MAX16008_11 Datasheet, PDF (9/13 Pages) Maxim Integrated Products – Low-Voltage, High-Accuracy, Quad Window Voltage Detectors in Thin QFN

Low-Voltage, High-Accuracy, Quad Window
Voltage Detectors in Thin QFN
Detailed Description
The MAX16008/MAX16009 are adjustable quad win-
dow voltage detectors in a small thin QFN package.
These devices are designed to provide a higher level of
system reliability by monitoring multiple supply voltages
and providing a fault signal when any of the voltages
exceeds its overvoltage threshold or falls below its
undervoltage threshold.
These devices offer user-adjustable thresholds that
allow voltages to be monitored down to 0.4V. The
devices allow the upper and lower trip thresholds of
each window detector to be set externally with the use
of three external resistors.
Each monitored threshold has an independent open-
drain output for signaling a fault condition. The outputs
can be wire OR’ed together to provide a single fault
output. The open-drain outputs are internally pulled up
with a 30µA current, but can be externally driven to
other voltage levels for interfacing to other logic levels.
Both devices feature a margin input to disable the out-
puts during margin testing or any other time after
power-up operations. The MAX16009 offers a reset out-
put that deasserts after a reset timeout period after all
voltages are within their threshold specification. The
reset timeout is internally set to 140ms (min), but can
be externally adjusted to other reset timeouts using an
external capacitor. In addition, the MAX16009 offers a
manual reset input.
Applications Information
Voltage Monitoring
The MAX16008/MAX16009 feature undervoltage and
overvoltage comparators for window detection (see
Figure 2). UVOUT_/OVOUT_ deassert high when the
monitored voltage is within the “selected window.”
When the monitored voltage falls below the lower limit
of the window (V_TRIPLOW), UVOUT_ asserts low; or if
the monitored voltage exceeds the upper limit
(V_TRIPHIGH), OVOUT_ asserts low. The application in
Figure 2 shows the MAX16008/MAX16009 enabling the
DC-DC converter when the monitored voltage is in the
selected window.
+5V
R1
R2
R3
UVIN_
V_CC
UVOUT_
OVOUT_
MAX16008/
OVIN_ ^MAX16009
IN
EN _DC-DC OUT
REGULATOR
GND
Figure 2. MAX16008/MAX16009 Monitor Circuit
The resistor values R1, R2, and R3 can be calculated
as shown:
V_TRIPLOW
=
V_TH
⎛
⎝⎜
R _TOTAL
R2 + R3
⎞
⎠⎟
V_TRIPHIGH
=
V_TH
⎛
⎝⎜
R
TOTAL
R3
⎞
⎠⎟
where R_TOTAL = R1 + R2 + R3.
Use the following steps to determine the values for R1,
R2, and R3:
1) Choose a value for R_TOTAL, the sum of R1, R2, and
R3. Because the MAX16008/MAX16009 have very
low input bias current (2nA typ), R_TOTAL can be up
to 2MΩ. Large-value resistors help minimize power
consumption. Lower-value resistors can be used to
maintain overall accuracy.
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