Diodes AP1184 - Manual (Page 5)

AP1184
4A ULTRA LOW DROPOUT POSITIVE ADJUSTABLE OR
FIXED-MODE REGULATOR
AP1184 Rev. 5 5 of 12 SEPTEMBER 2008
www.diodes.com © Diodes Incorporated
Electrical Characteristics
(Continued)
Unless otherwise specified, these specifications apply over, C in = 1uF, C out = 10uF, and T j = 0 to 150 o C. Typical value refer to T A = 25 o C.
V ou t
= V sense .
Sym. Parameter Test Condition Min Typ. Max Unit
I
adj
Adjust Pin Current V
ctrl
= 2.75V, V
in
= 2.05,V
adjj
= 0 50 150 µA
θ
JA
Thermal Resistance
Junction-to-Ambient TO263-5L: Control Circuitry/Power Transistor (Note 4)
TO220-5L: Control Circuitry/Power Transistor (Note 5) 61
31 O C/W
O
C/W
θ
JC
Thermal Resistance
Junction-to-Case TO263-5L: Control Circuitry/Power Transistor (Note 4)
TO220-5L: Control Circuitry/Power Transistor (Note 5) 7
5
O
C/W
O
C/W
Notes: 3. AP1184-ADJ incorporates an internal thermal shutdown that protects the device when the junction temperature exceeds the allowable
maximum junction temperature.
4. Test conditions for TO263-5L : Devise mounted on 2oz copper, minimum recommended pad layout , FR-4 PCB.
5. Test conditions for TO220-5L : with copper area of approximately 3in
2 , 1oz.
Package Max Pd. Remarks
TO263-5L/TO220-5L 2.4W~4.4W With heat sink or amount of copper board needed.
Functional Descriptions
Introduction
The AP1184 regulator is a 5 terminal device designed specifically to provide extremely low dropout voltages comparable to the PNP type
without the disadvantage of the extra power dissipation due to the base current associated with PNP regulators. This is done by bringing
out the control pin of the regulator that provides the base current to the power NPN and connecting it to a voltage that is greater than the
voltage present at the V
in
pin. This flexibility makes the AP1184 ideal for applications where dual inputs are available such as a computer
motherboard with an ATX style power supply that provides 5V and 3.3V to the board. One such application is the new graphic chip sets
that require anywhere from 2.4V to 2.7V supply. The AP1184 can easily be programmed with the addition of two external resistors to any
voltages within the range of 1.25V to 15.5V. Another major requirement of these graphic chips is the need to switch the load current from
zero to several amps in tens of nanoseconds at the processor pins, which translates to an approximately 300 to 500ns of current step at
the regulator. In addition, the output voltage tolerances are also extremely tight and they include the transient response as part of the
specification.
The AP1184 is specifically designed to meet the fast current transient needs as well as providing an accurate initial voltage, reducing the
overall system cost with the need for fewer number of output capacitors. Another feature of the device is its true remote sensing capability
that allows accurate voltage setting at the load rather than at the device.
Output Voltage Setting
The AP1184-ADJ can be programmed to any voltages in the range of 1.25V to 15.5V with the addition of R1 and R2 external resistors
according to the following formula: