LM39101-5.0 参数 Datasheet PDF下载

1A Low-Voltage Low-Dropout Regulator

LM39100/39101/39102

Minimum Load Current

The LM39100/1/2 regulator is specified between finite loads.If the output current is too small, leakage currents

dominate and the output voltage rises. A 10mA minimum load current is necessary for proper regulation.

Adjustable Regulator Design

The LM39102 allows programming the output voltage any-where between 1.24V and the 16V maximum operating

rating of the family. Two resistors are used. Resistors can be quite large, up to 1MΩ, because of the very high input

impedance and low bias current of the sense comparator: The resistor values are calculated by :

R1=R2(Vout/1.240-

1)

Where VO is the desired output voltage. Figure 1 shows component definition. Applications with widely varying load

currents may scale the resistors to draw the minimum load current required for proper operation (see below).

Power SOP-8 Thermal Characteristics

One of the secrets of the LM39101/2’s performance is its power SO-8 package featuring half the thermal resistance

of a standard SO-8 package. Lower thermal resistance means more output current or higher input voltage for a given

package size.Lower thermal resistance is achieved by joining the four ground leads with the die attach paddle to

create a single-piece electrical and thermal conductor. This concept hasbeen used by MOSFET manufacturers for

years, proving very reliable and cost effective for the user.Thermal resistance consists of two main elements, θ

JC(junction-to-case thermal resistance) and θCA (case-to-ambient thermal resistance). See Figure2. θJC is the

resistance from the die to the leads of the package. θCA is the resistance from the leads to the ambient air and it

includes θCS (case-to-sink thermal resistance) and θSA (sink-to-ambient thermal resistance).Using the power SOP-

8 reduces the θJC dramatically and allows the user to reduce θCA. The total thermal resistance,θJA (junction-to-

ambient thermal resistance) is the limiting factor in calculating the maximum power dissipation capabil-ity of the

device. Typically, the power SOP-8 has a θJC of20°C/W, this is significantly lower than the standard SOP-8 which is

typically 75°C/W. θCA is reduced because pins 5 through 8 can now be soldered directly to a ground plane which

significantly reduces the case-to-sink thermal resis-tance and sink to ambient thermal resistance.Low-dropout linear

regulators from HTC are rated to amaximum junction temperature of 125°C. It is important not to exceed this

maximum junction temperature during operation of the device. To prevent this maximum junction temperature from

being exceeded, the appropriate ground plane heatsink must be used.

Figure3 shows copper area versus power dissipation with each trace corresponding to a different temperature rise

above ambient.From these curves, the minimum area of copper necessary for the part to operate safely can be

determined. The maxi-mum allow able temperature rise must be calculated to deter-mine operation along which

curve.

∆T = TJ(max) – TA(max)

TJ(max) = 125°C

TA(max) = maximum ambient operating temperature

For example, the maximum ambient temperature is 50°C, the∆T is determined as follows:

∆T = 125°C – 50°C

∆T = 75°C

HTC

8