MAX6845UKD4-T Maxim Integrated, MAX6845UKD4-T Datasheet - Page 5

• Manufacturer Part Number: MAX6845UKD4-T
• Description: Supervisory Circuits NULL
• Manufacturer: Maxim Integrated
• Series: MAX6841, MAX6842, MAX6843, MAX6844, MAX6845r

Specifications of MAX6845UKD4-T

• Number Of Voltages Monitored: 1
• Monitored Voltage: 0.9 V to 1.5 V
• Output Type: Active Low, Open Drain
• Manual Reset: Resettable
• Watchdog: No Watchdog
• Battery Backup Switching: No Backup
• Power-up Reset Delay (typ): 0.15 ms
• Supply Voltage - Max: 1.8 V
• Chip Enable Signals: No
• Maximum Power Dissipation: 571 mW
• Power Fail Detection: No
• Supply Current (typ): 8.1 uA
• Supply Voltage - Min: 0.55 V

A microprocessor’s (µP’s) reset input starts the µP in a
known state. The MAX6841–MAX6845 assert a reset dur-
ing power-up, power-down, and brownout conditions.
When the V
old (MAX6841/MAX6842) or RESET IN falls below the
adjustable threshold (MAX6843/MAX6844/MAX6845),
reset asserts and stays asserted for a fixed timeout delay
(Table 2) after V
reset threshold. The MAX6841–MAX6845 are available
with five typical timeout options for each part: 150µs
(voltage detector), 1.5ms, 30ms, 210ms, and 1.68s.
The MAX6841/MAX6842 have two reset outputs
(RESET and RESET); one is the inverse of the other.
The MAX6841 has one active-high push-pull output and
one active-low push-pull output. The MAX6842 has one
active-high push-pull output and one active-low open-
drain output. The MAX6843 features an active-low
push-pull output. The MAX6844 features an active-
high push-pull output, and the MAX6845 has an active-
low open-drain output stage. Connect a pullup resistor
from the open-drain RESET output to any voltage
between 0 and 6V.
Many µP-based systems require a manual reset capa-
bility, allowing the operator, a test technician, or exter-
nal logic circuitry to initiate a reset. Reset remains
asserted while MR is low, and for a fixed timeout delay
after MR returns high. This input has an internal 20kΩ
pullup resistor, so it can be left open if it is not used.
MR can be driven with CMOS logic level or with open-
drain/collector outputs. To create a manual reset func-
V
CC
CC
V
supply voltage falls below a preset thresh-
REF
CC
Ultra-Low-Voltage µP Reset Circuits and
_______________________________________________________________________________________
PULLUP
or RESET IN has risen above the
MR
Detailed Description
GND
TIMEOUT
Manual Reset Input
MANUAL
DETECT
PERIOD
RESET
RESET
MR
Reset Output
MAX6841
MAX6842
OUTPUT
RESET
RESET
RESET
tion, connect a normally open momentary switch from
MR to ground; external debounce circuitry is not
required. If MR is driven from long cables or the device
is used in a noisy environment, connect a 0.1µF capac-
itor from MR to ground to provide additional noise
immunity.
The MAX6843/MAX6844/MAX6845 feature a RESET IN
input, which allows users to adjust the reset threshold
voltage. The internal reference voltage is 187.4mV with
respect to V
can be used to set voltage monitoring thresholds, as
shown in Figure 1. The resistive-divider network must
be referenced to V
Figure 1. Setting the Adjustable Threshold Externally
RESET IN
V
CC
V
R1 =
CC
WHERE V
V
CC-TH
R1
R2
Voltage Detectors
CC
V
IS THE V
CC-TH
V
V
REF
REF
R2
. An external resistive-divider network
REF
= 187.4mV (WITH RESPECT TO V
= 187.4mV
- 1
CC
CC
PULLUP
THRESHOLD.
Functional Diagrams
RESET IN
MR
MR
. As V
GND
MAX6843
MAX6844
MAX6845
GND
V
CC
CC
TIMEOUT
MANUAL
DETECT
PERIOD
RESET
RESET
MR
falls, the voltage at
CC
) AND
( ) ARE FOR
MAX6844
MAX6843
MAX6844
MAX6845
OUTPUT
RESET
(RESET)
RESET
RESET IN
RESET
RESET
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