ISL80136

8

FN7970.2

August 11, 2015

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Functional Description

Functional Overview

The ISL80136 is a high performance, high voltage, low-dropout

regulator (LDO) with 50mA sourcing capability. The part is rated

to operate across the -40°C to +125°C temperature range.

Featuring ultra-low quiescent current, it makes an ideal choice

for “always-on” applications. It works well under a “load dump

condition” where the input voltage could rise up to 40V. The

device also features current limit and thermal shutdown

protection.

Enable Control

The ISL80136 features an Enable pin. When it is pulled low, the

IC goes into shutdown mode. In this condition, the device draws

less than 2µA. Driving the pin high turns the device on. For

always on operation, the EN pin can be tied directly to IN.

Current Limit Protection

The ISL80136 has internal current limit functionality to protect

the regulator during fault conditions. During current limit, the

output sources a fixed amount of current largely independent of

the output returns to normal voltage regulation mode.

Thermal Fault Protection

In the event that the die temperature exceeds typically +165°C,

the output of the LDO will shut down until the die temperature

cools down to typically +145°C. The level of power dissipated,

combined with the ambient temperature and the thermal

impedance of the package, will determine if the junction

temperature exceeds the thermal shutdown temperature. Also

see the section on “Power Dissipation”.

Application Information

Input and Output Capacitors

For the output, a ceramic capacitor (X5R or X7R) with a

capacitance of 10µF is recommended for the ISL80136 to

maintain stability. The ground connection of the output capacitor

should be routed directly to the GND pin of the device and also

placed close to the IC. A minimum of 0.1µF (X5R or X7R) is

recommended at the input.

Output Voltage Setting

The output voltage is programmed using an external resistor

divider, as shown in Figure 14.

The output voltage is calculated using Equation 1:

Power Dissipation

The junction temperature must not exceed the range specified in

“Recommended Operating Conditions” on page 4. The power

dissipation can be calculated using Equation 2:

the maximum allowable junction temperature rise (

in Equation 3:

To calculate the maximum ambient operating temperature, use

the junction-to-ambient thermal resistance (

Equation 4:

Board Layout Recommendations

A good PCB layout is important to achieve expected

performance. Consideration should be taken when placing the

components and routing the trace to minimize the ground

impedance, and keep the parasitic inductance low. The input and

output capacitors should have a good ground connection and be

placed as close to the IC as possible. The ADJ feedback trace

should be away from other noisy traces. Connect the exposed

pad to the ground plane using as many vias as possible within

the pad for the best thermal relief.

IN

OUT

EN

(ISL80136)

ADJ

GND

0.1µF

10µF

R1

R2

FIGURE 14. SETTING OUTPUT VOLTAGE

1.223V

R1

R2

-------- 1

+







=

(EQ. 1)

–

 I

OUT



+



=

(EQ. 2)

T

J



–

=

(EQ. 3)



+

=

(EQ. 4)