SPX2730 Просмотр технического описания (PDF) - Signal Processing Technologies

Номер в каталоге

Компоненты Описание

производитель

SPX2730

3A High Current Low Dropout Voltage Regulator Adjustable & Fixed Output, Fast Response

Signal Processing Technologies 

APPLICATION HINTS

The SPX2730/31/32/33 incorporates protection against over-

current faults, reversed load insertion, over temperature

operation, and positive and negative transient voltage.

However, the use of an output capacitor is required in order to

insure the stability and the performances.

Thermal Consideration

Although the SPX2730/31/32/33 offers limiting circuitry for

overload conditions, it is necessary not to exceed the

maximum junction temperature, and therefore to be careful

about thermal resistance. The heat flow will follow the lowest

resistance path, which is the Junction-to-case thermal

resistance. In order to insure the best thermal flow of the

component, a proper mounting is required. Note that the case

of the device is electrically connected to the output. The

case has to be electrically isolated, a thermally conductive

spacer can be used. However do not forget to consider its

contribution to thermal resistance.

Assuming:

VIN = 10V, VOUT = 5V, IOUT = 1.5A, TA = 50°C/W,

θHeatsink Case= 6°C/W, θHeatsink Case = 0.5°C/W, θ JC = 3°C/W

Power dissipation under this condition

PD = (VIN – VOUT) * IOUT = 7.5W

Junction Temperature

TJ = TA + PD * (θCase – HS + θ HS θ JC)

For the Control Section

TJ = 50 + 7.5*(0.5 + 6=3) = 121.25°C

121.25°C < TJ (max) for the Control & Power Sections.

In both case reliable operation is insured by adequate junction

temperature.

Capacitor Requirements

The output capacitor is needed for stability and to minimize

the output noise. The required value of the capacitor varies

with the load. However, a minimum value of 10µF Aluminum

will guarantee stability over load. A tantalum capacitor is

recommended for a fast load transient response

If the power source has high AC impedance, a 0.1µF capacitor

between input & ground is recommended. This capacitor

should have good characteristics up to 250 kHz.

Minimum Load Current

To ensure a proper behavior of the regulator at light load, a

minimum load of 10mA for SPX2730/31/32/33 is required.

SPX2730/31/32/33

Adjustable Regulator Design

SPX2732/33are adjustable regulators and maybe programmed

for any value between 1.25V and 16V using two resistors.

The relation between the resistors is given by:

R1=R2 (VOUT/1.240 –1)

Resistors have a large value up to 1mΩ in order to reduce the

current consumption. This might be interesting in the case of

widely varying load currents.

Error Flag

SPX2731/33 features an error indicating either an over current

fault or a low input voltage. This flag pulls low when such a

problem occurs and may sink 10mA. It is inoperative during

thermal shutdown.

Enable Input

SPX2731/32 features enable input allowing turning ON &

OFF the device. EN has been designed to be compatible with

TTL/CMOS logic. When the regulator is ON, the current

flowing through this pin is approximately 20µA.

VIN

SPX2730

VOUT

Fig.1 Basic Fixed Output Regulator

VIN

1

4

2 SPX2732/33

3

5

VOUT

R1

R2

VOUT = VREF X [ 1 + (R1/R2) ]

For best results, the total series resistance should be

small enough to pass the minimum regulator load current

Fig. 2 Adjustable Output Voltage Regulator

Rev. 12/7/00

Share Link: