AME1084 Datasheet, PDF (6/16 Pages) Analog Microelectronics – 5A Low Dropout Positive Voltage Regulator

Analog Microelectronics, Inc.
AME1084
5A Low Dropout
Positive Voltage Regulator
n Application Description
1. Output voltage adjustment
Like most regulators, the AME1084 regulates
the output by comparing the output voltage to
an internally generated reference voltage. On
the adjustable version, the VREF is available ex-
ternally as 1.25V between V_OUT 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:
V_OUT = V_REF ( 1 +
R2
R1
) + I_ADJ x R2
On fixed versions of AME1084, the voltage di-
vider is provided internally.
3. Current limit protection
AME1084 is protected against overload conditions.
Current protection is triggered at typical 7.5A.
4. Stability and load regulation
AME1084 requires a capacitor from VOUT to GND t o
provide compensation feedback to the internal gain
stage. This is to ensure stability at the output termi-
nal. Typically, a 10µF tantalum or 50µF aluminum
electrolytic is sufficient.
Note: It is important that the ESR for this capacitor
does not exceed 0.5Ω.
The output capacitor dose not have a theoretical
upper limit and increasing its value will increase
stability. COUT = 100µF or more is typical for high cur-
rent regulator design.
V _IN
C₁
IN
OUT
ADJ
I_ADJ
5 0 µA
V_REF
V_OUT
=
V_REF
(1+R2
R1
)
+
I_ADJ
x
R2
V_OUT
R1
For the adjustable version, the best load regulation is
accomplished when the top of theresistor divider
(R1) is connected directly to theoutput pin of the
AME1084. When so connected, R_P is not multiplied
by the divider ratio.
For fixed output versions, the top of R1 is internally
connected to the output. The ground pin can be con-
R2
nected to low side of the load to eliminate ground loop
errors.
Figure 3
V _IN
2. Thermal protection
AME1084 has thermal protection which limits
junction temperature to 150^OC. However, de-
vice functionality is only guaranteed to a maxi-
mum junction temperature of +125^OC.
R_P
Parasitic
Line Resistance
IN
OUT
ADJ
R1
(Connect R1 to case)
R_L
R2
The power dissipation and junction tempera-
ture for AME1084 in TO-220 package are given
by
P_D = (V_IN - V_OUT) x I_OUT
T_JUNCTION = T_AMBIENT + ( P_D x θ_JA)
Note: T_JUNCTION must not exceed 125^OC
Connect
R2 to load
Figure 4
6