Datasheet

µPs and circuitry do not operate when V
CC
drops below
1V. For the MAX6804 application where RESET must
be valid down to 0, adding a pulldown resistor between
RESET and GND removes stray leakage currents,
holding RESET low (Figure 2a). The pulldown resistor
value is not critical; 100kW is large enough not to load
RESET, and small enough to pull it low. For the MAX6803,
where RESET must be valid to V
CC
= 0, a 100kW pullup
resistor between RESET and V
CC
will hold RESET high
when V
CC
falls below 0.7V (Figure 2b).
Since the MAX6805 has an open-drain, active-low
out-put, it typically uses a pullup resistor. With this device,
RESET will most likely not maintain an active condi-
tion, but will drift to a non-active level due to the pullup
resistor and the reduced sinking capability of the open-
drain device. Therefore, this device is not recommend-
ed for applications where the RESET pin is required to
be valid down to V
CC
= 0.
Figure 2. Ensuring Reset Valid down to V
CC
= 0
V
CC
GND
MAX6804
RESETMR
100kΩ
(a)
V
CC
GND
MAX6803
RESET
100kΩ*
(b)
*ASSUMES HIGH-Z RESET INPUT TO THE µP
MR
www.maximintegrated.com
Maxim Integrated │ 5
MAX6803/MAX6804/
MAX6805
4-Pin, Low-Power
µP Reset Circuits with Manual Reset
MAX6804
V
CC
V
CC
RESETMR
RESET
GND
PUSHBUTTON
SWITCH
V
CC
GND
µP
1
2
4
3
V
CC
MR(RESET)
GND
MAX6803
MAX6804
MAX6805
SOT143
TOP VIEW
RESET
( ) ARE FOR MAX6803
Typical Operating Circuit
Pin Conguration