1.5 A Adjustable and 3.3 V
Fixed Output Linear
Regulator
The NCP1086 linear regulator provides 1.5 A at 3.3 V or adjustable
output voltage. The adjustable output voltage device uses two external
resistors to set the output voltage within a 1.25 V to 5.5 V range.
The regulators is intended for use as post regulator and
microprocessor supply. The fast loop response and low dropout
voltage make this regulator ideal for applications where low voltage
operation and good transient response are important.
The circuit is designed to operate with dropout voltages less than
1.4 V at 1.5 A output current. Device protection includes overcurrent
and thermal shutdown.
This device is pin compatible with LT1086 family of linear
regulators and has lower dropout voltage.
The regulators are available in TO−220−3, surface mount
2
D
PAK−3, and SOT−223 packages.
Features
• Output Current to 1.5 A
• Output Accuracy to ±1% Over T emperature
• Dropout Voltage (Typical) 1.05 V @ 1.5 A
• Fast Transient Response
• Fault Protection Circuitry
♦ Current Limit
♦ Thermal Shutdown
• Pb−Free Packages are Available
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TO−220−3
T SUFFIX
CASE 221A
1
2
3
D2PAK−3
DP SUFFIX
1
2
3
1
2
3
CASE 418AB
SOT−223
ST SUFFIX
CASE 318E
Adjustable
Output
Tab = V
OUT
Pin 1. Adj
2. V
OUT
3. V
IN
3.3 V Fixed
Output
Tab = V
OUT
Pin 1. GND
2. V
OUT
3. V
IN
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 9 of this data sheet.
DEVICE MARKING INFORMATION
See general marking information in the device marking
section on page 10 of this data sheet.
7.0V
Operating Temperature Range−40 to +70°C
Junction Temperature150°C
Storage Temperature Range−60 to +150°C
Lead Temperature Soldering: Wave Solder (through hole styles only) Note 1
Reflow (SMD styles only) Note 2
260 Peak
230 Peak
°C
ESD Damage Threshold2.0kV
Maximum ratings are those values beyond which device damage can occur. Maximum ratings applied to the device are individual stress limit
values (not normal operating conditions) and are not valid simultaneously . If these limits are exceeded, device functional operation is not implied,
damage may occur and reliability may be affected.
1. 10 second maximum.
2. 60 second maximum above 183°C.
ELECTRICAL CHARACTERISTICS (C
T
≤ +150°C, unless otherwise specified, I
J
Characteristic
IN
full load
= 10 mF, C
= 1.5 A.)
= 22 mF Tantalum, V
OUT
OUT
+ V
DROPOUT
< VIN < 7.0 V, 0°C ≤ TA ≤ 70°C,
Test ConditionsMinTypMaxUnit
ADJUSTABLE OUTPUT VOLTAGE
Reference Voltage (Notes 3 and 4)
Line Regulation1.5 V ≤ VIN − V
Load Regulation (Notes 3 and 4)VIN − V
Dropout Voltage (Note 5)I
Current LimitVIN − V
Minimum Load Current (Note 6)VIN = 7.0 V; V
Adjust Pin CurrentVIN − V
VIN − V
10 mA ≤ I
OUT
= 1.5 V; V
OUT
≤ 1.5 A
OUT
OUT
= 1.5 V; 10 mA ≤ I
OUT
= 0 V,
Adj
≤ 5.75 V; I
1.241
(−1%)
= 10 mA−0.020.2%
OUT
≤ 1.5 A−0.040.4%
OUT
1.2541.266
(+1%)
= 1.5 A−1.051.4V
= 3.0 V; TJ ≥ 25°C1.63.1−A
OUT
= 0−0.62.0mA
Adj
OUT
= 3.0 V; I
= 10 mA−50100
OUT
V
mA
Thermal Regulation (Note 7)30 ms pulse; TA = 25°C−0.0020.02%/W
Ripple Rejection (Note 7)f = 120 Hz; I
Line Regulation2.0 V ≤ VIN − V
Load Regulation (Notes 3 and 4)VIN − V
Dropout Voltage (Note 5)I
OUT
Current LimitVIN − V
Quiescent CurrentI
OUT
= 1.5 V, 0 ≤ I
OUT
≤ 3.7 V; I
OUT
= 2.0 V; 10 mA ≤ I
OUT
≤ 1.5 A3.25
OUT
3.33.35
(−1.5%)
= 10 mA−0.020.2%
OUT
≤ 1.5 A−0.040.4%
OUT
V
(+1.5%)
= 1.5 A−1.051.4V
= 3.0 V1.63.1−A
OUT
= 10 mA−5.010mA
Thermal Regulation (Note 7)30 ms pulse; TA = 25°C−0.0020.02%/W
3. Load regulation and output voltage are measured at a constant junction temperature by low duty cycle pulse testing. Changes in output
voltage due to thermal gradients or temperature changes must be taken into account separately.
4. Specifications apply for an external Kelvin sense connection at a point on the output pin 1/4” from the bottom of the package.
5. Dropout voltage is a measurement of the minimum input/output differential at full load.
6. The minimum load current is the minimum current required to maintain regulation. Normally the current in the resistor divider used to set the
output voltage is selected to meet the minimum requirement.
7. Guaranteed by design, not 100% tested in production.
8. Thermal shutdown is 100% functionally tested in production.
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2
NCP1086
ELECTRICAL CHARACTERISTICS (continued) (C
0°C ≤ T
≤ 70°C, TJ ≤ +150°C, unless otherwise specified, I
The NCP1086 voltage regulator series provides
adjustable and 3.3 V output voltages at currents up to 1.5 A.
The regulator is protected against overcurrent conditions
and includes thermal shutdown.
The NCP1086 series has a composite PNP−NPN output
transistor and requires an output capacitor for stability. A
detailed procedure for selecting this capacitor is included in
the Stability Considerations section.
Adjustable Operation
The adjustable output device has an output voltage range
of 1.25 V to 5.5 V. An external resistor divider sets the
output voltage as shown in Figure 15. The regulator
maintains a fixed 1.25 V (typical) reference between the
output pin and the adjust pin.
APPLICATIONS INFORMATION
A resistor divider network R1 and R2 causes a fixed
current to flow to ground. This current creates a voltage
across R2 that adds to the 1.25 V across R1 and sets the
overall output voltage. The adjust pin current (typically
50 mA) also flows through R2 and adds a small error that
should be taken into account if precise adjustment of V
is necessary.
The output voltage is set according to the formula:
V
OUT
The term I
Adj
pin current.
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5
OUT
R1 ) R2
+ V
REF
ǒ
R1
Ǔ
) I
R2
Adj
× R2 represents the error added by the adjust
NCP1086
R1 is chosen so that the minimum load current is at least
2.0 mA. R1 and R2 should be the same type, e.g. metal film
for best tracking over temperature.
V
IN
C
1
V
IN
NCP1086
Figure 15. Resistor Divider Scheme
Adj
V
OUT
I
Adj
V
OUT
V
REF
R
1
C
2
R
2
The adjustable output linear regulator has an absolute
maximum specification of 7.0 V for the voltage difference
between V
and V
IN
. However, the IC may be used to
OUT
regulate voltages in excess of 7.0 V. The main
considerations in such a design are powerup and short circuit
capability.
In most applications, ramp−up of the power supply to V
IN
is fairly slow, typically on the order of several tens of
milliseconds, while the regulator responds in less than one
microsecond. In this case, the linear regulator begins
charging the load as soon as the V
IN
to V
differential is
OUT
large enough that the pass transistor conducts current. The
load at this point is essentially at ground, and the supply
voltage is on the order of several hundred mV, with the result
that the pass transistor is in dropout. As the supply to V
IN
increases, the pass transistor will remain in dropout, and
current is passed to the load until V
reaches the point at
OUT
which the IC is in regulation. Further increase in the supply
voltage brings the pass transistor out of dropout. The result
is that the output voltage follows the power supply ramp−up,
staying in dropout until the regulation point is reached. In
this manner, any output voltage may be regulated. There is
no theoretical limit to the regulated voltage as long as the
V
IN
to V
differential of 7.0 V is not exceeded.
OUT
However, the possibility of destroying the IC in a short
circuit condition is very real for this type of design. Short
circuit conditions will result in the immediate operation of
the pass transistor outside of its safe operating area.
Overvoltage stresses will then cause destruction of the pass
transistor before overcurrent or thermal shutdown circuitry
can become active. Additional circuitry may be required to
clamp the V
IN
to V
differential to less than 7.0 V if
OUT
fail−safe operation is required. One possible clamp circuit is
illustrated in Figure 16; however, the design of clamp
circuitry must be done on an application by application
basis. Care must be taken to ensure the clamp actually
protects the design. Components used in the clamp design
must be able to withstand the short circuit condition
indefinitely while protecting the IC.
EXTERNAL
SUPPLY
V
IN
NCP1086
Figure 16. Short Circuit Protection Circuit for High
Voltage Application
Stability Considerations
Adj
V
OUT
V
OUT
The output or compensation capacitor helps determine
three main characteristics of a linear regulator: startup delay ,
load transient response and loop stability.
The capacitor value and type is based on cost, availability,
size and temperature constraints. A tantalum or aluminum
electrolytic capacitor is best, since a film or ceramic
capacitor with almost zero ESR can cause instability. The
aluminum electrolytic capacitor is the least expensive
solution. However, when the circuit operates at low
temperatures, both the value and ESR of the capacitor will
vary considerably. The capacitor manufacturers’ data sheet
provides this information.
A 22 mF tantalum capacitor will work for most
applications, but with high current regulators such as the
NCP1086 series the transient response and stability improve
with higher values of capacitance. The majority of
applications for this regulator involve large changes in load
current, so the output capacitor must supply the
instantaneous load current. The ESR of the output capacitor
causes an immediate drop in output voltage given by:
DV + DI ESR
For microprocessor applications it is customary to use an
output capacitor network consisting of several tantalum and
ceramic capacitors in parallel. This reduces the overall ESR
and reduces the instantaneous output voltage drop under
load transient conditions. The output capacitor network
should be as close as possible to the load for the best results.
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6
NCP1086
V
Conductor Parasitic
V
Conductor Parasitic
Protection Diodes
When large external capacitors are used with a linear
regulator it is sometimes necessary to add protection diodes.
If the input voltage of the regulator gets shorted, the output
capacitor will discharge into the output of the regulator. The
discharge current depends on the value of the capacitor, the
output voltage and the rate at which V
drops. In the
IN
NCP1086 series linear regulator, the discharge path is
through a large junction and protection diodes are not
usually needed. If the regulator is used with large values of
output capacitance and the input voltage is instantaneously
shorted to ground, damage can occur. In this case, a diode
connected as shown in Figure 17 or Figure 18 is
recommended.
IN4002 (optional)
V
IN
C
1
V
IN
NCP1086
Adj
V
OUT
V
OUT
R
1
C
2
R
2
R
IN
V
IN
NCP1086
V
OUT
C
Resistance
R
LOAD
Figure 19. Conductor Parasitic Resistance Effects
Can Be Minimized with the Above Grounding
Scheme for Fixed Output Regulators
For the adjustable regulator, the best load regulation
occurs when R1 is connected directly to the output pin of the
regulator as shown in Figure 20. If R1 is connected to the
load, R
is multiplied by the divider ratio and the effective
C
resistance between the regulator and the load becomes
R1 ) R2
ǒ
R
C
R1
Ǔ
where RC = conductor parasitic resistance.
Resistance
R
LOAD
Figure 17. Protection Diode Scheme for Large Output
Capacitors (Adjustable Output)
IN4002 (optional)
V
IN
C
1
V
IN
NCP1086
GND
V
OUT
V
OUT
C
2
R
IN
V
IN
NCP1086
Adj
V
OUT
C
R
1
R
2
Figure 20. Grounding Scheme for the
Adjustable Output Regulator to Minimize
Parasitic Resistance Effects
Figure 18. Protection Diode Scheme for Large Output
Capacitors (3.3 V Fixed Output)
Output Voltage Sensing
Since the NCP1086 is a three terminal regulator, it is not
possible to provide true remote load sensing. Load
regulation is limited by the resistance of the conductors
connecting the regulator to the load.
For best results the fixed output regulator should be
connected as shown in Figure 19.
Calculating Power Dissipation and
Heatsink Requirements
The NCP1086 linear regulator includes thermal shutdown
and current limit circuitry to protect the device. High power
regulators such as these usually operate at high junction
temperatures so it is important to calculate the power
dissipation and junction temperatures accurately to ensure
that an adequate heatsink is used.
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7
NCP1086
The case is connected to V
, and electrical isolation
OUT
may be required for some applications. Thermal compound
should always be used with high current regulators such as
these.
The thermal characteristics of an IC depend on the
following four factors:
1. Maximum Ambient Temperature T
2. Power dissipation P
D
(W)
3. Maximum junction temperature T
4. Thermal resistance junction to ambient R
A
(°C)
J
(°C)
JA
q
(°C/W)
These four are related by the equation
TJ+ TA) PD R
qJA
(eq. 1)
The maximum ambient temperature and the power
dissipation are determined by the design while the
maximum junction temperature and the thermal resistance
depend on the manufacturer and the package type.
The maximum power dissipation for a regulator is:
P
D(max)
+
{
V
IN(max)
* V
OUT(min)
}
I
OUT(max)
) V
IN(max)IQ
(eq. 2)
where:
V
V
I
OUT(max)
I
Q
is the maximum input voltage,
IN(max)
OUT(min)
is the minimum output voltage,
is the maximum output current, for the application
is the maximum quiescent current at I
OUT(max)
.
A heatsink effectively increases the surface area of the
package to improve the flow of heat away from the IC and
into the surrounding air.
Each material in the heat flow path between the IC and the
outside environment has a thermal resistance. Like series
electrical resistances, these resistances are summed to
determine R
, the total thermal resistance between the
JA
q
junction and the surrounding air.
1. Thermal Resistance of the junction to case, R
JC
q
(°C/W)
2. Thermal Resistance of the case to Heatsink, R
CS
q
(°C/W)
3. Thermal Resistance of the Heatsink to the ambient
SA
q
(°C/W)
air, R
These are connected by the equation:
R
qJA
The value for R
+ R
JA
q
qJC
) R
qCS
) R
qSA
is calculated using Equation 3 and the
(eq. 3)
result can be substituted in Equation 1.
The value for R
is 3.5°C/W. For a high current
JC
q
regulator such as the NCP1086 the majority of the heat is
generated in the power transistor section. The value for
R
depends on the heatsink type, while R
SA
q
depends on
CS
q
factors such as package type, heatsink interface (is an
insulator and thermal grease used?), and the contact area
between the heatsink and the package. Once these
calculations are complete, the maximum permissible value
of R
can be calculated and the proper heatsink selected.
JA
q
For further discussion on heatsink selection, see application
note “Thermal Management,” document number
AND8036/D via our website at www.onsemi.com.
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
INCHES
DIMAMINMAXMINMAX
0.249 0.2636.306.70
B 0.130 0.1453.303.70
C 0.060 0.0681.501.75
D 0.024 0.0350.600.89
F0.115 0.1262.903.20
G 0.087 0.0942.202.40
H 0.0008 0.0040 0.020 0.100
J
J 0.009 0.0140.240.35
K 0.060 0.0781.502.00
L 0.033 0.0410.851.05
M0 10 0 10
____
S 0.264 0.2876.707.30
MILLIMETERS
K
SOLDERING FOOTPRINT*
2.0
0.079
2.3
0.091
2.0
0.079
1.5
0.059
*For additional information on our Pb−Free strategy
and soldering details, please download the
ON Semiconductor Soldering and Mounting
Techniques Reference Manual, SOLDERRM/D.
PACKAGE THERMAL DATA
Parameter
R
q
JC
R
q
JA
Typical3.53.515°C/W
Typical5010−50*156°C/W
* Depending on thermal properties of substrate. R
TO−220−3D2PAK−3SOT−223Unit
3.8
0.15
q
JA
2.3
0.091
= R
SCALE 6:1
+ R
q
JC
6.3
0.248
q
CA
mm
ǒ
inches
Ǔ
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13
NCP1086
ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.
“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All
operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights
nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications
intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should
Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates,
and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death
associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal
Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
LITERATURE FULFILLMENT:
Literature Distribution Center for ON Semiconductor
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For additional information, please contact your
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NPC1086/D
14
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