Detailed Description

The MAX5087 high-voltage linear regulator includes an

integrated µP reset circuit with an adjustable reset time-

out period (see the Adjustable Reset Timeout Period

(CT) section). The device guarantees a 400mA load

current and is available with a preset output voltage of

3.3V (MAX5087A) or 5V (MAX5087B). Both devices can

be configured to provide an adjustable output voltage

from 2.5V to 11V. The internal reset circuit monitors the

regulator output voltage and asserts RESET low when the

regulator output falls below the reset threshold voltage.

Other features include an enable (regulator control input),

21µA (max) shutdown current, short-circuit protection

(see the Output Short-Circuit Current Limit section), and

thermal shutdown (see the Thermal Protection section).

Regulator

The MAX5087 accepts an input voltage range from

6.5V to 45V and offers a fixed output voltage of 3.3V or

5V. For an adjustable output voltage operation, use an

external resistive divider network connected between

OUT, SET, and GND (see Figure 2).

Enable Input (EN)

EN is a logic-level enable input that turns the device

on/off. Drive EN high to turn on the device and drive EN

low to place the device in shutdown. The MAX5087

draws 11µA (typ) of supply current when in shutdown.

EN withstands voltages up to +45V, allowing EN to be

connected to IN for an always-on operation.

Remote Sensing (OUTSENSE)

The 3.3V (MAX5087A) and 5V (MAX5087B) output volt-

age versions connect OUTSENSE for load voltage

sensing. Leave OUTSENSE open when using

adjustable output voltage version.

Reset Output (RESET)

A supervisor circuit is fully integrated in the MAX5087

and uses the same reference voltage as the regulator.

voltage threshold, and remains low at least for the time-

threshold.

Adjustable Reset Timeout Period (CT)

The MAX5087 features a user-adjustable reset timeout.

Connect a capacitor from CT to GND to set the reset

timeout period (see Figure 2) and use the following

equation to calculate the timeout period:

nected from CT to GND.

Thermal Protection

an internal thermal sensor signals the shutdown logic,

which turns off the pass transistor, allowing the IC to

cool. The thermal sensor turns the pass transistor on

again after the IC’s junction temperature cools by 25°C,

resulting in a cycled output during continuous thermal-

overload conditions. Thermal protection protects the

MAX5087 in the event of fault conditions. During contin-

uous operation, do not exceed the absolute maximum

Output Short-Circuit Current Limit

The MAX5087 features a current limit. The output can

be shorted to GND for an indefinite period of time (for

output short-circuit protection is only guaranteed for

45V, 400mA, Low-Quiescent-Current

Linear Regulator with Adjustable Reset Delay

8

_______________________________________________________________________________________

6.5V TO 45V

2.5V TO 11V

47

μF

15

μF

OUT

ON

OFF

OUTSENSE

SET

IN

R1

R2

EN

TO

μP

RESET

CT

GND

MAX5087

Figure 2. Setting the Adjustable Output Voltage