*9 TEXAS INSTRUMENTS
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•DSL Triple Outputs:
+15V, +3.3V, +1.5V
(Independantly Regulated)
•Input Voltage Range:
36V to 75V
•1500VDC Isolation
•On/Off “Standby” Control
•Current Limit
•Short Circuit Protection
(All Outputs)
Features
Ordering Information
PT4801o = +15/+3.3/+1.5 Volts
Typical Application
Pin-Out Information
Pin Function
1 Remote (On/Off)
2 No Pin
3–V
in
4–V
in
5 N/C
6+V
in
7+V
in
8 No Pin
9 No Pin
10 Vo1
Pin Function
11 COM
12 Vo2 Adjust
13 No Pin
14 Vo2
15 Vo2
16 COM
17 COM
18 Vo3
19 Vo3 Adjust
20 No Pin
PT4801—48V
Description
The PT4801 Excalibur™ module is an
isolated triple-output DC/DC converter
that provides +15V, +3.3V, and +1.5V
power supply voltages from a standard
(-48V) telecom central office (CO) supply.
A typical application is a chip-set for an
8 or 16-channel ADSL/DSL line card, or
other mixed signal circuitry. The output
voltage combination provides power for a
processor core, digital logic, and analog
support circuitry. The Vo2 and Vo3 outputs
are also designed to meet the power-up/
down sequencing requirements of popular
DSP ICs.
The PT4801 is housed in a space-
saving solderable copper case. A heatsink
is not required. The vertical configura-
tion occupies only 1.6 in2 of PCB area.
Cin = Optional 33µF
Co1/Co2= Optional 10µF to 330µF per output. (See note 6)
25-W Triple Output Isolated DC/DC
Converter for DSL Applications SLTS143A
(Revised 1/29/2002)
DSL/ADSL
IC Chip Set
+V
IN
–V
IN
+15VDC
+3.3VDC
+1.5VDC
PT4801
6, 7
3, 4
10
14, 15
18
16, 17
11
1
Vo
1
COM
COM
Vo
2
Vo
3
+V
IN
–V
IN
Remote
On/Off
Vo
2
adjVo
3
adj 1219
Vo
2
Adjust
Vo
3
Adjust
Co
1
Co
3
Co
2
C
IN
•Fixed Frequency Operation
•Over-Temperature Shutdown
•Under-Voltage Lockout
•Space Saving Package:
1.6 sq. in. PCB Area (suffix N)
•Solderable Copper Case
•Safety Agency Approvals:
UL 60950
CSA C22.2 60950
VDE EN60950
PT Series Suffix (PT1234x)
Case/Pin Order Package
Configuration Suffix Code
Vertical N(ENJ)
Horizontal A(ENK)
SMD C(ENL)
(Reference the applicable package code draw-
ing for the dimensions and PC board layout)
W TEXAS INSTRUMENTS
For technical support and more information, see inside back cover or visit www.ti.com
PT4801—48V
25-W Triple Output Isolated DC/DC
Converter for DSL Applications
Electrical Specifications (Unless otherwise stated, Ta =25°C, Vin =48V, Cin =0µF, Cout =0µF, and Io =Iotyp)
PT4801 SERIES
Characteristics Symbols Conditions Min Typ Max Units
Output Power PoEach output: Vo1 ( 15V) — 15 18.75 (1)
Vo2 (3.3V) — 6.6 9.9 (1) W
Vo3 (1.5V) — 2.25 3.0 (1)
All three outputs: — — 25 (1) W
Output Current IoVo1 ( 15V) 0 1.0 1.25 A
(Io1 >0.25A) Vo2 (3.3V) 0 2.0 3.0 (2) A
Vo3 (1.5V) 0 1.5 2.0 (2)
(Io1 ≤0.25A) Vo2 (3.3V) 0 — 2.0 (2) A
Vo3 (1.5V) 0 — 1.5 (2)
Maximum (Io1 + Io2 + Io3) — — 6.0 (3) A
Input Voltage Range Vin Continuous 36 — 75 V
Surge (1 minute) — — 80 V
Set-point Voltage Tolerance Vo tol Vo115.0 — 15.75
Vo23.25 3.3 3.35 V
Vo31.45 1.5 1.55
Temperature Variation Regtemp –40° ≤Ta ≤ +85°C, Io =Iomin — ±0.5 — %Vo
Line Regulation Regline All outputs, Over Vin range, Io =Iotyp — 0.5 1.0 %Vo
Load Regulation Regload All outputs, Io =10% to 100%Iomax — 0.5 1.0 %Vo
Total Output Voltage Variation ∆Vo tot Includes set-point, line load, Vo115.0 — 15.75
–40°C ≤Ta ≤ +85°C Vo23.2 3.3 3.4 V
Vo31.4 1.5 1.6
Efficiency ηIo1 =0.5A, Io2 =1.0A, Io3 =1.0A — 78 — %
Io1 =1.0A, Io2 =3.0A, Io3 =2.0A — 81 —
Vo Ripple (pk-pk) Vr20–20Mz bandwidth, Io =Iotyp Vo1— 75 150
Vo2—3350mV
pp
Vo3—3050
Transient Response ttr 25% load step from Io ≥0.5Iotyp — 300 — µSec
Vos Vo over/undershoot Vo1—35%V
o
Vo2— 100 150 mVpp
Vo3— 100 150
Output Voltage Adjust Voadj Vo2 3.135 — 3.465 V
Vo3 1.425 — 1.5 (4)
Switching Frequency ƒsOver Vin and Io ranges 550 650 750 kHz
Under-Voltage Lockout UVLO Vin increasing — 34 — V
Vin decreasing — 33 —
Remote On/Off (Pin x) Referenced to –Vin (pin 1)
Input High Voltage VIH 2.5 — 15 (5) V
Input Low Voltage VIL –0.2 — +0.8
Input Low Current IIL — –10 — µA
Standby Input Current Iin standby pins 1 & 2 connected — 8 16 mA
Internal Input Capacitance Cin — 0.76 — µF
External Output Capacitance Co1,Vo
10 — 330 (6) µF
Co2, Co3Vo 2 & Vo3 (each) 0 — 330 (6)
Isolation Voltage Input–output/input–case 1500 — — V
Capacitance Input to output — 3000 — pF
Resistance Input to output 10 — — MΩ
Operating Temperature Range T
aOver Vin Range –40 — +85 (7) °C
Case Temperature +100 °C
Over Temperature Protection OTP +125 °C
Storage Temperature Ts— –40 — +125 °C
Mechanical Shock Method 2002.3 — 500 — G’s
Mil-STD-883D, 1 msec, ½ Sine, mounted
Mechanical Vibration Method 2007.2, Suffixes A, C — 20 (8 —G’s
Mil-STD-883D 20-2000 Hz, Soldered
Weight — Vertical/Horizontal — 50 — grams
Flammability — Meets UL 94V-O
Notes:
(1) The sum-total power delivered from all three output, Vo1, Vo2, and Vo3 cannot exceed 25 watts.
(2) When the load current from Vo1 is less than 0.25A, the maximum current available from Vo2, and Vo3 is reduced to 2A and 1.5A respectively.
(3) The sum-total current from all three outputs Vo1, Vo2, and Vo3 cannot exceed 6Adc.
(4) Vo3 cannot be adjusted higher than the nominal output voltage. Consult the applicable application note for information on output voltage adjusment.
(5) The Remote On/Off input has an internal pull-up. If left open circuit the PT4801 will operate when input power is applied. A low-leakage (<100nA).
MOSFET is recommended to control this input. The open-circuit voltage is less than 10V. See application notes for interface considerations.
(6) External output capacitance is not required for proper operation. Up to 100µF of external capacitance may be added to each output to improve the response
to load transients. Do not exceed 330µF at any one output. Allowances must be made for load circuit capacitance and the total external capacitor tolerance.
Excessive output capacitance will affect converter start up. Low ESR capacitors, including Os-con® and tantalum types, may be used.
(7) See Safe Operating Area curves, or consult the factory for the appriopriate derating.
(8) The case pins on the through-hole package types (suffixes A & N) must be soldered. For more information, see the applicable package outline drawing.
*9 TEXAS INSTRUMENTS
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Note A: All Characteristic data in the above graphs has been developed from actual products tested at 25°C. This data is considered typical data for the ISR.
Note B: SOA curves represent operating conditions at which internal components are at or below manufacturer’s maximum rated operating temperatures.
Typical Characteristics
PT4801—48V
25-W Triple Output Isolated DC/DC
Converter for DSL Applications
PT4801 Characteristic Data (See Note A)
Efficiency vs Output Current
Power Dissipation vs Output Current
Ripple vs Output Current; @Vin =48V
Load Regulation vs Output Current; Vo1 =+15V
Load Regulation vs Output Current; Vo2 =+3.3V
Load Regulation vs Output Current; Vo3 =+1.5V
PT4801 SOA vs Output Power
Safe Operating Area, Vin =48V (See Note B)
50
60
70
80
90
0 20406080100
% Load
(
All Out
p
uts
)
Efficiency - %
36V
48V
75V
VIN
0
20
40
60
80
100
0 20406080100
% Load
(
All Out
p
uts
)
Ripple - mV
(
+15V
)
(
1.5V
)
(
3.3V
)
Out
p
ut
0
2
4
6
8
10
0 20406080100
% Load
(
All Out
p
uts
)
Pd - Watts
75V
48V
36V
VIN
15.1
15.2
15.3
15.4
15.5
0 20406080100
% Load
(
All 3 Out
p
uts
)
Load Regulation ∆Vo
75
48
36
VIN
3.28
3.288
3.296
3.304
3.312
3.32
0 20406080100
% Load
(
All 3 Out
p
uts
)
Load Regulation ∆Vo
36
48
75
VIN
1.48
1.488
1.496
1.504
1.512
1.52
0 20406080100
% Load
(
All 3 Out
p
uts
)
Load Regulation ∆Vo
36
48
75
VIN
20
30
40
50
60
70
80
90
0 5 10 15 20 25
Out
p
ut Power
(
W
)
Ambient Temperature (°C)
400LFM
200LFM
120LFM
60LFM
Nat conv
Airflow
b» N
{’3 TEXAS INSTRUMENTS
For technical support and more information, see inside back cover or visit www.ti.com
Using the Remote On/Off Control on the PT4801
Triple-Output Voltage DC/DC Converter
The three output voltages of the PT4801 triple-output
DC/DC converter may be simultaneously disabled using
the Remote On/Off control. This control is used in appli-
cations that require power-up/shutdown sequencing, or
wherever there is a requirement to control the on/off sta-
tus of the module with external circuitry.
On/off control of the PT4801 is provided by pin 1. If
pin 1 is left open-circuit the regulator operates normally,
and provides a regulated output at all three outputs, Vo1
(pin 10), Vo2 (pins 14, 15), and Vo3 (pin 18), whenever a
valid input voltage is applied to ±Vin. If a low voltage is
then applied to pin 1, the module’s output will be disabled
and the input current it draws will drop to a typical value
of 8mA. The Remote On/Off input may also be used to hold
the module’s output in the ‘off’ state during the period
that input power is applied. The input is ideally controlled
using an open-collector (or open-drain) discrete transistor
(See Figure 1) 3.
Table 1 Remote On/Off Control Parameters 1, 2
Parameter Min Typ Max
Enable (VIH) 2.5V — 15V 3
Disable (VIL) –0.1V — 0.8V
Notes:
1. The Remote On/Off input uses –Vin (pins 3 & 4) as a
ground reference, and cannot be directly controlled
from circuitry referenced to the isolated output ±Vo.
2. The internal circuitry comprises of a high impedance (3µA
-10µA) current source. The open-circuit voltage is less
than 10V.
3. A low-leakage MOSFET (<100nA) is recommended. A
pull-up resistor is not required, but may be necessary to
ensure that the Remote On/Off pin exceeds VIH(min)
(see Table 1). Do not use a pull-up resistor to the +Vin
input, or drive the pin above VIH(max).
4. The PT4801 converter incorporates an “Under Voltage
Lockout” (UVLO) function. This function will overide
the Remote On/Off control until the input voltage
applied to ±Vin, is above the UVLO threshold. Consult
the data sheet specifications for the on/off input voltage
voltage thresholds.
5. Keep the on/off transition to less than 1ms. This prevents
erratic operation of the converter, whereby the output
voltage may drift un-regulated between 0V and the rated
output voltage during power-up.
Figure 1
Power-Up Sequence: Turning Q1 in Figure 1 off, removes
the low-voltage signal at pin 1 and enables the outputs of
the PT4801 converter. After a delay of about 5ms, the
Vo1 output will begin to rise first. This is closely followed
by Vo2, and Vo3, which are internally sequenced to rise in
unison. The total power-up time is less than 25ms and is
relatively independent of load, and temperature. Figure 2
shows waveforms of all three output voltages, Vo1, Vo2,
and Vo3 following Q1 turning off. The turn off of Q1
corresponds to the fall in the applied Vgs. The wave-
forms were measured with a 48V input voltage.
Figure 2
PT4801
+V
IN
–V
IN
High =Off
+Vo
1
+Vo
2
+Vo
3
Co
1
Co
3
Co
2
C
IN
PT4801
6, 7
3, 4
10
14, 15
18
16, 17
1
Vo
1
COM
COM
Vo
2
Vo
3
+V
IN
–V
IN
Remote
On/Off
Vo
2
adj
Vo
3
adj
12
19
11
Q
1
BSS138
COM
R
g
C
g
s
R
g
& C
gs
, See Note 6
Vo1 (5V/Div)
Vo2 (2V/Div)
Vo3 (2V/Div)
HORIZ SCALE: 5ms/Div
Q1 Vgs (5V/Div)
6. In Figure 1, Q1 is a low-threshold MOSFET. The
components Rg and Cgs are added to improve noise
immunity.
Application Notes
u
*9 TEXAS INSTRUMENTS
Application Notes
For technical support and more information, see inside back cover or visit www.ti.com
PT4801
Adjusting the Output Voltage of the PT4801
Triple-Output DC/DC Converter
The low-voltage outputs from the PT4801 triple-output
DC/DC converter, Vo2 (3.3V) and Vo3 (1.5V), can be
independently adjusted from the factory trimmed preset
value. Note that the primary use of this feature is for
margin testing of the on-board supply voltages. A per-
manent increase in output voltage is not advised 1. Also,
due to design limitations, Vo3 cannot be adjusted higher
than its nominal value.
To adjust each output, a single external resistor is added
to the circuit in either the “Adjust Up” or “Adjust Down”
position (See Figure 1) 2. Table 1 gives the allowable
adjustment range for each output as Va (min) and Va (max).
Vo2 Adjust Up: Add a resistor R2 between pin 12
(Vo2 Adj), and pin 11 (COM) 1.
Vo2 Adjust Down: Add a resistor (R1) between
pin 12 (Vo2 Adj), and pin 14 (Vo2).
Vo3 Adjust Up: Vo3 cannot be adjusted higher.
Vo3 Adjust Down: Add a resistor (R3) between pin 19
(Vo3 Adj), and pin 18 (Vo3).
Refer to Figure 1 and Table 2 for both the placement and
value of the adjust resistor.
Notes:
1. The high-side adjust range of the Vo2 output may be
limited by the input voltage and/or the load current
status of all three outputs. This situation would most
likely be encountered when Vo1 is lightly loaded and
either Vo2 or Vo3 is operating close to full load.
2. Use only a single 1% resistor in either the (R1) or R2
location to adjust Vo2, and in the (R3) location to
adjust Vo3. Place the resistor as close to the ISR as
possible.
3. Never connect capacitors to either of the output
adjust control pins. Any capacitance added to these
control pins will affect the stability of the respective
regulated output.
The adjust up and adjust down resistor values can be
calculated using the following formulas. Be sure to select
the correct formula parameter from Table 1 for the output
being adjusted.
(R1) or (R3)=Ro (Va – Vr)– RskΩ
(Vo – Va)
R2= Ro · Vr– RskΩ
(Va – Vo)
Where Vo= Original output voltage
Va= Adjusted output voltage
Vr= Reference voltage (Table 1)
Ro= Multiplier resistor (Table 1)
Rs= Series resistance (Table 1)
Figure 1
+V
IN
–V
IN
Vo
1
(+15VDC)
Vo
2
Vo
3
PT4801
6, 7
3, 4
10
14, 15
18
16, 17
11
1
Vo1
COM
COM
Vo2
Vo3
+VIN
–VIN
Remote
On/Off Vo2adj
Vo3adj
Co1
Co3
Co2
CIN
R2
Adjust Up
(R1)
Adjust
Down
(R3)
Adjust
Down
12
19
COM
\ um mom
41 SK)
{’3 TEXAS INSTRUMENTS
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Application Notes
continued
PT4801
3.135 (87.1)kΩ
3.15 (101.0)kΩ
3.165 (118.0)kΩ
3.18 (139.0)kΩ
3.195 (166.0)kΩ
3.21 (202.0)kΩ
3.225 (253.0)kΩ
3.24 (329.0)kΩ
3.255 (456.0)kΩ
3.27 (710.0)kΩ
3.285
3.3
3.315
3.33 409.0kΩ
3.345 259.0kΩ
3.36 184.0kΩ
3.375 139.0kΩ
3.39 110.0kΩ
3.405 88.1kΩ
3.42 72.1kΩ
3.435 59.6kΩ
3.45 49.6kΩ
3.465 41.5kΩ
R1/R3 = (Blue), R2/R4 = Black
Vo1 Bus
Adj. Resistor (R1)/R2
Vo(nom) 3.3V
Va(req’d)
Table 1
ADJUSTMENT RANGE AND FORMULA PARAMETERS
Vo2 Bus Vo3 Bus
Adj. Resistor (R1)/R2 (R3)
Vo(nom) 3.3V 1.5V
Va(min) 3.135V 1.425V
Va(max) 3.465V * —
Vr 1.225V 1.225V
Ro (V·kΩΩ
ΩΩ
Ω)11.0 7.5
Rs (kΩΩ
ΩΩ
Ω)40.2 5.36
* See Note 1
1.425 (14.6)kΩ
1.44 (21.5)kΩ
1.455 (33.0)kΩ
1.47 (55.9)kΩ
1.485 (125.0)kΩ
1.5
Vo2 Bus
Adj. Resistor (R3)
Vo(nom) 1.5V
Va(req’d)
Table 2
ADJUSTMENT RESISTOR VALUES
VDE Inshllation Instrllctinns
| {(19%
*9 TEXAS INSTRUMENTS
Application Notes
For technical support and more information, see inside back cover or visit www.ti.com
VDE Approved Installation Instructions (Installationsanleitung)
Nennspannnug (Rated Voltage): PT4801 36 to 72 Vdc, Transient to 80Vdc
Nennaufnahme (Rated Input): PT4801 1.5 Adc
Nennleistung (Rated Power): 25 Watts Maximum
Ausgangsspannung (Sec. Voltage): PT4801 Series
PT4801, +15/ +3.3/ +1.5 Vdc, 1.25 Adc/ 3.0 Adc/ 2.0 Adc
Ausgangsstrom (Sec. Current): Maximum total current is 6.0 Adc or 25 Watts
oder (or)
Ausgangsleistung (Sec. Power):
Angabe der Umgebungstemperatur
(Information on ambient temperature): +85 °C maximum
Besondere Hinweise (Special Instructions):
Es ist vorzusehen, daß die Spannungsversorgung in einer Endanwendung über eine isolierte
Sekundaerschaltung bereit gestellt wird. Die Eingangspannung der Spannungsversorgungsmodule muss
eine verstaerkte Isolierung von der Wechselstromquelle aufweisen.
Die Spannungsversorgung muss gemaess den Gehaeuse-, Montage-, Kriech- und Luftstrecken-,
Markierungs- und Trennanforderungen der Endanwendung installiert werden. Bei Einsatz eines TNV-3-
Einganges muss die SELV-Schaltung ordnungsgemaess geerdet werden.
(The power supply is intended to be supplied by isolated secondary circuitry in an end use application.
The input power to these power supplies shall have reinforced insulation from the AC mains.
The power supply shall be installed in compliance with the enclosure, mounting, creepage, clearance,
casualty, markings, and segregation requirements of the end-use application. When the input is TNV-3,
the SELV circuitry must be reliably grounded.)
Offenbach,
VDE Prüf- und Zertifizierungsinstitut
Abteilung /
Department TD
(Jürgen Bärwinkel)
Ort /
Place
: Datum /
Date
:
(Stempel und Unterschrift des Herstellers / Stamp
and signature of the manufacturer)
PT4801
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