MAX6412 Maxim, MAX6412 Datasheet - Page 7

• Manufacturer Part Number: MAX6412
• Description: Low-Power / Single/Dual-Voltage uP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay
• Manufacturer: Maxim

Figure 4. MAX6418/MAX6419/MAX6420 Monitoring Two Voltages
The MAX6418/MAX6419/MAX6420 contain both facto-
ry-trimmed threshold voltages and an adjustable reset
threshold input, allowing the monitoring of two voltages,
V
when either of the voltages falls below its respective
threshold voltage.
The reset timeout period is adjustable to accommodate
a variety of µP applications. Adjust the reset timeout
period (t
SRT and ground. Calculate the reset timeout capacitor
as follows:
where t
CC
Low-Power, Single/Dual-Voltage µP Reset Circuits
and V
RP
with Capacitor-Adjustable Reset Timeout Delay
RP
is in seconds and C
C
) by connecting a capacitor (C
MON_TH
SRT
(MAX6418/MAX6419/MAX6420)
= (t
C
Application Information
SRT
_______________________________________________________________________________________
R1
R2
Selecting a Reset Capacitor
V
RP
MON_TH
(see Figure 4). Reset is asserted
- 275µs) / (2.73
Dual-Voltage Monitoring
RESET IN
GND
SRT
SRT
V
1.26V
CC
is in Farads
LASER-TRIMMED
RESISTORS
✕
10
SRT
6
MAX6418
MAX6419
MAX6420
)
) between
CIRCUITRY
RESET
V
CC
(RESET)
RESET
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 MAX6412–MAX6420 can be operated in a voltage
detector mode by floating the SRT pin. The reset delay
times for V
are not significantly different. The reset output is
deasserted smoothly without false pulses.
SRT
must be a low-leakage (<10nA) type capacitor,
MAX6420
ONLY
CC
R
L
Operating as a Voltage Detector
rising above or falling below the threshold
µP
SRT
7