Detailed Description

The MAX16999 is a low-quiescent-current linear regula-

tor designed for applications requiring high reliability,

such as automotive applications. This device can supply

loads up to 100mA and is available in factory-preset out-

put voltages from 0.5V to 3.3V (see the

Selector Guide).

As illustrated in Figure 1, the MAX16999 linear regulator

consists of a reference, an error amplifier, a p-channel

MOSFET pass transistor, and an internal feedback volt-

age-divider. A power-on reset section signals if the out-

put voltage has come out of regulation. The reset signal

timeout is defined by the charging time of an external

capacitor attached to CRES.

To increase system reliability, the MAX16999 features a

POR reset timeout along with overcurrent and overtem-

perature protection. A power-on reset timeout guaran-

tees startup even with a faulty timing capacitor.

Parameters are guaranteed up to +125°C junction tem-

perature. The EN signal is latched in its last state even

if the signal line becomes disconnected.

Logic-Controlled Enable

The MAX16999 provides a logic-enable input (EN). For

normal operation drive EN to logic-high. When EN is

driven high, the linear regulator starts to regulate by

increasing the output voltage up to the preset value. To

disable the device, drive EN low to set OUT to high

impedance—this enables a pulldown current from

CRES to discharge the capacitor. Once the device is

disabled, the input supply current reduces to less than

0.3µA. The EN input is latched into its last state by a

120kΩ internal resistor. To change state, the latch

needs to be overridden. When EN is low, the RESET

output is high impedance.

POR Timer

two internal timers are simultaneously activated. The

reset timer is realized by means of a pullup current

old of 600mV (typ), RESET goes high impedance.

The internal reset timer is set by the value of the exter-

using the following formula:

given in seconds.

The second timer is an internal fault timer and ensures

the regulator does not stay off indefinitely because of a

fault on CRES such as a short. The fault timer runs for a

maximum of 100ms. A logic block monitors both inter-

nal timers to determine the shortest timeout. If the first

timeout is the fault timer, the pullup current is switched

off in order to avoid unnecessary current consumption

and a resistive pulldown is also activated. If

the timeout behavior.

Current Limit

Once the output voltage reaches regulation, the output

current is limited to 150mA (typ). If the output current

exceeds the current limit, the output voltage begins to

decrease.

Thermal-Overload Protection

Thermal-overload protection limits total power dissipa-

tion in the MAX16999. When the junction temperature

exceeds +165°C, a thermal sensor turns off the pass

transistor, allowing the IC to cool. The thermal sensor

turns the pass transistor on again after the junction tem-

perature cools by 15°C, resulting in a pulsed output

during continuous thermal-overload conditions.

Thermal-overload protection safeguards the MAX16999

in the event of fault conditions. For continuous opera-

tion, do not exceed the absolute maximum junction-

temperature rating of +150°C. Table 1 lists maximum

DC output currents (milliamps) that are allowed for

down of the MAX16999.

tC

x

x

V

A

POR DELAY

CRES

_

=

60

Ultra-Low Output Voltage, Low-Quiescent-Current

Linear Regulator for High-Temperature Applications

8

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