DS1815R-5-U+ Maxim Integrated, DS1815R-5-U+ Datasheet - Page 8

• Manufacturer Part Number: DS1815R-5-U+
• Description: Supervisory Circuits
• Manufacturer: Maxim Integrated
• Series: DS1815r

Specifications of DS1815R-5-U+

• Number Of Voltages Monitored: 1
• Monitored Voltage: 0 V to 5.5 V
• Undervoltage Threshold: 2.98 V
• Overvoltage Threshold: 3.15 V
• Output Type: Active Low, Push-Pull
• Manual Reset: Not Resettable
• Watchdog: No Watchdog
• Battery Backup Switching: No Backup
• Power-up Reset Delay (typ): 250 ms
• Supply Voltage - Max: 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOT-23
• Chip Enable Signals: No
• Minimum Operating Temperature: - 40 C
• Power Fail Detection: Yes
• Supply Current (typ): 35 uA
• Supply Voltage - Min: 0 V
• Part # Aliases: 90-1815R+U05

where V
and V
R1 and R2 can have very high values to minimize cur-
rent consumption due to low leakage currents. Set R2
to some conveniently high value (500kΩ, for example)
and calculate R1 based on the desired reset threshold
voltage, using the following formula:
The MAX6748 and MAX6749 do not monitor V
ply voltage, therefore, V
µP Reset Circuits with Capacitor-Adjustable
Reset/Watchdog Timeout Delay
8
Figure 3. Adding an External Manual Reset Function to the
MAX6748–MAX6751
Figure 4a. Watchdog Timing Diagram, WDS = GND
_______________________________________________________________________________________
TH
RESET
NORMAL MODE (WDS = GND)
WDI
MON_TH
R1 = R2 x (V
is the reset input threshold (1.235V). Resistors
V
V
OV
OV
CC
CC
R1
R2
V
MON_TH
is the desired reset threshold voltage
MON_TH
RESET IN
GND
CC
must be greater than 1.5V to
MAX6748
MAX6749
MAX6750
MAX6751
/V
RESET IN
V
CC
- 1) (Ω)
V
t
WD
CC
CC
sup-
guarantee RESET IN threshold accuracy and timing
performance. The MAX6748 and MAX6749 can be con-
figured to monitor V
V
The MAX6750 and MAX6751 contain both factory-
trimmed threshold voltages and an adjustable reset
threshold input, allowing the monitoring of two voltages,
V
when either of the voltages falls below it respective
threshold voltages.
Many µP-based products require manual reset capabil-
ity, to allow an operator or external logic circuitry to initi-
ate a reset. The manual reset input (MR) can connect
directly to a switch without an external pullup resistor or
debouncing network. MR is internally pulled up to V
and, therefore, can be left unconnected if unused.
MR is designed to reject fast, falling transients (typically
100ns pulses) and it must be held low for a minimum of
1µs to assert the reset output. A 0.1µF capacitor from
MR to ground provides additional noise immunity. After
MR transitions from low to high, reset remains asserted
for the duration of the reset timeout period.
A manual reset option can easily be implemented
with the MAX6748–MAX6751 by connecting a normally
open momentary switch in parallel with R2 (Figure 3).
When the switch is closed, the voltage on RESET IN
goes to zero, initiating a reset. Similar to the MAX6746/
MAX6747 manual reset, reset remains asserted while
the voltage at RESET IN is zero and for the reset time-
out period after the switch is opened.
MON_TH.
CC
and V
Manual Reset (MAX6746/MAX6747)
MON_TH
t
(see Figure 2). RESET is asserted
RP
CC
Dual-Voltage Monitoring
voltage by connecting V
(MAX6750/MAX6751)
CC
CC
to