max5091aata Maxim Integrated Products, Inc., max5091aata Datasheet - Page 10

• Manufacturer Part Number: max5091aata
• Description: Max5091 28v, 100ma, Low-quiescent-current Ldo With Reset And Power-fail Input/output
• Manufacturer: Maxim Integrated Products, Inc.

28V, 100mA, Low-Quiescent-Current LDO
with Reset and Power-Fail Input/Output
The MAX5091 high-voltage, LDO regulator operates
from +5V to +28V input voltage. The device withstands
up to 40V transients, providing protection against tem-
porary overvoltage conditions like load dump. The
MAX5091 incorporates internal feedback resistors for
factory-preset voltages of either +5V (MAX5091A) or
+3.3V (MAX5091B). The regulator is capable of driving
up to 100mA of load current and features a typical cur-
rent limit of 260mA. The regulator uses a pnp pass ele-
ment and provides low 0.5V dropout while delivering
100mA load current. The output of the regulator follows
closely to the input during turn-on. See the Output
Voltage vs. Input Voltage graph in the Typical
Operating Characteristics. This makes the usable input
voltage range for 3.3V and 5V output down to 3.7V and
5.5V, respectively. The MAX5091 is designed to oper-
ate with very low quiescent current during always-on
operation when not in dropout. The regulator is stable
with a wide variety of capacitors including low-ESR
ceramic 10µF (0603 case size). The load-transient
response curves depict the stability of the LDO when
using different capacitance and ESR ranges. See the
Capacitor Selection and Regulator Stability section in
the Applications Information.
The MAX5091 integrates a power-on-reset circuit. RES
is an open-drain output that requires a pullup resistor to
V
current while keeping the RES voltage below 0.4V. The
internal reset circuit monitors the regulator output volt-
age and RES asserts an active-low output when the
regulator output falls below a reset threshold of typical-
ly 0.9 x V
is below the reset threshold, and remains low for the
duration of the reset timeout period (t
timeout period is programmable and can be set with an
external capacitor connected from CT to ground. The
duration of the delay as a function of CT is:
The default reset timeout period is 35µs when no
capacitor is connected from CT to ground.
10
where V
OUT
______________________________________________________________________________________
. The open-drain MOSFET can sink up to 825µA
t
RD
CCTH
OUT
=
. The RES output remains low when V
C
CT
=
×
I
2 1
CT
.
V
CCTH
V and
Detailed Description
+
I
CT
Reset Output ( RES )
(
35
=
×
2
10
×
−
RD
6
10
)
Regulator
). The reset
−
6
A
.
OUT
The MAX5091 includes an uncommitted comparator for
monitoring the input voltage or for detecting power-fail
conditions. The input SI is the noninverting input of the
comparator. The open-drain output SO asserts low
when voltage at the input SI drops below the threshold
voltage, V
cally has a hysteresis of 100mV. Use the following
equation to calculate the resistor-divider for program-
ming the trip voltage (V
Typical Application Circuit.
where V
300kΩ.
The enable (EN) is a TTL-compatible logic input. Logic
low at EN turns off the regulator and reduces the cur-
rent consumption to 17µA (typ). It is internally pulled up
to a logic-high voltage (3.6V max) by an internal resis-
tor. Thus, the MAX5091 is enabled by default when V
is applied and EN is left unconnected. The regulator,
reset supervisor circuit, and the sense comparator can
be manually shut down by pulling EN low. For shut-
down operation, the pulldown network must be capable
of sinking 3µA max, since the internal pullup resistor
sets the maximum pullup current at 3µA. The external
pulldown device should not leak more than 1µA current
when it is in the off-state.
The MAX5091 features a current limiter that monitors
the output current and controls the pass transistor’s
gate voltage, limiting the output current to typically
260mA. The output can be continuously shorted to
ground without damaging the device at V
that the output short-circuit current may increase the
power dissipation significantly and raise the junction
temperature to its thermal-shutdown threshold. In such
a case, the MAX5091 is temporarily turned off.
When the junction temperature exceeds T
(typ), an internal thermal sensor signals the shutdown
logic to turn off the pass transistor and allow the IC to
cool. The thermal sensor turns the pass transistor on
again after the IC’s junction temperature cools by
+20°C (typ), resulting in a cycled output during contin-
uous thermal-overload conditions. Thermal shutdown
protects the MAX5091 in the event of fault conditions.
For continuous operation, do not exceed the absolute
maximum junction temperature of T
ST
ST
= 1.16V (typ). Choose R
V
(see Figure 1). The sense comparator typi-
TRIP
=
(V
ST
TRIP
R
×
) during power-fail. See the
L
R )
Thermal Shutdown
H
SI/SO Comparator
+
J
L
= +150°C.
between 100kΩ to
V
Current Limit
ST
Enable Input
S
J
≤ 16V. Note
= +165°C
S