MAX884CSA Datasheet Download

Part No.:
MAX884CSA
Download:
Download Datasheet
Description:
[5V/3.3V or Adjustable, Low-Dropout, Low IQ, 200mA Linear Regulators]
File Size:
137 K
Page:
16 Pages
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Manufacturer:
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
PCB Prototype
 MAX884CSA Datasheet Page:3MAX884CSA Datasheet Page:4MAX884CSA Datasheet Page:5MAX884CSA Datasheet Page:6MAX884CSA Datasheet Page:8MAX884CSA Datasheet Page:9MAX884CSA Datasheet Page:10MAX884CSA Datasheet Page:11 
5V/3.3V or Adjustable, Low-Dropout,
Low I
Q
, 200mA Linear Regulators
______________________________________________________________Pin Description
PIN
MAX882
MAX883/
MAX884
1
2
3, 6
4
5
7
8
NAME
FUNCTION
Low-Battery Output is an open-drain output that goes low when LBI is less than 1.2V. Connect to
IN or OUT through a pull-up resistor. LBO is undefined during shutdown mode
(MAX883/MAX884).
Feedback for setting the output voltage. Connect to GND to set the output voltage to the prese-
lected 3.3V or 5V. Connect to an external resistor network for adjustable-output operation.
Ground pins—also function as heatsinks in the SO package. All GND pins must be soldered to
the circuit board for proper power dissipation. Connect to large copper pads or planes to
channel heat from the IC.
Regulator Output. Fixed or adjustable from 1.25V to 11.0V. Sources up to 200mA. Bypass with a
2.2µF capacitor.
Regulator Input. Supply voltage can range from 2.7V to 11.5V.
Standby. Active-low comparator input. Connect to GND to disable the output or to IN for normal
operation. A resistor network (from IN) can be used to set a standby mode threshold.
Shutdown. Active-low logic input. In OFF mode, supply current is reduced below 1µA and
V
OUT
= 0V
Low-Battery comparator Input. Tie to IN when not used.
MAX882/MAX883/MAX884
1
2
3, 6
4
5
7
8
LBO
SET
GND
OUT
IN
STBY
OFF
LBI
_______________Detailed Description
The MAX882/MAX883/MAX884 are micropower, low-
dropout linear regulators designed primarily for battery-
powered applications. They feature Dual-Mode™
operation, allowing a fixed output of 5V for the MAX883
and 3.3V for the MAX882/MAX884, or an adjustable output
from 1.25V to 11V. These devices supply up to 200mA
while requiring less than 15µA quiescent current. As illus-
trated in Figure 1, they consist of a 1.20V reference, error
amplifier, MOSFET driver, P-channel pass transistor, dual-
mode comparator and feedback voltage divider.
The 1.20V reference is connected to the error amplifier’s
inverting input. The error amplifier compares this refer-
ence with the selected feedback voltage and amplifies
the difference. The MOSFET driver reads the error signal
and applies the appropriate drive to the P-channel pass
transistor. If the feedback voltage is lower than the refer-
ence, the pass transistor’s gate is pulled lower, allowing
more current to pass and increasing the output voltage. If
the feedback voltage is too high, the pass transistor gate
is pulled up, allowing less current to pass to the output.
The output voltage is fed back through either an inter-
nal resistor voltage divider connected to the OUT pin,
or an external resistor network connected to the SET
pin. The dual-mode comparator examines the SET pin
voltage and selects the feedback path used. If the SET
pin is below 65mV, internal feedback is used and the
output voltage is regulated to 5V for the MAX883 or
3.3V for the MAX882/MAX884. Additional blocks
include a foldback current limiter, reverse-current pro-
tection, a thermal sensor, shutdown or standby logic,
and a low-battery-detection comparator.
Internal P-Channel Pass Transistor
The MAX882/MAX883/MAX884 feature a 200mA P-
channel MOSFET pass transistor. This provides several
advantages over similar designs using PNP pass tran-
sistors, including longer battery life.
The P-channel MOSFET requires no base drive, which
reduces quiescent current considerably. PNP based reg-
ulators waste large amounts of current in dropout when
the pass transistor saturates. They also use high base-
drive currents under large loads. The MAX882/MAX883/
MAX884 do not suffer from these problems and consume
only 11µA of quiescent current during light loads, heavy
loads, and dropout.
Output Voltage Selection
The MAX882/MAX883/MAX884 feature Dual Mode™
operation. In preset voltage mode, the MAX883’s out-
put is set to 5V and the MAX882/MAX884’s output is set
to 3.3V, using internal trimmed feedback resistors.
Select this mode by connecting SET to ground.
In preset voltage mode, impedances between SET and
ground should be less than 100kΩ. Otherwise, spurious
conditions could cause the voltage at SET to exceed
the 65mV dual-mode threshold.
7
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