AME, Inc.
1A Low Dropout
Positive Voltage Regulator
AME1117
nApplication Description
1. Output Voltage Adjustment
3. Current Limit Protection
Like most regulators, the AME1117 regulates the out-
put by comparing the output voltage to an internally gen-
erated reference voltage. On the adjustable version, the
VREF is available externally as 1.25V between VOUT and
ADJ. The voltage ratio formed by R1 and R2 should be
set to conduct 10mA (minimum output load). The output
voltage is given by the following equation:
AME1117 is protected against overload conditions. Cur-
rent protection is triggered at typically 1.5A.
4. Stability and Load Regulation
AME1117 requires a capacitor from VOUT toGND to pro-
vide compensation feedback to the internal gain stage.
This is to ensure stability at the output terminal. Typi-
cally, a 10mF tantalum or 50mF aluminum electrolytic is
sufficient.
R2
VOUT = VREF ( 1 +
) + IADJ x R2
R1
On fixed versions of AME1117, the voltage divider is
provided internally.
(Note: It is important that the ESR for this capacitor does not ex-
ceed 0.5W.)
The output capacitor does not have a theoretical upper
limit and increasing its value will increase stability. COUT
= 100mF or more is typical for high current regulator de-
sign.
VIN
VOUT
IN
OUT
ADJ
VREF
R1
C1
For the adjustable version, the best load regulation is
accomplished when the top of the resistor divider (R1) is
connected directly to the output pin of the AME1117.
When so connected, RP is not multiplied by the divider
ratio.
IADJ
55mA
R2
For fixed output versions, the top of R1 is internally
connected to the output. The ground pin can be connected
to the low side of the load in order to eliminate ground
loop errors.
R2
R1
) + IADJ x R2
VOUT = VREF (1+
2. Thermal Protection
RP
Parasitic
Line Resistance
AME1117 has thermal protection which limits junction
temperature to 150oC. However, device functionality is
only guaranteed to a maximum junction temperature of
+125oC.
VIN
IN
OUT
ADJ
R1
(Connect R1 to case)
RL
The power dissipation and junction temperature for
AME1117 is given by
R2
PD = (VIN - VOUT) x IOUT
TJUNCTION = TAMBIENT + ( PD x qJA)
Note: TJUNCTION must not exceed 125oC
Connect
R2 to load
Rev.S.02
10
AME [ ANALOG MICROELECTRONICS ]
