LTC1728ES5-5#PBF Linear Technology, LTC1728ES5-5#PBF Datasheet - Page 10

• Manufacturer Part Number: LTC1728ES5-5#PBF
• Manufacturer: Linear Technology

Specifications of LTC1728ES5-5#PBF

• Voltage Supervisor Type: Voltage Monitor
• Number Of Voltage Supervisors: 3
• Monitored Supervisor Voltage: 3.086/4.675/Adj
• Reset Threshold Voltage (min): 3.036/4.6/AdjV
• Reset Threshold Voltage (max): 3.135/4.75/AdjV
• Operating Supply Voltage (min): 1V
• Operating Supply Voltage (max): 7V
• Package Type: TSOT-23
• Operating Temperature Classification: Industrial
• Operating Temp Range: -40C to 85C
• Pin Count: 5
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

APPLICATIO S I FOR ATIO
Supply Monitoring
The LTC1727 is a low power, high accuracy triple supply
monitoring circuit with three monitor outputs and a
200ms microprocessor reset output.
The LTC1728 is a low power, high accuracy triple supply
monitoring circuit with a single 200ms microprocessor
reset output.
All three V
olds for reset not to be invoked. The LTC1727/LTC1728
will assert reset during power-up, power-down and brown-
out conditions on any one or all of the V
Power Detect
The LTC1727/LTC1728 are powered from the 3.3V/3V
input pin (V
input pin (V
pin has the highest 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
can power the part. This ensures that RST will be low when
either V
any one of the V
threshold, RST will stay a logic low. Once all of the V
inputs rise above their 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.
On the LTC1727, each of the comparator outputs will be
low until the V
tor rises above the appropriate predetermined threshold.
The COMP3, and COMP5/COMP25 outputs are guaran-
teed to be in the correct logic state for either V
the internal bandgap reference to be valid before the
correct logic state can be output. Therefore, the COMPA
output will be held low until V
V
LTC1727/LTC1728
10
V
CC5
CC5
/V
/V
CC25
CC25
CC5
CC
/V
is greater than 2V (typ).
CC25
greater than 1V. The COMPA output requires
CC3
inputs must be above predetermined thresh-
CC25
CC
), the 1.8V input pin (V
) or the 5V input pin (V
input that is monitored by that compara-
/V
CC
U
CC18
inputs is below its predetermined
or V
U
CC5
CCA
CC3
/V
is above 1V and V
CC25
reaches 1V. As long as
W
CC
/V
inputs are above
CC18
CC
CC5
CC18
inputs.
), whichever
or V
), the 2.5V
U
CC
CC3
inputs
CC3
CC3
pin,
CC
or
or
Power-Down
On power-down, once any of the V
its threshold, RST is held at a logic low. A logic low of 0.3V
is guaranteed until both V
below 1V.
Glitch Immunity
The RST output of the LTC1727/LTC1728 have two forms
of glitch immunity built in. First, the input monitors require
the input voltage to transition at least 10% of the input
threshold (0.1 • V
approximately 50µs in order to force the monitor output
low. The duration of the transition must be longer for
voltage transitions of lesser magnitude (see Figure 1).
Secondly, the reset pulse width of approximately 200ms
acts to debounce the RST output ensuring that the RST
output will always be in the correct state.
The individual monitor outputs of the LTC1727 do not
have hysteresis and will track the monitor inputs relative
to the monitor’s input threshold (V
V
on it may cause the individual monitor outputs (COMPA,
COMP25, COMP3 and COMP5) to toggle on the ripple as
the input voltage passes the input threshold. The slow
response time of the LTC1727’s input monitors has a
tendency to integrate signals on the inputs improving their
immunity to noise and ripple.
RT5
). A very slow moving input voltage with ripple riding
Figure 1. Transient Duration vs Comparator Overdrive
450
400
350
300
250
200
150
100
50
0
RESET MONITOR OVERDRIVE VOLTAGE (% OF V
0.1
RTH
) below the input threshold for
1
CC3
and V
10
CC5
CC
RTA
1727/28 F01
inputs drop below
/V
, V
CC25
RT25
100
CC
)
/V
, V
CC18
RT3
drop
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and