MAX670 Maxim, MAX670 Datasheet - Page 7

• Manufacturer Part Number: MAX670
• Description: Low-Voltage / SOT23 P Supervisors with Power- Fail In/Out / Manual Reset / and Watchdog Timer
• Manufacturer: Maxim

Figure 3. RESET Output Timing Diagram
Figure 4. Interfacing to Different Logic-Supply Voltage
Figure 5. Setting the Auxiliary Monitor
Voltage µP Supervisory Circuits in SOT Package
RESET
V
IN_
TH_
IN2 = +3.3V
MAX6700
MAX6710
IN2
GND
V
t
RD
INTH
R1
R2
_______________________________________________________________________________________
RESET
Low-Voltage, High-Accuracy, Triple/Quad
10%
100kΩ
V
REF
RESET
= 0.62V
R1 = R2
GND
+5V
V
t
RP
CC
(
V
0.62V
INTH
V
TH_
- 1
)
90%
V
monitored voltage. IN2 powers all other options for the
MAX6710 and is a monitored voltage. When any supply
drops below its threshold, the reset output asserts low
and remains low while either IN1 or IN2 is above 1.0V.
The MAX6700/MAX6710 offer several monitor options
with adjustable reset thresholds. The threshold voltage at
each adjustable IN_ input is typically 0.62V. To monitor a
voltage >0.62V, connect a resistor-divider network to the
circuit as shown in Figure 5.
or, solved in terms of R1:
Because the MAX6700/MAX6710 have a guaranteed
input current of ±0.2µA (±0.4µA for IN1) on their
adjustable inputs, resistor values up to 100kΩ can be
used for R2 with <1% error. The MAX6700/MAX6710Q
include an internal voltage clamp (1.5V typ) at each of
the adjustable voltage inputs. An input voltage higher
than 1.5V induces a higher input current.
Connect unused monitor inputs to a supply voltage
greater in magnitude than their specified threshold volt-
ages. For unused IN_ adjustable inputs, connect a 1MΩ
series resistor between the unused input and IN2 (or
V
tion (device power-supply pin). Do not connect unused
monitor inputs to ground or allow them to float.
Figure 6 shows an application circuit adding manual reset
to the MAX6710. Depressing the pushbutton switch short-
circuits the analog input to ground and initiates a RESET
pulse. The switch must be open for at least 140ms in
order to deassert the RESET output. No external switch
debounce is required. Use a small capacitor to improve
noise immunity when using long leads from the pushbut-
ton switch to the adjustable input.
The MAX6700/MAX6710 are normally powered from the
monitored IN2 or from the V
inputs are immune to short supply transients. For higher
immunity in noisy applications, connect a 0.1µF bypass
capacitor from the IN2 input to ground. Add capacitance
to IN1, IN3, and IN4 to increase their noise immunity.
CC
CC
) to limit the bias current. Use IN2 for normal opera-
Power-Supply Bypassing and Grounding
powers the MAX6700/MAX6710Q and is not a
V
R1 = R2 ((V
INTH
Adding Manual Reset Capability
= 0.62V x (R1 + R2) / R2
INTH
Adjustable Thresholds
CC
/ 0.62V) - 1)
supply input. All monitored
Unused Inputs
(MAX6710)
7