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MAX16050ETI

Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability

Maxim Integrated 

MAX16050/MAX16051

Voltage Monitors/Sequencer Circuits with

Reverse-Sequencing Capability

Reset Voltage VCCR

The MAX16050/MAX16051 monitor VCC to ensure the

DISC_, OUT_, and RESET pins are at the right level

when VABP goes below VUVLO. VCCR is the lowest

value of VCC for which these three pin types are guar-

anteed to be low. When a falling VCC goes below 2.2V

typical, the regulated supply voltage VABP falls below

VUVLO. See VABP vs. VCC curve in the Typical Operating

Characteristics. When VABP is below VUVLO, and VCC

is higher than VCCR, DISC_, OUT_, and RESET are all

asserted low. For VCC below VCCR, these pin voltages

are indeterminate. The FAULT output behaves differently.

Its voltage becomes indeterminate as soon as VABP falls

below VUVLO.

Charge-Pump Output (CP_OUT)

The MAX16050/MAX16051 feature an on-chip charge

pump that drives its output voltage to 5V above VCC, and

it can be used as a pullup voltage to drive one or more

external n-channel MOSFETs (see the Typical Operating

Circuit). The charge-pump output can be modeled as a

25μA current source with a compliance voltage of (VCC

+ 5V); the slew rate can be controlled by connecting

a capacitor from the gate of the MOSFET to ground.

When using CP_OUT to provide the pullup voltage for

multiple MOSFETs, ensure that the voltage is enough to

enhance a MOSFET despite the load of the other pullup

resistors (which may be connected to outputs that are

deasserted low).

Disabling Channels

If any channel is not used, connect the associated SET_

input to ABP. Connect DISC_ of the disabled channel to

GND. Do not leave the SET_ or DISC_ inputs discon-

nected. Disabling any one channel does not disable the

other channels. This channel exclusion feature adds more

flexibility to the device in a variety of different applications.

SHDN and EN Inputs

The shutdown input (SHDN) initiates a reverse sequenc-

ing event. When SHDN is brought low, the device will

sequentially power down in reverse order. During this

period, all DISC_ inputs are monitored to make sure the

voltage of each supply falls below 250mV before allowing

the next supply to shut down. The next OUT_ goes low

as soon as the previous DISC_ input drops below 250mV

without any capacitor-adjusted delay. This continues until

all supplies are turned off. SHDN is internally pulled up

to ABP.

When EN falls below its threshold, the device per-

forms a simultaneous power-down and does not reverse

sequence. When either SHDN or EN initializes the

power-down event, the reset output (RESET) immediately

asserts. At the end of the power-down event, when all

DISC_ voltages are below 250mV, the bus removal output

(REM) goes high impedance. SHDN and EN must be low

for a minimum pulse width before the device responds.

See the Electrical Characteristics Table.

For applications where both EN and SHDN go low, the

MAX16050/MAX16051 will ignore EN if it is taken low any

time after SHDN is asserted. However, for a simultane-

ous power-down using the EN pin, SHDN must not be

asserted within the EN to OUT_ Delay after EN is taken

low. Otherwise, it can initiate a reverse-sequence shut-

down. See the Electrical Characteristics Table.

Reset Output (RESET)

The MAX16050/MAX16051 include a reset output.

RESET is an open-drain output and requires an external

pullup resistor.

When any of the monitored voltages falls below its thresh-

old, SHDN is pulled low, EN falls below its threshold, or

FAULT is pulled low, RESET asserts and stays asserted

for at least the minimum reset timeout period after all of

these conditions are removed. Connect a capacitor from

TIMEOUT to GND to adjust the reset timeout period.

Connect TIMEOUT to ABP for the fixed timeout of 128ms

(typ). Leave TIMEOUT unconnected for a 10μs (typ)

timeout period.

FAULT Input/Output

The FAULT input/output asserts to signal a fault if any

of the SET_ monitored voltages falls below its threshold

while EN = SHDN = high. FAULT is internally pulled up

to ABP by a 100kΩ resistor. FAULT also can be used as

an input. Pull FAULT low to simultaneously shut down the

OUT_ outputs.

For multichip solutions, all of the FAULT input/outputs can

be connected together. In case of a fault condition, all out-

puts on every device are turned off and the internal pull-

down circuitry is activated simultaneously. FAULT must be

low for at least tFAULT_PW before the device responds.

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