1A Low Dropout Fast Response Positive Adjustable Regulator and Fixed
1.8V, 2.5V, 2.85V and 3.3V
Features
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Guaranteed Output Voltage Accuracy within 2%
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Fast Transient Response
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Guaranteed Dropout Voltage at Multiple
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Currents
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Load Regulation : 0.1% Typ.
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Line Regulation : 0.03% Typ.
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• Low Dropout Voltage : 1.1V Typ. at I
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• Current Limit : 1A Typ. at T
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• On-Chip Thermal Limiting : 150°C Typ.
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• Adjustable Output : 1.25~10.7V
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• Standard 3-pin TO-220, TO-252, TO-263 and
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SOT-223 Power Packages
=25°C
J
OUT
=1A
Applications
General Description
The APL1117 is a low dropout three-terminal adjustable regulators with 1A output current capability. In
order to obtain lower dropout voltage and faster transient response, which is critical for low voltage applications , the APL1117 has been optimized. The
device is available in an adjustable version and fixed
output voltages of 1.8V, 2.5V, 2.85V and 3.3V. The
output available voltage range of an adjustable version is from 1.25~10.7V with an input supply below
12V. Dropout voltage is guaranteed at a maximum of
1.3V at 1A. Current limit is trimmed to ensure specified output current and controlled short-circuit current.
On-chip thermal limiting provides protection against
any combination of overload that would create excessive junction temperatures. The APL1117 is available
in the industry standard 3-pin TO-220, TO-252, TO263, and the low profile surface mount SOT-223
power packages which can be used in applications
where space is limited.
Pin Description
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• Active SCSI Terminators
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• Low Voltage Logic Supplies
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• Battery-Powered Circuitry
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• Post Regulator for Switching Power Supply
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TAB is V
TAB IS V
ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and advise
customers to obtain the latest version of relevant information to verify before placing orders.
Note 1 : See thermal regulation specifications for changes in output voltage due to heating effects. Load line regulations are mea sured at a constant junction temperature by low duty cycle pulse testing.
Note 2 : Dropout voltage is specified over the full output current range of the device. Dropout voltage is defined as the minimum input/output
differential measured at the specified output current. Test points and limits are also shown on the Dropout Voltage curve.
Note 3 : Minimum load current is defined as the minimum output current required to maintain regulation.
The APL1117 develops a 1.25V reference voltage
between the output and the adjust terminal. By placing a resistor between these two terminals, a constant Current is caused to flow through R1 and down
through R2 to set the overall output voltage. Normally
this current is chosen to be the specified minimum
load current of 10mA. For fixed voltage devices R1
and R2 are included in the device.
OUT
APL1117
I
ADJ
60µA
= V
OUTIN
ADJ
REF
(1+ )+ I
R2
R1
ADJ
V
R2
REF
R1
R2
V
OUT
V
IN
V
Figure 1. Basic Adjustable Regulator
Rp
V
IN
APL1117
OUTIN
ADJ
PAR A SIT IC
LINE RESISTANCE
R1
CONNECT
R1 TO CASE
R2
CONNECT
R2 TO LOAD
R
Figure 2. Connections for Best Load Regulation
Input Capacitor
An input capacitor of 10µF or greater is
recommended. Tantalum, or aluminum electrolytic
capacitors can be used for bypassing. Larger Values will improve ripple rejection by bypassing the in-
L
Load Regulation
When the adjustable regulator is used. Load regulation will be limited by the resistance of the wire connecting the regulator to the load. The data sheet specification for load regulation is measured at the output
pin of the device. Best load regulation is obtained
when the top of the resistor divider (R1) is tied directly to the output pin of the device, not to the load.
For fixed voltage devices the top of R1 is internally
connected to the output, and the ground pin can be
connected to low side of the load. If R1 were connected to the load, RP is multiplied by the divider
ratio, the effective resistance between the regulator
and the load would be:
Rp X (1+ ), Rp = Parasitic L ine Resistance
R2
R1
put to the regulator.
Output Capacitor
The APL1117 requires an output capacitor to maintain stability and improve transient response. Proper
capacitor selection is important to ensure proper
operation. The APL1117 output capacitor selection
is dependent upon the ESR (equivalent series
resistance) of the output capacitor to maintain stability.
When the output capacitor is 10uF or greater, the
output capacitor should have an ESR less than 1Ω.
This will improve transient response as well as promote stability. A low-ESR solid tantalum capacitor
works extremely well and provides good transient response and stability over temperature.
Aluminum electrolytics can also be used, as long as
the ESR of the capacitor is <1Ω. The value of the
output capacitor can be increased without limit. Higher
capacitance values help to improve transient response
and ripple rejection and reduce output noise.
Ripple Rejection
The curves for Ripple Rejection were generated using an adjustable device with the adjust pin bypassed.
With a 22µF bypassing capacitor 75dB ripple rejection is obtainable at any output level. The impedance
of the adjust pin capacitor, at the ripple frequency,
should be < R1. R1 is normally in the range of 100Ω-
200Ω. The size of the required adjust pin capacitor
is a function of the input ripple frequency. At 120Hz,
with R1=100Ω, the adjust pin capacitor should be
13µF. For fixed voltage devices, and adjustable de-
Figure 3&4 shows for the TO-252 and SOT-223 the
measured values of θ(J-A) for different copper area
sizes using a 2 layers, 1.6mm, and 6Sq. cm FR-4
PCB with 2oz. copper and a ground plane layer on
the backside area used for heatsinking. It can be
used as a rough guideline in estimating thermal
resistance.
50
TA=25°C
45
40
35
Thermal Resistance
30
(Juntion to Ambient) (°C/W)
25
02468101214
Top Copper Area (cm2)
vices without an adjust pin capacitor, the output ripple
will increase as the ratio of the output voltage to the
reference voltage (VOUT /VREF ).
Thermal Considerations
APL1117 has thermal protection which limits junction
temperature to 150°C. However, device functionality
is only guaranteed to a maximum junction temperature of +125°C.
Both the TO-220, TO-252, TO-263 and SOT-223
packages use a copper plane on the PCB and the
PCB itself as a heatsink. To optimize the heat sinking
ability of the plane and PCB, solder the tab of the
package to the plane.
The thermal resistance for each application will be
affected by thermal interactions with other components on the board. Some experimentation will be
necessary to determine the actual value.
The power dissipation of APL1 117 is equal to :
PD = (VIN - VOUT) x IOUT
Maximum junction temperature is equal to :
TJUNCTION = TAMBIENT + (PD x θJA)
Note: TJUNCTION must not exceed 125°C