MAX6412 View Datasheet(PDF) - Maxim Integrated
Part Name
Description
Manufacturer
MAX6412 Datasheet PDF : 12 Pages
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MAX6412–MAX6420
Low-Power, Single/Dual-Voltage μP Reset Circuits
with Capacitor-Adjustable Reset Timeout Delay
3.3V
VCC
MAX6414
MAX6417
MAX6420
10kΩ
RESET
5.0V
5V SYSTEM
GND
CMOS-logic inputs connected to RESET can drift to
undetermined voltages. This presents no problems in
most applications, since most μPs and other circuitry do
not operate with VCC below 1V.
In those applications where RESET must be valid down
to 0, adding a pulldown resistor between RESET and
ground sinks any stray leakage currents, holding RESET
low (Figure 6). The value of the pulldown resistor is not
critical; 100kΩ is large enough not to load RESET and
small enough to pull RESET to ground. For applications
using the MAX6413, MAX6416, and MAX6419, a 100kΩ
pullup resistor between RESET and VCC will hold RESET
high when VCC falls below 1V (Figure 7). Open-drain
RESET versions are not recommended for applications
requiring valid logic for VCC down to 0V.
Figure 5. MAX6414/MAX6417/MAX6420 Open-Drain RESET
Output Allows use with Multiple Supplies
Interfacing to Other Voltages for Logic
Compatibility
The open-drain outputs of the MAX6414/MAX6417/
MAX6420 can be used to interface to μPs with other logic
levels. As shown in Figure 5, the open-drain output can be
connected to voltages from 0 to 5.5V. This allows for easy
logic compatibility to various microprocessors.
Negative-Going VCC Transients
In addition to issuing a reset to the μP during power-up,
power-down, and brownout conditions, these supervisors
are relatively immune to short-duration negative-going
transients (glitches). The Maximum Transient Duration vs.
Reset Threshold Overdrive graph in the Typical Operating
Characteristics shows this relationship.
The area below the curve of the graph is the region in
which these devices typically do not generate a reset
pulse. This graph was generated using a negative-going
pulse applied to VCC, starting above the actual reset
threshold (VTH) and ending below it by the magnitude
indicated (reset-threshold overdrive). As the magnitude of
the transient decreases (farther below the reset thresh-
old), the maximum allowable pulse width decreases.
Typically, a VCC transient that goes 100mV below the
reset threshold and lasts 50μs or less will not cause a
reset pulse to be issued.
Ensuring a Valid RESET or RESET
Down to VCC = 0V
When VCC falls below 1V, RESET/RESET current sinking
(sourcing) capabilities decline drastically. In the case of
the MAX6412, MAX6415, and MAX6418, high-impedance
VCC
MAX6412 VCC
MAX6415
MAX6418
RESET
GND
100kΩ
Figure 6. Ensuring RESET Valid to VCC = 0V
VCC
MAX6413 VCC
MAX6416
MAX6419
100kΩ
RESET
GND
Figure 7. Ensuring RESET Valid to VCC = 0V
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