LTC2917/LTC2918

7

29178f

GND: Device Ground.

⎯M⎯R (LTC2918 only): Manual Reset Input (Active Low). A

low level on the ⎯M⎯R input causes the part to issue a reset,

which is released one reset timeout after the input goes

thus may interface directly to a momentary pushbutton.

Leave open if unused.

⎯R⎯S⎯T: Open Drain ⎯R⎯S⎯T Output. Asserts low when VM is

below the threshold selected by SEL1, SEL2 and TOL input

pins. Held low for an adjustable timeout after VM input is

above threshold.

RT: Reset Timeout Control Pin. Attach an external capaci-

RT open to generate a reset timeout of approximately

proximately 200ms.

SEL1, SEL2: Monitor Voltage Select Three-State Input.

SEL1, and SEL2 control the nominal threshold voltage

unconnected in open state. (See Table 1).

TOL (LTC2917 only): Three-State Input for Supply Tol-

erance Selection (–5%, –10% or –15%). Controls the

tolerance band at which the VM supply is monitored.

(See Table 2)

ensures that the part is out of under voltage lockout and

that the voltage thresholds are accurate. Operates as a

direct supply input for voltages up to 5.5V. Operates as a

shunt regulator for supply voltages greater than 5.7V and

should have a resistor between this pin and the supply

used without a current-limiting resistor, pin voltage must

not exceed 5.7V.

VM: Voltage Monitor Input to ⎯R⎯S⎯T comparator. SEL1, SEL2

and TOL inputs select the exact threshold that asserts the

⎯R⎯S⎯T output.

WDI: Watchdog Input. This pin must be driven to change

state within a time less than the watchdog upper bound-

ary time, or ⎯R⎯S⎯T will be asserted low. On the LTC2917-B,

LTC2918-B, the period must also be greater than the

watchdog lower boundary time, and only falling edges

are considered. Tie WT and WDI to GND to disable the

watchdog timer.

WT: Watchdog Timer Control Pin. Attach an external

timeout of approximately 1.6s. Leave WT open to generate

a timeout of approximately 3.2ms. Tie WT and WDI to

GND to disable the watchdog timer.

Exposed Pad (DFN Only): Exposed pad may be left open

or connected to device ground.

PIN FUNCTIONS

0

0

1

2

3

4

5

6

1234

29178 G10

5

SEL1 = SEL2 = TOL = 0V

VM = 0.5V

0

0

1

2

3

4

5

6

123

4

29178 G11

5

RST AT 150mV

RST AT 50mV

0

0.6

0.8

1.0

8

29178 G12

0.4

0.2

0

2

4

6

10

NO PULL-UP R

TYPICAL PERFORMANCE CHARACTERISTICS