Datasheet

MAX6342–MAX6345
6-Pin µP Reset Circuit with
Power-Fail Comparator
_______________________________________________________________________________________ 5
MAX6344MAX6342
— 6
Active-High Push-Pull Reset Output. It remains high for 180ms
after V
CC
rises above the reset threshold or MR goes from low
to high.
6 —
Active-Low Reset Output. Push-pull for MAX6342/MAX6345.
Open-drain for MAX6343. It remains low for 180ms after V
CC
rises above the reset threshold or MR goes from low to high.
5 5
Manual-Reset Input. Pull low to force a reset. RESET or RESET
remains active as long as MR is low and for the reset timeout
period after MR goes high. Leave unconnected or connect to
V
CC
if unused.
Pin Description (continued)
MAX6343
—
6
5
MAX6345
6
5
—
RESET
RESET
MR
FUNCTION
PIN
NAME
_______________Detailed Description
Reset Output
A µP’s reset input starts the µP in a known state. These
µP supervisory circuits assert reset to prevent code-
execution errors during power-up, power-down, or
brownout conditions.
RESET and RESET are guaranteed to be asserted at a
valid logic level for V
CC
> +1V (see the Electrical Char-
acteristics table). Once RESET asserts, it remains
asserted for at least 100ms (t
RP
) after V
CC
rises above
its threshold value or after MR returns high (Figures 1
and 2).
Open-Drain RESET Output
The MAX6343 has an active-low, open-drain reset out-
put. This output sinks current when RESET is asserted.
Connect a pull-up resistor from RESET to any positive
supply voltage up to +5.5V (Figure 3). Select a resistor
value large enough to register a logic low (see the Elec-
trical Characteristics table), and small enough to regis-
ter a logic high while supplying all input current and
leakage paths connected to the RESET line. A 10kΩ
pull-up is sufficient in most applications.
Manual Reset
The MAX6342/MAX6343/MAX6344s’ manual-reset input
(MR) allows reset to be triggered by a pushbutton
switch. The switch is effectively debounced by the 1µs
min reset pulse width. MR is CMOS-logic compatible.
RESET
GENERATOR
V
CC
6
(RESET)
5
RESET
4
PFO
1.25V
GND
100kΩ
V
TH
( ) ARE FOR MAX6344 ONLY.
1
MR
2
V
CC
3
PFI
MAX6342
MAX6343
MAX6344
RESET
GENERATOR
6
RESET
5
RESET
4
PFO
1.25V
GND
V
TH
1
2
V
CC
3
PFI
MAX6345
Figure 1. MAX6342/MAX6343/MAX6344 Functional Diagram
Figure 2. MAX6345 Functional Diagram