MAX8882/MAX8883
Detailed Description
The MAX8882/MAX8883 are low-noise, low-dropout,
low-quiescent-current linear regulators designed primar-
ily for battery-powered applications. These parts are
available with preset output voltages ranging from 1.8V
to 3.3V, and the parts can supply loads up to 160mA.
Shutdown
MAX8882
The MAX8882 has a single shutdown control input
(SHDN). Drive SHDN low to shut down both outputs,
reducing supply current to 10nA. Connect SHDN to a
logic-high, or IN, for normal operation.
MAX8883
The MAX8883 has independent shutdown control
inputs (SHDNA and SHDNB). Drive SHDNA low to shut
down OUTA. Drive SHDNB low to shut down OUTB.
Drive both SHDNA and SHDNB low to shut down the
entire chip, reducing supply current to 10nA. Connect
both SHDNA and SHDNB to a logic-high, or IN, for nor-
mal operation.
Internal P-Channel Pass Transistor
The MAX8882/MAX8883 feature two 1Ω P-channel
MOSFET pass transistors. A P-channel MOSFET pro-
vides several advantages over similar designs using
PNP pass transistors, including longer battery life. It
requires no base drive, which reduces quiescent cur-
rent significantly. PNP-based regulators waste consid-
erable current in dropout when the pass transistor
saturates, and they also use high base-drive currents
under large loads. The MAX8882/MAX8883 do not suf-
fer from these problems and only consume 165µA of
quiescent current whether in dropout, light-load, or
heavy-load applications (see the Typical Operating
Characteristics). While a PNP-based regulator has
dropout voltage that is independent of the load, a P-
channel MOSFET’s dropout voltage is proportional to
load current, providing for low dropout voltage at heavy
loads and extremely low dropout voltage at lighter
loads.
Current Limit
The MAX8882/MAX8883 contain two independent cur-
rent limiters, one for each regulator, which monitor and
control the pass transistor’s gate voltage, limiting the
guaranteed maximum output current to 160mA mini-
mum. The output can be shorted to ground for an indef-
inite time without damaging the part.
Thermal-Overload Protection
Thermal-overload protection limits total power dissipa-
tion in the MAX8882/MAX8883. When the junction tem-
perature exceeds T
J
= +160°C, the thermal sensor sig-
nals the shutdown logic, turning off the pass transistor
and allowing the IC to cool. The thermal sensor will turn
the pass transistor on again after the IC’s junction tem-
perature cools by 10°C, resulting in a pulsed output
during continuous thermal-overload conditions.
Thermal-overload protection is designed to protect the
MAX8882/MAX8883 in the event of fault conditions. For
continual operation, do not exceed the absolute maxi-
mum junction-temperature rating of T
J
= +150°C.
Operating Region and Power Dissipation
The MAX8882/MAX8883’s maximum power dissipation
depends on the thermal resistance of the case and cir-
cuit board, the temperature difference between the die
junction and ambient air, and the rate of air flow. The
power dissipation across the device is P = I
OUT
(V
IN
-
V
OUT
) (Figure 1). The maximum power dissipation is:
P
MAX
= (T
J
- T
A
) / (T
JB
+ T
BA
)
where T
J
- T
A
is the temperature difference between
the MAX8882/MAX8883 die junction and the surround-
ing air, T
JB
(or T
JC
) is the thermal resistance of the
package, and T
BA
is the thermal resistance through the
printed circuit board, copper traces, and other materi-
als to the surrounding air.
The GND pin of the MAX8882/MAX8883 performs the
dual functions of providing an electrical connection to
the ground and channeling heat away. Connect the
GND pin to ground using a large pad or ground plane.
Dual, Low-Noise, Low-Dropout, 160mA Linear
Regulators in SOT23
6 _______________________________________________________________________________________
Figure 1. MAX8882/MAX8883 Safe Operating Region
