 A, is recommended. Active current limiting can be
implemented with a current limited Hot-Swap controller.
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 is determined from the safe operating area (SOA). The
SOA is the area beneath the applicable airflow rate curve on the graph of temperature derating vs output current.
(See Typical Characteristics.) Operating the converter within the SOA limits ensures that all the internal
components are at or below their stated maximum operating temperatures.
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PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
Using the Output Enable Control on the PTB48520 Auto-Track Compatible DC/DC Converter
The VO Enable (pin 2) control is an active low input that allows the output voltage from the converter to be turned
on and off while it is connected to the input source. The VO Enable input is referenced to the –VI (pin 3)(1), on the
primary side of the converter isolation, and has its own internal pullup. The open-circuit voltage is approximately
20% of the applied input source voltage.
For the converter to function normally, pin 2 must be pulled low to –VI potential(2). The converter output then
produces a regulated voltage whenever a valid source voltage is applied between +VI (pin 1) and –VI (pin 3)(3). If
the voltage at pin 2 is allowed to rise above VIH(min), (see specification table), the output from the converter is
turned off.
Figure 6 is an application schematic that shows the typical use of the Output Enable function. Note the discrete
transistor (Q1). Either a discrete MOSFET or bipolar transistor is recommended to control this input. Table 2
gives the threshold requirements.
When placed in Off state, the output neither sources or sinks output current. The load voltage then decays as the
output capacitance is discharged by the load circuit. With the output turned off, the current drawn from the input
source is typically reduced to 2 mA.
(1) The VO Enable control uses –VI (pin 3) as ground reference. All voltages are with respect to –VI.
(2) Use an open-collector (or open-drain) discrete transistor to control the VO Enable input. A pullup resistor is not necessary. To disable the
converter, the control pin should be pulled low to less than +0.8 V. If the Output Enable feature is not used, pin 2 should be permanently
connected to –VI (pin 3).
(3) The converter incorporates a UVLO. The UVLO does not allow the converter to power up until the input voltage is close to its minimum
specified operating voltage. This is regardless of the state of the Output Enable control. Consult the specifications for the UVLO
thresholds.
Table 2. Output Enable Control Requirements(1)
PARAMETER
MIN TYP
MAX
UNIT
V
VIH
2
VIL
0.8
15
V
VO/C [Open-Circuit]
II [pin 1 at –Vin]
V
–0.8
mA
(1) The VO Enable control uses –VI (pin 3) as its ground reference. All voltages are with respect to –VI.
4
Track
PTB48520W
8
+Sense
10
V Seq
+V
1
2
O
I
+V
I
9
V Bus
O
1 = Enable
7
V Enable
O
V Adjust
O
L
O
A
D
R2
887 W
Q1
BSS138
R1
10 kW
5
6
COM
V
O
3
−V
I
−V
I
−Sense
Figure 6. Output Enable Operation
Turn-On Time: In the circuit of Figure 6, turning Q1 off allows the voltage at pin 2 to rise to its internal pullup
voltage. This disables the converter output. When Q1 is then turned on, it applies a low-level voltage to pin 2,
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PTB48520W
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SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
and enables the output of the converter. The converter produces a regulated output voltage within 50 ms.
Figure 7 shows the output response of the converter after Q1 is turned on. The turnon of Q1 corresponds to the
drop in the Q1 Vds waveform. Although the output voltage rise time is short (<10 ms), the indicated delay time
(td) varies depending on the input voltage and the module’s internal timing. The output voltage of the module was
set to 3.3 V. The waveforms were measured with 48-Vdc input voltage and a 10-A resistive load.
V Bus (1 V/div)
O
I (0.5 A/div)
I
t
d
Q1 V (10 V/div)
ds
t − 5 ms/div
Figure 7. Output Enable Power-Up Characteristic
Sequenced Power Up with POL Modules
Overview
The dc/dc converter has two outputs, VO Seq and VO Bus. VO Bus is the main output from the converter. VO Seq
is an output that is derived from VO Bus and can be sequenced with other supply voltages during power up. Both
outputs are regulated to the same set-point voltage, except that the rise in the VO Seq output is controlled by the
pin called Track, and delayed during power-up events. The delay allows the converter to both power and
sequence with one or more non-isolated, 3.3-V input, Auto-Track compatible modules1. The rise of all output
voltages is coordinated using a control signal common to the Track inputs of all Auto-Track compliant modules.
The hold-off delay built into the PTB48520W holds the track control signal low to comply with the power-up
requirements of the downstream non-isolated modules.
Auto-Track Features
Figure 8 shows a block diagram of the converter Auto-Track features. During power up, VO Bus (pin 9) rises
promptly, whenever the converter is connected to a valid input source and its output is enabled. VO Seq (pin 10)
is the Auto-Track compatible output that is derived from VO Bus but controlled by the voltage presented at the
Track input (pin 4). The control relationship is on a volt-for-volt basis, and is active from 0 V up to a voltage just
below the VO Bus output. Between these two limits, the voltage at VO Seq follows that at the Track input. Once
the Track input is at the VO Bus voltage, raising it higher has no further effect. The voltage at VO Seq cannot go
higher than VO Bus, and if connected to +Sense (pin 8), then regulates at the set-point voltage.2
The control relationship between VO Seq and the Track input is the same as other Auto-Track compatible
outputs, across all module types. By connecting the Track input of the converter to the Track inputs of other
Auto-Track modules, all the associated output voltages can be made to follow the same rising control voltage
during power-up transitions.3 A suitable rising voltage is produced by the Track input internal R-C time constant.
An external ramp waveform4, 5 may also be used.
10
PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
The Track input of the dc/dc converter includes a pullup resistor (RTRK) to VO Bus, and a 1-µF capacitor (CTRK) to
VO COM. This enables the Track input to rise automatically once the internal MOSFET turns off. In sequencing
applications, the non-isolated modules are powered by the VO Bus output. The internal MOSFET holds the Track
voltage at ground for 20 ms after the VO Bus output is in regulation. This gives the non-isolated modules time to
initialize so that their outputs can rise with the VO Seq output.
V Bus
O
Smart Sense
To Feedback
Error Amplifier
+Sense
V Seq
O
−
+
R
(TRK)
24.9 kW
Track
C
(TRK)
1 mF
Supply
Supervisor
20-ms
Delay
COM
V
O
Figure 8. Block Diagram of Auto-Track Features
Notes:
1. Auto-Track compatible modules incorporate a Track input that can take direct control of the output voltage
during power-up transistions. The control relationship is on a volt-for-volt basis and is active between the 0 V
and the module's set-point voltage. Once the Track input is above the set-point voltage, the module remains
at its set point. Connecting the Track input of a number of such modules together allows their outputs to
follow a common control voltage during power up.
2. When +Sense (pin 8) is connected to the Vo Seq output (pin 10), the Vo Seq output is tightly regulated to the
set-point voltage. In this configuration, the voltage at the VO Bus output (pin 9) is up to 100 mV higher.
3. The VO Seq output cannot sink load current. This constraint does not allow the module to coordinate a
sequenced power down.
4. The slew rate for the Track input signal must be between 0.1 V/ms and 1 V/ms. Above this range, the Vo Seq
output may no longer accurately follow the Track input voltage. A slew rate below this range may thermally
stress the converter. These slew rate limits are met whenever the Track input voltage is controlled by the
internal R-C time constant of the modules being sequenced.
5. Whenever an external voltage is used to control the Track input, the source current must be limited. A
resistance value of 2.74-kΩ is recommended for this purpose. This is necessary to protect the internal
transistor to the converter's Track control input. This transistor holds the track control voltage at ground
potential for 20 ms after the VO Bus output is in regulation.
11
PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
Typical Power-Up Sequencing Configuration
Figure 10 shows how the converter (U1) can be configured to provide two 3.3-V sources, that allow it to both
power and sequence with one or more non-isolated POL modules. The example shows two PTH03050W
modules (U2 and U3), each rated for up 6 A of output current. Additional voltages, as well as modules with a
higher output current capability can also be specified to meet a specific application. The number of downstream
modules, their respective output voltage and load current rating is only limited by the amount of current available
at the VO Bus output. This is 25 A, less the current allocated to the load circuit via the VO Seq output.
The output voltage adjust range is 1.8 V to 3.6 V, which is compatible with the 3.3-V input non-isolated POL
modules. In these applications, the output voltage must always be set to 3.3 V (R1 = 887 Ω). Note that this sets
the output voltage of both the VO Bus and VO Seq outputs. The 3.3-V input non-isolated modules, U2 and U3,
can be set to any voltage over the range, 0.8 V to 2.5 V. In this example, they are set to 2.5 V (R2 = 2.21 kΩ)
and 1.8 V (R3 = 5.49 kΩ), respectively. Figure 9 shows the power-up waveforms from Figure 10 when the Track
control input to all three modules are simply connected together.
The converter provides input power to the downstream non-isolated modules via the VO Bus output. This output
rises first to allow the downstream modules to complete their power-up initialization. VO Seq (3.3 V), and the
outputs V(POL)1 (2.5 V) and V(POL)2 (1.8 V), supply the load circuit. These three outputs are controlled by the track
control voltage, which the converter holds at ground potential for 20 ms. When the track control voltage is finally
allowed to rise, the three outputs rise simultaneously to their respective set-point voltages.
V Bus (1 V/div)
O
V Seq (1 V/div)
O
V 1 (1 V/div)
(POL)
V 2 (1 V/div)
(POL)
t = 20 ms
d
t − 20 ms/div
Figure 9. Power-Up Waveforms with POL Modules
12
PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
U1
4
8
Track
PTB48520W
V SEQ (3.3 V)
O
+Sense
2
U2
3
10
9
Track
V Seq
O
+V
I
1
2
V 1 (2.5 V)
(POL)
+V
I
6
PTH03050W
V Bus
O
V
I
V
O
7
Inhibit GND Adjust
V Enable
V Adjust
O
O
C3
100 mF
4
1
5
C1
100 mF
R2
2.21 kW
R1
887 W
5
6
COM
V
O
−V
I
3
−V
I
−Sense
2
U3
3
Track
PTH03050W
V 2 (1.8 V)
(POL)
6
V
I
V
O
Inhibit GND Adjust
C4
100 mF
4
1
5
C2
100 mF
R3
5.49 kW
Figure 10. Power-Up Sequencing With Non-Isolated POL Modules
Stand-Alone Operation
The wide output voltage adjust range makes the PTB48520W an attractive product as a stand-alone dc/dc
converter. In these applications, it is not required to power up or sequence with any non-isolated POL modules.
The output voltage can be adjusted to any value over the range, 1.8 V to 3.6 V, and the Auto-Track features
simply disregarded.
Figure 11 shows the recommended configuration when the module is used as a stand-alone converter. In this
case, a sequenced output voltage is not required, and the main output (VO Bus) can be used to supply the load.
Both the Track pin and the VO Seq output are simply left open circuit. The (+)Sense pin is connected to the VO
Bus output for improved load regulation.
When the converter is operated in this mode, the output from VO Bus rises promptly on power up. The converter
also exhibits slightly less power dissipation along with a corresponding improvement in operating efficiency.
13
PTB48520W
www.ti.com
SLTS233A–NOVEMBER 2004–REVISED APRIL 2005
4
Track
PTB48520W
8
+Sense
10
9
V Seq
1
O
+V
I
+V
I
V Bus
O
L
O
A
D
7
C1
100 mF
V Adjust
O
2
3
V Enable
O
R
Set
5
6
COM
V
O
−V
I
−V
I
−Sense
Figure 11. Stand-Alone Configuration
14
PACKAGE OPTION ADDENDUM
www.ti.com
20-Jul-2012
PACKAGING INFORMATION
Status (1)
Eco Plan (2)
Pb-Free (RoHS)
TBD
MSL Peak Temp (3)
Samples
Orderable Device
Package Type Package
Drawing
Pins
Package Qty
Lead/
Ball Finish
(Requires Login)
PTB48520WAH
PTB48520WAS
PTB48520WAZ
NRND
NRND
NRND
Through-
ERP
ERQ
ERQ
10
10
10
9
9
9
SN
N / A for Pkg Type
Hole Module
Surface
SNPB
Level-1-235C-UNLIM/
Level-3-260C-168HRS
Mount Module
Surface
Pb-Free (RoHS)
SNAGCU Level-3-260C-168 HR
Mount Module
(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), Pb-Free (RoHS Exempt), 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.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
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.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
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相关型号：
PTB48540CAZ
IC 1-OUTPUT 10 W DC-DC REG PWR SUPPLY MODULE, ROHS COMPLIANT, PACKAGE-13, Power Supply Module
TI
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