LTC2903 LINER [Linear Technology], LTC2903 Datasheet - Page 7

• Manufacturer Part Number: LTC2903
• Description: Low Voltage Supervisorwith 27 Selectable Thresholds and Watchdog Timer
• Manufacturer: LINER [Linear Technology]

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
high. The pin has an internal 100k pull-up to V
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-
tor (C
RT open to generate a reset timeout of approximately
400μs. Tie RT to V
proximately 200ms.
SEL1, SEL2: Monitor Voltage Select Three-State Input.
SEL1, and SEL2 control the nominal threshold voltage
that VM is set to monitor. Connect to V
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.
Connect to V
(See Table 2)
V
PIN FUNCTIONS
TYPICAL PERFORMANCE CHARACTERISTICS
CC
: Power Supply input. Bypass this pin to ground with
6
5
4
3
2
1
0
RT
0
⎯ R ⎯ S ⎯ T Output Voltage vs V
10k PULL-UP R TO V
SEL1 = SEL2 = TOL = 0V
VM = 0.5V
) to GND to set a reset timeout of 9ms/nF. Leave
1
CC
SUPPLY VOLTAGE, V
, GND, or leave unconnected in open state.
2
CC
CC
to generate a reset timeout of ap-
3
CC
CC
(V)
4
29178 G10
5
CC
, GND or leave
6
5
4
3
2
1
0
⎯ R ⎯ S ⎯ T Pull-Down Current vs V
0
CC
, and
1
SUPPLY VOLTAGE, V
2
a 0.1μF ceramic capacitor. A minimum of 1.5V on V
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
to limit V
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
capacitor (C
ary timeout time of 72ms/nF. Tie WT to V
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.
3
RST AT 50mV
RST AT 150mV
CC
(V)
CC
4
CC
input current to no greater than 5mA. When
WT
29178 G11
) to GND to set a watchdog upper bound-
5
LTC2917/LTC2918
1.0
0.8
0.2
0.6
0.4
0
0
⎯ R ⎯ S ⎯ T V
NO PULL-UP R
V
CC
= 2.5V
OL
2
vs I
T
A
= 25°C
RST
4
I
RST
CC
(mA)
T
T
A
A
= 125°C
6
to generate a
= –40°C
8
29178 G12
29178f
7
CC
10