MAX6422US37-T Maxim Integrated, MAX6422US37-T Datasheet - Page 5

• Manufacturer Part Number: MAX6422US37-T
• Description: Supervisory Circuits
• Manufacturer: Maxim Integrated
• Series: MAX6340, MAX6421, MAX6422, MAX6423, MAX6424, MAX6425, MAX6426r

Specifications of MAX6422US37-T

• Number Of Voltages Monitored: 1
• Monitored Voltage: 1.6 V to 5 V
• Undervoltage Threshold: 3.608 V
• Overvoltage Threshold: 3.793 V
• Output Type: Active High, Push-Pull
• Manual Reset: Not Resettable
• Watchdog: No Watchdog
• Battery Backup Switching: No Backup
• Power-up Reset Delay (typ): 4.375 ms
• Supply Voltage - Max: 5.5 V
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SOT-143
• Chip Enable Signals: No
• Maximum Power Dissipation: 320 mW
• Minimum Operating Temperature: - 40 C
• Power Fail Detection: No
• Supply Current (typ): 2.5 uA
• Supply Voltage - Min: 1 V

where t
The reset delay time is set by a current/capacitor-con-
trolled ramp compared to an internal 0.65V reference.
An internal 240nA ramp current source charges the
external capacitor. The charge to the capacitor is
cleared when a reset condition is detected. Once the
reset condition is removed, the voltage on the capacitor
ramps according to the formula: dV/dt = I/C. The C
capacitor must ramp to 0.65V to deassert the reset.
C
ceramic is recommended.
The MAX6340/MAX6421–MAX6426 can be operated in a
voltage detector mode by floating the SRT pin. The reset
delay times for V
threshold are not significantly different. The reset output is
deasserted smoothly without false pulses.
Figure 2. Wired-OR Reset Circuit
SRT
must be a low-leakage (<10nA) type capacitor;
RP
is in seconds and C
C
SRT
Low-Power, SC70/SOT µP Reset Circuits with
Operating as a Voltage Detector
MAX6340
MAX6423
MAX6425
MAX6426
= (t
OPEN-DRAIN
CC
V
_______________________________________________________________________________________
DD
Capacitor-Adjustable Reset Timeout Delay
LOGIC
RP
RESET
N
rising above or falling below the
- 275µs) / (2.73
GND
N
V
SRT
CC
10kΩ
is in farads.
RESET
✕
µP
10
6
)
SRT
The open-drain outputs of the MAX6340/MAX6423/
MAX6425/MAX6426 can be used to interface to µPs with
other logic levels. As shown in Figure 1, the open-drain
output can be connected to voltages from 0 to 5.5V. This
allows for easy logic compatibility to various µPs.
To allow auxiliary circuitry to hold the system in reset,
an external open-drain logic signal can be connected
to the open-drain RESET of the MAX6340/MAX6423/
MAX6425/MAX6426, as shown in Figure 2. This config-
uration can reset the µP, but does not provide the reset
timeout when the external logic signal is released.
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 graph Maximum Transient
Duration vs. Reset Threshold Overdrive 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 V
reset threshold (V
tude indicated (reset-threshold overdrive). As the mag-
nitude of the transient decreases (farther below the
reset threshold), the maximum allowable pulse width
decreases. Typically, a V
below the reset threshold and lasts 50µs or less does
not cause a reset pulse to be issued.
When V
ing (sourcing) capabilities decline drastically. In the
case of the MAX6421/MAX6424, high-impedance
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 V
In those applications where RESET must be valid down
to zero, adding a pulldown resistor between RESET
and ground sinks any stray leakage currents, holding
RESET low (Figure 3). The value of the pulldown resis-
tor is not critical; 100kΩ is large enough not to load
RESET and small enough to pull RESET to ground. For
applications using the MAX6422, a 100kΩ pullup resis-
Interfacing to Other Voltages for Logic
CC
falls below 1V, RESET/RESET current-sink-
Ensuring a Valid RESET or RESET
Negative-Going V
Applications Information
TH
) and ending below it by the magni-
CC
below 1V.
CC
CC
, starting above the actual
transient that goes 100mV
Down to V
Wired-OR Reset
CC
Compatibility
Transients
CC
= 0
5