LM1085 [HTC]
3A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed); 3A L.D.O.稳压器（可调和固定）
| 型号： | LM1085 |
| 厂家： | 
HTC KOREA TAEJIN TECHNOLOGY CO. |
| 描述： | 3A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed) |
| 文件： | 总8页 (文件大小：307K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
3A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)
LM1085
FEATURES
TO-263 PKG
● Output Current of 3A
● Fast Transient Response
● 0.04% Line Regulation
● 0.2% Load Regulation
● Internal Thermal and Current Limiting
● Adjustable or Fixed Output Voltage(1.5V, 1.8V, 2.5V, 3.3V, 5.0V)
● Surface Mount Package TO-263 3LD & TO-252 3L
● 100% Thermal Limit Burn-in
TO-252 PKG
● Low Dropout Voltage 1.5V at 3A Output Current
● Moisture Sensitivity Level 3
1. ADJ / GND 2. OUTPUT 3. INPUT
* Heatsink surface connected to Pin 2.
APPLICATIONS
● High Efficiency Linear Regulators / Power Supply
● High Efficiency "Green" Computer Systems
● Constant Current Regulators
ORDERING INFORMATION
Device
Package
● Portable Instrumentation
LM1085R-X.X
LM1085RS-X.X
TO-263 3LD
TO-252 3LD
● SMPS Post-Regulator
● Adjustable Power Supplies
(X.X=VOUT=1.5V, 1.8V, 2.5V, 3.3V, 5.0V, ADJ)
● Powering VGA & Sound Card
DESCRIPTION
The LM1085 series of positive adjustable and fixed regulators are designed to provide 3A with high efficient.
All internal circuitry is designed to operate down to 1.5V input to output differential.
On-chip trimming adjusts the reference voltage to 1%.
It's low dropout voltage and fast transient response make it ideal for low voltage microprocessor applications.
Internal current and thermal limiting provides protection against any overload condition that would create
excessive junction temperature.
TEST & TYPICAL APPLICATION CIRCUIT
LM1085-3.3V
LM1085-ADJ
Note
VREF=VOUT-VADJ=1.25V(Typ.)
(1) C1 needed if device is far away from filter capacitors.
(2) C2 minimum value required for stability
IADJ=55㎂(Typ.)
VOUT = VREF x (1+RF2/RF1) + IADJ x RF2
Nov. 2010-Rev. 1.4
HTC
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3A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)
LM1085
BLOCK DIAGRAM
ABSOULTE MAXIMUM RATINGS
CHARACTERISTIC
SYMBOL
VIN
VALUE
12
UNIT
V
Supply Voltage
TA
-10 ~ 70
0 ~ 125
-65 ~ 150
3
Operating Temperature Range
℃
℃
TJ
Junction Temperarture
Tstg
Tjc
Storage Temperature Range
℃
C/W
C/W
Thermal Resistance Junction to Case TO-263
Thermal Resistance Junction to Ambient TO-263
Lead Temperature (Soldering) 10 sec.
Maximum Output Current
Tja
60
Tsol
Imax
300
℃
3
A
HTC
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3A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)
LM1085
ELECTRICAL CHARACTERISTICS IOUT=100mA, TA=25°C, unless otherwise specified
PARAMETER
1.5V Version
TEST CONDITIONS
MIN
1.470
1.764
2.450
3.234
4.900
TYP
1.5
1.8
2.5
3.3
5.0
MAX
1.530
1.836
2.550
3.366
5.100
UNIT
0<IOUT<3A, 2.75V<VIN
Output Voltage
1.8V Version
V
V
V
V
V
0<IOUT<3A, 2.75V<VIN
0<IOUT<3A, 3.5V<VIN
0<IOUT<3A, 4.75V<VIN
0≤IOUT≤3A, 5.5V≤VIN
Output Voltage
2.5V Version
Output Voltage
3.3V Version
Output Voltage
5.0V Version
Output Voltage
All Voltage Options
VIN≤7V, P≤PMAX
1.238
1.225
1.25
1.25
5
1.263
1.275
13
Reference Voltage (VREF
)
V
1.5V≤(VIN-VOUT)≤5.75V, 10mA≤IOUT≤3A
1.5V≤(VIN-VOUT)≤5.75V
mA
%
Min. Load Current(Note 3)
Line Regulation (ΔVREF(VIN)) 2.75V≤VIN≤7V, IOUT=10mA, TJ=25℃
Load Regulation (ΔVREF(VOUT)) 10mA≤IOUT≤3A, (VIN-VOUT)=3V, TJ=25℃
0.05
0.1
1.3
0.3
0.4
%
ΔVREF=1% , IOUT=3A
1.5
V
Dropout Voltage
VIN-VOUT=3V
Current Limit
3.2
4.5
0.3
A
IOUT(MAX)
1.4V≤(VIN-VOUT) Adjustable Only
TA=125℃, 1000Hrs
Long Term Stability
Thermal Regulation
(ΔVOUT(Pwr))
1
%
TA=25℃, 30ms pulse
0.01
0.02
%/W
%/Vo
℃/W
10Hz to 10Khz TA=25℃
Junction to Tab
0.003
Output Noise, RMS
3
Thermal Resistance
Junction to Ambient
60
HTC
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3A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)
LM1085
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 1. Dropout Voltage vs Output Current
Figure 3. Load Regulation vs. Output Current
Figure 5. Adjust Pin Current vs Temperature
Figure 2. Reference Voltage vs Temperature
Figure 4. Minimum Load Current
Figure 6. Ripple Rejection vs. Frequency
(Fixed Versions)
HTC
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3A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)
LM1085
Figure 7. Ripple Rejection vs. Frequency (Adjustable Versions)
APPLICATIONS INFORMATION
LM1085-ADJ
ADJ
Figure 8. Resistor Divider Scheme for the Adjustable Version
LM1085-XX
Figure 9. Protection Diode Scheme for Fixed Output Regulators
HTC
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3A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)
LM1085
APPLICATION INFORMATION
The LM1085 series of adjustable and fixed regulators are easy to use and have all the protection features
expected in high performance voltage regulators : short circuit protection and thermal shut-down. Pin compatible
with older three terminal adjustable regulators, these devices offer the advantage of a lower dropout voltage,
more precies reference tolerance and improved reference stability with temperature.
STABILITY
The circuit design used in the LM1085 series requires the use of an output capacitor as part of the device
frequency compensation.
The addition of 150uF aluminum electrolytic or a 22uF solid tantalum on the output will ensure stability for
all operating conditions. When the adjustment terminal is bypassed with a capacitor to improve the ripple
rejection, the requirement for an output capacitor increases. The value of 22uF tantalum or 150uF aluminum
covers all cases of bypassing the adjustment terminal. Without bypassing the adjustment terminal smaller
capacitors can be used with equally good results.
To ensure good transient response with heavy load current changes capacitor values on the order of 100uF
are used in the output of many regulators. To further improve stability and transient response of these devices
larger values of output capacitor can be used.
PROTECTION DIODES
Unlike older regulators, the LM1085 family does not need any
protection diodies between the adjustment pin and the output and
from the output tu the input to prevent over-stressing the die.
Internal resistors are limiting the internal current paths on the
LM1085 adjustment pin, therfore even with capacitors on the
adjustment pin no protection diode is needed to ensure device
safety under short-circuit conditions.
LM1085
Diodes between the input and output are not usually needed.
Figure 10.
Microsecond surge currents of 50A to 100A can be handled by
the internal diode between the input and output pins of the device. In norminal operations it is difficult to get
those values of surge currents even with the use of large output capacitances. If high value output capacitors
are used, such as 1000uF to 5000uF and the input pin is instantaneously shorted to ground, damage can occur.
A diode from output to input is recommended, when a crowbar circuit at the input of the LM1085 is used.
Normal power supply cycling or even plugging and unplugging in the system will not generate current large
enough to do any damage.
The adjustment pin can be driven on a transient basis ±25V, with respect to the output without any device
degradation. As with any IC regulator, none the protection circuitry will be functional and the internal
transistors will break diwn if the maximum inout to output voltage differential is exceeded.
HTC
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3A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)
LM1085
RIPPLE REJECTION
The ripple rejection values are measured with the adjustment pin bypassed. The impedance of the adjust pin
capacitor at the ripple frequency should be less than the value of R1 (normally 100Ω to 120Ω) for a proper
bypassing and ripple rejection approaching the values shown. The size of the required adjust pin capacitor is
a function of the input ripple frequency. If R1=100Ω at 120Hz the adjust pin capacitor should be 25uF.
At 100kHz only 0.22uF is needed.
The ripple rejection will be a function of output voltage, in circuits without an adjust pin bypass capacitor.
The output ripple will increase directly as a ratio of the output voltage to the reference voltage (VOUT/VREF
)
OUTPUT VOLTAGE
The LM1085 series develops a 1.25V reference voltage between
the output and the adjust terminal. Placing a resistor between these
two terminals causes a constant current to flow through R1 and down
throuth R2 to set the overall output voltage.
LM1085
This current is normally the specified minium load current of 10mA.
Because IADJ is very small and constant it represents a small error
and it can usually be ignored.
Figure 11.
LOAD REGULATION
True remote sheet specification it is not possible to provide,
because the LM1085 is a three terminal device.
LM1085
The resistance of the wire connecting the regulator to the load
will limit the load regulation.
The data sheet specification for load regulation is measured at the
bottom of the package. Negative side sensing is a true Kelvin
connection, with the bottom of the output divider returned to the
negative side of the load.
The best load regulation is obtained when the top of the resistor
divider R1 is connected directly to the case not to the load. If R1
were connected to the load, the effective resistance between the
regulator and the load would be:
Figure 12.
[RPX(R2+R1)]/R1 , RP = Parasitic Line Resistance
Connected as shown Figure.12 R is not multiplied by the divider ratio. Using 16-gauge wire the parasitic line
P
resistance is about 0.004Ω per foot, transllating to 4mV/ft at 1A load current.
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3A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)
LM1085
THERMAL CONSIDERATIONS
The LM1085 series have internal power and thermal limiting circuitry designed to protect the device under
overload cinditions. However maximum junction temperature ratings should not be exceeded under continous
normal load conditions.
Careful consideration must be given to all sourses of thermal resistance from junction to ambient, including
junction-to- ase, case-to-heat sink interface and heat sink resistance itself. To ensure safe operating
temperatures and reflect more accurately the device temperature, new thermal resistance specifications have
been developed. Unlike order reguators with a single junction-to-case thermal resistance speccification, the
data section for these new regulators provides a separate thermal resistance and maximum juntion temperature
for both the Control Section and the Power Transistor. Calculations for both temperatures under certain
conditions of ambient temperature and heat sink resistance and to ensure that both thermal limits are met.
Junction-to-case thermal resistance is specified from the IC junction to the bottom of the case directly below
the die. This is the lowest resistance path for the heat flow. In order to ensure the best possible thermal flow
from this area of the package to the heat sink proper mounting is required. Thermal compound at the case-
to-heat sink interface is recommended. A thermarlly conductive spacer can be used, if the case of the device
must be electrically isolated, but its added contribution to thermal resistance has to be considered.
spacer can be used, if the case of the device must be electrically isolated, but its added contribution
to thermal resistance has to be considered.
HTC
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