LTC2917/LTC2918
Low Voltage Supervisor
with 27 Selectable Thresh-
olds and Watchdog Timer
DESCRIPTION
The LTC®2917-A/LTC2917-B and LTC2918-A/LTC2918-B
are low voltage single-supply monitors with selectable
thresholds and an adjustable watchdog timer. The parts
operate from 1.5V to 5.5V and consume a quiescent cur-
rent of only 30μA.
FEATURES
■
9 Selectable Supply Voltages
12V, 5V, 3.3V, 2.5V, 1.8V
1.5V, 1.2V, 1V, +ADJ (0.5V)
■
3 Selectable Tolerances
–5%, –10%, –15% (LTC2917)
■
Manual Reset Input (LTC2918)
Two three state inputs select one of nine internally pro-
grammedthresholdswithouttheneedforexternalresistors.
FortheLTC2917,anadditionalthreestateinputdetermines
the tolerance (–5%, –10%, –15%). The tolerance for the
LTC2918isfixedat–5%.Thresholdaccuracyisguaranteed
at 1.5% over the entire operating temperature range.
Glitch filtering ensures reliable reset operation without
false triggering.
■
1.5V to 5.5V Supply Operation
■
Adjustable Watchdog Timeout
■
Windowed Watchdog Timeout for Higher Reliability
Applications (LTC2917-B, LTC2918-B)
■
6.2V Shunt Regulator for High Voltage Operation
■
Guaranteed to 125˚C
■
Guaranteed Threshold Accuracy: 1.5%
■
Low Quiescent Current: 30μA Typical
■
The reset timeout and the watchdog timeout may be set
with no external components, or adjusted using an exter-
nal capacitor. A windowed watchdog feature is available
for high-reliability applications (B1 versions). A separate
manual reset input on the LTC2918-A/LTC2918-B allows
a simple push button interface.
Power Supply Glitch Immunity
■
Guaranteed RST for V ≥ 0.8V
CC
■
10-Lead MSOP Packages and (3mm × 2mm) DFN
Packages
APPLICATIONS
■
Handheld Devices
Operation to 125°C makes the LTC2917-A/LTC2917-B
and LTC2918-A/LTC2918-B suitable for automotive ap-
plications.
■
Cell Phone Base Stations
■
Automotive Control Systems
■
Network Servers
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
■
Optical Networking Systems
TYPICAL APPLICATION
1.8V Supply Monitor with Manual
Monitor Selection Table
Reset and Internal Timers Selected
1.8V
NOMINAL VOLTAGE
SEL1
SEL2
12V
5V
V
V
V
V
CC
CC
CC
CC
0.1μF
10k
Open
GND
3.3V
V
CC
2.5V
Open
Open
Open
GND
GND
GND
V
CC
LTC2918-A
μP
1.8V
Open
GND
VM
RST
WDI
RST
I/O
RT
1.5V
29178 TA01
WT
MR
SEL1
SEL2
1.2V
V
CC
GND
t = 1.6s
WDU
t = 200ms
RST
1V
Open
GND
ADJ (0.5V)
29178f
1