Datasheet

MAX8526/MAX8527/MAX8528
1.425V to 3.6V Input, 2A,
0.2V Dropout LDO Regulators
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Detailed Description
The MAX8526/MAX8527/MAX8528 are low-input, low-
dropout, PMOS regulators capable of delivering up to
2A of output current with as little as 200mV of head-
room from input to output. The PMOS output stage can
be driven from input voltages down to +1.425V without
sacrificing stability or transient performance. Since this
regulator has a PMOS output device, supply current is
not a significant function of load or input headroom.
Internal p-Channel Pass Transistor
The MAX8526/MAX8527/MAX8528 feature a 50mΩ
(typ) p-channel MOSFET pass transistor. Unlike similar
designs using pnp pass transistors, p-channel MOSFETs
require no base drive, which reduces quiescent current.
pnp-based regulators also waste considerable current in
dropout when the pass transistor saturates, and use high
base-drive currents under large loads. The MAX8526/
MAX8527/MAX8528 do not suffer from these problems
and consume only 500µA (typ) of quiescent current
under heavy loads, as well as in dropout.
Short-Circuit/Thermal Fault Protection
The MAX8526/MAX8527/MAX8528 are fully protected
from a short circuit at the output through current-limit-
ing and thermal-overload circuitry. In the fault condition
when the output is shorted to ground, the output cur-
rent is limited to 4A. Under these conditions, the part
quickly heats up. When the junction temperature reach-
es +165°C, the thermal-overload circuitry turns off the
output, allowing the part to cool down. When the junc-
tion temperature cools to +150°C, the output turns
back on and tries to reestablish regulation. Current
limiting and thermal protection continue until the fault is
removed. For continuous operation, do not exceed the
absolute maximum junction temperature rating of
T
J
= +150°C.
Output Voltage Selection
The MAX8526/MAX8527/MAX8528 feature an
adjustable output voltage from 0.5V to 3.4V, using two
external resistors connected as a voltage-divider to FB
as shown in Figure 1. The output voltage is set by the
following equation:
where typically V
FB
= 0.5V. Choose R2 <
5kΩ to opti-
mize quiescent current, accuracy, and high-frequency
power-supply rejection. To simplify resistor selection:
Soft-Start
Inherent soft-start limits inrush current. Peak inrush cur-
rent is dependent on the value of C
OUT
and can be
calculated as follows:
Shutdown Mode
The MAX8526/MAX8527/MAX8528 include an enable
input. To shut down the device, pull EN to GND. For
normal operation, connect the EN to IN. During shut-
down, an internal 10kΩ resistor pulls down the output.
Power-OK (POK, MAX8527 Only)
The MAX8527 features a power-OK output to indicate
the status of the output. POK remains high when the
regulator output is within ±10% of its nominal output
voltage. If the output voltage falls/rises outside this
range, POK transitions low. This open-drain output
requires an external pullup resistor to IN. An internal
delay circuit prevents the POK from switching for 50µs
(typ) after the trip threshold is initially reached. If the
part is in shutdown mode, POK is low.
Power-On Reset (POR, MAX8528 Only)
The MAX8528 features a power-on reset output that
transitions high 150ms (typ) after the output has risen
above 90% of its final value. This open-drain output
requires an external pullup resistor to IN. If the part is in
shutdown mode, falls below 90% of the nominal output
voltage, or experiences a short-circuit/thermal fault,
POR immediately transitions low.
II
CF
INRUSH LOAD
OUT
=+
()
⎛
⎝
⎜
⎞
⎠
⎟
µ
66
RR
V
V
OUT
FB
12 =
⎛
⎝
⎜
⎞
⎠
⎟
-1
VV
R
R
OUT FB
=+
⎛
⎝
⎜
⎞
⎠
⎟
1
1
2
MAX8526
MAX8527
MAX8528
2.2µF
10µF
ENABLE
SHUTDOWN
IN
IN
POK (MAX8527) OR
POR (MAX8528)
EN
IN
IN
OUT
OUT
GND
FB
OUT
OUT
100kΩ*
R1
R2
ADJUSTABLE
OUTPUT
*FOR MAX8527 AND MAX8528
+1.425V TO +3.6V
Figure 1. Typical Application Circuit