PT3404A [TI]
IC 1-OUTPUT 24 W DC-DC REG PWR SUPPLY MODULE, Power Supply Module;
| 型号： | PT3404A |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | IC 1-OUTPUT 24 W DC-DC REG PWR SUPPLY MODULE, Power Supply Module 转换器 |
| 文件： | 总13页 (文件大小：284K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
PT3400 Series
35-W 48-V Input Isolated
DC/DC Converter
SLTS164B - JULY 2002 - REVISED OCTOBER 2002
Features
• Input Voltage Range:
36V to 75V
• Differential Remote Sense
• Over-Current Protection
• Space Saving Package
• Solderable Copper Case
• Safety Approvals Pending
• 35W Output Power
• 90% Efficiency
• 1500 VDC Isolation
• Low Profile (8 mm)
• Adjustable Output Voltage
• Dual-Logic On/Off Enable
• Power-Up Sequence Control
Description
Ordering Information
Pin-Out Information
Pin Function
PT3401r = 3.3V/10A (33W)
PT3402r = 2.5V/12A (30W)
The PT3400 Excalibur™ power modules
are a series of 35-W rated DC/DC converters
housed in a low-profile space-saving copper
case. Fully isolated for telecom applications,
the series includes a number of standard volt-
ages, including 1.0 VDC. Other applications
include industrial, high-end computing, and
other distributed power applications that
require input-to-output isolation.
PT3400 modules incorporate a feature
that simplifies the design of multiple voltage
power supplies in DSP and ASIC applications.
Using the SEQ control pin, the output voltage
of two PT3400 modules in a power supply
system can be made to self sequence at power-
up. Other features include output voltage
adjust, over-current protection, input under-
voltage lockout, and a differential remote
sense to compensate for any voltage drop
between the converter and load.
1
2
3
4
5
6
7
8
9
EN 1
EN 2*
–Vin
PT3403r = 1.8V/12A (21.6W)
PT3404r = 1.5V/16A (24W)
PT3405r = 1.4V/16A (22.4W)
PT3406r = 1.2V/16A (19.2W)
PT3407r = 1V/16A (16W)
+Vin
SEQ
PT3408r = 5V/7A
(35W)
Vout Adj
–Vsense
–Vout
–Vout
PT Series Suffix
(PT1234x)
Case/Pin
Order
Package
10 –Vout
11 +Vout
12 +Vout
13 +Vout
14 +Vsense
Configuration
Suffix
Code
Vertical
Horizontal
SMD
N
A
C
(EPL)
(EPM)
(EPN)
(Reference the applicable package code draw-
ing for the dimensions and PC board layout)
* Negative logic
Shaded functions indicate those
pins that are referenced to –Vin
.
Standard Application
Remote Sense (+)
+VOUT
14
+VIN
+VSENSE
4
+VIN
11–13
+VOUT
+
L
O
A
D
1
EN 1
† COUT
330µF
PT3400
2
EN 2
–VIN
–VOUT
8–10
7
–VOUT
–VIN
* Remote Sense (–)
3
–VSENSE
Vo Adj
SEQ
5
†
*
An output capacitor is required on models
with an output voltage less than 2.5V.
6
VO Adj
SEQ
–Vsense (pin 7) must be connected to -Vout
either at the load or directly to pin 8 of the
converter.
,
For technical support and more information, see inside back cover or visit www.ti.com
PT3400 Series
35-W 48-V Input Isolated
DC/DC Converter
SLTS164B - JULY 2002 - REVISED OCTOBER 2002
Specifications (Unless otherwise stated, Ta =25°C, Vin =48V, Cin =0µF, Io =Iomax, and Cout as required)
PT3400 Series
Characteristic
Symbol
Conditions
Min
Typ
Max
Units
Output Current
Io
Over Vin range
Vo ≤1.5V
Vo = 1.8V/2.5V
Vo =3.3V
0
0
0
0
—
—
—
—
16
12
10
7
A
Vo = 5V
Input Voltage Range
Set Point Voltage Tolerance
Temperature Variation
Line Regulation
Vin
Over Io Range
36
—
—
—
—
—
—
48
1
0.8
5
5
1
75
2
VDC
%Vo
%Vo
mV
mV
mV
Vo tol
Regtemp
Regline
–40° ≤Ta ≤ +85°C, Io =Iomin
Over Vin range
—
20
15
15
10
Vo =5.0V
Vo ≤3.3V
Vo =5.0V
Vo ≤3.3V
(1)
(1)
Load Regulation
Regload
Over Io range
1
mV
Total Output Voltage Variation
Efficiency
∆Votot
Includes set-point, line, load,
—
2
3
%Vo
–40° ≤Ta ≤ +85°C
η
Io =70% of Iomax
Vo = 5V
Vo =3.3V
Vo =2.5V
Vo =1.8V
Vo =1.5V
Vo =1.4V
Vo =1.2V
Vo = 1V
—
—
—
—
—
—
—
—
91
90
89
85
84
84
82
80
—
—
—
—
—
—
—
—
%
Vo Ripple (pk-pk)
Vr
20MHz bandwidth
Vo ≥3.3V
Vo ≤2.5V
—
—
50
25
—
—
mVpp
Transient Response
ttr
∆Vtr
Vadj
0.1A/µs load step, 50% to 75% Iomax
Vo over/undershoot
—
—
–5
–0
100
4
—
—
—
—
µs
%Vo
Output Adjust
Vo ≥2.5V
Vo ≤1.8V
+5
%Vo
+10
Over-Current Threshold
ITRIP
Vin =36V
Vo =5.0V
Vo =3.3V
—
—
—
—
9
—
—
—
—
12.5
16
20
Vo = 2.5V/1.8V
Vo ≤1.5V
A
Switching
Under-Voltage Lockout
Frequencyƒs
Over Vin range
250
—
—
300
34
32
350
—
—
kHz
V
UVLO
Rising
Falling
Enable On/Off (Pins 1, 2)
Input High Voltage
Referenced to –Vin (pin 3)
(2)
VIH
VIL
5
—
—
Open
+0.4
V
Input Low Voltage
–0.3
Input Low Current
IIL
Iin
Cin
Cout
—
0.5
—
—
—
TBD
TBD
TBD
mA
5
µF
Standby Input Current
Internal Input Capacitance
External Output Capacitance
standbypins
1
&
3
connected
—
mA
—
1.0
(3)
(3)
Vo=1.0V
Vo≤1.8V
Vo≥2.5V
470
330
0
—
—
—
µF
Isolation Voltage
Capacitance
Resistance
Input–output/input–case
Input to output
1500
—
—
—
—
—
V
1500
—
pF
MΩ
Input to output
10
(4)
(5)
Operating Temperature Range
Solder Reflow Temperature
Storage Temperature
T
Treflow
T
s
Over Vin range
Surface temperature of module pins or case
—
–40
—
–40
—
—
—
85
°C
°C
°C
a
(6)
215
125
ReliabilityMTBF
Mechanical Shock
Mechanical Vibration
Per
Bellcore
TR-332
6
2.8
—
—
10 Hrs
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,
20-2000Hz, PCB mounted
—
TBD
—
G’s
(7)
(7)
Vertical
Horizontal
—
—
—
TBD
TBD
34
—
—
—
G’s
Weight
—
grams
Flammability—
Materials
meet
UL
94V-0
Notes: (1) If the remote sense feature is not being used, –Vsense (pin 7) must be connected to –Vout (pin 8).
(2) The On/Off Enable inputs (pins 1 & 2) have internal pull-ups. They may either be connected to –Vin or left open circuit. Leaving pin 1 open-circuit and
connecting pin 2 to –Vin allows the the converter to operate when input power is applied. The maximum open-circuit voltage of the Enable pins is 10V.
(3) An output capacitor is required for proper operation for all models in which the output voltage is 1.8VDC or less. For models with an output voltage of
2.5V or higher an output capacitor is optional.
(4) For operation below 0°C, Cout must have stable characteristics. Use low ESR tantalum capacitors, or capacitors with a polymer type dielectric.
(5) See Safe Operating Area curves or contact the factory for the appropriate derating.
(6) During reflow of SMD package version do not elevate the module case, pins, or internal component temperatures above a peak of 215°C. For further
guidance refer to the application note, “Reflow Soldering Requirements for Plug-in Surface Mount Products,” (SLTA051).
(7) The case pins on through-hole pin configurations (N & 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
PT3400 Series
35-W 48-V Input Isolated
DC/DC Converter
SLTS164B - JULY 2002 - REVISED OCTOBER 2002
PT3408, 5VDC (See Note A)
PT3401, 3.3 VDC (See Note A)
PT3402, 2.5 VDC (See Note A)
Efficiency vs Output Current
Efficiency vs Output Current
Efficiency vs Output Current
100
90
80
70
60
50
100
90
80
70
60
50
100
90
80
70
60
50
VIN
VIN
VIN
36.0V
48.0V
60.0V
75.0V
36.0V
48.0V
60.0V
75.0V
36.0V
48.0V
60.0V
75.0V
0
1
2
3
4
5
6
7
0
2
4
6
8
10
0
2
4
6
8
10
12
Iout (A)
Iout (A)
Iout (A)
Ripple vs Output Current
Ripple vs Output Current
Ripple vs Output Current
50
40
30
20
10
0
50
40
30
20
10
0
50
40
30
20
10
0
VIN
VIN
VIN
75.0V
60.0V
48.0V
36.0V
75.0V
60.0V
48.0V
36.0V
75.0V
60.0V
48.0V
36.0V
0
2
4
6
8
10
12
0
1
2
3
4
5
6
7
0
2
4
6
8
10
Iout (A)
Iout (A)
Iout (A)
Power Dissipation vs Output Current
Power Dissipation vs Output Current
Power Dissipation vs Output Current
6
5
4
3
2
1
0
6
5
4
3
2
1
0
6
5
4
3
2
1
0
VIN
VIN
VIN
75.0V
60.0V
48.0V
36.0V
75.0V
60.0V
48.0V
36.0V
75.0V
60.0V
48.0V
36.0V
0
1
2
3
4
5
6
7
0
2
4
6
8
10
0
2
4
6
8
10
12
Iout (A)
Iout (A)
Iout (A)
Safe Operating Area (See Note B)
PT3408; VIN =60V
Safe Operating Area (See Note B)
PT3401; VIN =60V
Safe Operating Area (See Note B)
PT3402; VIN =60V
90
80
70
60
50
40
30
20
90
80
70
60
50
40
30
20
90
80
70
60
50
40
30
20
Airflow
Airflow
Airflow
200LFM
120LFM
60LFM
200LFM
120LFM
60LFM
200LFM
120LFM
60LFM
Nat conv
Nat conv
Nat conv
0
1
2
3
4
5
6
7
0
2
4
6
8
10
0
2
4
6
8
10
12
Iout (A)
Iout (A)
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
Typical Characteristics
PT3400 Series
35-W 48-V Input Isolated
DC/DC Converter
SLTS164B - JULY 2002 - REVISED OCTOBER 2002
PT3403, 1.8 VDC (See Note A)
PT3404/5, 1.5/1.4 VDC (See Note A)
PT3406, 1.2 VDC (See Note A)
Efficiency vs Output Current
Efficiency vs Output Current
Efficiency vs Output Current
100
90
80
70
60
50
100
100
90
80
70
60
50
90
80
70
60
50
VIN
VIN
VIN
36.0V
48.0V
60.0V
75.0V
36.0V
48.0V
60.0V
75.0V
36.0V
48.0V
60.0V
75.0V
0
3
6
9
12
0
4
8
12
16
0
4
8
12
16
Iout (A)
Iout (A)
Iout (A)
Ripple vs Output Current
Ripple vs Output Current
Ripple vs Output Current
50
40
30
20
10
0
25
25
20
15
10
5
20
15
10
5
VIN
VIN
VIN
75.0V
60.0V
48.0V
36.0V
75.0V
60.0V
48.0V
36.0V
75.0V
60.0V
48.0V
36.0V
0
0
0
3
6
9
12
0
4
8
12
16
0
4
8
12
16
Iout (A)
Iout (A)
Iout (A)
Power Dissipation vs Output Current
Power Dissipation vs Output Current
Power Dissipation vs Output Current
6
5
4
3
2
1
0
6
5
4
3
2
1
0
6
5
4
3
2
1
0
VIN
VIN
VIN
75.0V
60.0V
48.0V
36.0V
75.0V
60.0V
48.0V
36.0V
75.0V
60.0V
48.0V
36.0V
0
4
8
12
16
0
3
6
9
12
0
4
8
12
16
Iout (A)
Iout (A)
Iout (A)
Safe Operating Area (See Note B)
PT3403; VIN =60V
Safe Operating Area (See Note B)
PT3404; VIN =60V
Safe Operating Area (See Note B)
PT3406; VIN =60V
90
80
70
60
50
40
30
20
90
80
70
60
50
40
30
20
90
80
70
60
50
40
30
20
Airflow
Airflow
Airflow
200LFM
120LFM
60LFM
200LFM
120LFM
60LFM
200LFM
120LFM
60LFM
Nat conv
Nat conv
Nat conv
0
2
4
6
8
10
12
0
4
8
12
16
0
4
8
12
16
Iout (A)
Iout (A)
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
Typical Characteristics
PT3400 Series
35-W 48-V Input Isolated
DC/DC Converter
SLTS164B - JULY 2002 - REVISED OCTOBER 2002
PT3407, 1.0 VDC (See Note A)
Efficiency vs Output Current
100
90
80
70
60
50
VIN
36V
48V
60V
75V
0
4
8
12
16
Iout (A)
Ripple vs Output Current
25
20
15
10
5
VIN
75V
60V
48V
36V
0
0
4
8
12
16
Iout (A)
Power Dissipation vs Output Current
6
5
4
3
2
1
0
VIN
75V
60V
48V
36V
0
4
8
12
16
Iout (A)
Safe Operating Area (See Note B)
PT3406; VIN =60V
90
80
70
60
50
40
30
20
Airflow
200LFM
120LFM
60LFM
Nat conv
0
4
8
12
16
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
Application Notes
PT3400 Series
Operating Features of the PT3400 Series
of Isolated DC/DC Converters
Under-Voltage Lockout
An Under-Voltage Lock-Out (UVLO) inhibits the opera-
tion of the converter until the input voltage is above the
UVLO threshold (see the data sheet specification). Below
this voltage, the module’s output is held off, irrespective
of the state of either the EN1 & EN2 enable controls.
The UVLO allows the module to produce a clean transi-
tion 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 1V of hysteresis.
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 5A, is
recommended. Active current limiting can be imple-
mented 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 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 1-1.
If EN2 (pin 2) is connected to -Vin (pin 3) and EN1 (pin 1)
is left open, the module will automatically power up when
the input voltage rises above the UVLO threshold (see
data sheet ‘Standard Application’ schematic). Once
operational, the converter will conform to its operating
specifications when the minimum specified input voltage
is reached.
Figure 1-1
Over-Current Protection
To protect against load faults, the PT3400 series incor-
porates output over-current protection. Applying a load
that exceeds the converter’s over-current threshold (see
applicable specification) will cause the regulated output
to shut down. Following shutdown the module will peri-
odically attempt 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 succesive shutdown and power up until the load
fault is removed. Once the fault is removed, the converter
then automatically recovers and returns to normal op-
eration.
Recommended direction for airflow is
into (perpendicular to) the longest side
Primary-Secondary Isolation
Electrical isolation is provided between the input termi-
nals (primary) and the output terminals (secondary). All
converters 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 4, inclusive.
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
PT3400 Series
Adjusting the Output Voltage of the 30W-Rated
PT3400 Series of Isolated DC/DC Converters
The output voltage of the PT3400 Excalibur™ series of
isolated DC/DC converters may be adjusted over a limited
range from the factory-trimmed nominal value. Adjust-
ment is accomplished with a single external resistor. The
placement the resistor determines the direction of adjust-
ment, either up or down, and the value of the resistor the
magnitude of adjustment. Table 3-1 gives the allowable
adjustment range for each model in the series as Va (min)
and Va (max) respectively. Note that converters with an
Notes:
1. The output voltage of the PT3401 (3.3V),
PT3402 (2.5V), and PT3408 (5V) may be adjusted either
higher or lower. All other models, which have an output
voltage of 1.8V or less, can only be adjusted higher.
2. Use only a single 1% resistor in either the R1 or (R2)
location. Place the resistor as close to the converter as
possible.
1
output voltage of 1.8V or less can only be adjusted up .
3. Never connect capacitors to Vo Adj. Any capacitance added
Adjust Up: An increase in the output voltage is obtained
by adding a resistor, R1 between Vo Adj (pin 6), and –Vsense
(pin 7).
to this pin will affect the stability of the converter.
4. If the output voltage is increased, the maximum load
current must be derated according to the following
equation.
Adjust Down (PT3401, PT3402, & PT3408 Only): Add a
resistor (R2), between Vo Adj (pin 6) and +Vsense (pin 14).
Vo × Io(rated)
Io(max)
=
Va
Refer to Figure 3-1 and Table 3-2 for both the placement and
value of the required resistor, R1 or (R2).
In any instance, the load current must not exceed the
converter’s rated output current Io(rated) in Table 3-1.
The values of R1 [adjust up], and (R2) [adjust down], can
also be calculated using the following formulas.
2 · Ro
Va – Vo
R1
=
=
– Rs
kΩ
kΩ
(R2)
Ro (Va – 2)
Vo – Va
– Rs
Where, Va = Adjusted output voltage
Vo = Original output voltage
Ro = Resistor constant in Table 3-1
Rs = Internal series resistance in Table 3-1
Figure 3-1
Remote Sense (+)
+VOUT
14
+VSENSE
+VIN
4
1
+VIN
11–13
+VOUT
(R2)
Adj Down
EN 1
EN 2
–VIN
+
L
O
A
D
† COUT
330µF
PT3400
2
R 1
Adjust Up
–VIN
–VOUT
3
8–10
–VOUT
* Remote Sense (–)
7
–VSENSE
SEQ
5
Vo Adj
6
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes continued
PT3400 Series
Table 3-1
DC/DC CONVERTER ADJUSTMENT RANGE AND FORMULA PARAMETERS
Series Pt #
Io (rated) 4
PT3408
7A
PT3401
10A
PT3402
12A
PT3403
12A
PT3404
16A
PT3405
16A
PT3406
16A
PT3407
16A
Vo(nom)
Va(min)
Va(max)
Ro (kΩ)
Rs (kΩ)
5V
3.3V
2.5V
1.8V
N/A
1.98V
6.49
66.5
1.5V
N/A
1.65V
7.5
100.0
1.4V
N/A
1.54V
7.5
100.0
1.2V
N/A
1.32V
7.5
100.0
1.0V
N/A
1.2V
7.5
66.5
1
1
1
1
1
4.75V
5.25V
8.87
66.5
3.135V
3.465V
9.76
2.375V
2.625V
10.0
66.5
29.4
Table 3-2
DC/DC CONVERTER ADJUSTMENT RESISTOR VALUES
Series Pt #
PT3408
PT3401
PT3402
PT3403
PT3404
PT3405
PT3406
PT3407
Vo(nom)
5V
3.3V
2.5V
1.8V
1.5V
1.4V
1.2V
1.0V
Va(req’d)
Va(req’d)
1.975
1.950
1.925
1.900
1.875
1.850
1.825
1.800
7.7kΩ
20.0kΩ
37.3kΩ
5.25
5.20
5.15
5.10
5.05
5.00
4.95
4.90
4.85
4.80
4.75
4.5kΩ
22.2kΩ
51.8kΩ
111.0kΩ
288.0kΩ
63.3kΩ
107.0kΩ
193.0kΩ
453.0kΩ
(457.0)kΩ
(191.0)kΩ
(102.0)kΩ
(57.7)kΩ
(31.1)kΩ
1.650
1.625
1.600
1.575
1.550
1.525
1.500
1.475
1.450
1.425
1.400
0.0kΩ
20.0kΩ
50.0kΩ
100.0kΩ
200.0kΩ
500.0kΩ
3.465
3.432
3.399
3.366
3.333
3.330
3.267
3.234
3.201
3.168
3.135
51.8kΩ
81.4kΩ
131.0kΩ
229.0kΩ
525.0kΩ
20.0kΩ
50.0kΩ
100.0kΩ
200.0kΩ
500.0kΩ
(308.0)kΩ
(116.0)kΩ
(51.9)kΩ
(19.9)kΩ
(0.0)kΩ
1.32
1.30
1.28
1.26
1.24
1.22
1.20
1.15
1.10
1.08
1.06
1.04
1.02
1.00
25.0kΩ
50.0kΩ
87.5kΩ
150.0kΩ
275.0kΩ
650.0kΩ
2.625
2.600
2.575
2.550
2.525
2.500
2.475
2.450
2.425
2.400
2.375
131.0kΩ
171.0kΩ
237.0kΩ
371.0kΩ
771.0kΩ
8.5kΩ
33.5kΩ
83.5kΩ
121.0kΩ
184.0kΩ
309.0kΩ
683.0kΩ
(161.0)kΩ
(60.6)kΩ
(27.3)kΩ
(10.6)kΩ
(0.0)kΩ
R1 = Black
R2 = (Blue)
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
PT3400 Series
Using the On/Off Enable Controls on the
PT3400 Series of DC/DC Converters
Negative Output Enable (Positive Inhibit)
To configure the converter for a negative enable function,
EN1 is left open circuit, and the system On/Off control
signal is applied to EN2. Applying less than 0.8V (with
respect to -Vin ) to EN2, enables the converter outputs. An
example of this configuration is provided in Figure 2-2.
Note: The converter will only produce an output voltage if a
valid input voltage is applied to Vin.
The PT3400 series of DC/DC converters incorporate
two output enable controls. EN1 (pin 1) is the ‘positive
enable’ input, and EN2 (pin 2) is the ‘negative enable’
input. Both inputs are electrically referenced to -Vin
(pin 3), at the input or primary side of the converter.
The enable pins are ideally controlled with an open-
collector (or open-drain) discrete transistor. A pull-up
resistor is not required. If a pull-up resistor is added, the
pull-up voltage must be limited to 15V. The logic truth
table for EN1 and EN2 is given in Table 2-1, below.
Figure 2-2; Negative Enable Configuration
DC/DC
Module
Table 2-1; On/Off Enable Logic
1
EN 1
2
EN1 (pin 1)
EN2 (pin 2)
Output Status
EN 2
BSS138
0
1
×
×
0
1
Off
On
Off
1 =Outputs On
–VIN
3
–Vin
Logic ‘0’ = –Vin (pin 3) potential
Logic ‘1’ = Open Circuit
On/Off Enable Turn-On Time
Automatic (UVLO) Power-Up
The total turn-on time of the module is the combination
of a short delay period, followed by the time it takes the
output voltage to rise to full regulation. When the con-
verter is enabled from the EN1 or EN2 control inputs, the
turn-on delay time (measured from the transition of the
enable signal to the instance the outputs begin to rise)
is typically 50 milliseconds. By comparison, the rise time
of the output voltage is relatively short, and is between 1
and 2 milliseconds. The rise time varies with input voltage,
output load current, output capacitance, and the SEQ pin
function. Figure 2-3 shows the power-up response of a
PT3401 (3.3V), following the removal of the ground
signal at EN1 in Figure 2-1.
Connecting EN2 to -Vin and leaving EN1 open-circuit
configures the converter for automatic power up (see data
sheet ‘Standard Application’). The converter control
circuitry incorporates an ‘under-voltage lockout’ (UVLO),
which disables the converter until a minimum input
voltage is present at
Vin (see data sheet specifications).
The UVLO ensures a clean transition during power up
and power down, allowing the converter to tolerate a
slowly rising input voltage. For most applications EN1
and EN2, can be configured for automatic power-up.
Positive Output Enable (Negative Inhibit)
To configure the converter for a positive enable function,
connect EN2 to -Vin, and apply the system On/Off control
signal to EN1. In this configuration, applying less than
0.8V (with respect to -Vin) to EN1 disables the converter
outputs. Figure 2-1 is an example of this implemention.
Figure 2-3; PT3401 Enable Turn-On
Vo (2V/Div)
Figure 2-1; Positive Enable Configuration
DC/DC
Module
V
(5V/Div)
EN1
1
EN 1
2
EN 2
BSS138
Delay Time
1 =Outputs Off
–VIN
HORIZ SCALE: 5ms/DIV
3
–Vin
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
PT3400 Series
Table 4-1; PT3400 Module Type Identification
Using the Power-Up Sequencing Feature of the
PT3400 Series of DC/DC Converters
PART No.
PT3401
PT3402
PT3403
PT3404
PT3405
PT3406
PT3407
VOUT
TYPE A
TYPE B
(3.3V)
(2.5V)
(1.8V)
(1.5V)
(1.4V)
(1.2V)
(1.0V)
×
×
×
Introduction
Power-up sequencing is a term used to describe the
order and timing that supply voltages power up in a
multi-voltage power supply system. Multi-voltage power
supply architectures are a common place requirement in
electronic circuits that employ high-performance mi-
croprocessors or digital signal processors (DSPs). These
circuits require a tightly regulated low-voltage supply
for the processor core, and a higher voltage to power
the processor’s system interface or I/O circuitry. Power-
up sequencing is often required between two such voltages
in order to manage the voltage differential during the brief
period of power-up. This reduces stress and improves the
long term reliability of the dual-voltage devices and their
associated circuitry. The most popular solution is termed
“Simultaneous Startup,” whereby the two affected voltages
both start at the same time and then rise at the same rate.
×
×
×
×
Table 4-2; Value of C3 in Sequencing Setup
MODULE #1 MODULE #2
C3
COMMENTS
A
B
A
A
B
B
Wire link
Wire link
Waveforms given in Figure 4-2
Waveforms given in Figure 4-3
Waveforms given in Figure 4-4
(5)
0.1µF
Notes
1. The two converters configured for sequenced power up
must be located close together on the same printed circuit
board.
Configuration for Power-up Sequencing
The PT3400 series converters have a feature that allows
individual modules to be easily configured for simulta-
neous startup. Using the SEQ control (pin 5), two PT3400
modules are simply interconnected with just a few passive
components. This eliminates much of the application
circuitry that would otherwise be required for this type of
setup. The schematic is given in Figure 4-1. The setup is
relatively simple but varies slightly with the combination
2. When configured for power-up sequencing, a minimum
of 1,000µF output capacitance is recommended at the
output of each converter.
3. The best results are obtained if a load of 1A or greater is
present at both converter outputs.
4. The capacitors, C1 and C2, should each be placed close to
their associated converter, Module #1, and Module #2
respectively. Combining C1 and C2 to a single capacitor of
equivalent value is not recommended.
(5)
of output voltages being sequenced. Capacitor C3 is only
required when the modules selected are a mix between
a high-voltage module (3.3V through 1.8V), and a low-
voltage module (≤1.5V). For all other configurations
C3 is replaced by a wire link. For clarification Table 4-1
indicates which modules are a high voltage type (Type A),
and which are a low voltage type (Type B). Table 4-2
provides guidance as to the one combination that requires
the capacitor C3. Examples of waveforms obtained from a
sequenced start-up between two PT3400 series modules
are provided in Figure 4-2, Figure 4-3, and Figure 4-4.
In each case the voltage difference during the synchronized
portion of the power up sequence is typically within 0.4V.
Both the timing and tracking of output voltages during
the power-up sequence will vary slightly with input voltage,
temperature, and with differences in the output capaci-
tance and load current between the two converter modules.
5. The capacitor C3 is only required whenever a Type A and
Type B converter are connected together for sequenced
power-up. In this event C3 should always be connected to
the SEQ control (pin 5) of the Type B module, or the
converter with the lowest output voltage. For all other
converter configurations C3 is not required, and is
replaced by a copper trace or wire link.
6. The capacitors selected for C1, C2, & C3 should be of
good quality and have stable characteristics. Capacitors
with an X7R dielectric, and 5% tolerance are
recommended.
7. The enable controls, EN1 & EN2, are optional for a
sequenced pair of converters. If an enable signal is desired,
EN1 or EN2 of both converters units must be controlled
from a single transistor.
This power-up sequencing solution may not be suitable
for every application. To ensure compatibility the appli-
cation should be tested against all variances. For additional
support please contact a Plug-in Power applications
specialist.
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
PT3400 Series
Figure 4-1; Configuration for Power-Up Sequencing
Module #1
(Highest Vo)
+VIN
4
14
Remote Sense (+)
+VIN
+Sense
Vo1
11–13
+VOUT
1
2
EN 1
EN 2
+
† COUT
1,000µF
LOAD
8–10
–VIN
–VOUT
3
–VIN
7
Remote Sense (–)
–Sense
SEQ
Vo Adj
5
6
C1
0.1µF
(Note 4)
Module #2
(Lowest V o)
4
1
14
Remote Sense (+)
+VIN
+Sense
Vo2
11–13
+VOUT
Q1
BSS138
(Note 8)
EN 1
EN 2
+
2
† COUT
1,000µF
LOAD
1 =Inhibit
8–10
–VOUT
3
–VIN
7
Remote Sense (–)
–Sense
SEQ
Vo Adj
5
6
C3
†
For sequencing configurations, a 1,000µF
electrolytic capacitor is recommended at
the output of each converter. See Note 2.
(Note 5 &
Table 4-2)
C2
0.1µF
(Note 4)
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
PT3400 Series
Figure 4-3; Power-Up Sequence Example with Two Type ‘A’ Modules
The adjacent plot shows an example of power-
up sequencing between two Type ‘A’ modules.
In this example the PT3401 (3.3V) and PT3402
(2.5V) are featured. Each converter had a con-
stant current load of 5A applied to its respective
output.
Vo1 (1V/Div)
Vo2 (1V/Div)
HORIZ SCALE: 5ms/Div
Figure 4-2; Power-Up Sequence Example with Two Type ‘B’ Modules
The adjacent plot shows an example of power-
up sequencing between two Type ‘B’ modules.
In this example the PT3405 (1.4V) and PT3406
(1.2V) are featured. Each converter had a con-
stant current load of 5A applied to its respective
output.
Vo1 (0.5V/Div)
Vo2 (0.5V/Div)
HORIZ SCALE: 5ms/Div
Figure 4-4; Power-Up Sequence Example Using Type ‘A’ & ‘B’ Modules
The adjacent plot shows an example of power-
up sequencing between a Type ‘A’ and a Type
‘B’ module. In this example the PT3401 (3.3V)
and PT3405 (1.4V) are featured. Each converter
had a constant current load of 5A applied to its
respective output.
Vo1 (1V/Div)
Vo2 (1V/Div)
HORIZ SCALE: 5ms/Div
For technical support and more information, see inside back cover or visit www.ti.com
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