For assistance or to order, call
(800) 531-5782
Revised 12/17/99
PT6520
Series
8 AMP ADJUSTABLE ISR
WITH SHORT-CIRCUIT PROTECTION
•
•
•
•
•
•
•
8A Single Device Power
Up to 92% efficiency (PT6521)
Small SIP Footprint
Standby Function
Internal Short-Circuit Protection
Adjustable Output Voltage
Soft Start
Application Notes
Mechanical Outline
Product Selector Guide
The PT6520 series is Power T
rends’
new high performance +3.1 to 6V
input, 8 Amp, 14-Pin SIP (Single In-
line-Package) Integrated Switching
Regulator (ISR). This high-perfor-
mance ISR allows easy integration of
high-speed, low-voltage microproces-
sors, ASICs, DSPs and their support
logic into existing 3.3V or 5V systems
without redesigning the central power
supply. The high-performance PT6522
solves the problem of providing the low
terminating voltages required by BTL/
Futurebus+, CTT, HP, and GTL Buses
from existing 3.3V or 5V power rails
without redesigning the central power
supply.
Pin-Out Information
Pin
Function
Remote Sense
Do not connect
STBY*-Standby
Ordering Information
PT6521!
= 3.3 Volts
†
PT6522!
= 1.5 Volts
†
PT6523!
= 2.5 Volts
†
PT6526!
= 1.8 Volts
†3.3V Input Bus Capable
PT Series Suffix
(PT1234X)
Case/Pin
Configuration
Heat Tab Configuration
None
Side
Standard Application
V
O
ADJ
REMOTE SENSE
14
1
V
IN
4,5,6
3
PT6520
7,8,9,10
11,12,13
V
OUT
C
1
STBY*
COM
+
Q
1
C
2
+
LOAD
COM
C
1
= Required 330µF electrolytic *
C
2
= Required 330µF electrolytic *
* See notes
1
2
3
4
5
6
7
8
9
10
11
12
13
14
V
in
V
in
V
in
GND
GND
GND
GND
V
out
V
out
V
out
V
out
Adjust
Vertical Through-Hole
Horizontal Through-Hole
Horizontal Surface Mount
P
D
E
R
G
B
Pkg Style 400
Note: Back surface
of product is
conducting metal.
PT6520
Specifications
Characteristics
(T
a
= 25°C unless noted)
Output Current
Short Circuit Current Threshold
Input Voltage Range
Output Voltage Tolerance
Output Adjust Range
PT6520 SERIES
Symbols
I
o
I
sc
V
in
∆V
o
V
o
Conditions
Over V
in
range
V
in
=+5V, Ta
0.1≤ I
o
≤
8.0A
V
in
= +5V, I
o
= 8.0A
T
a
= 0 to +70°C
V
nom
= 3.3V
V
adj
= (PT6521)
V
nom
= 1.5V
V
adj
= (PT6522)
V
adj
= (PT6523)
V
nom
= 2.5V
Pin 14 to Pin1 or GND
4.5V
≤
V
in
≤
5.5V, I
o
= 8.0A (PT6521)
3.1V
≤
V
in
≤
5.5V, I
o
= 8.0A(PT6522/3/6)
0.1
≤
I
o
≤
8.0A, V
in
= +5V, w/remote sense
V
in
= +5V, I
o
= 8.0A
I
o
step from 4A to 8.0A
V
o
over/undershoot
V
in
= +5V, I
o
= 3.0A
V
in
= +5V, I
o
= 8.0A
(PT6521)
(PT6522)
(PT6523)
(PT6521)
(PT6522)
(PT6523)
V
o
=3.3V
V
o
=2.5V, 1.8V, 1.5V
Min
0.1
(1)
—
4.5
3.1
V
o
-0.03
2.75
1.47
2.25
—
—
—
—
—
—
—
—
—
—
—
300
-40
(3)
—
-40
Typ
—
12.0
—
—
—
—
—
—
±5
±5
35
50
70
92
80
88
89
75
85
350
—
—
Max
8.0
22.5
5.5
5.5
V
o
+0.03
3.75
(2)
1.73
(2)
2.85
(2)
±10
±10
—
—
—
—
—
—
—
—
—
400
+85
(4)
+125
Units
A
Apk
V
V
V
Line Regulation
Load Regulation
V
o
Ripple/Noise
Transient Response
with C
o
= 330µF
Efficiency
Reg
line
Reg
load
V
n
t
tr
V
os
η
mV
mV
mVpp
µsec
mV
%
Switching Frequency
Absolute Maximum
Operating T
emperature Range
Storage Temperature
ƒ
o
T
a
T
s
Over V
in
and I
o
ranges
kHz
°C
°C
(Continued)
2
Power Trends, Inc.
27715 Diehl Road, Warrenville, IL 60555
(800) 531-5782
Fax: (630) 393-6902
http://www.powertrends.com
For assistance or to order, call
(800) 531-5782
PT6520
Specifications
(From previous page)
Characteristics
(T
a
= 25°C unless noted)
Mechanical Shock
Mechanical Vibration
Weight
Symbols
Conditions
Per Mil-STD-883D, Method 2002.3,
1msec, half sine, fixture mounted
Min
—
—
—
Typ
500
7.5
14
Series
Max
—
—
—
Units
G’s
G’s
grams
PT6520 SERIES
Notes:
(1)
(2)
(3)
(4)
The ISR will operate down to no load with reduced specifications.
V
in
min =3.1V, or V
o
+0.5V, whichever is less. (See related application notes on adjusting the output voltage).
For operation below 0°C, Cin and Cout must have stable characteristics. Use either low ESR tantalum or Oscon® capacitors
See Safe Operating Area curves for appropriate derating.
Input/Output Capacitors :
The PT6520 Series requires a 330µF electrolytic or tantalum input and output capacitor for proper operation in all applications. In addition the input
capacitance, C
1
, must be rated for a minimum of 1.2Arms ripple current. For transient or dynamic load applications, additional capacitance may be required.
C H A R A C T E R I S T I C
PT6521, PT6523, PT6526; V
IN
=5.0V
Efficiency vs Output Current
100
90
80
D A T A
(See Note A)
(See Note A)
PT6523, PT6526; V
IN
=3.3V
100
90
Efficiency vs Output Current
Efficiency (%)
Efficiency (%)
80
V
OUT
70
60
50
40
0
1
2
3
4
5
6
7
8
3.3V
2.5V
1.8V
V
OUT
70
60
50
40
0
1
2
3
4
5
6
7
8
2.5V
1.8V
Output Current (A)
Output Current (A)
Power Dissipation vs Output Current
5
5
Power Dissipation Output Current
4
4
PDiss (Watts)
3
V
OUT
1.8V
2.5V
3.3V
PDiss (Watts)
3
V
OUT
2.5V
1.8V
2
2
1
1
0
0
1
2
3
4
5
6
7
8
0
0
1
2
3
4
5
6
7
8
Output Current (A)
Output Current (A)
Safe Operating Area Curves
(See Note B)
PT6521, V
IN
=5.0V
90
80
70
60
50
40
30
20
0
1
2
3
4
5
6
7
8
Safe Operating Area Curves
(See Note B)
PT6526, V
IN
=3.3V
90
80
70
60
50
40
30
20
0
1
2
3
4
5
6
7
8
Ambient Temperature ( C)
Airflow
200LFM
120LFM
60LFM
Nat conv
Ambient Temperature ( C)
Airflow
200LFM
120LFM
60LFM
Nat conv
Output Current (A)
Output Current (A)
Note A:
The data in the above graphs has been developed from actual products tested at 25 °C. The data is considered typical for the ISR.
Note B:
The SOA curves represent conditions at which internal components are at or below the manufacturer’s maximum rated operating temperatures.
Power Trends, Inc.
27715 Diehl Road, Warrenville, IL 60555
(800) 531-5782
Fax: (630) 393-6902
http://www.powertrends.com
3
For assistance or to order, call
(800) 531-5782
Application
Notes
PT6520 Series
More Application Notes
Adjusting the Output Voltage of the PT6520 Low
Input Voltage Bus ISRs
The output voltage of the Power Trends PT6520 Series ISRs
may be adjusted higher or lower than the factory trimmed pre-
set voltage with the addition of a single external resistor. Table 1
gives the allowable adjustment range for each model in the series
as V
a
(min) and V
a
(max).
Adjust Up:
An increase in the output voltage is obtained by
adding a resistor R2, between pin 14 (V
o
adjust) and pins 7-10
(GND).
Adjust Down:
Add a resistor
(R1),
between pin 14 (V
o
adjust)
and pin 1 V
o
(sense)
3
.
Refer to Figure 1 and Table 2 for both the placement and value
of the required resistor, either
(R1)
or R2 as appropriate.
Notes:
1. Use only a single 1% resistor in either the
(R1)
or R2 loca-
tion. Place the resistor as close to the ISR as possible.
2. Never connect capacitors from V
o
adjust to either GND,
V
out
, or the Remote Sense pin. Any capacitance added to
the V
o
adjust pin will affect the stability of the ISR.
3. If the Remote Sense feature is not being used, the resistor
(R1)
may be connected between pin 14 (V
o
adjust) and pins
11-13 (V
out
).
4. Adjusting the output voltage of the PT6523 (2.5V model)
higher than the factory pre-trimmed output voltage may
increase the minimum input voltage specified for the part.
This model must comply with the following requirements.
PT6523:
V
in
(min)
Figure 1
1
V o(sense)
4,5,6
Vin
11,12,13
Vin
PT6520
GND
7,8,9,10
Vout
Vo
STBY
3
Vo(adj)
14
+
(R1)
Adj Down
C
out
R2
Adj Up
+
C
in
L
O
A
D
COM
COM
The values of
(R1)
[adjust down], and R2 [adjust up], can
also be calculated using the following formulas.
10⋅(V
a
– 1.27)
(V
o
– V
a
)
(R1)
=
– R
s
k
Ω
R2
=
12.7
V
a
- V
o
– R
s
k
Ω
Where: V
o
= Original output voltage
V
a
= Adjusted output voltage
R
s
= Series resistance value from Table 1
= (V
a
+ 0.5)V or 3.1V, whichever is greater.
Table 1
PT6520 ADJUSTMENT AND FORMULA PARAMETERS
Series Pt #
Vo (nom)
Va (min)
Va (max)
Rs (kΩ)
Ω
PT6522
1.5
1.47
1.73
49.9
PT6526
1.8
1.75
2.0
49.9
PT6523
2.5
2.25
2.85
33.2
PT6521
3.3
2.75
3.75
24.9
Power Trends, Inc.
27715 Diehl Road, Warrenville, IL 60555
(800) 531-5782
Fax: (630) 393-6902
http://www.powertrends.com
3
For assistance or to order, call
(800) 531-5782
PT6520 Series
Application
Notes
Table 2
PT6520 ADJUSTMENT RESISTOR VALUES
Series Pt #
V
o
(nom)
V
a
(req’d)
1.47
1.5
1.55
1.6
1.65
1.7
1.75
1.8
1.85
1.9
1.95
2.0
2.05
2.1
2.15
2.2
2.25
2.3
2.35
2.4
2.45
2.5
2.55
2.6
2.65
2.7
2.75
2.8
2.85
2.9
2.95
3.0
3.05
3.1
3.15
3.2
3.25
3.3
3.35
3.4
3.45
3.5
3.55
3.6
3.65
3.7
3.75
R1 =
(Red)
R2 = Black
229.0kΩ
102.0kΩ
59.8kΩ
38.6kΩ
25.9kΩ
17.4kΩ
11.4kΩ
6.9kΩ
3.3kΩ
Requires Vin
>3.1Vdc
4/.
221.0kΩ
93.8kΩ
51.5kΩ
30.3kΩ
17.6kΩ
9.1kΩ
3.1kΩ
(2.0)kΩ
(5.7)kΩ
(10.2)kΩ
(15.9)kΩ
(23.1)kΩ
(32.8)kΩ
(46.3)kΩ
(66.6)kΩ
(100.0)kΩ
(168.0)kΩ
(371.0)kΩ
(6.0)kΩ
(18.3)kΩ
(38.8)kΩ
(79.8)kΩ
(203.0)kΩ
204.0kΩ
77.1kΩ
34.8kΩ
13.6kΩ
204.0kΩ
77.1kΩ
34.8kΩ
13.6kΩ
(46.1)kΩ
PT6522
1.5
(16.8)kΩ
PT6526
1.8
PT6523
2.5
PT6521
3.3
4
Power Trends, Inc.
27715 Diehl Road, Warrenville, IL 60555
(800) 531-5782
Fax: (630) 393-6902
http://www.powertrends.com
For assistance or to order, call
(800) 531-5782
Application
Notes
PT6520 Series
More Application Notes
Using the Standby Function on the PT6520 3.3/5V
Bus Converters
The PT6520 series are high efficiency regulators that are de-
signed to operate off low input bus voltages. The regulators are
also pin-compatible with Power Trends’ PT6500/6600 series.
These devices feature a standby function, which may be used in
applications that require power-up/shutdown sequencing, and
wherever there is a requirement for the output status of the
module to be controlled by external circuitry.
The standby function is provided by the
STBY*
control, pin 3.
If pin 3 is left open-circuit the regulator operates normally, and
provides a regulated output when a valid supply voltage is ap-
plied to V
in
(pins 4, 5, & 6) with respect to GND (pins 7-10). If
a low voltage
3
is then applied to pin 3 the regulator output will
be disabled and the input current drawn by the ISR will typically
drop to 5mA
4
. The standby control may also be used to hold-off
the regulator output during the period that input power is ap-
plied.
Pin 3 is ideally controlled with an open-collector (or open-drain)
discrete transistor (See Figure 1). The open-ciruit voltage is
typcially 12.6V. Table 1 gives the circuit parameters for this
control input.
Table 1 Standby Control Circuit Parameters
(2, 3)
Parameter
Min
Typ
Max
On/Off Threshold
Istby
Vstby
0.2V
0.5mA
12.6V
15V
Figure 1
1
Vo(sense)
V
in
+
C
in
4,5,6
Vin
PT6520
GND
7,8,9,10
Vo
11,12,13
V
o
+
STBY
3
Vo(adj)
14
C
out
COM
Q1
BSS138
COM
Inhibit
Turn-On Time:
In the circuit of Figure 1, turning Q
1
on applies a
low voltage to the Standby control (pin 3) and disables the regu-
lator ouput. Correspondingly, turning Q
1
off removes the
low-voltage signal and enables the output. Once enabled, the
output will typically experience a 10–15ms delay followed by a
predictable ramp-up of voltage. The regulator should provide a
fully regulated output voltage within 40ms. The waveform of
Figure 2 shows the output voltage response of a PT6521 (3.3V)
following the turn-off of Q
1
at time t = 0.0 secs. The waveform
was measured with a 5Vdc input voltage, and 0.6Ω load.
Notes:
1. The operation of the Standby/Inhibit is similar for all Power
Trends’ modules, but the flexibility and threshold tolerances
will be different. For specific information on this function
for other regulator models, consult the applicable application
note.
2 The standby control input requires no external pull-up resis-
tor. The open-circuit voltage of the STBY* pin is typically
12.6V.
3. The standby control input is
Not
compatible with TTL or
other devices that incorporate a totem-pole output drive.
Use only a true open-collector device, preferably a discrete
bipolar transistor (or MOSFET). T ensure the regulator
o
output is disabled, the control pin must be pulled to less than
0.2Vdc with a low-level 0.5mA sink to ground.
4. When the regulator output is disabled the current drawn
from the input source is typically reduced to 5mA.
Figure 2
V
out
(2V / Div)
0
5
10
15
20
25
30
35
t (milli - secs)
Power Trends, Inc.
27715 Diehl Road, Warrenville, IL 60555
(800) 531-5782
Fax: (630) 393-6902
http://www.powertrends.com
5
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