MAX15011ATJ+ Datasheet MAX15009ATJ+, MAX15009ATJ+T, MAX15011ATJ+ | P13-P15

Detailed Description

The MAX15009/MAX15011 integrate a 300mA LDO

voltage regulator, a current-limited switched output,

and an OVP controller (MAX15009 only). These devices

operate over a wide supply voltage range from 5V to

40V and are able to withstand load-dump transients up

to 45V.

The MAX15009/MAX15011 feature a 300mA LDO regu-

lator that consumes 70µA of current under light-load

conditions and feature a fixed 5V or an adjustable out-

put voltage (1.8V to 11V). Connect FB_LDO to ground

to select a fixed 5V output voltage or select the LDO

output voltage by connecting an external resistive volt-

age-divider at FB_LDO. The regulator sources at least

300mA of current and includes a current limit of 330mA

(min). Enable the LDO by pulling EN_LDO high.

The switch features accurate current-limit sensing cir-

cuitry and is capable of controlling remote loads. Once

enabled, an internal charge pump generates the over-

drive voltage for an internal MOSFET. The switch then

starts to conduct and OUT_SW is charged up to

OUT_LDO

. The switch is enabled when the output volt-

age of the LDO is above the RESET threshold voltage

(92.5% of the LDO nominal output value).

An overcurrent condition exists when the current at

OUT_SW, I

OUT_SW

, exceeds the 200mA (typ) internal

factory-set current-limit threshold or the externally

adjustable current-limit threshold. During a continuous

overcurrent event, the capacitor connected at

OC_DELAY, C

OC_DELAY

, is charged up to a voltage of

1.235V with a current, I

OC_DELAY_UP

. When this voltage

is reached, an overcurrent latch is set and the gate of

the internal MOSFET is discharged, reducing I

OUT_SW

OC_DELAY

is then discharged through a pulldown cur-

rent, I

OC_DELAY_DOWN

OC_DELAY_UP

/ 16) and the

internal MOSFET remains off until C

OC_DELAY

has been

discharged to 0.1V. After this user-programmable turn-

off delay, the switch turns back on. This charge/

discharge is repeated if the overcurrent condition per-

sists. The switch returns to normal operation once the

overcurrent condition has been removed.

The OVP controller (MAX15009 only) relies on an exter-

nal MOSFET with adequate voltage rating (V

DSS

) to

protect downstream circuitry from overvoltage tran-

sients. The OVP controller drives the gate of the exter-

nal n-channel MOSFET, and is configurable to operate

as an overvoltage protection switch or as a closed-loop

voltage limiter.

GATE Voltage (MAX15009 Only)

The MAX15009 uses a high-efficiency charge pump to

generate the GATE voltage for the external n-channel

MOSFET. Once the input voltage, V

, exceeds the

undervoltage lockout (UVLO) threshold, the internal

charge pump fully enhances the external n-channel

MOSFET. An overvoltage condition occurs when the

voltage at FB_PROT goes above the threshold voltage,

TH_PROT

. After V

TH_PROT

is exceeded, GATE is quick-

ly pulled to PGND with a 63mA pulldown current. The

MAX15009 includes an internal clamp from GATE to

SOURCE that ensures that the voltage at GATE never

exceeds one diode drop below SOURCE during gate

discharge. The voltage clamp also prevents the GATE-

to-SOURCE voltage from exceeding the absolute maxi-

mum rating for the V

of the external MOSFET in case

the source terminal is accidentally shorted to 0V.

Overvoltage Monitoring (MAX15009 Only)

The OVP controller monitors the voltage at FB_PROT

and controls an external n-channel MOSFET, isolating,

or limiting the load during an overvoltage condition.

Operation in OVP switch mode or limiter mode

depends on the connection between FB_PROT and the

external MOSFET.

Overvoltage Switch Mode

When operating in OVP switch mode, the FB_PROT

divider is connected to the drain of the external MOS-

FET. The feedback path consists of the voltage-divider

tapped at FB_PROT, FB_PROT’s internal comparator,

the internal gate charge pump/gate pulldown, and the

external n-channel MOSFET (Figure 1). When the pro-

grammed overvoltage threshold is exceeded, the inter-

nal comparator quickly pulls GATE to ground and turns

MAX15009/MAX15011

Automotive 300mA LDO Regulators with

Switched Output and Overvoltage Protector

______________________________________________________________________________________ 13

FB_PROT

SGND

GATE

SOURCE

PROTECTOR

OUTPUT

MAX15009

Figure 1. Overvoltage-Limiter Switch Configuration (MAX15009)

MAX15009/MAX15011

Automotive 300mA LDO Regulators with

Switched Output and Overvoltage Protector

14 ______________________________________________________________________________________

off the external MOSFET, disconnecting the power

source from the load. In this configuration, the voltage

at the source of the MOSFET is not monitored. When

the voltage at FB_PROT decreases below the overvolt-

age threshold, the MAX15009 raises the voltage at

GATE, reconnecting the load to the power source.

Overvoltage-Limiter Mode (MAX15009 Only)

When operating in overvoltage-limiter mode, the feed-

back path consists of SOURCE, FB_PROT’s internal

comparator, the internal gate charge pump/gate pull-

down, and the external n-channel MOSFET (Figure 2).

This configuration results in the external MOSFET oper-

ating as a hysteretic voltage regulator.

During normal operation, GATE is enhanced 8.1V above

. The external MOSFET source voltage is monitored

through a resistive voltage-divider between SOURCE

and FB_PROT. When V

SOURCE

exceeds the adjustable

overvoltage threshold, an internal pulldown switch

discharges the gate voltage and quickly turns the

MOSFET off. Consequently, the source voltage begins

to fall. The V

SOURCE

fall time is dependent on the MOS-

FET’s gate charge, the internal charge-pump current,

the output load, and any load capacitance at SOURCE.

When the voltage at FB_PROT is below the overvoltage

threshold by an amount equal to the hysteresis, the

charge pump restarts and turns the MOSFET back on.

In this way, the OVP controller attempts to regulate

SOURCE

around the overvoltage threshold. SOURCE

remains high during overvoltage transients and the

MOSFET continues to conduct during an overvoltage

event. The hysteresis of the FB_PROT comparator and

the gate turn-on delay force the external MOSFET to

operate in a switched on/off sequence during an over-

voltage event.

Exercise caution when operating the MAX15009 in volt-

age-limiting mode for long durations. Care must be

taken against prolonged or repeated exposure to over-

voltage events while delivering large amounts of load

current as the power dissipation in the external MOS-

FET may be high under these conditions. To prevent

damage to the MOSFET, implement proper heatsinking.

The capacitor tied between SOURCE and ground may

also be damaged if the ripple current rating for the

capacitor is exceeded.

As the transient voltage decreases, the voltage at

SOURCE falls. For fast-rising transients and very large

MOSFETs, connect an additional capacitor from GATE

to PGND. This capacitor acts as a voltage-divider work-

ing against the MOSFET’s drain-to-gate capacitance. If

using a very low gate charge MOSFET, additional

capacitance from GATE to ground might be required to

reduce the switching frequency.

Control Logic

The MAX15009/MAX15011 LDO features two logic

inputs, EN_LDO and HOLD, making these devices suit-

able for automotive applications. For example, when

the ignition key signal drives EN_LDO high, the regula-

tor turns on and remains on even if EN_LDO goes low,

as long as HOLD is forced low and stays low after initial

regulator power-up. In this state, releasing HOLD turns

the regulator output (OUT_LDO) off. This feature makes

it possible to implement a self-holding circuit without

external components. Forcing EN_LDO low and HOLD

high (or unconnected) places the regulator into shut-

down mode, reducing the supply current to less than

16µA. Table 1 shows the state of OUT_LDO with

respect to EN_LDO and HOLD. Leave HOLD uncon-

nected or connect directly to OUT_LDO to allow the

EN_LDO input to act as a standard on/off logic input for

the regulator.

FB_PROT

SGND

GATE

SOURCE

PROTECTOR

OUTPUT

MAX15009

Figure 2. Overvoltage Limiter (MAX15009)

Applications Information

Load Dump

Most automotive applications run off a multicell 12V

lead-acid battery with a nominal voltage that swings

between 9V and 16V, depending on load current,

charging status, temperature, and battery age, etc. The

battery voltage is distributed throughout the automobile

and is locally regulated down to voltages required by

the different system modules. Load dump occurs when

the alternator is charging the battery and the battery

becomes disconnected. Power in the alternator (behav-

ing now essentially as an inductor) flows into the dis-

tributed power system and elevates the voltage seen at

each module. The voltage spikes have rise times typi-

cally greater than 5ms and decay within several hun-

dred milliseconds but can extend out to 1s or more

depending on the characteristics of the charging sys-

tem. These transients are capable of destroying semi-

conductors on the first fault event.

The MAX15009/MAX15011 feature load-dump transient

protection up to +45V.

Setting the Output Voltage

The MAX15009/MAX15011 feature dual-mode opera-

tion: these devices operate in either a preset voltage

mode or an adjustable mode. In preset voltage mode,

internal feedback resistors set the linear regulator out-

put voltage (V

OUT_LDO

) to 5V. To select the preset 5V

output voltage, connect FB_LDO to SGND.

To select an adjustable output voltage between 1.8V

and 11V, use two external resistors connected as a

voltage-divider to FB_LDO (Figure 3). Set the output

voltage using the following equation:

OUT_LDO

= V

FB_LDO

x (R

+ R

) / R

where V

FB_LDO

= 1.235V and R

≤ 50kΩ.

Setting the

RESET

Timeout Period

The reset timeout period is adjustable to accommodate

a variety of applications. Set the reset timeout period by

connecting a capacitor, C

RESET

, between CT and

SGND. Use the following formula to select the reset

timeout period, t

RESET

= C

RESET

x V

CT_TH

/ I

where t

RESET

is in seconds and C

RESET

is in µF.

CT_TH

is the CT ramp threshold in volts and I

is the

CT ramp current in µA, as described in the

Electrical

Characteristics

table.

MAX15009/MAX15011

Automotive 300mA LDO Regulators with

Switched Output and Overvoltage Protector

______________________________________________________________________________________ 15

FB_LDO

SGND

OUT_LDO

MAX15009

MAX15011

Figure 3. Setting the LDO Output Voltage

Table 1. EN_LDO/

HHOOLLDD

Truth/State Table

OPERATION STATE EN_LDO HOLD OUT_LDO COMMENT

Initial State Low Don’t care OFF

EN_LDO is pulled to SGND through an internal pulldown. HOLD

is unconnected and is internally pulled up to OUT_LDO. The

regulator is disabled.

Turn-On State High Don’t care ON

EN_LDO is externally driven high turning regulator on. HOLD is

pulled up to OUT_LDO.

Hold Setup State High Low ON

HOLD is externally pulled low while EN_LDO remains high

(latches EN_LDO state).

Hold State Low Low ON

EN_LDO is driven low or left unconnected. HOLD remains

externally pulled low keeping the regulator on.

Off State Low

High or

unconnected

OFF

HOLD is driven high or left unconnected while EN_LDO is low.

The regulator is turned off and EN_LDO/HOLD logic returns to the

initial state.

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P24

MAX15011ATJ+

Mfr. #:

Buy MAX15011ATJ+

Manufacturer:

Maxim Integrated

Description:

LDO Voltage Regulators Automotive 300mA w/Switched Output

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MAX15011ATJ+

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