LTC1985ES5-1.8 Linear Technology, LTC1985ES5-1.8 Datasheet - Page 5

• Manufacturer Part Number: LTC1985ES5-1.8
• Description: Micropower Precision Triple Supply Monitor with Push-Pull Reset Output in a 5-Lead SOT-23 Package
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
TI I G DIAGRA
Supply Monitoring
The LTC1985 is a low power, high accuracy triple supply
monitoring cirucit with a single 200ms microprocessor
reset output.
All three V
olds for reset not to be invoked. The LTC1985 will assert
reset during power-up, power-down and brownout condi-
tions on any one or all of the V
3V or 1.8V Power Detect
The LTC1985 is powered from the 3V input pin (V
the 1.8V input pin (V
potential. This ensures the part pulls the RST pin low as
soon as either input pin is 1V.
Power-Up
Upon power-up, either the V
the part. This ensures that RST will be low when either
V
inputs is below its predetermined threshold, RST will stay
a logic low. Once all of the V
CC18
W
or V
U
CC
CC3
inputs must be above predetermined thresh-
reaches 1V. As long as any one of the V
U
CC18
), whichever pin has the highest
U
W
CC18
CC
CC
V
inputs rise above their
RST
or V
inputs.
CCX
W
CC3
V
pin, can power
RTX
U
CC3
V
CC
) or
Monitor Timing
CC
thresholds, an internal timer is started and RST is released
after 200ms.
RST is reasserted whenever any one of the V
drops below its predetermined threshold and remains
asserted until 200ms after all of the V
their thresholds.
Power-Down
On power-down, once any of the V
threshold, RST is held at a logic low. A logic low of 0.3V is
guaranteed until both V
Override Functions
The V
This is an obvious solution since the trip points for V
and V
V
V
operating off of a 1.8V supply will result in the continuous
assertion of RST.
CCA
CC3
t
RST
. Likewise, the V
CCA
must always be used. Tying V
CC18
pin, if unused, can be tied to either V
will always be greater than the trip point for
1985-18 TD
CC18
CC3
, if unused, can be tied to V
and V
CC18
CC
LTC1985-1.8
inputs drop below its
CC
drop below 1V.
CC3
inputs are above
to V
CC3
CC
CC18
or V
inputs
CC18
CC3
5
and
CC3
.
.