MAX8866REUA+T Datasheet MAX8866TEUA+T, MAX8865TEUA+T, MAX8865TEUA+ | P7-P9

MAX8865T/S/R, MAX8866T/S/R

Dual, Low-Dropout, 100mA Linear Regulators

_______________________________________________________________________________________ 7

_______________Detailed Description

The MAX8865/MAX8866 are dual, low-dropout, low-qui-

escent-current linear regulators designed primarily for

battery-powered applications. They supply adjustable

1.25V to 5.5V outputs or preselected 2.80V

(MAX886_R), 2.84V (MAX886_S), or 3.15V (MAX886_T)

outputs for load currents up to 100mA. As illustrated in

Figure 1, these devices have a 1.25V reference and two

independent linear regulators. Each linear regulator

consists of an error amplifier, MOSFET driver, P-channel

pass transistor, Dual Mode™ comparator, and internal

feedback voltage divider.

The 1.25V bandgap reference is connected to the error

amplifiers’ inverting inputs. Each error amplifier com-

pares this reference 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 reference, the pass-transistor 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_

voltage and selects the feedback path. If SET_ is below

60mV, internal feedback is used and the output voltage

is regulated to 2.80V for the MAX886_R, 2.84V for the

MAX886_S, or 3.15V for the MAX886_T. Both regulators

are preset for the same voltage. The reference and the

thermal sensor are shared between the regulators.

Duplicate blocks exist for current limiters, reverse bat-

tery protection, and shutdown logic.

Internal P-Channel Pass Transistor

The MAX8865/MAX8866 feature 1.1Ω typical P-channel

MOSFET pass transistors. This provides several advan-

tages over similar designs using PNP pass transistors,

including longer battery life.

The P-channel MOSFET requires no base-drive current,

which reduces quiescent current significantly. PNP-

based regulators waste considerable amounts of cur-

rent in dropout when the pass transistor saturates. They

also use high base-drive currents under large loads.

The MAX8865/MAX8866 do not suffer from these prob-

lems, and consume only 145µA of quiescent current,

whether in dropout, light load, or heavy load applica-

tions (see

Typical Operating Characteristics

Output Voltage Selection

The MAX8865/MAX8866 feature Dual Mode operation:

they operate in either a preset voltage mode or an

adjustable mode.

______________________________________________________________Pin Description

Regulator 1 Output. Fixed or adjustable from 1.25V to 5.5V. Sources up to 100mA. Bypass with a 1µF

capacitor to GND.

OUT11

PIN FUNCTIONNAME

IN2 Regulator Input. Supply voltage can range from +2.5V to +5.5V. Bypass with 2µF to GND.

3 Ground. Solder to large pads or the circuit board ground plane to maximize thermal dissipation.

OUT24

Regulator 2 Output. Fixed or adjustable from 1.25V to 5.5V. Sources up to 100mA. Bypass with a 1µF

capacitor to GND.

GND

SET25

Feedback Input for Setting the Output 2 Voltage. Connect to GND to set the output voltage to the preset 2.80V

(MAX886_R), 2.84V (MAX886_S), or 3.15V (MAX886_T). Connect to an external resistor divider for adjustable-

output operation.

SET1

Active-Low Shutdown 2 Input. A logic low turns off regulator 2. On the MAX8866, a logic low also causes the

output voltage to discharge to GND. Connect to IN for normal operation.

SHDN1

Active-Low Shutdown 1 Input. A logic low turns off regulator 1. On the MAX8866, a logic low also causes the

output voltage to discharge to GND. Connect to IN for normal operation.

Feedback Input for Setting the Output 1 Voltage. Connect to GND to set the output voltage to the preset 2.80V

(MAX886_R), 2.84V (MAX886_S), or 3.15V (MAX886_T). Connect to an external resistor divider for adjustable-

output operation.

SHDN2

MAX8865T/S/R, MAX8866T/S/R

Dual, Low-Dropout, 100mA Linear Regulators

8 _______________________________________________________________________________________

SHUTDOWN

LOGIC

ERROR 

AMP

1.25V

REF

OUT1

SET1

DUAL-MODE

COMPARATOR

60mV

SHDN1

MAX8865

MAX8866

MOS DRIVER

WITH I

LIMIT

THERMAL

SENSOR

REVERSE

BATTERY

PROTECTION

SHUTDOWN

LOGIC

ERROR 

AMP

OUT2

SET2

DUAL-MODE

COMPARATOR

60mV

* AUTO-DISCHARGE, MAX8866 ONLY

GND

SHDN2

MOS DRIVER

WITH I

LIMIT

REVERSE

BATTERY

PROTECTION

Figure 1. Functional Diagram

MAX8865T/S/R, MAX8866T/S/R

Dual, Low-Dropout, 100mA Linear Regulators

_______________________________________________________________________________________ 9

In preset voltage mode, internal, trimmed feedback

resistors set the MAX886_R outputs to 2.80V, the

MAX886_S outputs to 2.84V, and the MAX886_T out-

puts to 3.15V. Select this mode by connecting SET_ to

ground. If SET_ can’t be grounded in preset voltage

mode, limit impedances between SET_ and ground to

less than 100kΩ. Otherwise, spurious conditions could

cause the voltage at SET_ to exceed the 60mV Dual

Mode threshold.

In adjustable mode, select an output between 1.25V

and 5.5V using two external resistors connected as a

voltage divider to SET_ (Figure 2). The output voltage is

set by the following equation:

OUT_

= V

SET_

(1 + R1 / R2)

where V

SET_

= 1.25V. To simplify resistor selection:

Choose R2 = 100kΩ to optimize power consumption,

accuracy, and high-frequency power-supply rejection.

The total current through the external resistive feedback

and load resistors should not be less than 10µA. Since

the V

SET_

tolerance is typically less than ±25mV, the

output can be set using fixed resistors instead of trim

pots. Connect a 10pF to 25pF capacitor across R1 to

compensate for layout-induced parasitic capacitances.

Shutdown

A low input on a SHDN_ _ pin individually shuts down one

of the two outputs. In shutdown mode, the selected

pass transistor, control circuit, and all biases are turned

off. When both sections are turned off, the reference

and thermal shutdown are also turned off and the sup-

ply current is typically reduced to 0.16nA. Connect

SHDN_ _ to IN for normal operation. The MAX8866 output

voltages are actively discharged to ground when indi-

vidual regulators are shut down (see

Typical Operating

Characteristics

Current Limit

The MAX8865/MAX8866 include a current limiter for

each output section that monitors and controls the pass

transistor’s gate voltage, estimating the output current

and limiting it to about 220mA. For design purposes,

the current limit should be considered 120mA (min) to

320mA (max). The outputs can be shorted to ground for

an indefinite time period without damaging the part.

Thermal Overload Protection

Thermal overload protection limits total power dissipa-

tion in the MAX8865/MAX8866. When the junction tem-

perature exceeds T

= +170°C, the thermal sensor

sends a signal to the shutdown logic, turning off the

pass transistors and allowing the IC to cool. The ther-

mal sensor will turn the pass transistors on again after

the IC’s junction temperature typically cools by 20°C,

resulting in a pulsed output during continuous thermal

overload conditions.

Thermal overload protection is designed to protect the

MAX8865/MAX8866 in the event of fault conditions.

Stressing the device with high load currents and high

input-output differential voltages (which result in elevat-

ed die temperatures above +125°C) may cause a

momentary overshoot (2% to 8% for 200ms) when the

load is completely removed. This can be remedied by

raising the minimum load current from 0µA (+125°C) to

100µA (+150°C). For continuous operation, do not

exceed the absolute maximum junction temperature

rating of T

= +150°C.

Operating Region and Power Dissipation

Maximum power dissipation of the MAX8865/MAX8866

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

). The resulting maximum power dissipation is:

MAX

= (T

- T

) / θ

where (T

- T

) is the temperature difference between

the MAX8865/MAX8866 die junction and the surround-

ing air, and θ

is the thermal resistance of the pack-

age to the surrounding air (244°C/W).

R1 = R2

OUT

SET

−













MAX8865

MAX8866

OUT_

SET_

GND

SHDN_

OUT

1µF

IN

2µF

BATTERY

OUTPUT

VOLTAGE

20pF

Figure 2. Adjustable Output Using External Feedback

Resistors

P1-P3 P4-P6 P7-P9 P10-P12

MAX8866REUA+T

Mfr. #:

Buy MAX8866REUA+T

Manufacturer:

Maxim Integrated

Description:

LDO Voltage Regulators 100mA Linear Regulato

Lifecycle:

New from this manufacturer.

Delivery:

DHL FedEx Ups TNT EMS

Payment:

T/T Paypal Visa MoneyGram Western Union

MAX8866REUA+T

MAX8866REUA+T

Products related to this Datasheet