Shutdown Discharge (MAX4833)

OUT discharges through a 900

Ω internal resistor during

shutdown mode.

Reverse OUT to IN Current

When the output voltage is greater than the input volt-

age, the internal pass transistor turns off. To avoid

reverse-charging the input source, the current at IN is

Current Limit

The MAX4832/MAX4833 include an accurate internal

current-limiting circuit. OUT can be shorted to ground

indefinitely without damaging the part.

The MAX4832 latches off if the load current exceeds the

current limit for more than the blanking time (see the

FLAG Output section). During soft-start, the device does

not latch off to an overload condition. During an overload

condition, the MAX4833 holds the current at current limit

until the thermal limit is reached. Once the junction tem-

perature reaches +165°C, thermal shutdown occurs.

Thermal Shutdown

the LDO’s pass transistor turns off allowing the junction

to cool. The LDO’s pass transistor turns on again after

the IC’s junction temperature cools by 15°C, resulting in

a pulsed output during continuous thermal-overload

conditions.

Soft-Start

During power-up, the soft-start ensures that the output

ramps up slowly reducing inrush current peaks. See

the soft-start response time plots in the Typical

given by the following equation:

1ms minimum soft-start time is fixed internally to ensure

that the output rises slowly even without any external

capacitor at SS pin to ground. The device is in soft-start

mode when either the voltage at IN or SHDN is cycled

high to low to high.

Applications Information

Capacitor Selection and Regulator

Stability

For stable operation over the full temperature range and

with load currents up to 100mA, use a 3.3µF (min)

ceramic output capacitor with an ESR <0.2

Ω. To reduce

noise and improve load transient response, stability, and

power-supply rejection, use larger output capacitor

values such as 10µF (note that some ceramic capacitors

exhibit large capacitance and ESR variation with temper-

ature). X7R capacitors provide good performance over

the -40°C to +85°C operating temperature range.

To improve power-supply rejection and transient

response, use a 0.1µF capacitor between IN and GND.

The MAX4832/MAX4833 remain stable with purely

resistive loads or current loads up to 100mA.

15kV Operational ESD Protection

A 3.3µF or higher value ceramic capacitor from OUT to

GND provides a 15kV (Human Body Model) protection

at OUT. The ESR value of the capacitor should be less

than 0.2

Ω.

Reset Transient Immunity

The reset circuit is relatively immune to short duration,

Characteristics show a graph of the Maximum Transient

Duration vs. Reset Threshold Overdrive for which reset is

threshold by the magnitude indicated (reset threshold

overdrive). The graph shows the maximum pulse width

triggering the reset pulse. As the amplitude of the tran-

sient increases (i.e., goes further below the reset thresh-

old), the maximum allowable pulse width decreases.

reset threshold and lasts up to 54µs does not trigger a

reset pulse.

Layout

When using the TDFN package, connect its exposed

paddle to GND to provide a low thermal resistance

path for heat transfer from the IC junction to the printed

circuit board.

100mA LDO Linear Regulators with

Current-Limiting Switch

_______________________________________________________________________________________

9