LTC2909 datasheet(6/16 Pages) LINER

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LTC2909

2909fa

PI FU CTIO S

ADJ1 (Pin 1/Pin 8): Adjustable Voltage Input 1. Input to

voltage monitor comparator 1 (0.5V nominal threshold).

The polarity of the input is selected by the state of the

SEL pin (refer to Table 1). Tie to REF if unused (with SEL

= VCC or Open).

ADJ2 (Pin 2/Pin 7): Adjustable Voltage Input 2. Input to

voltage monitor comparator 2 (0.5V nominal threshold).

The polarity of the input is selected by the state of the

SEL pin (refer to Table 1). Tie to GND if unused (with SEL

= GND or Open).

REF (Pin 3/Pin 6): Buffered Reference Output. 1V nominal

reference used for the offset of negative-monitoring appli-

cations. The buffered reference can source and sink 1mA.

The reference can drive a capacitive load of up to 1000pF.

Larger capacitance may degrade transient performance.

This pin does not require a bypass capacitor, nor is one

recommended. Leave open if unused.

GND (Pin 4/Pin 5): Device Ground.

⎯R⎯S⎯T (Pin 5/Pin 4): Open-Drain Inverted Reset Logic Output.

Asserts low when any positive polarity input voltage is

below threshold or any negative polarity input voltage is

above threshold or VCC is below UVLO threshold. Held low

for a timeout after all voltage inputs are valid. Requires an

external pull-up resistor and may be pulled above VCC.

(TSOT-23/DFN Package)

VCC (Pin 6/Pin 3): Power Supply. Bypass this pin to

ground with a 0.1μF (or greater) capacitor. Operates as

a direct supply input for voltages up to 6V. Operates as a

shunt regulator for supply voltages greater than 6V and

should have a resistor between this pin and the supply

to limit VCC input current to no greater than 10mA. When

used without a current-limiting resistor, pin voltage must

not exceed 6V. UVLO options allow VCC to be used as an

accurate third ﬁxed 10% UV supply monitor.

TMR (Pin 7/Pin 2): Reset Timeout Control. Attach an

external capacitor (CTMR) to GND to set a reset timeout

of 9ms/nF. A low leakage ceramic capacitor is recom-

mended for timer accuracy. Capacitors larger than 1μF

(9 second timeout) are not recommended. See Applica-

tions Information for further details. Leaving this pin open

generates a minimum timeout of approximately 400μs. A

2.2nF capacitor will generate a 20ms timeout. Tying this

pin to ground will enable the internal 200ms timeout. Ty-

ing this pin to VCC will disable the reset timer and put the

part in comparator mode. Signals from the comparator

outputs will then go directly to

⎯R⎯S⎯T.

SEL (Pin 8/Pin 1): Input Polarity Select Three-State Input.

Connect to VCC, GND or leave unconnected in open state

to select one of three possible input polarity combinations

(refer to Table 1).

Exposed Pad (Pin 9, DFN Only): The Exposed Pad may be

left unconnected. For better thermal contact, tie to a PCB

trace. This trace must be grounded or unconnected.

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